THE ELECTRONICS AND ELECTRICAL

ENGINEERING LABORATORY (EEEL)

One of NIST’s seven measurement and standards laboratories,

EEEL conducts research, provides measurement services, and

helps set standards in support of the fundamental electronic

technologies of semiconductors, magnetics, and superconductors; information and communications technologies, such as

fiber optics, photonics, microwaves, electronic displays,

electronics manufacturing supply chain collaboration; forensics

and security measurement instrumentation; fundamental and

practical physical standards and measurement services for

electrical quantities; maintaining the quality and integrity of

electrical power systems; and the development of nanoscale

and microelectromechanical devices. EEEL provides support to

law enforcement, corrections, and criminal justice agencies,

including homeland security.

EEEL consists of six programmatic divisions and two matrixmanaged offices:

Electricity Division

Semiconductor Electronics Division

Radio-Frequency Technology Division

Electromagnetic Technology Division

Optoelectronics Division

Magnetic Technology Division

Office of Microelectronic Programs

Office of Law Enforcement Standards

This publication describes the technical programs of the

Optoelectronics Division. Similar documents describing

the other Divisions and Offices are available.

Contact NIST/EEEL, 100 Bureau Drive, MS 8100,

Gaithersburg, MD 20899-8100, telephone 301-975-2220,

http://www.eeel.nist.gov. These publications are updated

biennially.

Product Disclaimer: Certain commercial products and services may be named herein to fully describe

the work performed. This does not constitute a recommendation or endorsement by the National

Institute of Standards and Technology.

Cover caption: A band diagram depicting the operation of a single-photon turnstile is overlaid by a

picture of an optical fiber cable, a representation of laser-based surgery, and a Poincaré sphere used

to graphically describe optical polarization. All are examples of diverse optoelectronic applications

served by the Division.

Image of laser surgery courtesy of Eyesearch.com.
ELECTRONICS AND ELECTRICAL

ENGINEERING LABORATORY

OPTOELECTRONICS

DIVISION

PROGRAMS, ACTIVITIES, AND

ACCOMPLISHMENTS

NISTIR 6627

January 2003

U.S. DEPARTMENT OF COMMERCE

Donald L. Evans, Secretary

Technology Administration

Phillip J. Bond, Under Secretary of Commerce for Technology

National Institute of Standards and Technology

Arden L. Bement, Jr., Director
CONTENTS

From the Division Chief ..........................................................................................................iii

About the Optoelectronics Division ....................................................................................... iv

Primary Standards for Laser Radiometry .............................................................................. v

Optoelectronics Division Staff ............................................................................................... vi

CW Laser Radiometry............................................................................................................ 1

Pulsed-Laser Radiometry ....................................................................................................... 4

High-Speed Measurements .................................................................................................... 7

Interferometry and Polarimetry ............................................................................................ 10

Spectral and Nonlinear Properties ........................................................................................ 14

Optical Materials Metrology ................................................................................................. 18

Nanostructure Fabrication and Metrology ............................................................................ 22

Semiconductor Growth and Devices .................................................................................... 25

Appendix A: Major Laboratory Facilities............................................................................. 29

Appendix B: NRC Post-Doctoral and Other Research Opportunities ................................ 30

Appendix C: Conferences and Workshops .......................................................................... 32

Appendix D: Calibration Services ........................................................................................ 33

Appendix E: Standard Reference Materials ........................................................................ 35
Optoelectronics Division iii

FROM THE DIVISION CHIEF

New and better-understood measurement techniques. Instrument calibrations and artifact calibration standards that are traceable to U.S. national standards. Assistance in the development

of industry standards for product specification.

We are a group of about 60 scientists, engineers, and support staff, and these are some of the

contributions we make to the optoelectronics industry. Herein, you will find examples of our

accomplishments through the end of fiscal year 2002 (September 30, 2002) and an indication of

our present work and plans. More current information is available on our web site. Please

contact us if we can be of assistance.

We take metrology seriously. In optoelectronics, as in many other fields, it is a key part of the

industrial infrastructure that establishes competitiveness. Consistently specified products are

essential in fair trade, and measurements are a key element in efficient manufacturing. The

cost of measurements often ranges between 10 % and 30 % of the cost of producing a product.

So while the optoelectronics industry, along with many other high-technology fields, continues to

struggle, advancing the field of optoelectronics metrology remains an important task.

We maintain the U.S. national standards for laser power and energy measurements (see page

34) and use them to provide the broadest range of laser calibration capabilities available anywhere. Each year we perform over 200 calibrations of power- or energy-measuring instruments for over 50 customers. We also provide artifact calibration standards, which we call

Standard Reference Materials, for over a dozen parameters, most of them related to optical

communications (see page 36 for details). These components provide customers with the

capability of performing periodic instrument calibrations, traceable to national standards, in their

own laboratories.

We develop measurement techniques that can be used, online and in situ, in the manufacture of

optoelectronic materials, and provide reference data on the optical properties of important optoelectronic materials. And we work closely with major standards-developing organizations, especially the Telecommunications Industry Association (TIA), the International Electrotechnical

Commission (IEC), and the International Organization for Standards (ISO), in producing industry standards.

A personal note: It has been my privilege to work in this area at NIST since 1969 and to lead the

Optoelectronics Division since it was formed in 1994. I will retire in early January 2003, at

about the time this document is released. Dr. Kent Rochford, who has substantial experience in

optoelectronics metrology, both at NIST and in industry, has been appointed my successor. I

know that, under his leadership, the Division will continue to play an important role in the industry.

Gordon W. Day, Division Chief

Optoelectronics Division

National Institute of Standards and Technology

325 Broadway

Boulder, CO 80305-3328

(303) 497-5342

Fax: (303) 497-7671

Optoelectronics@boulder.nist.gov

http://www.boulder.nist.gov/div815 Gordon W. Day and Kent Rochford
iv Electronics and Electrical Engineering Laboratory

ABOUT THE OPTOELECTRONICS DIVISION

MISSION

The mission of the Optoelectronics Division is to provide the optoelectronics industry and its

suppliers and customers with comprehensive and technically advanced measurement capabilities, standards, and traceability to those standards.

HISTORY

The Division is located in Boulder, Colorado, as a part of the NIST Boulder Laboratories. It was

established in 1994, succeeding an earlier NIST organizational unit, the Optical Electronic Metrology Group of the Electromagnetic Technology Division. The Division’s roots extend to the

first NIST (NBS) work on optoelectronics — research begun in the early 1960s to develop

techniques for measuring the output power, or energy, of a laser. Since the late 1960s, NIST

research on measurement and standards to support the development and application of lasers

has been centered in the Boulder Laboratories. Research related to optical communications

was added in the mid-1970s, and expanded substantially in the late 1980s; it now represents

more than half of the Division’s effort.

ORGANIZATION

The Division is organized into three Groups. Two Groups — the Sources and Detectors Group

and the Optical Fiber and Components Group — focus on the characterization of optoelectronic

components. The third, the Optoelectronic Manufacturing Group, focuses on measurements

that can lead to more efficient manufacturing of optoelectronic materials and components.

RESEARCH AND SERVICES

Most of the research performed in the Division is conducted either with NIST-appropriated

funds or under contract to other U.S. Government agencies. Results are normally placed in the

public domain through publication in the open literature. Some results become the subject of

patents, and are available for license. The Division also conducts proprietary research in collaboration with industry and universities through Cooperative Research and Development Agreements (CRADAs).

The Division and its predecessor organizations have been providing calibration services for the

characterization of lasers and detectors since 1967, and each year conducts over 200 calibrations for about 50 customers. It also provides the industry with standard reference materials,

which are artifact standards that can be used to calibrate a customer’s own instrumentation.

The Division maintains close contact with the optoelectronics industry through major industry

associations, including the Optoelectronics Industry Development Association (OIDA), and the

Lasers and Electro-optics Manufacturer’s Association (LEOMA). Division staff members

represent NIST to the major domestic and international standards organizations active in optoelectronics — the Telecommunications Industries Association (TIA), the International

Electrotechnical Commission (IEC), the International Organization for Standardization (ISO),

and the American National Standards Institute (ANSI) — and provide impartial technical expertise in their negotiations.
Optoelectronics Division v

PRIMARY STANDARDS FOR LASER RADIOMETRY

A SiC absorbing cavity for the 157 nm excimer laser

calorimeter. Developed over the past few years, we

now provide power and energy calibrations at this

wavelength to support the semiconductor photolithography industry.

The Laser-Optimized Cryogenic Radiometer, developed in the late 1990s, and used for the highest

accuracy measurements with low-level cw lasers,

100 μW to 1 mW at wavelengths from 0.4 μm to

2 μm.

The C-Series Calorimeter, originally developed in the

1970s for use with cw lasers in the range from 50 μW

to 1 W and 0.4 μm to 2 μm wavelength. Improved

versions in current use for calibrations.

The K-Series Calorimeter, developed in the 1970s, for

high-power cw lasers in the range from 1 W to 1,000 W

and wavelengths from 0.4 μm to 20 μm. In current use

for calibrations.

Three versions of this standard are used for pulsedlaser calibrations. The Q-Series, developed in the

1980s is used for 1.06 μm lasers. The QUV and

QDUV calorimeters, developed in the 1990s are in

current use for calibrations at 248 nm and 193 nm,

respectively.

The BB Calorimeter, developed around 1980 for the

U.S. Air Force Metrology Laboratory, and in current

use for cw lasers with power levels up to 100 kW.
vi Electronics and Electrical Engineering Laboratory

OPTOELECTRONICS DIVISION STAFF

SOURCES AND DETECTORS (815.01)

DOWELL, Marla L. (GL) 7455

MERRILL, Sandra L., Secretary 3842

CASE, William E. (GS) 3741

CHRISTENSEN, David H. 3354

CLEMENT, Tracy S. (PT) 3052

CROMER, Christopher L. (PL) 5620

ELHELBAWY, Mona A. (S) 4304

HADLER, Joshua A. 4451

HALE, Paul D. (PL) 5367

JONES, Richard D. 3439

KEENAN, Darryl A. 5583

LEHMAN, John H. (PL) 3654

LEONHARDT, Rodney W. 5162

LI, Xiaoyu 3621

LIVIGNI, David J. 5898

OBARSKI, Gregory E. 5747

PHELAN, Jr., Robert J. (GS) 3696

SIMPSON, Philip A. (GS) 3789

TOBIAS, Iris L. 5253

VAYSHENKER, Igor 3394

YANG, Shao 5409

Legend:

GL = Group Leader

GS = Guest Scientist

PD = Post-Doctoral Appointment

PREP PD = PREP Postdoctoral

PL = Project Leader

PT = Part Time

S = Student

*Telephone numbers are: (303) 497-XXXX

 (the four-digit extension as indicated)

OPTICAL FIBER AND COMPONENTS

(815.03)

GILBERT, Sarah L. (GL) (PL) 3120

NORCROSS, Anna D., Secretary 4384

CORWIN, Kristan L. (PD) 4217

CRAIG, Rex M. 3359

DENNIS, Tasshi 3507

DRAPELA, Timothy J. 5858

DYER, Shellee D. 7463

ESPEJO, Robert J. (S) 7630

ETZEL, Shelley M. (PT) 3287

FRANZEN, Douglas L. (GS) 3346

KOFLER, Jonathan D. 4276

NEWBURY, Nathan R. 4227

ROWE, Mary A. (PREP PD) 7879

SWANN, William C. 7381

WASHBURN, Brian R. (PREP PD) 4447

WILLIAMS, Paul A. (PL) 3805

OPTOELECTRONIC MANUFACTURING

(815.04)

HICKERNELL, Robert K. (GL) 3455

REPETTO, Francesca, Secretary 5187

BERRY, Joseph J. (PD) 5268

BERTNESS, Kristine A. (PL) 5069

COBRY, Keith D.

 (PREP UnderGrad CU) 3942

FU, Chih-Chiang (S) 5572

GRAY, Matthew H. (PREP PD) 7953

HARVEY, Todd 3340

KLEIN, Benjamin (PREP PD) 7460

LEHMAN, Susan Y. (PREP PD) 7554

MIRIN, Richard P. (PL) 7955

ROSHKO, Alexana 5420

SANFORD, Norman A. (PL) 5239

SCHLAGER, John B. 3542

SILVERMAN, Kevin L. 7948

SU, Mark (PREP PD) 7368

DIVISION OFFICE 815.00

Name Extension*

DAY, Gordon W., Chief

 (through January 2003) 5204

ROCHFORD, Kent B., Chief

 (starting January 2003) 5285

SMITH, Annie J., Secretary 5342

BAUER, Beth, Admin. Assist. 5123

McCOLSKEY, Kathy S.,

 Administrative Officer 3288
Optoelectronics Division 1

CW LASER RADIOMETRY

PROJECT GOALS

Develop measurement methods and standards for

characterizing laser sources and detectors used with

continuous-wave (CW) laser radiation. Develop

and maintain measurement services for laser power

and energy, optical-fiber power, and related parameters (spectral responsivity, linearity, etc.).

The Optoelectronics Division’s new Optical Fiber

Power Meter transfer standards covering the

wavelength range 450 nm to 1800 nm. These optical

detectors have been optimized to provide highaccuracy measurements of optical fiber power

traceable to the division’s Laser Optimized Cryogenic

Radiometer (LOCR).

CUSTOMER NEEDS

Accurate characterization of optoelectronic sources

and detectors is important in the development and

use of industrial technologies such as lightwave

telecommunications, laser-based medical instrumentation, materials processing, photolithography,

data storage, and laser safety equipment. This

Project focuses on selected critical parameters intrinsic to sources and detectors, especially the calibration of optical-fiber power meters and laser power

or energy meters at commonly used wavelengths

and powers or energies. In addition, special test

measurements are available for linearity, spectral

responsivity, and spatial and angular uniformity of

laser power meters and detectors. Project members

participate in national and international standards

committees developing standards for laser safety,

laser radiation measurements (such as beam profile

and pointing stability), and optical-power-related

measurements. They extend and improve source

and detector characterizations, including development of low-noise, spectrally flat, highly uniform

pyroelectric detectors; high-accuracy transfer standards for optical-fiber and laser power measurements; and advanced laser systems for laser power

and energy measurements.

TECHNICAL STRATEGY

Meeting the needs of the laser and optoelectronics

industries and anticipating emerging technologies

requires investigation and development of improved measurement methods and instrumentation

for high-accuracy laser metrology over a wide range

of powers, energies, and wavelengths.

NIST has historically used electrically calibrated

laser calorimeters to provide traceability to the SI

units for laser power and energy. We also now

have measurement capability based on a Laser

Optimized Cryogenic Radiometer (LOCR), which

provides improvement in accuracy by an order of

magnitude for laser power measurements, compared

to electrically-calibrated radiometers. To meet the

increasing demands for higher accuracy over a

larger range of optical power and wavelength, it is

necessary to improve the accuracy of calibration

services through the development of better transfer standards, traceable to LOCR.

DELIVERABLE: By 2004, reduce by at least a factor

of 2 the uncertainties for all calibrations of laser

energy and power supplied to customers. In some

cases, this will be accomplished through the development of improved laser power transfer standards with

greater range in optical power and wavelength.

