A11102 4 fl S S 1

S

HA2^2|«T OF STANDARDS & TECH R.I.C. 32

All 10248551

5

^^W”c^ulENTATION of the nbs apd

AND PIN CALIBRATION SYSTEMS FOR

MEASURING PEAK POWER AND

ENERGY OF LOW-LEVEL 1.064 fxm

LASER PULSES

REFERENCE

NBS

PUBLICATIONS

A.L. Rasmussen

A.A. Sanders

National Bureau of Standards

U.S. Department of Commerce

Boulder, Colorado 80303

December 1985

~QC

100

• U56

85-3032

1985

ERRATA SHEET

NBSIR 85-3032

tits RESEARCH INFORMATION

Page Locati on Incorrect Item

3 2.3, second line November

3 3. , second paragraph

,

third line

etched glass

4 4. ,n . ,2. mn

4. ,n. ,3. mft 17 6. 1.1,4., first line 1.5 mn

25 6. 3. 4, 2., second line .(end of sentence)

6. 3. 4, 4., second line .(end of sentence)

27 6. 3. 9, 3., second and from the LED pulsed

third lines beam

29 6. 4. 1,9., first and 3 105

second lines 3 105

30 6.4.3,11., second line 200 ns 36 6.7.2. ,B.,1. APD TS with aperture

below.

37 G. , 3. AP

43 Table 1, line (2) 147

44 Table 2, line (1) 104

47 H., third line etched glass

49 G. ,6. ,a . , and b. mft 50 H. , line 2, fourth word of

51 7., second paragraph,

second line

with

57 7., right, second line <200 ns

61 Source of uncertainty. Precision beami tern 3 down , f i rst

col umn splitter attenuator

61 Date , item 4 down

,

third column

4/82

63 8.3,3., first line are

66 References, [1], November

[8], third line Paper 2097

Correction

October

ground-gl ass m

1 mm

for pulse rate,

for cw input time

interval

from the LED.

3 . 105

3 . 105

180 ns APD TS with aperture attached (see

8. below).

HP

47

106

ground-glass

Mn

omit "of"

within

<180 ns Precision beamsplitter attenuator

(beam unpolarized)

8/85

is

October

25(2)

67

OTS R£S£AKCH INFORMATION CENTER

DOCUMENTATION OF THE NBS APD AND

PIN CALIBRATION SYSTEMS FOR

MEASURING PEAK POWER AND

ENERGY OF LOW-LEVEL 1.064 |xm

LASER PULSES

A.L. Rasmussen

A. A. Sanders

Electromagnetic Technology Division

Center for Electronics and Electrical Engineering

National Engineering Laboratory

National Bureau of Standards

Boulder, Colorado 80303

December 1985

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

CONTENTS

Page

1. Introduction and Background 1 1.1 Introduction 1 1.2 Background 2 2. Description of the NBS APD and PIN Peak Power and Energy