The continuing development of technology in the

telecommunications industry has led to demands

for higher performance and higher accuracy for

optical-fiber power meter characterization and calibration. In addition, the Department of Defense

(DOD) has begun to accelerate the use of optical

fiber in many of its new weapons systems. By developing improved standards for optical fiber power

and by developing instrumentation to accurately

quantify the uncertainties of the new standards,

we can meet these demanding requirements.

DELIVERABLE: By 2003, reduce the uncertainties for

optical-fiber power meter calibrations supplied to

customers. This will be accomplished through the

development of higher-accuracy transfer standards

and instrumentation to characterize these devices and

accurately assess uncertainty budgets.

Technical Contact:

John H. Lehman

Staff-Years (FY2003):

4.5 professionals

1.0 technicians
Many new systems being developed for the telecommunications industry demand higher power for

optical-fiber power meter (OFPM) characterization

and calibration. As much as several watts in fiber

is being used in systems to pump laser sources for

new applications. By developing the capability to

provide calibrations for OFPM up to 10 watts, we

can meet this need.

DELIVERABLE: By 2004, provide high power

capability up to 10 W for optical fiber power meter

calibrations.

Advances in laser technology are continuously

producing lasers with new wavelengths and power

levels. We are involved in an ongoing effort to

expand wavelength and power-range capabilities

through implementation of new tunable solid-state

laser technology to keep up with customer needs

for calibration services at NIST. These new laser

systems will be capable of providing a new wavelength requested by a customer with a minimum of

development time and cost by having a flexible suite

of laser systems available in the laboratory.

DELIVERABLE: By 2005, develop a suite of tunable

solid-state lasers to cover the entire spectral range

from the deep UV to the thermal IR. This laser system

will continue to evolve as new technology becomes

available to provide new calibration services as needs

arise.

The heart of a new tunable Ti:Sapphire laser that will

expand the capabilities of the Optoelectronics

Division’s calibration services in laser power and

optical fiber power. Shown is the laser crystal being

pumped by a doubled Nd:YAG laser beam. The new

laser system will provide many more wavelengths and

higher power capabilities.

2 Electronics and Electrical Engineering Laboratory

ACCOMPLISHMENTS

# Completed refurbishment of the calibration facilities for CW laser power and energy calibrations.

This included the low power CW, high-accuracy

LOCR, optical fiber power, and laser source laboratories.

Shown is the newly refurbished laser laboratory, which

supplies laser radiation for CW laser power and

optical fiber power meter calibrations. The refurbishment included completely refinishing the room, all new

facilities (temperature, lighting, electrical supply, and

cooling water), and new laser tables.

# Completed the documentation of the Division’s

Laser Optimized Cryogenic Radiometer, and have

obtained approval to begin a calibration service

based on the LOCR. This radiometer serves as the

basis for traceability of optical power measurements

for several calibration services offered by the Division, including CW laser power and optical fiber

power measurements.

# Modeled the errors associated with optical fiber transfer standards using angular uniformity

data obtained with the angular response characterization system. The newest designs for optical fiber transfer standards show an error of less than

0.1 % using fiber up to NA of 0.26. When completely implemented into our calibration systems,

the new transfer standard will be capable of measurements with a total expanded uncertainty of

0.4 %.

# Delivered both Si and Ge versions of the latest

optical fiber transfer standards to Navy and Army

sponsors. These detectors will improve the accuracy of their optical fiber power calibration and reduce inter-service variation.

# Built and tested a tunable Ti:Sapphire laser

with a tuning range of 700 nm to 900 nm. Also installed a dye laser to extend this range to 550 nm.

This enables the calibration of detectors over a

wide range of visible wavelengths.
Optoelectronics Division 3

Shown is a new tunable dye laser that will expand the

capabilities of the Optoelectronics Division’s calibration services in laser power and optical fiber power.

The new laser system will provide additional wavelengths for laser power meter calibrations.

CALIBRATIONS

The Optoelectronics Division provides calibration

services for laser and optical-fiber power at many

wavelengths and power levels from the ultraviolet,

the far-IR spectral regions, and from picowatt to

kilowatt power levels. See Appendix D for a list of

calibrations.

EQUIPMENT SUPPLIED

TO OTHER AGENCIES AND

NATIONAL LABORATORIES

# Delivered both Si and Ge versions of the latest

optical fiber transfer standard to Navy and Army

sponsors. These detectors will improve the accuracy of their optical fiber power calibration and reduce inter-service variation.

# Various transfer standards for laser and optical-fiber power delivered to DOD sponsors.

STANDARDS COMMITTEE

PARTICIPATION

American National Standards Institute: John H.

Lehman is a member of committee Z136, subcommittees SSC-01 and SSC-04, which deal with safe

use and measurement of lasers.

Telecommunications Industry Association: Igor

Vayshenker is a member of subcommittee FO-4.9,

which deals with Metrology and Calibration.

RECENT PUBLICATIONS

Lehman, J.H.; Radojevic, A.M.; Osgood Jr., R.M., “Domain-Engineered Thin-Film LiNbO3

 Pyroelectric-Bicell

Optical Detector,” IEEE Phot. Tech. Lett. 13: 851-853

(Aug 2001).

Houston, J.M.; Livigni, D.J, “Comparison of Two Cryogenic Radiometers at NIST,” NIST JRES 106: 641-647

(Jul-Aug 2001).
4 Electronics and Electrical Engineering Laboratory

PULSED-LASER RADIOMETRY

PROJECT GOALS

Develop measurement methods and standards for

characterizing pulsed-laser sources and detectors.

There is ongoing development work in the following areas: standards development, calibration services, and advising customers on in-house measurements.

CUSTOMER NEEDS

Accurate measurement methods and standards for

characterizing pulsed-laser sources and detectors

are critical in a number of industrial applications.

Project members work closely with industry to develop standards, new technology, and appropriate

measurement techniques for pulsed-laser measurements. These efforts include development work in

standards development, calibration services, and

advising customers on in-house measurements. The

bulk of our work is concentrated on ultraviolet (UV)

laser metrology using excimer lasers.

Excimer lasers are used in a wide range of industrial

applications. In addition to optical lithography for

semiconductor manufacturing, excimer lasers are

used in corneal sculpting procedures for vision correction, for example in photorefractive keratectomy

(PRK) and Laser In-situ Keratomileusis (LASIK),

as well as in micromachining of small structures

such as inkjet printer nozzles. However, the bulk of

our efforts are concentrated on UV laser metrology

in support of semiconductor photolithography.

Increasing information technology requirements

have yielded a strong demand for faster logic circuits and higher-density memory chips. This demand has led to the introduction of deep-ultraviolet (DUV) laser-based lithographic tools for

semiconductor manufacturing. These tools, which

employ KrF (248 nm) and ArF (193 nm) excimer lasers, have led to an increased demand for accurate

laser measurements at the DUV laser wavelengths.

As a result, NIST, with International SEMATECH

support, has developed primary standard calorimeters for measurements of both 193 nm and 248 nm

excimer laser power and energy.

TECHNICAL STRATEGY

Beginning with the first edition of the National Technology Roadmap for Semiconductors in 1992, the

semiconductor industry has made an organized,

concerted effort to reduce the feature sizes of integrated circuits. As a result, there has been a continual shift towards shorter exposure wavelengths

in the optical lithography process. Because of their

inherent characteristics, DUV lasers, specifically

KrF (248 nm) and ArF (193 nm), and more recently

F2

 (157 nm) excimer lasers, are the preferred sources

for high-resolution lithography at this time.

We have recently completed the construction of a

SiC absorbing cavity for the 157 nm excimer laser

calorimeter. The cavity is mounted on the thermal

reference flange. A temperature-stabilized reference

jacket (not shown) is mounted on the thermal reference

flange. This jacket maintains a constant temperature

reference. The injected energy is a function of the

temperature difference between the cavity and the

jacket.

system to perform absolute calibrations of 157 nm

excimer laser detectors. The primary customers for

this new calibration service are semiconductor

manufacturers and their suppliers, e.g., detector,

laser, and stepper manufacturers. This service, like

other NIST excimer laser calibration services, uses

an electrical-substitution calorimeter as a primary

standard to provide direct traceability to SI units

for laser power and energy measurements. Calorimeters, while having the advantage of providing

the highest level of accuracy for these measurements, have a slow response time. Therefore, because calorimeter-based calibrations are both timeconsuming and expensive, typically only a few calibration points are measured. However, most laser

detectors are typically used over a range larger than

that covered by a single calibration point. As a

result, additional measurement uncertainty will be

introduced if the detector response is not linear

and the nonlinearity is not quantified. Range discontinuity, e.g., change in response due to a nonlinear change in detector amplification, can also

introduce additional measurement uncertainty.

Thermal Reference

Heater

Cavity

Technical Contact:

Christopher Cromer

Staff-Years (FY2003):

5.0 professionals
Optoelectronics Division 5

Measurements of detector nonlinearity and range

discontinuity will give complete information of the

detector’s response over the entire measurement

range, with the added benefit that the measurement technique is much faster, and therefore cost

is much less compared to adding more calibration

points.

DELIVERABLE: By 2003, develop the capability to

perform measurements of detector nonlinearity at 248

and 157 nm (currently available at 193 nm).

In addition to existing DUV laser measurement services, there is increasing demand for measurements

of laser dose (energy density), where the detector

samples a fraction of the total laser beam. Accurate

measurements of laser dose are important because

small-area detectors are widely used to monitor laser-pulse energy density at the wafer plane of a

lithographic tool. Accurate measurements of laser

dose are especially crucial to the development of

new mask resist materials, since lower dose requirements lead to greater wafer throughput and also

extend the lifetime of an exposure tool’s optical

components as well.

Schematic diagram of the 157 nm excimer laser

energy/power meter calibration system. The system

consists of three nitrogen-purged stainless steel

enclosures that minimize cross-contamination between

the sub-systems. During a calibration, the customer’s

meter is substituted for either of the two standard

calorimeters, labeled “C” in the figure.

Excimer lasers are seeing increased use in the

micromachining of small structures, such as inkjet

nozzles and optical waveguides. Laser-beam characterization measurements are critical in some of

these processes since excimer laser beams are

astigmatic.

DELIVERABLE: By 2005, extend the wavelength

range of the dose meter service beyond our current

193 nm service to include the capability to perform

measurements with 248 and 157 nm excimer lasers.

Recently there has been increasing demand to extend the wavelength range of laser target ranging

and designation systems to the eye-safe laser regime. These laser systems provide positional information, such as distance and incident angle, for

use in locating targets. There is a need to extend

existing pulsed Nd:YAG laser power and energy

calibration services to include measurements at

1.55 μm and to reduce the overall uncertainty associated with these measurements.

DELIVERABLE: By 2004, develop capabilities for

measurements of high pulse energy at 1.55 μm.

Design, build, and characterize an improved calibration

service for measurements of pulsed Nd:YAG laser

power and energy.

Homogenized 193 nm excimer beam profile used for

dose calibrations, measured with a pyroelectric array

camera. The beam uniformity of the laser beam is

1.3 % (determined using ISO 13694 procedures).

ACCOMPLISHMENTS

# Designed, constructed, and tested a system

for characterizing detector nonlinearities at 193 nm.

This versatile system can be used to characterize a

wide range of UV detectors and has generated interest among detector manufacturers and International SEMATECH. This service may be an inexpensive alternative to customers who are more

concerned with the relative rather than the absolute response of their detectors. The primary reason for its lower cost is the reduced turnaround

time; a linearity measurement takes approximately

one-third the time of a full calibration.

# Characterized the nonlinearity of several commercial 193 nm detectors. Evaluated the performance

of several commercial detectors using the nonlinearity system.

# Completed construction of two 157 nm calorimeters. We have also completed a series of electrical

calibration measurements on both calorimeters, in
air as well as nitrogen-purged environment. From

these electrical calibrations, we deduce that the sensitivity of the 157 nm calorimeter is improved by

factor of five over that for the NIST 193 nm calorimeters. We also performed an intercomparison of the

157 nm calorimeter and with the NIST 248 nm calorimeters. The optical performance of the working

calorimeter, as demonstrated by this intercomparison,

exceeds initial design specifications.

CALIBRATIONS

The Pulsed-Laser Radiometry Project provides

pulsed-laser calibration services for laser power and

energy using excimer and pulsed-Nd:YAG lasers.

See Appendix D for a complete list of available

wavelengths and laser power/energy ranges.

STANDARDS COMMITTEE

PARTICIPATION

International Standards Organization: Marla L.

Dowell is a member of working group TC 172/SC 9/

WC 1, which deals with terminology and test methods for lasers.

American National Standards Institute: John H.

Lehman is a member of committee Z136, subcommittees SSC-01 and SSC-04, which deal with safe

use and measurement of lasers.

U.S. National Committee/International Electrotechnical Commission: John H. Lehman is a member of

technical committee TC76, working groups 1 and 3,

which deal with laser radiation measurement and

safety.

RECENT PUBLICATIONS

Dowell, M.L.; Jones, R.D.; Laabs, H.; Cromer, C.L.; Morton,

R., “New Developments in Excimer Laser Metrology at

157 nm,” Proc., SPIE Microlithography Conference, March

3-8, 2002, Santa Clara, CA, 63-69 (2002).

Dowell, M.L., “Progress Report: 157 nm Excimer Laser

Calorimeter Development,” SEMATECH Tech. Report: 1-

13 (Jul 15, 2002).

Chen, D.H.; Dowell, M.L.; Cromer, C.L.; Zhang, Z.M.,

“Thermal Response and Inequivalence of Pulsed Ultraviolet-Laser Calorimeters,” J. Thermophysics and Heat Transfer 16(1): 36-42 (Jan 2002).

Laabs, H.; Jones, R.D.; Cromer, C.L.; Dowell, M.L.;

Liberman, V., “Damage Testing of Partial Reflectors at

157 and 193 nm,” Proc. Optical Materials for High Power

Lasers Symp., Oct 1-3, 2001, Boulder, CO (2001).

Dowell, M.L.; Cromer, C.L.; Jones, R.D.; Keenan, D.A.;

Scott, T.R., “New Developments in Deep Ultraviolet Laser Metrology for Photolithography,” AIP Conf. Proc,

2001, Vol. 550, 361-363 (2001).

6 Electronics and Electrical Engineering Laboratory

Dowell, M.L., “Pulsed-laser Metrology at NIST,” Optics

and Photonics News 28 (February 2001).

Dowell, M.L., “The Power of Light: Choosing the Right

Detector is Key to Accurate Beam Power Measurements,”

OE Magazine, 56 (January 2001).

Dowell, M.L.; Cromer, C.L.; Jones, R.D.; Keenan, D.A.;

Scott, T., “New Developments in Deep Ultraviolet Laser

Metrology for Photolithography,” Characterization and

Metrology for ULSI Technology: 2000, D. Seiler, A. Diebold,

T. Shaffner, R. McDonald, W. Bullis, P. Smith, and E.

Secula, Eds., AIP, New York, pp. 391-394 (2001).
Optoelectronics Division 7

HIGH-SPEED MEASUREMENTS

PROJECT GOALS

Provide advanced metrology, standards and measurement services relating to temporal properties

of optical sources and detectors used in association with optoelectronic systems.

The electro-optic measurement system, shown here

being operated by Tracy Clement, measures an

electrical pulse on a LiTaO3

 wafer. De-embedding

techniques are then used to determine the voltage

generated by the photodiode being tested at its coaxial

output connector. © Geoffrey Wheeler

CUSTOMER NEEDS

High-bandwidth measurements are needed to support systems that take advantage of the potential

bandwidth of optical fiber. Systems presently being installed operate at 5 to 10 gigabits per second

using pure time-division multiplexing (TDM). Research is being done on the next generation of TDM

systems at 40 gigabits per second and higher in

laboratories around the world. Methods are needed

to accurately characterize the scalar and vector frequency response of high-speed sources, detectors,

and instrumentation to three to five times the system modulation rate. Burst-mode operation in asynchronous transfer mode networks requires additional characterization at very low frequencies.

Increasingly tight tolerances in both digital and

analog systems require frequency-response measurements with low uncertainty.

Measurements of source and detector noise are

required to predict low bit-error rates in computer

interconnects, and high carrier-to-noise ratios in

analog systems, and to support measurements of

the noise figure of optical amplifiers. The intensive

use of laser target designators and range finders

by the armed forces requires traceable calibration

standards for low-level pulse peak power and energy at 1064 nm and 1550 nm.

TECHNICAL STRATEGY

NIST has developed highly accurate heterodyne

techniques at 850 nm, 1319 nm, and 1550 nm for

measuring frequency response of detectors. A calibration service has been established for frequencyresponse transfer standards operating at 1319 nm,

consisting of a photodiode combined with a microwave power sensor. This system is capable of measuring this type of standard from 300 kHz to 110

GHz or more. We have similar capabilities at 850 nm

and 1550 nm, along with a service for calibrating

the frequency-response magnitude of bare photodiodes to at least 50 GHz. Calibration of bare photodiodes is more complicated because it requires

calibrated microwave power and scattering-parameter measurements.

Optoelectronic phase response, when combined

with the magnitude response, is called the vector

response. The vector frequency response of a

photoreceiver is the Fourier transform of its impulse response. Vector response is required for

design of high-speed optoelectronic systems, but

at present there are no accepted standard methods

for this measurement.

Researchers in the High-Speed Measurements

Project have demonstrated time-domain techniques

for measuring optoelectronic vector response with

verifiable accuracy up to 110 GHz using electrooptic sampling. By developing these measurements

our project is pioneering a new paradigm for timedomain measurements with frequency-domain calibrations.

DELIVERABLE: We intend to have a Calibration

Service for frequency response phase that uses

these new calibration strategies available in 2003.

By 2005 we will develop methods for extending

frequency response calibrations beyond 110 GHz.

Optical communications analyzers or reference receivers used for measuring digital eye-patterns on

optical signals have many similarities to electrical

oscilloscopes, but also have advantages of their

own. In particular, they can be calibrated over a

very high bandwidth because they do not require

band-limited microwave calibrations. Use of this

Technical Contact:

Paul D. Hale

Staff-Years (FY2003):

4.0 professionals

0.5 technician

1.0 contractor
calibration on typical measurements, however, possesses some unique problems. For example, we

must develop methods for removing time-base distortions and deconvolving the oscilloscope response. In collaboration with Divisions in EEEL

and ITL, we are currently applying our expertise in

receiver measurements to these problems.

DELIVERABLE: During 2003 NIST will work with the

IEC to document procedures developed at NIST for

calibrating the frequency response of optical

waveform measurement equipment. 

DELIVERABLE: We will develop methods that improve

the accuracy of eye-diagram and other time-domain

measurements by calibrating and removing instrument

errors in optical oscilloscopes in 2004.

NIST is developing optical-noise measurement systems for calibrating laser relative-intensity noise

(RIN) and optical-amplifier noise-figure measurements. We have documented a calibration artifact

for RIN and are currently investigating ways of

applying this artifact to noise-figure measurements.

DELIVERABLE: In 2003 we will document a method

for applying RIN standards to calibrating optical

amplifier noise figure measurements.

ACCOMPLISHMENTS

# Developed an electro-optic sampling system

to sample high-speed electrical waveforms on a

coplanar waveguide with ultrashort laser pulses

via the electro-optic effect. Standard microwave

techniques are used to calibrate the response of a

photoreceiver at its 1 mm electrical port, which is

physically removed from the sampling plane. The

frequency range of the calibration is limited only

by the 1 mm coaxial connectors. The characterized

photoreceiver has a bandwidth of about 80 GHz;

the signal-to-noise ratio of the measurement is

greater than 150:1 at 110 GHz.

# Preliminary measurements of a commercially

available photodiode demonstrated an (uncorrected) impulse response FWHM of 5.4 ps, a response spectrum that has rolled off by only 10 to

13 dB at 110 GHz, and a phase response flat to

within ± 10 degrees up to 110 GHz. The photodiode also displayed response linear in power with

outputs as high as 0.1 V into 50 Ohms, making it

suitable for comparison with heterodyne measurements.

Electro-optic sampling is capable of determining the

vector frequency response of a photodiode, that is, it

can determine both the magnitude and phase response

of the photodiode.

# Accurately characterized the modulation response magnitude and phase of a commercially

available photoreceiver to 110 GHz, nearly three

times the bit rate of 40 Gb/s optoelectronic systems. High-speed photo-receivers are commonly

used in fiber optic communications systems and

test equipment. Measurement of the modulation

response of the photoreceiver over a frequency

range much larger than its bandwidth is necessary

for accurately modeling its response in the time

domain, providing critical information for digital

communications systems.

STANDARDS COMMITTEE

PARTICIPATION

Telecommunication Industry Association: Gregory

Obarski is a member of subcommittee FO-4.5, which

deals with optically amplified devices, sub-systems,

and systems. Gregory Obarski and Paul Hale are

members of subcommittee FO-4.9, which deals with

fiber optic test and measurement instrumentation

and related calibration issues.

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8 Electronics and Electrical Engineering Laboratory
International Electrotechnical Commission: Paul

Hale is a member of technical committee TC86, working group 4, which deals with Fiber Optic Test

Equipment Calibration. Gregory Obarski is a member of subcommittee 86C, working group 3, which

deals with Optical Amplifiers.

MEASUREMENT SERVICES

The Optoelectronics Division provides measurement services relating the temporal properties of

optical sources and detectors used with optoelectronic systems including: optical receiver frequency

response (scalar or vector), impulse response, lowlevel pulse power and energy, and relative intensity noise. For more information see Appendix D or

contact Paul Hale at (303) 497-5367.

RECENT PUBLICATIONS

Clement, T.S.; Hale, P.D.; Williams, P.A., “Tutorial: Fiber

and Component Metrology for High-Speed Communication,” Proc., Optical Fiber Communication Conf., Mar 17-

22, 2002, Anaheim, CA, WZ1 (March 2002).

Wang, C.W.; Hale, P.D.; Coakley, K.J.; Clement, T.S., “Uncertainty of Oscilloscope Timebase Distortion Estimate,”

IEEE Trans. Instrum. Meas., 51, 53-58 (Feb 2002).

Clement, T.S.; Diddams, S.A.; Jones, D.J., “Lasers, Ultrafast

Pulse Technology,” Encycl. Phys. Sci. Tech. Third Edition, Vol. 8, 499-510 (Jan 2001).

Obarski, G.E., “NIST Program on Relative Intensity Noise

Standards for Optical Fiber Sources Near 1550 nm,” in

Proc., 16th Intl. Conf. on Noise in Physical Systems and

1/f Fluctuations, Oct 22-25, 2001, pp. 319-332.

Gokkavas, M.; Dosunmu, O.; Unlu, M.S.; Ulu, G.; Mirin,

R.P.; Christensen, D.H.; Ozbay, E., “High-Speed High-Efficiency Large-Area Resonant Cavity Enhanced p-i-n Photodiodes for Multimode Fiber Communications,” IEEE

Phot. Tech. Lett. 13 (Dec 2001).

Hale, P.D.; Clement, T.S.; Williams, D.F.; Balta, E.; Taneja,

N.D., “Measuring the Frequency Response of Gigabit Chip

Photodiodes,” IEEE J. Lightwave Technol. 19: 1333-1339

(Sept 2001).

Obarski, G.E.; Splett, J.D. “Transfer Standard for the Spectral Density of Relative Intensity Noise of Optical Fiber

Sources Near 1550 nm,” J. Opt. Soc. Am. B 18: 750-761

(Jun 2001).

Williams, D.F.; Hale, P.D.; Clement, T.S.; Morgan, J.M.,

“Calibrating Electro-Optic Sampling Systems,” Proc., Intl.

Microwave Symposium, May 20-25, 2001, Phoenix, AZ,

1527-1530 (May 2001).

Hale, P.D.; Clement, T.S.; Williams, D.F., “Frequency Response Metrology for High-Speed Optical Receivers,” Tech.

Dig., Optical Fiber Communication Conf. (OFC’01), Mar

17-22, 2001, Anaheim, CA, WQ1-1-3 (Mar 2001).

Coakley, K.J.; Hale, P.D., “Alignment of Noisy Signals,”

IEEE Trans. Instrum. Meas. 50: 141-149 (Feb 2001).

Optoelectronics Division 9
10 Electronics and Electrical Engineering Laboratory

INTERFEROMETRY AND POLARIMETRY

PROJECT GOALS

This project uses interferometric and polarimetric

techniques to provide calibration measurements,

standards, and expertise in support of the optoelectronics industry. Our current program primarily supports the optical fiber communications industry, but also has applications to optical fiber

sensors.

Graphical technique demonstrating the effects of

various amounts of polarization-dependent loss on the

transmitted polarization state.

CUSTOMER NEEDS

The telecommunication industry requires characterization of its optical-fiber-based communication

systems and components with improved temporal

and spectral resolution. Well-characterized measurements and artifact standards are needed to

ensure accuracy of measurements. This applies to

areas such as polarization- and wavelengthdependent propagation delay, polarizationdependent loss and polarization-dependent

spectral transmission.

Much of the metrology in telecommunications relates to well known properties. However, difficulties arise due to the high level at which these quantities must be resolved to enable current and future

systems with high data rate and high spectral efficiency. Increasing the overall data rate tends to

reduce a system’s tolerance to such parameters as

chromatic dispersion, relative group delay,

polarization-mode dispersion, polarizationdependent loss, and polarization-dependent spectral transmission. We are developing new measurement techniques for these parameters and are

working to increase the spectral and temporal resolution of existing methods.

Technical Contact:

Paul A. Williams

Staff-Years (FY2003):

5.75 professionals

0.4 technicians

1.0 student

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Chromatic dispersion in optical fiber arises from

the variation of the light’s propagation velocity as

a function of wavelength (it is the derivative of the

relative group delay (RGD) versus wavelength).

This variation in propagation velocity results in

broadening of the optical pulses used in communication systems. Broadened pulses interfere with

each other and are difficult to distinguish, causing

communication errors. System chromatic dispersion

must be dealt with by managing its spectral profile

through dispersion-tailored fibers, choice of zerodispersion wavelength, and dispersioncompensating fibers. This requires accurate measurement of the wavelength dependence of chromatic dispersion. Similarly, wavelength-dependent

relative group delay in components degrades system performance. Often, RGD must be measured in

components that have sub-nanometer optical

bandpass regions (requiring <100 pm spectral resolution). At the same time, high data rates require

that RGD be measured with sub-picosecond temporal resolution. These two requirements are in

opposition—fundamentally, spectral and temporal

resolution are inversely related. A challenge is to

optimize the mutual resolution of these quantities.

This same dilemma is experienced in polarization

mode dispersion (PMD) metrology where propagation velocity depends on the polarization state

of the light. Communication systems require PMD

measurement with a few tens of femtoseconds of

resolution with a spectral resolution of a few tens

of picometers. In addition, PMD is a statistical

quantity, making stability of a reference artifact difficult.

Non-temporal polarization effects such as polarization-dependent loss (PDL) and polarizationdependent wavelength shift (PDW) of optical filters cause variations in intensity as a function of

polarization and wavelength. These effects generally weaken the transmission signal in a way that

can vary with time and system conditions — again

causing communication errors. PDW of a channel

filter can also cause crosstalk between wavelength

channels.

PDL and PDW present unique metrology needs;

PDL can arise in almost every component in an

optical system, making assessment of PDL measurement accuracy difficult. PDW of filter spectra

is tedious to measure and rapid measurement techniques are needed. The interaction of PMD and

PDL in a communication system can lead to com-
Optoelectronics Division 11

plex and unexpected signal degradation. This interaction needs to be characterized so that system

behavior can be predicted from known fiber and

component properties.

Fiber Bragg gratings (FBGs) have applications in

both optical fiber communications and optical fiber

sensor systems. Strain sensor networks consisting of many FBGs can provide information on the

integrity of structures such as buildings and

bridges. To reliably extract strain information, sensor stability and demodulator accuracy must be

assessed.

TECHNICAL STRATEGY

In general, we approach these needs through the

development of high-resolution measurement techniques and rigorous uncertainty analysis. Transfer

of this metrology comes through calibration artifact distribution, measurement comparison, and

special tests.

Chromatic Dispersion: Our chromatic dispersion

measurement capabilities enable us to perform Special Test calibrations of customer fibers. We are

working to improve the accuracy of these measurements.

DELIVERABLE: In 2003, study and publish characterization of amplified spontaneous emission effects on

measured chromatic dispersion.

Relative Group Delay (RGD): Our RGD measurement work is directed toward assessing the achievable temporal resolution for our 200 MHz RF phase

shift system, and establishing fundamental standards with theoretically predictable RGD profiles.

DELIVERABLE: Complete uncertainty characterization

of RF phase shift and low-coherence interferometry

RGD systems in 2003.

Polarization-Mode Dispersion (PMD): Our work

is directed at absolute calibration of RF phase shift

measurements of PMD in narrow (5 GHz) bandwidths and characterization of measurement pitfalls in measurement of second-order PMD. We will

also consider possible artifacts for stable emulation of second-order PMD.

DELIVERABLES: In 2003, complete evaluation and

documentation of Modulation Phase Shift (MPS)

method for narrowband PMD measurement. In 2003

and 2004, assess calibration needs for second-order

PMD.

Polarization-Dependent Loss (PDL): We are validating a new PDL measurement technique based

on 6 launched polarization states (rather than 4).

This is a promising method for reducing the PDL

measurement uncertainty due to system birefringence. We are also studying the interaction between PDL and PMD and its effect on measurements.

DELIVERABLE: In 2003, complete evaluation of the 6-

state PDL measurement technique and its experimental

comparisons with the 4-state technique.

Component Spectral Transmission/Reflection: As

we co-develop techniques for spectral reflection

characterization of fiber Bragg gratings, we will be

comparing the results for different techniques and

evaluating the accuracy of each method.

DELIVERABLES: In 2003, complete uncertainty

characterization of tunable laser and low-coherence

interferometric spectral characterization techniques.

Fiber Bragg grating in temperature-controlled

chamber for spectral reflection measurement.

Optical Fiber Bragg Grating Characterization:

We are beginning a project to use low-coherence

interferometry for real-time monitoring of longitudinal index variations in fiber Bragg gratings during the grating writing process.

DELIVERABLES: In 2003, develop low-coherence

interferometric system capable of measuring spectral

characteristics of a remotely located fiber Bragg

grating; in 2003 and 2004, use this system to conduct

studies during fiber Bragg grating inscription.