Calibration Service 2

2.1 APD Silicon Photodiode Transfer Standard Capability 2 2.2 PIN Silicon Photodiode Transfer Standard Capability 3

2.3 Companion Publication on Transfer Standards 3

3. Design Philosophy Using APD and PIN Transfer Standards 3

4. APD and PIN Transfer Standard Calibration Support Equipment 4

5. APD and PIN Transfer Standard Calibration Support Equipment

Operation 5 5.1 Modulator Power Supply 8

5.2 Accousto-Optic Light Modulator 8

5.3 Shutter System for Timed Input 8

5.3.1 Time Generator 8

5.3.2 Dual Preset Controller 9

5.3.3 Pulse Driver Circuit (PD-6) 9

5.4 Square-Wave Generator 9

5.5 Relay Switch 9

5.6 Timer/Counter 10

5.7 Electronic Counter 10

5.8 Oscilloscope for Monitoring cw and Pulsed-Beam Operation.... 10

5.9 Red Light Indicator for Showing Pulsed-Beam Operation 11

5.10 DC Voltage Power Supply 11

5.11 APD Bias Power Supply 11

5.12 PIN Bias Power Supply 11

5.13 Pulse Generator 12

5.14 Oscilloscope for Readout 12

5.15 Digital Voltmeter for Bias Voltage Measurements 13

5.16 Pulse Height Analyzer for Readout 14

5.17 APD Transfer Standard Shutter System 15

5.17.1 Pulse Generator for Shutter System 15

5.17.2 Operation Indicator Switch 15

5.17.3 Pulse Driver Circuit (PD-5) 15

5.18 Amplifier and Light Sensor for Shutter Timing

Measurement 15

5.19 Pulser for Test Pulses 16

5.20 Charge Amplifier 16

5.21 Linear (Shaping) Amplifier 16

5.22 Wideband Amplifier 16

6. Procedures for the Modulated cw Measurement System and for

the Transfer Standards 17

6.1

The Modulated cw Measurement System 17

6.1.1 Laser Alignment and Operation Procedures 17

6.1.2 Laser to the Modulator Alignment and Operation

Procedures 19

6.1.3 Modulator Alignment and Operation Procedures 19

6.1.4 Procedures for Generating the Diameter and

Collimation of the Beams at about 1 m Distance

after Interacting with the Precision Beamsplitter

Attenuator 20

i i i
6.1.5 Modulator to Detector Alignment and Operation

Procedures 21

6.1.6 Procedures for Realignment of the Modulated

cw Measurement System 22

6.1.7 Shutter Timing Measurement Procedures 22

6.2 Redw 3 (TC15) Transfer Standard Alignment and

Operation Procedures 22

6.3 APD Transfer Standard (APD TS) Procedures 23

6.3.1 APD TS Alignment and General Operating

Procedures 23

6.3.2 APD TS System Parts 24

6.3.3 APD TS System Setup Procedures 24

6.3.4 APD TS Calibration Procedures--cw Interval,

Pulse Rate, and Background Measurements 25

6.3.5 APD TS Calibration Procedures--Peak Power

Measurements 25

6.3.6 APD TS Calibration Computation 26

6.3.7 APD TS Uniformity Measurement Procedures 27

6.3.8 APD TS Field of View Measurement Procedures 27

6.3.9 APD TS Impulse Response Correction Procedures 27

6.3.10 Procedures for Measuring the Inequivalence of

Pulsed and cw Power 28

6.3.11 APD Transfer Standard Optics 28

6.4 PIN Transfer Standard (PIN TS) Procedures 28

6.4.1 PIN TS Alignment and General Operation

Procedures 28

6.4.2 PIN TS System Parts 29

6.4.3 PIN TS System Setup Procedures 29

6.4.4 PIN TS Calibration Procedures--Preparation

Procedures and Pulse Rate and Background

Measurements 30

6.4.5 PIN TS Calibration Procedures--Energy

Measurements 31

6.4.6 PIN TS Calibration Computation. 32

6.4.7 PIN TS Uniformity Measurement Procedures 33

6.4.8 PIN TS Scan Procedures for Uniformity

Measurement 33

6.5 Temperature Controllers for APD and PIN Transfer

Standards 33

6.6 Procedures for Calibration of Customer's Instrument

at NBS 33

6.7 APD TS Measurement Instructions for the Customer's Site 35

6.7.1 General Instructions 35

6.7.2 APD Transfer Standard Operating Instructions 36

6.8 PIN TS Measurement Instructions for the Customer's Site 47

6.8.1 General Instructions 47

6.8.2 PIN Transfer Standard Operating Instructions 48

7. Analysis of the Systematic and Random Errors 51

7.1 Analysis of Errors of the APD Transfer Standards 56

7.2 Analysis of Errors of the PIN Transfer Standards 57

7.3 Calibration of Redw 3 (TC15) Transfer Standard 58
7.4

Summaries of the Uncertainties at the 95 Percent

Confidence Interval of Calibrations of the APD and the

PIN Transfer Standards 59

8. Procedures for Quality Control of the Modulated cw Measurement System and of the APD and PIN Transfer Standards 63

8.1 Alignment Verification 63

8.2 Optical Surface Maintenance 63

8.3 Laser Mode and Stability Requirements 63

8.4 Shutter for Timed Laser Input Calibration 63

8.5 Redw 3 Transfer Standard Calibration 63

8.6 Oscilloscope Calibration 63

8.7 Time and Frequency Measurement Equipment Calibration 64

8.8 APD and PIN Transfer Standard Calibration 64

8.9 APD and PIN Transfer Standard Uniformity and

Field of View Calibrations 64

8.10 Pulse Height Corrections of APD Transfer Standards