ACCOMPLISHMENTS

# New SRM for Polarization-Mode Dispersion

(PMD) — We have completed the development

and delivered certified units of a new Standard Reference Material for non-mode-coupled polarization

mode dispersion (SRM 2538). This is the second

SRM for PMD. The first, SRM 2518, emulates the

differential group delay in a long length of optical

fiber. The new artifact, SRM 2538, is a fiber-pigtailed quartz plate, designed to emulate the PMD

typically found in telecommunications components.
This new SRM is certified for mean Differential

Group Delay (DGD) over a wavelength range of

approximately 1275–1625 nm for measurements by

all PMD techniques.

# New Calibration Reference for PolarizationDependent Loss — The first NIST calibration

reference for Polarization Dependent Loss is now

available to the public as a part of the Measurement Assurance Program (MAP). The MAP artifact consists of a short section of polarizing fiber

spliced to a single-mode input fiber and a stepindex multimode output, and its PDL is certified

over the wavelength range of 1535–1560 nm. The

artifact is implemented as a MAP (rather than an

SRM) to mitigate the degradation to uncertainty

that is caused by exposure of the artifact to unpredictable temperatures. The MAP implementation

includes a recording thermometer to indicate the

temperature exposure of the device during the customer measurement process.

# Relative Group Delay Measurements Verified

— Along with a commercial collaborator, we have

independently measured the relative group delay

of a line in the same hydrogen cyanide gas absorption cell using low- coherence interferometry, RF

phase shift, and swept-wavelength optical interferometry, respectively. The agreement among all

measurements and our theoretical prediction is

within 0.3 ps when measured with a 6 pm wavelength resolution. This serves as a good test of the

accuracy of these measurement techniques and may

lead to a relative group delay transfer standard

based on hydrogen cyanide.

# Low-Coherence Measurement System Modeled — We have modeled and experimentally verified the effect of signal-to-noise ratio on lowcoherence interferometric measurements of relative

group delay (RGD) in optical components. The

model describes the often misunderstood tradeoff

between temporal and spectral resolution. We also

improved the wavelength resolution of the lowcoherence interferometer by installing a Nd:YAG

reference laser that provides a measured wavelength stability of 1 pm.

# Improved PDL Measurement Technique Developed — We have demonstrated an improved

“6-states” technique for measuring polarization

dependent loss (PDL), enabling the measurement

of PDL in the presence of birefringence. This new

method also reduces the measurement uncertainty

by a factor of 2 over the current “4-states” method.

# PMD Emulator Developed — We have assembled and tested a polarization-mode dispersion

(PMD) emulator capable of generating arbitrary

values of non-mode-coupled PMD with an uncertainty of 1.5 % (limited by the measurement system).

# Polarization-Dependent Wavelength Shift

Measurement Technique — In collaboration with

the Spectral and Nonlinear Properties Project, we

have developed and demonstrated a fast and accurate technique to measure the polarizationdependent shift of the center wavelength of fiber

Bragg gratings.

STANDARD REFERENCE MATERIALS

(SRM) AND MEASUREMENT

ASSURANCE PROGRAM (MAP)

(See Appendix D)

http://www.boulder.nist.gov/div815/NEWsrms.htm

SRM 2518, Polarization-Mode Dispersion (ModeCoupled); available

SRM 2538, Polarization-Mode Dispersion (NonMode-Coupled); available

SRM 2524, Optical Fiber Chromatic Dispersion Standard, no longer available – Contact Interferometry

and Polarimetry Project for alternative options.

SRM 2525, Linear Retardance Standard, no longer

available as an SRM – Contact Interferometry and

Polarimetry Project for availability of artifact under

the MAP program.

Polarization Dependent Loss MAP, Simulates wavelength-dependent PDL in optical components and

fiber. Certified for optical sources between 1535–

1560 nm, with singlemode input and multimode

output fiber. Available for loan.

STANDARDS COMMITTEE

PARTICIPATION

Telecommunication Industry Association: Rex M.

Craig, Timothy J. Drapela, and Paul A. Williams are

members of committee FO-4, which deals with standards issues relating to optical fibers, optical fiber

components, and optical fiber systems.

International Electrotechnical Commission: Timothy J. Drapela is a member of technical committee

TC86, which deals with active and passive fiber

optic metrology.

12 Electronics and Electrical Engineering Laboratory
RECENT PUBLICATIONS

http://www.boulder.nist.gov/div815/IPP.htm

Dennis, T.; Williams, P.A., “Relative Group Delay Measurements with 0.3 ps Resolution: Toward 40 Gbit/s Component Metrology,” Proc., Optical Fiber Communication

Conf. (OFC’02), paper WK3, pp. 254-256 (March 2002).

Dyer, S.D.; Espejo, R.J.; Williams, P.A., “High-Resolution

Group Delay Measurements of Hydrogen Cyanide Gas Cell

Using Low-Coherence Interferometry,” Tech. Digest, Symposium on Optical Fiber Measurements (SOFM 2002),

NIST Special Publication 988, pp. 45-48 (September 2002).

Clement, T.S.; Hale, P.D.; Williams, P.A., “Fiber and Component Metrology for High-Speed Communications,”

Proc., Optical Fiber Communication Conf. (OFC’02),

Tutorial WZ1 (March 2002).

Williams, P.A., “PMD Measurement Techniques – Avoiding Measurement Pitfalls,” Venice Summer School on Polarization Mode Dispersion, Venice, Italy, June 24-26, 2002.

Williams, P.A.; Kofler, J.D., “Measurement and Mitigation of Multiple Reflection Effects on a Differential Group

Delay Spectrum of Optical Components,” Tech. Digest,

Symposium on Optical Fiber Measurements (SOFM 2002),

NIST Special Publication 988, pp. 173-176, (September

2002).

Williams, P.A.; Etzel, S.M.; Kofler, J.D.; Wang, C.-M,

“Standard Reference Material 2538 for Polarization-Mode

Dispersion (Non-Mode-Coupled),” NIST Special Publication 260-145, (2002) in press.

Craig, R.M., “Visualizing the Limitations of Four-State

Measurement of PDL and Results of a Six-State Alternative,” Tech. Digest, Symposium on Optical Fiber Measurements (SOFM 2002), NIST Special Publication 988, pp.

121-124 (September 2002).

Swann, W.C.; Dyer, S.D.; Craig, R.M., “Four-state measurement method for polarization dependent wavelength

shift,” in Tech. Digest, Symposium on Optical Fiber Measurements (SOFM 2002), NIST Special Publication 988,

pp. 125-128 (2002).

Rose, A.H.; Day, G.W., “Optical Fiber Current and Voltage

Sensors for the Electric Power Industry,” in the Handbook

of Fiber Optic Sensing Technology, Chapter 27, Higuera,

J.M.L., ed., New York: Wiley & Sons, 569-618 (2002).

Rochford, K.B., “Polarization and Polarimetry,” in the

Encycl. of Phys. Sci. Tech., Third Edition, Vol. 12, 521-

538 (January 2002).

Optoelectronics Division 13
14 Electronics and Electrical Engineering Laboratory

SPECTRAL AND NONLINEAR PROPERTIES

GOALS

This project develops techniques for the measurement of spectral and nonlinear properties of optical

fiber and components and develops wavelength

calibration transfer standards to help industry calibrate equipment.

Kristan Corwin studying supercontinuum generation in

microstructure fiber. © Geoffrey Wheeler

Technical Contact:

Sarah L. Gilbert

Staff-Years (FY 2003):

4.25 professionals

0.4 technicians

2 post-doctorals

CUSTOMER NEEDS

This project concentrates on the needs of the optical fiber communications industry; we focus primarily on metrology for the characterization of optical fiber and components used in communication

systems. High-bandwidth optical fiber communication systems require accurate measurement of

spectral, polarization, dispersion, and nonlinear

properties of optical fiber and components. This

project concentrates on the spectral and nonlinear

properties, and the Interferometry and Polarimetry

Project concentrates on polarization and dispersion properties.

In an optical fiber communication system, wavelength division multiplexing (WDM) increases bandwidth by using many wavelength channels. Most

systems employ 50 or 100 GHz channel spacing (0.4

or 0.8 nm, respectively) in the 1540 to 1560 nm region, but narrower channel spacing may be used in

the future. It appears likely that systems will be

implemented in other wavelength regions as well,

particularly in the 1565–1625 nm WDM L-band.

WDM systems use a variety of optical components,

and new components are under development for

next-generation systems. For effective system operation, the wavelength dependence of WDM optical components must be characterized and controlled. We are developing spectral characterization techniques and wavelength calibration transfer

standards to help industry evaluate optical components and calibrate wavelength measuring instruments.

Future communication systems will increase the

total bandwidth by increasing both the number of

WDM channels and the bit rate per channel. Both

increases will lead to higher optical power in the

fiber, and will in turn increase the importance of

nonlinear effects. These nonlinear effects, such as

cross-phase modulation, self-phase modulation,

and 4-wave mixing can cause pulse broadening,

pulse distortion, and crosstalk, and ultimately limit

system performance. On the other hand, beneficial

nonlinear effects, such as Raman amplification, can

be used to improve overall system performance

through lower noise and the ability to amplify over

the full WDM region. Because of the increasing

importance of nonlinear effects, we are developing

measurement techniques to characterize these effects in optical fiber.

TECHNICAL STRATEGY

Supporting WDM fiber and component metrology

needs requires development and evaluation of new

measurement techniques, dissemination of this

knowledge, and, when appropriate, development

of Standard Reference Materials (SRM) or other

calibration aids to help industry calibrate instrumentation. The project currently focuses on two

areas: wavelength calibration standards for WDM

and nonlinear properties of optical fiber.

Wavelength calibration transfer standards: Wavelength standards are needed to calibrate instruments that measure the wavelengths of sources

and characterize the wavelength dependence of

WDM components. Fundamental references based

on atomic and molecular absorption or emission

lines provide the highest accuracy, but they are

not available in all wavelength regions. The project

currently produces four wavelength reference Standard Reference Materials (SRMs) based on fundamental molecular absorption lines: SRM 2514 (carbon monoxide 12C16O), SRM 2515 (carbon monoxide 13C16O), SRM 2517a (acetylene, high resolution) and

SRM 2519 (hydrogen cyanide). Together these

SRMs can be used to calibrate the wavelength scale

of instruments between 1510 and 1630 nm.
Optoelectronics Division 15

WDM may expand into other wavelength regions,

such as the 1300 to 1500 nm region. We have developed a hybrid multiple-wavelength reference

that incorporates the wavelength flexibility of artifact references and the stability of fundamental

molecular absorption references. Customized multiple wavelength reflectors can be generated by

writing multiple superimposed fiber Bragg gratings

(FBG) into optical fiber. Each grating is a reflector

for a specific wavelength of light; the wavelengths

are selected during the grating fabrication process.

Strain and temperature changes can cause the center wavelengths of these reflectors to change. On

the other hand, atomic and molecular absorption

lines are very stable under changing environmental conditions. If one of the FBG reflectors is located near an atomic or molecular absorption line,

it can be actively stabilized to that line. This stability is then transferred to the other gratings, because they are superimposed at the same location

in the fiber. We have demonstrated a hybrid reference based on this principle that provides multiple

calibration references in the 1300 and 1550 nm regions, which are stable to better than 1 pm.

DELIVERABLE: Transfer hybrid wavelength reference

technology to industry in 2003 and 2004.

DELIVERABLE: Develop high-resolution version of

SRM 2519 (hydrogen cyanide) by 2004.

Measured spectra of two sampled fiber Bragg gratings

interleaved on a single fiber for use in a hybrid

wavelength calibration reference.

High-accuracy wavelength standards: To calibrate

its equipment, NIST needs higher accuracy internal wavelength references. We have developed

references for this purpose at 1560 nm and 1314 nm

with uncertainties of a few megahertz. In collaboration with the NIST Time and Frequency Division,

we have begun to develop an accurate frequency

comb in the telecommunication wavelength region.

To generate an optical frequency comb in the near

infrared, pulses from a Cr:Forsterite femtosecond

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50

% Reflectance

Wavelength (nm)

ber, which broadens the laser spectrum to a

supercontinuum with a width of > 1000 nm. Since

the laser is pulsed, this broad supercontinuum will

actually be composed of discrete frequency lines –

a frequency comb – spaced by the laser repetition

rate. This optical frequency comb can be stabilized

and used to measure references throughout the

1280 to 1630 nm region.

We have developed two Cr:Forsterite femtosecond

lasers for optical frequency comb generation, one

with a 100 MHz repetition rate and one with a 400

MHz–1 GHz repetition rate. The output spectrum

of the 400 MHz laser is shown below. This spectrum can support a pulse width of ~30 fs; the average output power of the laser is 480 mW and it can

operate stably for many hours.

DELIVERABLES: Demonstrate accurate frequency

comb in the WDM telecommunications region and

establish a series of high-accuracy references for

NIST internal calibration in 2003 and 2004.

Output spectrum from the 400 MHz Cr:Forsterite

laser and the resulting supercontinuum spectrum

generated when this laser is transmitted through

6 meters of highly nonlinear fiber.

Nonlinear Properties: We are concentrating on

two areas: Raman amplification and supercontinuum generation in optical fiber. In Raman amplification, a strong pump beam amplifies a weaker

signal beam through stimulated Raman scattering.

The Raman gain depends strongly on the pumpsignal wavelength difference and weakly on the

absolute pump wavelength. There are well-known

techniques for measuring the strong dependence

on the pump-signal wavelength difference, but not

the weaker dependence on the absolute pump wavelength. In 2002, using the asymmetry of the Raman

gain curve, we developed a simple technique for

determining this weak, but potentially important,

pump-wavelength dependence.

Input Laser Spectrum

Supercontinuum

1200 1400 1600 1800 2000

Wavelength (nm)

10

5

0

-5

-10

-15

Power (dB)
DELIVERABLES: Fully document new technique for

measuring the pump-wavelength dependence of the

Raman gain; participate in round robin on Raman gain

measurements in 2003.

A striking example of the nonlinear effects in optical fiber is provided by supercontinuum generation in highly nonlinear fiber. Supercontinua can

be generated in the near infrared using a Cr:Forsterite laser, or in the visible using a Ti:Sapphire

laser. The supercontinua have a number of possible applications in telecommunications, including as a wavelength reference or as a WDM source

after spectral slicing. In addition, these supercontinua will find uses in optical coherence tomography and spectroscopy. For many applications, the

amplitude noise on the supercontinuum can be a

limiting factor. Unfortunately, the same nonlinear

processes that give rise to the supercontinuum also

amplify any input noise. In 2002, we conducted a

systematic study of this amplitude noise for a range

of input parameters and have identified both a lowfrequency noise component that arises from the

technical noise on the laser, and a broadband frequency noise component that arises from the initial shot noise on the input laser and spontaneous

Raman scattering.

DELIVERABLE: Conduct additional experimental and

theoretical studies of noise processes in frequency

comb and supercontinuum generation in microstructure fiber in 2003.

ACCOMPLISHMENTS

# WDM L-Band Wavelength Calibration Standard Reference Materials — Two wavelength calibration transfer standards for the new L-band of

WDM optical fiber communications have been developed. These standards, based on the absorption spectrum of carbon monoxide, are now available as SRMs 2514 and 2515. SRM 2514 can be

used to calibrate the wavelength scale of measurement equipment in the 1560 to 1595 nm region. The

unit is a single-mode optical-fiber-coupled absorption cell containing carbon monoxide 12C16O gas,

which has many absorption lines in this region.

SRM 2515 is nearly identical to SRM 2514, except

that it contains the 13C16O isotopic species of carbon monoxide. This isotopic species has numerous absorption lines at longer wavelengths, ranging from 1595 to 1630 nm. Forty-one line center

wavelengths of each SRM are certified with uncertainties ranging from 0.4 to 0.7 pm.

# NIST Traceable Reference Material (NTRM)

Program Established — In response to the large

demand for our wavelength calibration SRMs, we

have established an NTRM alternative: The NIST

Traceable Reference Material Program for Wavelength Reference Absorption Cells. An NTRM is

a commercially produced reference material with a

well-defined traceability linkage to existing NIST

standards. Although the NTRM gas absorption

cells are produced and distributed by commercial

vendors, the pressure and wavelength value assignments, and respective uncertainties, are made

by NIST.

# Polarization Dependent Wavelength Shift

(PDW) Measurement Technique Developed — In

collaboration with the Interferometry and Polarimetry Project, we have developed and demonstrated

a fast and accurate technique to measure the polarization-dependent wavelength shift of the center

wavelength of fiber Bragg gratings. This new technique uses only four polarization states to derive

the PDW. It is a rapid alternative compared to the

conventional measurement of the fiber Bragg grating spectrum for many (30 or more) different polarization states to approximate coverage of all polarization states.

# Hybrid Wavelength Calibration Reference Developed — We have completed our investigation

of interleaved, sampled fiber Bragg gratings (FBG)

for the 1300 and 1550 nm regions, which produce

multiple reflection peaks in each region. We have

evaluated the polarization-dependent wavelength

shift of sampled gratings and found that it is very

small (1-2 pm). We have also evaluated the stability of these gratings in the actively stabilized hybrid reference configuration. With one of the 1550

nm FBG peaks stabilized to a hydrogen cyanide

absorption line, we strained the fiber and measured

the center wavelength of a FBG peak in the 1300 nm

region. The active stabilization of the 1550 nm grating forced the 1300 nm peak to remain stable to

about 0.3 pm. If the gratings were not stabilized,

the 1300 nm peak would have shifted by about 200

pm under these strain conditions.

# Near-Infrared Frequency Comb — In collaboration with the NIST Time and Frequency Division,

a broad frequency comb (>1000 nm wide) in the

near infrared region was produced using a

Cr:Forsterite laser and nonlinear optical fiber. Once

stabilized, this comb will be used to measure highaccuracy wavelength references for the WDM region.

# Supercontinuum Noise Study — We have

completed an extensive study of the noise in a

supercontinuum produced by pulsed light in microstructure fiber. Amplitude noise has been mea16 Electronics and Electrical Engineering Laboratory
sured as a function of wavelength, pulse duration,

pulse chirp, and Fourier frequency, and collaboration with a university researcher has produced numerical simulations. The combination of these data

and simulations is the first definitive work on the

fundamental noise processes that occur in

supercontinuum generation using microstructure

fiber. This work clearly shows how to minimize the

noise, which can degrade the frequency comb produced in the fiber and limit its usefulness for accurate metrology.

# Measurement of Raman Gain — Measurements

of the pump-wavelength dependence of Raman

gain using two techniques have been completed.

The first technique involves measuring the integrated gain. The second, more elegant, technique

uses the asymmetry of the gain curve for the Stokes

and anti-Stokes regions. This new technique (developed at NIST) has the advantage that it is independent of the pump and signal powers and therefore has lower uncertainty. The dependence of

Raman gain on pump wavelength is important for

understanding the details of Raman amplifier performance, particularly gain tilt.

STANDARD REFERENCE MATERIALS

(SRM)

See Appendix E

http://www.boulder.nist.gov/div815/NEWsrms.htm

SRM 2513, Mode Field Diameter Standard for

Single-Mode Fiber; available.

SRM 2514, Wavelength Calibration Reference for

1560–1595 nm – Carbon Monoxide 12C16O; available.

SRM 2515, Wavelength Calibration Reference for

1595–1630 nm – Carbon Monoxide 13C16O; available.

SRM 2517a, High Resolution Wavelength Calibration Reference for 1510-1540 nm – Acetylene 12C2

H2;

available.

SRM 2519, Wavelength Calibration Reference for

1530–1560 nm – Hydrogen Cyanide H13C14N; available.

SRM 2520, Optical Fiber Diameter Standard; available.

Additional SRMs for optical fiber communications

produced by NIST: SRMs 2522 & 2523 for optical

fiber ferrule geometry and SRMs 2553-2555 for optical fiber coating diameter.

Optoelectronics Division 17

RECENT PUBLICATIONS

http://www.boulder.nist.gov/div815/SNPP.htm

Swann, W.C.; Gilbert, S.L., “Pressure-induced shift and

broadening of 1560–1630 nm carbon monoxide wavelength

calibration lines,” J. Opt. Soc. Am. B 19, pp. 2461-2467

(2002).

Gilbert, S.L; Swann, W.C., “Carbon Monoxide Absorption

References for 1560 nm to 1630 nm Wavelength Calibration – SRM 2514 (12C16O) and SRM 2515 (13C16O),” NIST

Special Publication 260-146 (2002).

Swann, W.C.; Dyer, S.D.; Craig, R.M., “Four-state measurement method for polarization dependent wavelength

shift,” in Tech. Digest, Symposium on Optical Fiber Measurements (SOFM 2002), NIST Special Publication 988,

pp. 125-128 (2002).

Dennis, T.; Curtis, E.A.; Oates, C.W.; Hollberg, L.; Gilbert,

S.L., “Wavelength References for 1300 nm Wavelength

Division Multiplexing,” J. Lightwave Technol. 20, pp 804-

810 (2002).

Gilbert, S.L.; Etzel, S.M.; Swann, W.C., “Wavelength Accuracy in WDM: Techniques and standards for component

characterization,” in Proc. Optical Fiber Communication

Conference (OFC 2002), (Optical Society of America,

Washington DC, 2002), paper ThC1, pp. 391-393.

Newbury, N.R., “Raman gain: pump-wavelength dependence in single-mode fiber,” Opt. Lett. 27: pp. 1232-1234

(2002).

Newbury, N.R., “Pump-wavelength Dependence of Raman

Gain,” OSA Trends in Optics & Photonics (TOPS), Vol.

77, Optical Amplifiers and Their Applications 2002, (Optical Society of America, Washington DC 2002) paper

OME9.

Newbury, N.R.; Corwin, K.L., “Comparison of simulated

and spontaneous scattering measurements of the full wavelength dependence of the Raman gain spectrum,” in Tech.

Digest, Symposium on Optical Fiber Measurements (SOFM

2002), NIST Special Publication 988, pp. 7-10 (2002).

Corwin, K.L.; Newbury, N.R.; Gilbert, S.L.; Weber, K.;

Diddams, S.A.; Hollberg, L.; Windeler, R.S., “Broadband

noise on supercontinuum generated in microstructure fiber,” in OSA Trends in Optics and Photonics (TOPS), Vol.

79, Nonlinear Optics, (Optical Society of America, Washington, DC, 2002), pp. 409-411.

Newbury, N.R.; Corwin, K.L.; Dudley, J.M.; Coen, S.;

Diddams, S.A.; Weber, K.; Windeler, R.S., “Measurements

and simulations of noise imposed on supercontinuum generated in microstructure fiber,” 15th Annual Meeting of

the IEEE Laser and Electro-Optics Society, Nov 10-14,

2002, Glasgow, Scotland.
18 Electronics and Electrical Engineering Laboratory

OPTICAL MATERIALS METROLOGY

PROJECT GOALS

Develop complementary metrology methods of

nonlinear optical analysis, near-field optical spectroscopy, X-ray diffraction imaging, and

cathodoluminescence for studies of optical, electronic, and structural features of bulk and thin-film

III-nitrides and nitride device structures. Accumulate a database of refractive index and birefringence

for AlGaN and InGaN alloy semiconductors. Develop prototype ultrafast and narrow-line cw solidstate waveguide lasers.

Ordinary refractive index of AlxGa1-xN measured by

prism coupling.

CUSTOMER NEEDS

Customer needs fall into two main categories: (1)

development of metrology suites for rapid non-destructive uniformity characterization of photonic

materials in terms of optical, electronic, and structural characteristics for bulk crystals and thin film;

and (2) specialized ultrafast and continuous-wave

solid-state waveguide lasers for applications in

analog-to-digital conversion, characterization of

high-speed optical detectors, and RF synthesis.

The success of our previous work in the nonlinear

optical characterization of LiNbO3

 has led in a very

natural way to extending this work into other important photonic materials such as the III-nitrides.

GaN and related materials have made enormous re400 500 600 700 800 900 1000 1100

wavelength (nm)

2.150

2.200

2.250

2.300

2.350

2.400

2.450

2.500

ordinary index no

Al mole fraction x (%)

 0.0 MOCVD (M)

 27.9 HVPE (H)

 36.3 H

 41.9 M

 50.7 M

 59.3 H

 61.8 M

 65.7 H

 66.6 M

 

Fig. 3(a)

400 500 600 700 800 900 1000 1100

wavelength (nm)

2.150

2.200

2.250

2.300

2.350

2.400

2.450

2.500

ordinary index no

Al mole fraction x (%)

 0.0 MOCVD (M)

 27.9 HVPE (H)

 36.3 H

 41.9 M

 50.7 M

 59.3 H

 61.8 M

 65.7 H

 66.6 M

 

Fig. 3(a)

400 500 600 700 800 900 1000 1100

wavelength (nm)

2.150

2.200

2.250

2.300

2.350

2.400

2.450

2.500

ordinary index no

Al mole fraction x (%)

 0.0 MOCVD (M)

 27.9 HVPE (H)

 36.3 H

 41.9 M

 50.7 M

 59.3 H

 61.8 M

 65.7 H

 66.6 M

 

Fig. 3(a)

400 500 600 700 800 900 1000 1100

wavelength (nm)

2.150

2.200

2.250

2.300

2.350

2.400

2.450

2.500

ordinary index no

Al mole fraction x (%)

 0.0 MOCVD (M)

 27.9 HVPE (H)

 36.3 H

 41.9 M

 50.7 M

 59.3 H

 61.8 M

 65.7 H

 66.6 M

 

Fig. 3(a)

cent economic impact with the realization of semiconductor lasers and LEDs emitting in the blue.

Other important applications of this material system include high-power, high-temperature transistors and solar-blind UV detectors. Problems with

bulk and thin film growth of these materials remain,

however, hindering the ability to meet the application demands. There persists a fundamental lack

of understanding of the role of defects on the electrical, optical, and structural properties of these

materials. These issues compel the development

of new correlated metrology methods, with resolution on the scale of 20 nm to 100 nm. Furthermore,

the lack of a database for the linear optical properties of the III-nitrides is hampering development of

engineering design tools for blue-emitting GaNbased laser diodes.

Compact, solid-state waveguide lasers and amplifiers are emerging as a technology with impact ranging from telecommunication to high-speed signal

processing to high-speed detector metrology. With

assistance from industrial and DARPA collaborators, NIST has been on the cutting edge of developing technology for these application areas. Customer needs range from the optical characterization

of laser glasses, to the testing of the impact of fabrication methods on laser performance, to the development of specialty lasers for detector frequency response measurements or all-optical,

analog-to-digital conversion applications.

TECHNICAL STRATEGY

Nonlinear optics (NLO), including secondharmonic generation (SHG) and two-photon luminescence (2PL) spectroscopy, offers rapid and versatile measurement capabilities that may be used

to examine bulk and thin film materials at various

stages of crystal growth and device processing.

Furthermore, NLO methods may be directly correlated to other conventional measurement methods.

Thus, material uniformity evaluated using NLO

methods may, in many cases, be directly related to

the material information derived from analytical

methods that are not conveniently adapted to the

manufacturing environment. For example, our strategy in applying nonlinear optical analysis methods to the study of bulk GaN single crystals has

relied on correlating the SHG results with X-ray

diffraction imaging performed at Brookhaven National Laboratory in collaboration with NIST Materials Science and Engineering Laboratory (MSEL).

SHG is extremely sensitive to such undesirable

Technical Contact:

Norman A. Sanford

Staff-Years (FY2003):

2.7 professionals

2.0 post-doctorals

λ
structural features as stacking faults, domain reversals, mixed cubic and hexagonal phases, and

subsurface polishing-induced damage. X-ray diffraction imaging reveals full-crystal images of stacking faults and domain reversals, but is less sensitive to the presence of mixed phases. Thus, a combination of SHG analysis and X-ray imaging methods results in a reduction in ambiguity compared

to the case where only one method is employed.

Depth-dependent artifacts are also problematic in

GaN. Polishing-induced structural damage is revealed with cathodoluminescence (CL) studies.

Further, SHG and CL analysis will examine the degree to which the damage can be removed using

chemically assisted ion-beam etching.

2PL spectroscopy offers a means by which the

uniformity of an active quantum well layer in a IIInitride laser or LED structure can be probed regardless of the thickness of the surrounding

layers. Standard direct above-bandgap photoluminescence (PL) spectroscopy is problematic since

the pump beam could be absorbed elsewhere in the

structure before exciting the regions of interest.

We will correlate 2PL measurements with CL results, obtained when the capping layer is thin

enough (∼20 nm) to allow CL examination of the

active region through the capping layer, with those

of a more realistic device structure where the active

layer is buried hundreds of nanometers within the

structure.

Analysis of thin-film GaN structures offers additional challenges due to the high density of structural defects and the impact of these defects on

optical, electronic, and transport properties of these

materials. Our strategy is to begin development of

collection-mode near-field optical methods and examine the group III-nitrides using SHG and photoluminescence (PL) spectroscopies on a resolution

scale of 20 to 100 nm.

DELIVERABLES: In 2003 and 2004, working closely

with collaborators in the NIST MSEL and Chemical

Science and Technology Laboratory (CSTL), we will

correlate near-field optical measurements and 2PL

studies with CL studies and other high-resolution

electron beam and X-ray metrologies. We will establish

the inclusion of time-resolved spectroscopy into our

suite of correlated measurements by 2004. In 2004

and 2005 we will apply nanoscale spatially resolved

spectroscopy to the study of low In-content material.

Establishing a database for linear optical properties of the AlGaN and InGaN compounds is also

important, as we are receiving requests from industry and universities for these data. We have compiled refractive-index and birefringence data for a

number of AlGaN samples ranging in composition

from pure GaN to pure AlN, using prism coupling

to waveguide modes. The wavelength span of the

measurements is currently from 442 nm to 1064 nm.

Extension of the measurements into the ultraviolet

region requires grating coupling and/or nonlinear

optical techniques. Calibration of composition of

epilayers using techniques such as EDS is critical.

Using x-ray diffraction, we are also measuring the

bowing of lattice constants as a function of composition .

DELIVERABLES: In 2003 we will add to the refractive

index database for AlGaN in the ultraviolet and deep

blue regions. In 2004-2005 we will establish methods

to measure the refractive index of layers in active GaN

devices.