from Impulse Response Measurements 64

9. Computer Programs for Computation and Treatment of APD

and PIN Transfer Standard Calibration Data 64

10. Location of Programs and Data Files..... 65

10.1 Main Disc APD Rasmussen 65

10.2 Main Disc PIN Rasmussen 66

10.3 Redw 3 (TC 15) 66

10.4 Impulse Response 66

11. Data File Identification 66

12. Computer Calibration Data of Redw 3 and APD and PIN

Transfer Standards 66

13. References 66

v

Documentation of the NBS APD and PIN Calibration

Systems for Measuring Peak Power and Energy

of Low-Level 1.064 ym Laser Pulses

A. L. Rasmussen and A. A. Sanders

National Bureau of Standards

Boulder, Colorado 80303

National Bureau of Standards APD (avalanche) and PIN silicon

photodiode transfer standards are documented for a calibration service to measure 1.064 ym laser pulses from ~10“ 8 to ~10-4 W peak

power and ~10-16 to ~10-11 J energy. A modulated cw measurement

system generating known low-level pulses is described. Calibration

support equipment, systematic and random errors, and computer programs and calibration data are also described.

Key words: APD transfer standards; beamsplitter attenuator;

calibration procedures; calibration service; low-level laser

measurements; modulated cw measurement system; 1.064 ym laser pulse

measurements; PIN transfer standards; pulse energy; pulse peak

power

1. Introduction and Background

1.1 Introduction

This report describes documentation, maintenance, and operational procedures for the APD and PIN calibration systems. These systems consist of APD

(avalanche) and PIN silicon photodiode transfer standards (TS) to measure peak

power and energy, respectively, of fast, low-level 1.064 ym laser pulses.

Similar systems were developed for the Air Force, Army, and Navy standards

laboratories.

The culmination of this effort is a low-level calibration service of APD

and PIN systems that are traceable to the national standards.

Disclaimer: Commercial equipment is identified to adequately specify procedures. This does not imply recommendation or endorsement by the National

Bureau of Standards, nor does it imply that the equipment identified is

necessarily the best available for the purpose.

1
1.2 Background

With the development of guidance receivers and range finders detecting

low-level 1.064 pm laser pulses reflected from objects, the need arose for

calibrating the peak power and energy of these pulses. Work was sponsored by

the Calibration Coordination Group and NBS to develop transfer standards

capable of measuring 1.064 pm, 10 to 30 ns laser pulses to 10" 16 J and 10" 8 W

within about 20 to 25 percent uncertainty.

As an intermediate goal, a nanojoule transfer standard was developed.

Commercial instruments already available were calibrated against an existing

transfer standard in a precision beamsplitting system from 10 -5 to 10" 9 J cw and from 10" 7 to 10 -11

J Q-switched pulses. Results were independent of

whether the energy was pulsed or cw. The instruments also integrated the

ambient light. Therefore, room light and the solid angle for light entering

the devices were reduced to low values. The remaining extraneous light was subtracted from the laser light measured. The instruments were also calibrated against each other.

For levels lower than the above, devices were built from commercial

state-of-the-art APD and PIN silicon photodiodes, preamplifier, and amplifier

components. An acousto-opti cal ly modulated cw measurement system was developed to generate nanosecond pulses and to calibrate the devices. The modulator fed a precision beamsplitter-attenuator system that generated cw and

pulsed (~200 ns FDHM [full duration half maximum]) beams of known power and

energy. APD and PIN transfer standards in the reflected beams of the beamsplitter attenuator were calibrated against a commercial or PIN transfer

standard in a higher-level beam. Some were also calibrated in a precision

beamspl i tter-attenuator system using Q-switched pulses ~30 ns FDHM. These

measurements showed that calibrations were independent of pulse duration.

Operating in the modulated cw measurement system, these APD and PIN

transfer standards were determined capable of calibrating other devices to

~10 -8 W peak power and ~10” 16 J energy, respectively, in less subdued room

light than the higher-level integrating devices described above. They are described in reference 1.

2. Description of the NBS APD and PIN Peak Power and Energy

Calibration Service

2.1 APD Silicon Photodiode Transfer Standard Capability

APD 5-1 and APD 5-5 (first digit 5 = APD and second digit instrument

identification)

.

Maximum collector area using aperture: 0.947 cm2.

Calibrated range: ~10-7 to ~10 -4

W for peak pulse power.

Minimum calibration region at NBS using the precision beamsplitter

attenuator: ~10” 8 W.

Power density range: determined by detector being calibrated.

2
2.2 PIN Silicon Photodiode Transfer Standard Capability

PIN 4-1 and PIN 4-3 (first digit 4 = PIN and second digit instrument

identification)

.

Diode collection area: PIN 4-1 0.819 cm 2

, PIN 4-3 1.002 cm2

.

Calibrated range: ~10" 14 to 10" 11 J for pulse energy.

Minimum calibration region at NBS using the precision beamsplitter

attenuator: ~10-16 J.

Energy density range: determined by detector being calibrated and

whether a collector is used.

These transfer standards are portable, so that personnel may make

measurements at the customer's site.

2.3 Companion Publication on Transfer Standards

"A system for measuring energy and peak power of low-level 1.064 ym laser

pulses," A. A. Sanders and A. L. Rasmussen, NBS Technical Note 1058, November

1982 (also listed as reference 1).

3. Design Philosophy Using APD and PIN Transfer Standards

To measure the low levels enumerated above, NBS chose to calibrate

transfer standards assembled from commerci al^ components because they are simpler to develop than absolute standards and components. NBS used available

transfer standards calibrated by existing national standards, the Q- and

C-series calorimeters, and precision beamsplitter attenuators. These were

used to generate pulses of known and variable power and energy at the levels

of interest. These pulses were used to calibrate the APD and PIN transfer

standards. APD signals were amplified by a transimpedance preamplifier or a preamplifier on the same chip and by a wideband amplifier at the lower levels

of calibration. PIN signals were amplified and integrated by a charge amplifier and by a linear amplifier. The peak voltages of the output of the APD

and the PIN systems are proportional to the peak power and the energy of the

pulses, respectively.

The APD has inherently small size and nonuniform responsi vi ty . To overcome these problems, the largest APD available at 3 mm diameter was used with

a focusing lens (collector) and etched glass diffuser in front of it. Still,

the responsi vity in volts/watt varied over the portion of the collector area designated for measurements. Consequently, the uniformity of the responsi vi ty

and the field of view were statistically determined. An ir-enhanced APD from

the same manufacturer, which became available after the APD transfer standards

were completed, can be used if the need occurs, because they are reported to

be more uniform and higher in responsivity than the APD described in this

report.

3
Since the APD systems designed have <100 MHz bandwidth, corrections to

the peak voltage of the fastest pulses are necessary for dependable calibrations as a function of pulse duration. These corrections are calculated from

the convolution of Gaussian pulses with the impulse response of the system.

The charge and linear amplifiers of the PIN system integrate the current

and shape the pulse. A pulse emerges whose peak voltage is proportional to

the energy in the original PIN pulse. Peak voltages of pulses are read out on an oscilloscope and/or a pulse height analyzer (PHA). The latter records the occurrence and amplitudes of pulses from which one can determine the average

amplitude and stability of the laser output.

Because of the appreciable temperature coefficients of components, the

APD and its preamplifier and the PIN were placed in a temperature-control led

environment. It consists of a thermally insulated box containing the components and a dc temperature controller circuit operating at some temperature

around 30° to 35°C. The silicon photodiode lies in the center of a hole

inside the box. A temperature meter outside or a ribbon thermometer indicates

the inside temperature.

The dc bias is rectified 20 kHz and contributes little noise to the APD

and PIN outputs.

4. APD and PIN Transfer Standard Calibration Support Equipment

a. Modulator power supply, IntraAction Corp. Model ME 40T, light modulator signal processor, S/N 2059.

b. Acousto-optic light modulator, IntraAction Corp. A0M 40 IR, S/N 1639.

c. Shutter system.

1. Time generator.

2. Dual preset controller, Computer Measurement Co., Model 913.

3. Pulse driver circuit (PD-6).

d. Square-wave generator, Interstate F77 20 MHz log linear sweep generator, NBS 147582.

e. Relay switch.

f. Timer/counter, HP 5300A measuring system and HP5304A timer/counter,

NBS 142535.

g. Electronic counter, HP 5245L, NBS 120743.

h. Oscilloscope, cw and pulsed beam operation monitor, Tektronix 535A,

NBS 111933.

i. Red light indicator for showing pulsed beam operation.

j. DC voltage power supply, HP 6214A.

k. APD bias power supplies, Bertan Assoc. Inc., Model 602B-15N (APD 5-1)

and Model 602B-15P (APD 5-5).

l. PIN bias power supplies, Bertan Assoc. Inc., Model 342.

m. Pulse generator, HP 8013A.

n. Oscilloscope readout, Tektronix 7904, NBS 145935.