We are developing cw and mode-locked waveguide

lasers using ion-exchange in rare-earth-doped

phosphate glasses. The optical, thermal, and

chemical properties of the glass are measured and

optimized in collaboration with a glass manufacturer. Unlike semiconductor laser sources, the solidstate sources benefit from a long upper-state, laser-transition lifetime (~10 ms) that allows low-noise

production of mode-locked pulses independent of

repetition rate and low-noise generation of narrowlinewidth light. Unlike fiber laser sources,

waveguide sources have sufficient rare-earth doping concentrations (~1020 cm-3) to provide sufficient gain and power in short (~2 cm) lengths. This

permits high repetition rates without the complications associated with harmonic mode locking. We

have demonstrated cw mode-locked operation using a semiconductor saturable absorber mirror

(SESAM). We will improve SESAM performance

by reducing the mirror’s nonsaturable loss and will

extend the frequency of our phase noise measurement capability. We will also lock the output of the

mode-locked laser to an optical frequency standard to measure absolute timing jitter. Narrowlinewidth lasers have been fabricated using a distributed Bragg reflector (DBR) etched directly onto

the waveguide structure.

DELIVERABLE: In 2003, working with the NIST

Physics Laboratory, we will measure the absolute

timing jitter of mode-locked waveguide lasers.

ACCOMPLISHMENTS

# Correlated the wavelength dependence of

the refractive index and birefringence of

Alx

Ga1-xN with Al fraction using energy dispersive

X-ray spectroscopy (EDS). The calibration of the

EDS permits a resolution of ± 2 % in the Al mole

fraction. Prism coupling methods have been extended

Optoelectronics Division 19
20 Electronics and Electrical Engineering Laboratory

to include the wavelengths 442 nm, 458 nm, 488 nm,

514 nm, 532nm, 632 nm, 690 nm, 750 nm,

850 nm, and 1064 nm. Extraordinary and ordinary

refractive indices were measured in the c-plane oriented Alx

Ga1-xN films grown on sapphire substrates. The uncertainty in the refractive index

measurements is ± 0.005, and all data is fit to firstorder Sellmeier equations over the wavelength span

indicated. Ordinary refractive index data were compared with those measured using reflectance/transmittance spectroscopy. Samples were grown both

by MOVCD and HVPE techniques, and the Al fractions x ranged from 0 to 0.71. Index measurements

are critical to the design of nitride-based, short

wavelength lasers for optical data storage and biological agent detection.

# Using x-ray diffraction analysis, compiled a

complete set of “a” and “c” lattice constant data

for the series of AlGaN samples. Correlated these

data with the results illustrating the dependence of

NLO coefficients on Al mole fraction. Showed that

for samples with the Al fraction exceeding roughly

30 %, the expected symmetry relationship between

second-order nonlinear coefficients X33 = -2X31 fails.

The AlGaN films are in a state of in-plane compressive strain with c axis to a axis strain ratios comparable to those in recently published work by other

authors. This work will complete the SHG study of

AlGaN and assist in correlating the results with

lattice constants and strain.

# Achieved a reduction in residual jitter by more

than two orders of magnitude in a passively modelocked waveguide laser operating at 1534 nm. The

round-trip frequency of the laser cavity was actively referenced to the frequency (472 MHz) of a

stable electronic oscillator using PZT control of

the cavity length and a phase-error detection circuit. In combination with temperature stabilization

and pump isolation, this lowered the residual rootmean-square timing jitter from greater than 10 ps to

as low as 83 fs over the range 100 Hz – 10 MHz.

Compact, low-jitter optical pulse sources are critical for high-data-rate communication systems and

optical sampling systems such as those used for

high-speed, analog-to-digital conversion or optical eye-pattern evaluation.

# Reduced the linewidth of an Er/Yb-doped, DBR

waveguide laser operating near 1550 nm to less

than 10 kHz through active and passive temperature stabilization. Demonstrated heterodyne beatnote production from two independent DBR solid

state waveguide lasers. The linewidth is comparable with the best reported results for stabilized

fiber ring lasers, but the waveguide lasers are simpler and more compact than those devices. Furthermore, the measured linewidth is much narrower

than the 1 MHz or greater linewidth typical for semiconductor DFB laser diodes. The waveguide lasers are important to RF synthesis and sensing

applications.

STANDARDS COMMITTEE

PARTICIPATION

Telecommunications Industry Association: John

B. Schlager is a member of working group FO-4.2.1,

which deals with the Modal Dependence of Multimode Fiber Bandwidth.

RECENT PUBLICATIONS/

PRESENTATIONS

Sanford, N.A.; Aust, J.A., “Uniformity Studies of Congruent LiNbO3

 by Means of Maker Fringe Analysis,” IEE

INSPEC series (Sep 2002). (invited)

Schlager, J.B.; Callicoatt, B.E.; Mirin, R.P.; Sanford, N.A.,

“Passively Mode-Locked Waveguide Laser with Low Residual Jitter,” IEEE Phot. Tech. Lett. 14 (Sep 2002).

Sanford, N.A.; Robins, L.; Steiner, B.; Davydov, A.;

Tsvetkov, D.V.; Dmitriev, V.A., “Optical, X-ray, and

Cathodoluminescence Studies of Bulk and Thin Film GaN,”

TDI, Inc., Gaithersburg, MD. S. Keller, U. K. Mishra, S. P.

Den Baars, Annual Meeting of the American Ceramics

Society, April 28-May 1, 2002, St. Louis, MO. (invited)

Hayden, J.S.; Simpson, R.D.; Conzone, S.D.; Hickernell,

R.K.; Callicoatt, B.; Roshko, A.; Sanford, N.A., “Passive

and Active Characterization of Hybrid Glass Substrates for

Telecommunication Applications,” Proc., SPIE, RareEarth-Doped Materials and Devices VI, Shibin Jiang, Robert W. Keys, Editors, Vol. 4645, 43-50 (2002).

Simpson, R.D.; Hayden, J. S.; Conzone, S. D.; Callicoatt,

B.; Roshko, A.; Sanford, N. A., “Hybrid Glass Structures

for Telecommunication Applications,” Proc., SPIE Integrated Optics: Devices, Materials, and Technologies VI, S.

Sidorin Yakov, Ari Tervonen, Editors, Vol. 4640, 29-36

(2002).

Callicoatt, B.E.; Schlager, J.B.; Silverman, K.L.; Hickernell,

R.K.; Mirin, R.P.; Sanford, N.A.; Hayden, J.S.; Conzone,

S.; Simpson, R., “Single-Frequency and Mode-Locked Er/

Yb Co-Doped Waveguide Lasers,” Proc., IEEE Lasers and

Electro-Optics Society 2001 Annual Mtg. (LEOS 2001),

San Diego, CA, Nov 11-15, 2001, Vol. 1, 576-577 (2001).

Sanford, N.A.; Davydov, A.V.; Tsvetkov, D.V.; Dmitriev,

V.A.; Keller, S.; Mishra, U.K.; Den Baars, S.P., “Optical,

Nonlinear Optical, and X-ray Analysis of GaN and AlGaN

Grown by HVPE and MOCVD on Sapphire,” Fourth International Conference on Nitride Semiconductors (ICNS-4),

July 16-20, 2001, Denver, CO, paper P17.7.

Sanford, N.A., “Nonlinear Optical Analysis of LiNbO3

 and

GaN”, 13th International Symposium on Integrated Ferroelectrics, March 11-14, 2001, Colorado Springs, CO, Paper 7.1.1I. (invited)
Sanford, N.A.; Steiner, B., “Examination of Bulk GaN Crystals by Nonlinear Optical Analysis and High-Resolution Xray Diffraction Imaging,” Materials Research Society

Spring Meeting, April 16-20, 2001, San Francisco, CA.

Paper E2.5.

Schlager, J.B.; Callicoatt, B.E.; Silverman, K.J.; Mirin, R.P.;

Sanford, N.A.; Veasey, D.L., “Mode Locked Erbium/Ytterbium Co-doped Waveguide Laser,” Conference on Lasers

and Electro-optics, CLEO-2001, May 2001, Baltimore,

MD. Paper CMS1.

Gopalan, V. (Penn State University); Sanford, N.A.; Aust,

J.A. (NIST, USA); Kitamura, K. (NIRIM, Japan), “Crystal

Growth, Characterization, and Domain Studies in Lithium

Niobate and Lithium Tantalate Ferroelectrics,” in Handbook of Advanced Electronic and Photonic Materials and

Devices, edited by H. S. Nalwa, Vol. 4: Ferroelectrics and

Dielectrics, Academic Press (2001). (invited)

Optoelectronics Division 21
22 Electronics and Electrical Engineering Laboratory

NANOSTRUCTURE FABRICATION AND METROLOGY

PROJECT GOALS

Develop modeling, fabrication, and measurement

methods for semiconductor nanostructures, including quantum dots and photonic crystals. Develop

fundamentally new devices for single-photon

sources and detectors and entangled-photon

sources.

Technical contact:

Richard Mirin

Staff-Years (FY2003):

2.6 professionals

3.0 post-doctorals

Emission spectrum of optically pumped, single InGaAs

quantum dot.

CUSTOMER NEEDS

Semiconductor nanostructures, especially selfassembled quantum dots and photonic crystals,

are emerging as an important future direction for

optoelectronics. Photonic crystals offer a wide

range of possibilities, ranging from improved lightemitting diodes to photonic integrated circuits to

spontaneous emission control. Semiconductor

quantum dots have an atomic-like density of states

that offers substantial opportunities for unique and

improved devices. These include ultra-low-threshold laser diodes and semiconductor optical amplifiers with reduced cross-gain modulation. Several

fundamental properties of quantum dots have yet

to be measured, including resonant absorption

cross-sections and homogeneous linewidth. These

properties set limitations on device operation.

The ability to generate and control single photons

offers new opportunities to meet customer needs

in quantum-based radiometric measurements where

optical power is measured by counting photons.

Quantum cryptography is an emerging form of

ultrasecure communications that requires an ondemand source of single photons. The singlephoton turnstile will allow us to meet the requirements of this new technology. The single-photon

turnstile can be extended to generate pairs of entangled photons. These entangled photon pairs

are useful for a wide range of applications, from

fundamental tests of quantum mechanics to reduced

dimensions with optical lithography.

TECHNICAL STRATEGY

We are using molecular beam epitaxy (MBE) to grow

self-assembled quantum dots. Reflection highenergy electron diffraction (RHEED), atomic force

microscopy (AFM), and transmission electron microscopy (TEM) techniques are applied to characterize quantum-dot morphology as a function of

growth parameters. Photon counting and cavity

ringdown methods are required to measure the optical properties of semiconductor nanostructures,

particularly single quantum dots or small ensembles

of dots.

DELIVERABLE: In 2003 we will measure the temperature-dependent absorption of single quantum dots

using cavity ring-down spectroscopy.

We have developed ultrafast pump-probe methods to characterize carrier lifetimes and are measuring the homogeneous linewidth of quantum dots

via transient four-wave mixing. Collaborators in

JILA and the NIST Physics Laboratory are contributing to various aspects of nanostructure measurement and modeling.

DELIVERABLE: We will measure the homogeneous

linewidth of self-assembled InGaAs quantum dots in

2003.

The fabrication of photonic crystals requires the

precision growth and anisotropic etching of semiconductor epilayers. We are using a chemically

assisted ion-beam (CAIBE) system to etch semiconductor nanocavities in layers grown by MBE.

Comprehensive modeling is key to the design and

understanding of these nanostructures. Photonic

crystal cavities and waveguides are expected to

play important roles in advanced optoelectronic

devices such as photonic integrated circuits.

DELIVERABLES: In 2003-4, we will investigate the

dependence of optical properties on the fabrication

parameters for 2D photonic crystal cavities embedded

in a ridge waveguide and compare with calculations.
DELIVERABLE: In 2003, we will apply finite-difference

time-domain (FDTD), full vector Maxwell, and Green’s

function methods to model these nanocavities and

interpret the results of optical and structural measurements.

Single-photon-turnstile (SPT) operation relies on a

large Coulomb blockade effect, which we have

shown to exist for self-assembled quantum dots.

We therefore expect the Coulomb blockade to be

observable near room temperature. The photon

repetition rate of the SPT is controlled by the frequency of an applied AC voltage, allowing precisely defined emission of single photons. The

ultimate goal is the embedding of a SPT inside a

photonic crystal nanocavity, which will enable enhanced emission efficiency and directionality. We

have implemented a Hanbury-Brown-Twiss apparatus to measure the photon statistics from our SPT.

A true single-photon device will exhibit photon

emission rates that are non-classical. Specifically,

photon anti-bunching is expected to be observed.

DELIVERABLES: We will demonstrate an optically

driven photon turnstile in 2003 and measure SPT

operation with a single-electron pump in 2004. We will

incorporate the SPT in a photonic crystal cavity and

characterize its operation in 2004. We will develop a

single-photon emitter based on rare-earth-dopants in

semiconductors in 2005.

ACCOMPLISHMENTS

# Measured the optical properties of a single

self-assembled quantum dot (QD). The quantum

dot was fabricated from InGaAs on a GaAs substrate using molecular beam epitaxy (MBE). The

areal density of QDs was 1 per μm2 as measured

using atomic force microscopy. This low density

requires careful control of several MBE growth

parameters, including total thickness and substrate

temperature. Mesas of varying size were etched

into the specimen to isolate small numbers of QDs

as well as individual QDs. A mesa containing a

single QD was optically excited using a 532 nm

laser to create excitons in the dot, and these excitons then collapsed to emit single photons that

were spectrally resolved using a grating and a CCD

camera. Several emission peaks around 950 nm

were observed from the single QD, including those

due to excitons, charged excitons, and biexcitons.

Understanding the optical emission from a single

QD is essential for the development of an ondemand, single-photon source, for application to

quantum-based radiometry and quantum cryptography.

# Measured polarization-dependent absorption

on various ensembles of self-assembled InGaAs

quantum dots in a waveguide. We devised a novel

method of measuring absorption in a waveguide,

in which a short laser pulse reflects back and forth

in a long, low-Q cavity, and the output pulse energies are measured using sum-frequency generation with a gating pulse scanned in delay length.

Absorption of both ground state and excited states

was measured. In the ground state the quantum

dots strongly absorb TE polarized light and do not

absorb TM polarized light. Depending on the areal

density of the quantum dots, the TE absorption

coefficient is 4-6 cm-1.

# Completed fabrication of the first generation

of quantum-dot optically-gated field effect transistors (QDOGFETs), being developed for singlephoton detection. The design includes an on-chip

resistance bridge that should allow measurements

of resistance change of 1 part in 106

. Preliminary

tests of the QDOGFET as a photodetector demonstrate sensitivity at the sub-picowatt level.

# Fabricated several photonic crystal nanocavities in GaAs thin films. The smallest nanocavity

has a modal volume that approaches the fundamental physical size limit for supporting an optical

mode. We used electron- beam lithography to write

a pattern, followed by chemically assisted ion-beam

etching (CAIBE) to transfer the pattern into the

GaAs. These nanocavities are modeled using a full

vector Maxwell solver.

# Developed a multi-bounce reflection spectroscopy setup to measure semiconductor distributed

Bragg reflectors (DBRs). Results show that the reflectance can be measured with an uncertainty of

0.05 %.