1. APD readout, dual trsce amplifier, 7A24, 50 n.

2. PIN 4-3 readout, dual trace amplifier, 7A12, 1 mft. 3. PIN 4-1 readout, dual trace amplifier, 7A26, 1 mft, NBS 146251.

4. Dual time base, 7B92A.

o. Digital voltmeter for bias voltage measurement, Dana 4600.

p. Pulse height analyzer readout, Tracor Northern TN-1706.

4
q. APD transfer standard shutter system.

1. Pulse generator, Wavetek Model 142 HF VCG generator.

2. Operation indicator switch.

3. Pulse driver circuit (PD-5).

r. Amplifier SC-2 and light sensor for shutter timing measurement.

s. Pulser, Tennelec, TC 812.

t. Charge amplifier, Tennelec, TC 162, S/N 326 (PIN 4-1) and S/N 293

(PIN 4-3).

u. Linear (shaping) amplifier, Tennelec, TC 222, S/N 386 (PIN 4-1) and

S/N 230 (PIN 4-3).

v. HP 462A wideband amplifier, S/N 551-01063.

5. APD and PIN Transfer Standard Calibration Support Equipment Operation

The seven diagrams below show how the calibration support equipment fit

into the various systems used.

Diagram 1. Acousto-optic light modulator system.

Diagram 2. Shutter system for timed input.

5
Diagram 3. Relay switch system for alternating between pulsed and

cw laser beams at a specific duty cycle.

Diagram 4. APD TS system.

6
Diagram 5. PIN TS system.

Diagram 6. APD TS shutter system.

Diagram 7. Amplifier and light sensor system for shutter timing measurement.

7
5.1 Modulator Power Supply

The modulator power supply (see diagrams 1 and 3) is set as follows:

Control

Carrier level

0 to 10

Video input

RF output

Setting or Connection

(1) APD and PIN about 0.5 to 6.0

(2) PIN only above 6.0 (first diffracted beam

slightly distorted)

(1) Pulse generator at least +3 V peak for pulsed

first diffracted beam.

(2) DC PS +3 V for cw first diffracted beam

(3) Analyzer connection of relay switch for

alternating between 1 and 2.

Acousto-optic light modulator

5.2 Acousto-Optic Light Modulator

The acousto-optic light modulator (see diagrams 1 and 3) is set as follows:

Control Setting or Connection

Input

Left-right

translator

Up-down translator

Vertical angle

Horizontal angle

RF output of modulator power supply

Center beam in front and rear windows

Center beam in front and rear windows

Adjust two rear screws near output window for

maximum first diffracted beam*

Rotate modulator in horizontal plane for

maximum first diffracted beam*

Modulator at beam focus region following the

first lens

5.3 Shutter System for Timed Input

The shutter system (see diagram 2) is set as follows:

5.3.1 Time Generator

Control

Off/on

Start

Reset

Time interval

- Output

Setting or Connection

On

Press to start time

Press to stop time

1, xl (one second)

Dual preset controller input

*With an ir-to-visible converter and a black screen immediately in front of

the nearest aperture, the beam is observed on the right of the main beam.

8
5.3.2 Dual Preset Controller

Control Setting or Connection

Off/on

Input

Red button

Reset input

Limit--pulse relay dial

Limit--recycle dial

Output

On

Time generator - output

In opens shutter,

Out closes shutter

Press for zero time

Limit, 20 (shutter opens at 20 s)

Limit, 120 (shutter closes at 120 s)

Pulse driver circuit

5.3.3 Pulse Driver Circuit (PD-6)

Control

Input

Shutter manual

Open/closed

Manual /automati

c

timer

Output

5.4 Square-Wave Generator

Setting or Connection

Dual preset controller output

Closed

Automatic timer

Shutter relays

The square-wave generator (see diagram 3) is set as follows for APD calibrations:

Control Setting or Connection

Sweep limit

Frequency multiplier

Offset

Waveform

Mode

Output P-P into

50 n Output Z0

= 50 n

On/off

About 4.93

Var. sym xl

sym 0.01

Above the line

Square

Conti nuous

15 V

2.0 V, oscilloscope input or red indicator

light and square-wave input of relay switch

On with 2-hour warmup

5.5 Relay switch

Relay switch (see diagram 3) is set as follows for APD calibrations:

Control Setting or Connection

+3 V dc

Input frequency

with 50 n feedthrough

termi nati on Input square wave

To analyzer

dc PS, +3 V Pulse generator output (+) when

used otherwise disconnected

Square-wave generator 50 n output

Video input of modulator power supply

9
5.6 Timer/Counter

The timer/counter (see diagrams 3 and 7) is set as follows:

Control

Com-Sep-Chk

A input

B input

A input

B input

Function switch

Auto

Level

5.7 Electronic Counter

Setting or Connection

Com

(1) Analyzer connection of relay switch with

pulse generator disconnected

(2) Pulse generator output

(3) SC2 amplifier gate output

No connection

XI, AC, and + XI, AC, and +

(1) Above, 0.1 ms for cw duration

(2) Above, auto for pulse rate

(3) Above, 1 ms for shutter gate time

Pulse generator output for counting

pulses

(1) Lower + and upper - for cw cycle

(2) Lower - and upper + for pulsed cycle

The electronic counter (see diagram 3) is set as follows:

Control Setting or Connection

Signal input

ac/dc

Sensitivity

(V RMS)

’

Time base

Functi on

ac, pulse generator output for frequency

0.1 (50 V max)

1 s Freq

5.8 Oscilloscope for Monitoring cw and Pulsed-Beam Operation

The oscilloscope (see diagram 3) is set as follows:

Control Setting or Connection

Channel

at 1 Mft input

dc/ac

Polarity

Volts/cm

Time base

Stabi 1 i ty/

triggering level

Triggering mode/

trigger slope

Horizontal display/

magni f i er Variable/time/cm

A

Square-wave generator

= pulsed, down = cw)

dc

Normal (+)

0.5

A

Triggering mode auto

Triggering mode auto

A/off

Off/5 ms (arbitrary)

-ft maximum output (up

10
5.9 Red Light Indicator for Showing Pulsed-Beam Operation

(See diagram 3.)

Control

Red light

on/off

Setting or Connection

Square-wave generator 50 ft maximum output (red light on = pulsed beam

operati on)

5.10 DC Voltage Power Supply

The dc power supply (see diagrams 1 and 3) is set as follows:

Control Setting or Connection

Meter selection

volts/amps

Adjust

vol tage/current

Termi nal

s

+ , 1

Volts

+ 3 V dc

+ and -,

(1) +3 V dc of relay switch

(2) Video input of modulator power supply

5.11 APD Bias Power Supply

The negative bias power supply for APD 5-1 and the positive bias power

supply for APD 5-5 (see diagram 4) are set as follows:

Control Setting or Connection

Rear output (- PS)

Rear output (+ PS)

HV adjust

Ten-turn pot

APD 5-1 bias* and VM - 338.0 V APD 5-5 bias* and VM + 410.0 V Do not adjust

Pretested for correct polarity and voltage

with the APD disconnected

5.12 PIN Bias Power Supply

The PIN bias power supply (see diagram 5) is set as follows:

Control Setting or Connection

Positi ve/negati ve polarity

Meter with magnifier

Switch 0, 0.5, and 1 kV

0 - 1000 V Ten-turn pot

On/off

Rear J1

high voltage output

Negative (never changed)

Not used

0 with switch handle removed

Pot-rdg 1+80

VM-rdg -180.0 V On

Neg bias of PIN diode

and ungrounded VM terminals

*Each APD has its own bias level.

11
5.13 Pulse Generator

The pulse generator (see diagrams 1 and 3) is set as follows:

Control Setting or Connection

Rate Hz

Pulse period (s)

Pulse delay (s)

Pulse width (s)

Amplitude (V) - Amplitude (V) + Offset (V) - Offset (V) + Output (-)

Output (+)

(1) APD about 500

(2) PIN < 300,000

(3) Manual single pulse

APD and PIN 0.1 ms - 10 ms PIN 1 \is - 0.1 ms

35 ns

10 ns - 1 y s, APD 200 ns and PIN 100-200 ns

5 scale, 3-4 V

5 scale, 3-4 V Off

Off

Time base of oscilloscope measuring pulses

(1) Video input of modulator power supply for

pulsed first diffracted beam

(2) Frequency input of relay switch (with

50 ft feedthrough termination) for alternating between cw and pulsed first diffracted beam

(3) Electronic counter ac input or timer/

counter A input with auto for measuring

pulse frequency

5.14 Oscilloscope for Readout

The readout oscilloscope with plug-ins (see diagrams 4 and 5) is set as

fol 1 ows:

(1) The 50 ft dual-trace amplifier for APD readout (used with one mainframe only) on left vertical.