RECENT PUBLICATIONS/

PRESENTATIONS

Mirin, R.P.; Roshko, A.; van der Puijl, M., “Formation of

InAs/GaAs Quantum Dots by Dewetting During Cooling,”

J. Vacuum Sci. Technol. B 20: 1489-1492 (Jul 2002).

Anders, S.; Kim, C.S.; Klein, B.; Keller, Mark W.; Mirin,

R.P.,” Bimodal Size Distribution of Self-Assembled InGaAs

Quantum Dots”, ys. Rev. B 66: 125309-1 – 125309-5

(Sep 2002).

Silverman, K.L.; Sonnenberg-Klein, B.D.; Mirin, R.P.;

Cundiff, S.T.; Furbush, K., “Direct Measurement of Polarization Resolved Transition Dipole Moment in InGaAs/

GaAs,” Tech. Dig., Conf. on Lasers and Electro-Optics

(CLEO ’02), May 19-24, 2002, Long Beach, CA, (2002).

Mirin, R.P.; Roshko, A.; van der Puijl, M; Norman, A.G.,

“Evolution of the Shapes of InAs and InGaAs Quantum

Dots,” Proc., North Amer. Conf. on Molecular Beam

Epitaxy, October 1-3, 2001, Providence RI (Jan 2001).

Optoelectronics Division 23
24 Electronics and Electrical Engineering Laboratory

Sonnenberg-Klein, B.; Silverman, K.L.; Mirin, R.P., “Multimode Lasing at Room Temperature from InGaAs/GaAs

Quantum Dot Lasers,” Proc., SPIE Vol. 4533, Semiconductor Lasers for Lightwave Communication Systems, Aug

21-22, 2001, Denver, CO, 1-8 (2001).

Gökkavas, M.; Dosunmu, O.; Ünlü, M.S.; Ulu, G.; Mirin,

R.P.; Christensen, D.H.; Özbay, E., “High-Speed HighEfficiency Large-Area Resonant Cavity Enhanced p-i-n

Photodiodes for Multimode Fiber Communications,” IEEE

Phot. Tech. Lett. 13 (Dec 2001).
SEMICONDUCTOR GROWTH AND DEVICES

PROJECT GOALS

Develop measurement methods and provide data

to support the efficient manufacture of semiconductor optoelectronic devices. Provide advanced

materials and devices to support research in industry, other parts of NIST, universities and government laboratories.

Gas-source molecular beam epitaxy growth system

used to study III-V crystal growth by Kris Bertness (in

picture) and others at NIST. © Geoffrey Wheeler

CUSTOMER NEEDS

The continued growth of the U.S. optoelectronics

industry depends on the high-yield manufacture

of devices with increasingly tight specifications.

Compound semiconductor materials form the basis

for LEDs, lasers, photodetectors, and modulators

critical to optical communication, display, data storage, and many other applications. Issues of materials purity and uniformity are at the foundation of

device yield and performance. Measurements of

starting materials and epitaxial layers must be supported by standard procedures and reference materials. Increasingly, the needs are for accurate inprocess measurements. Many semiconductor

devices now incorporate structures with a high degree of strain, and characterization of this strain

and its relationship to device failure is an important

area of research. In addition, specialty devices are

needed for use in metrology systems inside and

outside this project.

TECHNICAL STRATEGY

Inaccuracy of semiconductor composition measurement has impeded the achieving of consistency of

device performance across production lines. It has

also inhibited the collection of sufficiently accurate materials parameters for use in the simulation

of devices, which is critical to fast product cycle

times. The problems have been exacerbated by the

increase in outsourcing of epitaxial growth. A goal

of this project is to develop certification techniques

for standard reference materials having composition uncertainty specified to a level one tenth of

that of techniques currently in use by industry.

Our approach is to combine conventional methods

of composition determination (photoluminescence

(PL), photo-reflectance (PR), and x-ray diffraction

(XRD)) with less common methods (in situ monitoring, electron microprobe analysis (EMPA), and

quantitative chemical analysis) to enable certification of alloy composition. This program is paving

the way for production of standard reference materials (SRMs) in the AlGaAs alloy system. As part

of this research, we have quantified error sources

and accuracy limits of the indirect composition

measurement techniques, specifically PL and XRD,

currently in use by industry. We have also demonstrated the compositional accuracy that can be

achieved with direct microanalytical techniques

such as EMPA in combination with accurate reference artifacts and carefully chosen correction procedures.

DELIVERABLE: In 2003, we will offer AlGaAs

composition standards with relative mole fraction

uncertainty of ± 2% or less.

In a related project, the accuracy of InGaAsP composition analysis is being assessed through an

interlaboratory comparison of conventional ex-situ

characterization techniques: PL and XRD. This program seeks to develop reliable methods for measurement and data analysis that can be used

throughout the industry. A set of samples with

different compositions was analyzed by industrial

laboratories. By examining the different operating

and analytical conditions used in the various laboratories and how they affect the data, the importance of the measurement variables for the techniques are being assessed. A necessary aspect of

the study has been to distinguish between variations intrinsic to the materials and those caused by

the measurement systems or techniques. Systematic measurements in a controlled environment at

NIST will help clarify this and the appropriate measurement and calculation methods. Finally, we are

collaborating with the NIST Materials Science

and Engineering Laboratory to evaluate Raman

Technical Contact:

Kris Bertness

Staff-Years (FY2003):

2.6 professionals

1.0 post-doctoral

2.0 graduate students

Optoelectronics Division 25
26 Electronics and Electrical Engineering Laboratory

spectroscopy as a possible method to quantify

strain in InGaAsP.

DELIVERABLE: In 2003 we will report the analysis of

a controlled study of important variables in PL

measurements of InGaAsP at NIST. By 2004 we will

collaboratively determine the stress dependence of

the Raman and PL line positions. By 2005, we will

publish recommended procedures for the evaluation of

composition and strain in InGaAsP.

Contamination is a serious problem in phosphine,

arsine, silane, ammonia, and similar gases used in

the epitaxial growth of high-purity semiconductor

layers. Semiconductor device manufacturers have

expressed frustration with the irreproducibility of

source material purity from vendor lot to vendor

lot. The issue is described by industry as primarily

a measurement problem in that manufacturers frequently report impurity levels as “not detected”

for a series of lots that produce very different device results. The critical concentrations of the impurities are not well known; however, it is believed

that >10 nmol/mol oxygen or water in phosphine is

undesirable. In collaboration with researchers in

the NIST Chemical Science and Technology Laboratory, this project has developed a cavity-ringdown spectroscopic technique to measure impurities with very low concentrations in semiconductor source gases. In this technique a high-finesse

optical cavity is filled with the sample gas and then

pumped with light that is strongly absorbed by the

impurity molecule. The light is abruptly shuttered,

and the decay time can be simply related to the

impurity concentration. The advantages of this

technique are that its accuracy relies primarily on

accurate time measurement and detector linearity,

rather than measurement of absolute light intensities, and it is insensitive to absorption outside the

cavity. Water content has been measured in phosphine and nitrogen gas with and without in-line

purifiers. Further studies are correlating the impurity concentrations in phosphine with the quality

of semiconductor material and devices grown using the gas. Of particular interest is the effect of

impurities on nanostructures. Our system will also

be used to measure the line shape, absorption coefficients, and frequency of optical transitions for

water, phosphine and ammonia in the vicinity of

935 nm. This information is critical to facilitate the

use of high-sensitivity spectroscopy techniques

in these gases.

DELIVERABLE: By 2003, we will measure water

concentrations in ammonia to 1 μmol/mol. By 2003, we

will measure pressure-broadening coefficients of

water in phosphine for the stronger water absorption

lines. By 2005 we will increase the sensitivity of

impurity concentration measurement toward a goal of

5 nmol/mol.

Native-oxide layers have a significant impact on

compound semiconductor photonic devices due

to their ability to provide both electrical and optical

confinement, similar to native SiO2 in integrated Si

technology. They are used as confinement apertures and/or broadband antireflection (AR) coatings in vertical cavity surface emitting lasers

(VCSELs), photodetectors, light-emitting diodes,

and saturable Bragg mirrors. In particular, the use

of AlGaAs oxide apertures in VCSELs has resulted

in record low threshold currents and high efficiencies. However, AlGaAs layers undergo a relatively

large contraction during oxidation, resulting in strain

in the adjacent GaAs layers. This frequently causes

structures containing AlGaAs oxide layers to

delaminate and/or fail. To address this issue we are

collaborating with the NIST Materials Science and

Engineering Laboratory on imaging strain in these

materials using electron backscatter diffraction

(EBSD) and high-resolution convergent-beam

electron diffraction (CBED). These techniques allow the identification of strains as small as 0.02 %,

with lateral resolution on a nanometer scale. We

will study how the strain in these structures varies

as a function of the oxidation and post-oxidation

processing conditions. We are also pursuing means

to minimize the strain through appropriate choice

of materials and oxidation conditions.

DELIVERABLE: By 2003, we will characterize the

strain in GaAs layers adjacent oxidized AlGaAs

layers. By 2004, we will publish the results of the

study to minimize strain in devices employing native

oxides.

Quantum dots are semiconductor structures with

quantized energy levels that result in improved efficiency and tuning range for semiconductor lasers

and less sensitivity to environmental changes for

lasers and photodetectors. Dot formation is driven

by strain during epitaxial crystal growth, but measuring the strain in structures less than 100 nm in

lateral dimension presents new challenges. We are

contributing to this field by making careful studies

correlating substrate preparation and growth parameters with dot density and size as measured by

atomic force microscopy (AFM). We are also evaluating the shape of the dots and strain in the region

of the dots with transmission electron microscopy

(TEM).
DELIVERABLE: By 2003, we will evaluate the

uniformity of quantum dots as a function of substrate

preparation and growth conditions.

ACCOMPLISHMENTS

# Demonstrated the first measurement of water

concentrations in phosphine using ringdown cavity spectroscopy. The ringdown results showed

that the phosphine contained water at the several

micromoles/mole level, much larger than the specifications provided by the manufacturers. There was

indication that the phosphine cylinders can degrade substantially over time. With the same

ringdown system, we measured a water vapor background of 150 ± 15 nanomoles/mole in purified nitrogen, and from these data we set our current

detectivity limit at about 50 nanomoles/mole. This

technique was developed in collaboration with

NIST CSTL.

-2000 0 2000 4000

Frequency Shift (MHz)

50

40

30

20

Loss per Pass, LTOT x 106

unpurified PH3

purified PH3

Cavity ring-down spectroscopy data of phosphine gas

with and without in-line purification. The unpurified

phosphine gas contains 18.0 ± 1.7 μmol/mol of water,

while there is no detectable water in the purified

phosphine. The peaks in the purified phosphine gas

spectrum arise from weak phosphine absorption lines.

# Demonstrated that the oxidation kinetics of

AlGaAs follows a Deal-Grove model and determined

the reaction rates and diffusion coefficients. We

found that the oxidation of layers with Al compositions from 90 % to 94 % are surface-reaction limited, leading to oxidation depths that vary linearly

with time and oxidation rates that are exponentially

dependent on temperature. For layers with 96 % Al

and higher, the kinetics were in a mixed regime,

where both the surface reaction and diffusion control the oxidation. The diffusion coefficients in the

mixed regime are unusually high for a solid diffusion process, suggesting that diffusion takes place

either through nanoscale pores in the oxide or a

thin, dense layer near the semiconductor-oxide

interface.

# Developed methods to grow GaAs and AlGaAs

films of acceptable quality on Ge substrates rather

than the conventional growth on GaAs substrates.

The new methods will be used to calibrate composition of standard thin films materials using analytical chemistry techniques executed in NIST’s

Chemical Science and Technology Laboratory. The

analytical technique, inductively-coupled plasma

optical emission spectroscopy (ICP-OES), was used

this year to anchor the absolute calibration of the

composition of AlGaAs thin films. Our initial results using ICP-OES agreed with EMPA, PL, and

RHEED results within the uncertainty limits of all

three techniques. ICP-OES analysis is traceable to

the mole and has absolute calibration uncertainty

of less than 0.1 %. The Ge substrates were necessary, however, because any contamination from the

GaAs substrate would add larger uncertainty to

the measurement.

# Determined that the absolute calibration of the

reflectance in an in situ optical reflectance spectroscopy (ORS) system must be accurate to 0.05 %

in order to determine Al mole fraction x in

A1x

Ga1-xAs to an uncertainty of 0.003. Improving

the noise in the reflectance below a standard deviation of 0.3 % does not relax this requirement

until the noise is below 0.02 %. Neither the calibration goal nor the noise requirements are readily

achieved in practice. We plan to look at ways to

use growth rate information determined from other

methods to constrain the ORS data fits and thereby

obtain more accurate values for index of refraction

at growth temperature.

# Determined that the uncertainty in RHEED

growth rate measurements varies from 1 % to 7 %

depending on specimen size, control of RHEED

beam position, and data analysis method. We upgraded our RHEED equipment and refined our procedures to reach the lower end of this range for

further work on AlGaAs composition standards.

We also collaborated with NIST’s Information Technology Laboratory to identify the optimal use of

the redundant data collected in order to minimize

the error propagated to the Al mole fraction as determined from RHEED growth rate data.

# Measured strain in semiconductor nanostructures. In collaboration with the NIST Materials

Science and Engineering Laboratory (MSEL) we

obtained qualitative measurements of strain in the

vicinity of an AlGaAs oxidation front using electron backscatter diffraction (EBSD). The EBSD map

indicated that the highest strain was found near but

behind the oxidation front. We have also provided

Optoelectronics Division 27
28 Electronics and Electrical Engineering Laboratory

AlGaAs specimens to another group in MSEL for

micro-Raman studies. This past year the group

has made the first determination of the shifts in

Raman and photoluminescence peaks for AlGaAs

under biaxial stress.

# Analyzed the results of measurements of x-ray

and photoluminescence taken by five different companies, using eight different instrument sets in the

InGaAsP interlaboratory comparison. The specimens were grown by industrial collaborators. We

found that x-ray rocking-curve accuracy appeared

to be limited primarily by nonuniformity in the specimen strain and/or composition. Future study will

be carried out with specimens having greater uniformity. We have also undertaken a major equipment purchase to enhance our ability to determine

strain with x-ray. In contrast with the x-ray results,

the study revealed significant variations in photoluminescence peak wavelength measurements from

laboratory to laboratory. These variations were large

compared with wavelength grid spacing in dense

wavelength-division-multiplexed systems. The

variations were also large compared with specimen

uniformity. They appeared uncorrelated with the

instrument settings and environmental conditions

reported by participants. Because the variables

were measured in different labs with different tools

and differing degrees of precision, this does not

necessarily mean that real correlations do not exist.

Further systematic measurements at NIST will clarify

this issue.

RECENT PUBLICATIONS

Roshko, A.; Bertness, K.; Armstrong, J.; Marinenko, R.;

Salit, M.; Robins, L.; Paul, A.; Matyi, R., “X-ray, Photoluminescence and Composition Standards of Compound Semiconductors,” accepted for publication in Phys. Stat. Sol.

Roshko, A.; Bertness, K.A., “Interlaboratory Comparison

of InGaAsP Ex-situ Characterization,” accepted for publication in J. Crystal Growth.

Fu, C.; Bertness, K.A.; Wang, C., “Effects of Noise Level

in Fitting In-Situ Optical Reflectance Spectroscopy Data,”

submitted to J. Crystal Growth.

Harvey, T.E.; Bertness, K.A.; Wang, C.; Splett, J.D., “Accuracy of AlGaAs Rates and Composition Determination

Using RHEED Oscillations,” submitted to J. Crystal Growth.

Chen, Y.; Roshko, A.; Bertness, K.A.; Readey, D.W.;

Allerman, A.A.; Tan, M.; Tandon, A., “Comparison of

AlGaAs Oxidation in MBE and MOCVD Grown Samples,”

Proc., Mat. Res. Soc. Symposium., Vol. 692, Nov. 26-29,

2001, Boston, MA, H6.11.1-6 (2001).
APPENDIX A: MAJOR LABORATORY FACILITIES

SEMICONDUCTOR GROWTH AND OPTOELECTRONIC DEVICE FABRICATION

The Division makes use of a gas-source molecular-beam epitaxy system and associated in situ

and ex situ measurement equipment for III-V semiconductor growth and characterization. It

also maintains a cleanroom facility for thin-film deposition, photolithography, and wet and dry

etching. The facilities support the activities described above, particularly for the Optical Materials Metrology, Nanostructure Fabrication and Metrology, and Semiconductor Growth and

Devices Projects.

LASER POWER/ENERGY DETECTOR CALIBRATION SYSTEMS

The Optoelectronics Division has established and maintains several state-of-the-art measurement systems for calibrating most types of laser power and energy detectors. These measurement systems incorporate unique, specially designed, electrically calibrated, laser calorimeters

that are used as primary standards. The calorimeters are used in conjunction with beamsplitterbased optical systems to provide measurement services for laser power and energy that cover

a wide range of powers, energies, and wavelengths for detectors used with both cw and pulsed

lasers. This assembly of laser power and energy detector calibration systems represents the

best overall capability of this kind in the world. In many cases (e.g., excimer laser measurements at 248 nm, 193 nm, and 157 nm), the Division has the only measurement capability in the

world.

Optoelectronics Division 29
30 Electronics and Electrical Engineering Laboratory

APPENDIX B: NRC POST-DOCTORAL AND OTHER

RESEARCH OPPORTUNITIES

NATIONAL RESEARCH COUNCIL ASSOCIATESHIP OPPORTUNITIES

The National Institute of Standards and Technology (NIST), in cooperation with the National

Research Council (NRC), offers awards for post-doctoral research in many fields. These

awards provide a select group of scientists and engineers an opportunity for research in many

of the areas that are of deep concern to the scientific and technological community of the

nation. NIST, with direct responsibilities for the nation’s measurement network, involves its

laboratories in the most modern developments in the physical, engineering, and mathematical

sciences and the technological development that proceed from them. The Research Council,

through its Associateship Programs office, conducts an annual national competition to recommend and make awards to outstanding scientists and engineers at the post-doctoral level for

tenure as guest researchers at participating laboratories. The deadline for applications is February 1 for appointments beginning between July and the following January.

THE OBJECTIVES OF THE PROGRAMS ARE:

# To provide post-doctoral scientists and engineers of unusual promise and ability opportunities for research on problems, largely of their own choosing, that are compatible with the interest of the sponsoring laboratories.

# To contribute thereby to the overall efforts of the federal laboratories. Eligibility requirements include U.S. citizenship and receipt of Ph.D. within 5 years of application. NRC positions involve a two-year tenure at NIST, and the annual base salary for the 2003 program year

is $55,700.

For more detailed information, including instructions for applicants, please contact the Optoelectronics Division Office and request a copy of the NRC Post-Doctoral Opportunities booklet. You may also visit the NRC Research Associateship Program web page (http://nationalacademies.org/rap) to see a list of opportunities within our division.

OPPORTUNITIES FOR THE YEAR 2003 WITH THE OPTOELECTRONICS DIVISION

THROUGH THE NRC RESEARCH ASSOCIATESHIP PROGRAM:

# Deep Ultraviolet Laser Metrology

# High-Speed Optoelectronics Measurements

# High-Speed Optical Receivers and Optoelectronic Integrated Circuits

# Ultrashort Optical Pulse Characterization for High-Speed Measurements

# Modeling and Simulation of High-Speed Optoelectronic Devices

# Intensity Noise in Optical Fiber Amplifiers and Transmitters

# Chromatic Dispersion Metrology

# Polarization-Mode Dispersion Metrology

# Polarization Metrology for Optical Telecommunications

# Low-Coherence Interferometry for Fiber Optic and Component Metrology

# Nonlinear Properties of Optical Fiber and Components

# Wavelength Standards for Optical Communications

# Fiber Bragg Gratings and UV Photosensitivity
# Study of Compound Semiconductor Native Oxides

# Quantum-Dot Morphology

# Photonic Crystals and Optical MEMS

# Semiconductor Quantum Optics

# Ultrafast and CW Optical Frequency Synthesis

# Nanoscopic Wide-Bandgap Materials Characterization by CW and Ultrafast Nonlinear Optics

# In-Situ Metrology of Epitaxial Crystal Growth for Semiconductor Optoelectronics

PROFESSIONAL RESEARCH EXPERIENCE PROGRAM (PREP)

The Professional Research Experience Program (PREP) is designed to provide valuable laboratory experience to undergraduate and graduate students from the University of Colorado at

Boulder and from the Colorado School of Mines at Golden, and to recent Ph.D. recipients from

these and other universities. Students and postdocs are employed by the University of Colorado

or the Colorado School of Mines and normally carry out research at the NIST Boulder Laboratories.

Students are usually hired just before the spring, fall, or summer terms, and may be employed

for one or more terms. Post-doctorals may begin any time during the year. Applications are

accepted throughout the year.

NIST pays in-state tuition for PREP undergraduate students during the fall and spring semesters and an hourly wage. Graduate students receive in-state tuition and a stipend. Postdocs

receive a stipend.

Eligibility requirements include U.S. citizenship or permanent residency and, for students, a

minimum 3.0 GPA (grade point average).

An application form and further information are available from:

Phyllis Wright, Student Outreach Coordinator

NIST, MC 360

325 Broadway

Boulder, CO 80305

Phone: (303) 497-3244

Email: pkwright@boulder.nist.gov

http://www.boulder.nist.gov/exec/bdprepo.htm

Optoelectronics Division 31
32 Electronics and Electrical Engineering Laboratory

APPENDIX C: CONFERENCES AND WORKSHOPS

SYMPOSIUM ON OPTICAL FIBER MEASUREMENTS

The Optoelectronics Division, in cooperation with the Optical Society of America and the IEEE

Lasers and Electro-Optics Society, organizes the biennial Symposium on Optical Fiber Measurements held in Boulder in the fall of even-numbered years. Check the Division web page or call the

Division Office for the date of the next Symposium. This Symposium is a 21⁄2-day meeting devoted entirely to the topic of measurements on fiber, related components, and systems. It provides

a forum for reporting the results of recent measurement research and an opportunity for discussions that can lead to further progress. It consists entirely of contributed and invited papers.

Experimental and analytical papers on any measurement aspect of guiding lightwave technology

are solicited for the Symposium. Subjects and measurements include:

Optical Fibers

 Telecom, sensors, fiber lasers/amplifiers

Integrated Optics

 Planar waveguides, photonic crystals, MEMs

Components

 Amplifiers, lasers, detectors, modulators, switches, couplers

Systems

 Long haul, LANs/subscriber loops, WDM, TDM

Standards

Field and laboratory instrumentation

Examples of typical measurements include:

 Attenuation/loss

 Chromatic dispersion

 Crosstalk

 Cutoff wavelength

 Effective area

 Effective index

 Four wave mixing efficiency

 Index of refraction profile

 Mode-field diameter

 Nonlinear coefficients

 Polarization dependent loss

 Polarization-mode dispersion

A limited number of Digests from previous Symposia are available, as well as a CD-ROM with

collected papers from 1980–2000. For information on obtaining either, or for information on upcoming Symposia, please contact the Optoelectronics Division Office or visit our web page, http:/

/www.boulder.nist.gov/div815/.

Laser Measurements Short Course

The Optoelectronics Division, in cooperation with the University of Colorado at Boulder, offers an

annual Short Course on Laser Measurements. Check the Division web page or call the Division

Office for the date of the next short course. The 31⁄2-day course emphasizes the concepts, techniques, and apparatus used in measuring laser parameters. A tour of the NIST laser measurement

laboratories is included. The faculty consists of laser experts from NIST, industry, and other

government agencies. A degree in physics or electrical engineering, or equivalent experience is

assumed, and some experience in the use of lasers is desired for attendees.
APPENDIX D: CALIBRATION SERVICES

Laser Power and Energy Calibrations

Laser Wavelength Range

CW He Cd 325 nm 100 nW to 10 mW

Argon 488,514 nm 1 nW to 2 W

Doubled 532 nm 1 nW to 10 W

Nd:YAG

HeNe 633 nm 1 nW to 20 mW

Diode 830 nm 1 nW to 20 mW

Ti:Sapphire 700 to 1,000 nm Up to 1 W

Dye 550 to 700 nm Variable

Nd:YAG 1,064 nm 1 μW to 450 W (6 kW off-site)

1,319 nm 1 μW to 10 mW

Erbium 1,550 nm 1 μW to 10 mW

CO2 10.6 μm 35 mW to 900 W (6 kW off-site)

Pulsed KrF 248 nm 50 μJ/pulse to 150 mJ/pulse

3 mW to 7 W average

ArF 193 nm 20 μJ/pulse to 150 mJ/pulse

3 mW to 3 W average

Dose (Irradiance) Measurements

F2 157 nm 20 μJ/pulse to 20 mJ/pulse

3 mW to 4 W average

Nd:YAG 1,064 nm 10 μJ to 300 mJ/pulse (1 to 20 Hz prf)

10-4 to 10-8 W(peak)

10-11 to 10-15 J/pulse

Optoelectronics Division 33
34 Electronics and Electrical Engineering Laboratory

Optical Fiber Power Meters and Detectors

Parameter Wavelength Range Status

670, 780, 850, 980, 10 to 100 μW Calibration Service

1310, 1550 nm

Absolute Power 830 to 860 nm, 1270 to 10 to 100 μW Calibration Service

Calibration 1330 nm, 1510 to 1560 nm,

1580 to 1625 nm

980, 1290, 1550 nm 1 to 250 mW Special Test

1319 nm 300 kHz to Calibration Service

50 GHz

850 and 1550 nm 1 MHz to Special Test

50 GHz

Optical-Fiber Power 850, 1310, 1550 nm 60 to 90 dB Calibration Service

Meter Linearity

Reference Receiver 800 and 1550 nm 100 fs impulse source Special Test

Impulse Response

Optical-Detector Spatial 635, 850, 1300, 1550 nm Special Test

Uniformity

Optical-Fiber Power 400 to 1700 nm Calibration Service

Meter Spectral

Responsivity

Relative Intensity Noise 1550 nm 0.1 to 4.1 GHz Calibration Service

(RIN)

Optical Receiver

Frequency Response

For more information on calibration services for optoelectronics, contact:

Marla L. Dowell, Group Leader at (303) 497-7455, mdowell@boulder.nist.gov.
APPENDIX E: STANDARD REFERENCE MATERIALS

Standard Reference Materials

SRM Name Brief Description Availability

Number

Composition Standards

XXXX Composition Standards for None Yet Available 2003

Compound Semiconductors

 Wavelength Calibration Standards

2514 Wavelength Calibration Fiber-coupled molecular gas Available

Reference for 1560-1595 nm absorption cell with absorption lines

– Carbon Monoxide (12C16O) in the WDM L-band between 1560

and 1595 nm

2515 Wavelength Calibration Fiber-coupled molecular gas Available

Reference for 1595-1630 nm absorption cell with absorption lines

– Carbon Monoxide (13C16O) in the WDM L-band between 1595

and 1630 nm

2517a High-Resolution Wavelength Fiber-coupled molecular gas adsorp- Available

Calibration Reference for tion cell with narrow absorption

1510-1540 nm – Acetylene lines between 1510 and 1540 nm

(

12C2

H2)

2519 Wavelength Reference Fiber-coupled molecular gas Available

Absorption Cell- Hydrogen absorption cell with absorption lines

Cyanide (H13C14N) between 1530 and 1560 nm

 Polarization Mode Dispersion Standards

2518 Polarization Mode Device with stable and known value Available

Dispersion Standard of polarization mode dispersion that

simulates optical fiber

2538 Deterministic Polarization To simulate PMD in discrete Available

Mode Dispersion Standard components — wavelengths 1250 to

1650 nm

 Fiber and Fiber-Connector Geometry Standards

2513 Mode Field Diameter Optical fiber specimen with cleaved Available

Standard for Single-Mode end and calibrated mode field

Fiber diameter

2520 Optical Fiber Diameter Optical fiber specimen with cladding Available

Standard diameter values known to

approximately ±40 nm

 Continued on next page

Optoelectronics Division 35
The following fiber and fiber connector geometry SRMs are produced by NIST’s

Precision Engineering Division (821.00)

2522 Pin Gauge Standard for Wire used to size bores of connector ferrules; Available

Optical Fiber Ferrules diameter known to approximately ± 40 nm

2523 Optical Fiber Ferrule Ceramic connector ferrule with specified Available

Geometry Standard outside diameter and roundness

2553 Optical Fiber Coating Glass rod with index of refraction n =1.504 Available

Diameter and diameter of approximately 250 mm

known within ±0.1mm.

2554 Optical Fiber Coating Glass rod with index of refraction n =1.515 Available

Diameter and diameter of approximately 250 mm

known within ±0.1mm.

2555 Optical Fiber Coating Glass rod with index of refraction n =1.535 Available

Diameter and diameter of approximately 250 mm

known within ±0.1mm.

Technical information on SRMs 2522, and 2523, 2553 , 2554, and 2555

can be obtained from:

Precision Engineering Division (821.00)

National Institute of Standards and Technology

100 Bureau Drive, Stop 8210, Met A109

Gaithersburg, MD 20899-8210

 Phone: (301) 975-3463 Fax: (301) 869-0822

 Measurement Assurance Programs

2524 Optical Fiber Approximately 10 km of optical fiber with Contact

Chromatic Dispersion zero-dispersion wavelength known to Division

Standard approximately ± 0.08 nm

2525 Optical Retardance Nominally 90 degree retarder with retardance Contact

Standard known to approximately ± 0.1 ° Division

For additional technical information contact:

Optoelectronics Division (815.00)

National Institute of Standards and Technology

325 Broadway

Boulder, CO 80305

Phone: (303) 497-5342 Fax: (303) 497-7671

Email: optoelectronics@boulder.nist.gov

For Detailed Ordering and Shipping Information contact:

SRM Program Office

National Institute of Standards and Technology

100 Bureau Drive, Stop 2322

Gaithersburg, MD 20899-2322

Phone: (301) 975-6776 Fax: (301) 948-3730

email: SRMINFO@nist.gov

36 Electronics and Electrical Engineering Laboratory
Division/Office Publication Editor: Ms. Sandra Merrill and Ms. Annie Smith

Publication Coordinator: Gaylen R. Rinaudot

Printing Coordinators: Warren Overman

Verna M. Moore

Document Production: Technology & Management Services, Inc.

Gaithersburg, Maryland
January 2003

For additional information contact:

Telephone: (303) 497-5342

Facsimile: (303) 497-7671

On the Web: http://www.boulder.nist.gov/div815/