Control Setting or Connection

Ch2 50 ft Polarity

+Up/i nvert

Position

Vol ts/di

v

Off/dc

Trigger source/

display mode

APD output/wideband amplifier

(1) +Up without wideband amplifier

following APD

(2) Invert with wideband amplifier following APD

Two large divisions for baseline if possible

0.005 to 0.5 V/division

(1) Off for baseline where it coincides with

no input reading

(2) DC for pulses

Ch2/Ch2

(2) The 1 Mft dual-trace amplifier (the 12 unit) for PIN readout (used

with one mainframe only) on right vertical.

12
Control Setting or Connection

Chi 1 Mn, 24 pF Linear amplifier readout of PIN 4-3

Polarity +Up/invert +Up

Offset (same as Two large divisions for baseline if possible

position)

Volts/div 0.020 to 2 V/ division

AC/GND/DC/DC and offset (1) GND for baseline where it coincides with

no input reading

(2) DC for pulses

Display mode/ Chl/Chl

trigger mode

(3) The 1 m

with one dual-trace amplifier (the 26 unit) for PINmainframe only) on left vertical.

readout (used

Control Setting or Connection

Ch2 1 Mn, 24 pF

Polarity +Up/invert

Position

BW

Full/20 MHz

Volts/di

v

AC/ GND/ DC

Trigger source/

display mode

Linear amplifier readout of PIN 4-1

+Up

Two large divisions for baseline if possible

Full

0.020 to 2 V/division

(1) GND for baseline where it coincides with

no input reading

(2) DC for pulses

Ch2/ch2

(4) The dual

only) on time base for APD and PIN readouts (used with one mainframe

right vertical.

Control Setting or Connection

Main triggering

mode/coupl i ng/ source

SI ope/level

Tri g'

d

Position

Dly'd sweep operation

Term

Main trig in

Norm/dc/ext or line

Trig'd light on

Horizontal adjustment

Step 1. Dly'd time/div pulled out, rotated

for delayed sweep rate, and pushed in.

Step 2. Delayed sweep rate determined by

Dly'd time/div switch, Time/div or Dly

time switch, and Delay time mult dial

setting. Runs after delay time control

turned fully clockwise into detent.

Cal in.

Out 50 Q. Pulse generator output (-)

5.15 Digital Voltmeter for Bias Voltage Measurements

The digital voltmeter for bias voltage measurement (see diagrams 4 and 5)

is set as follows:

13
Control Setting or Connection

Function switch

Range

Input

DCV

1000 V Bias supply output connected to input and low

terminals without ground

5.16 Pulse Height Analyzer for Readout

The pulse height analyzer (see diagram 5), used for a second readout in

the PIN TS for the Air Force and the Navy, is set as follows:

Control Setting or Connection

ULD

LLD

Zero

About 10,0

About 0,50

Preset about 0,50 (adjustment will chame

cal i bration)

Mode

Gate

Input

PHA

Not used

Bipolar output of linear amplifier and oscilloscope amplifier (if used)

Hori zontal

Preset

Conversion gain

Offset

Region enter/erace

and cursor

Full

Cursor

1024 (occasionally 2048)

Zero

The channel number (proportional to the peak

voltage) is horizontal and the number of

pulses in each channel is vertical on the

display unit. The cursor can be made to stop

on a channel from which you can read the

channel number and the number of pulses in a channel

.

To integrate the number of pulses in a region, enter the lower and upper channel

limits using the enter switch and the cursor.

Vertical scale

Erase the integration of the region using

erase and the cursor < lower channel limit.

100-1 M

Time base

Pen

CAL XY and Ext

Clear data/time

Add/subtract

Acqui re Display unit

Vertical scale adjusted to find peak channel

with greatest number of pulses.

9 , °° Set

Not applicable

Clear as needed

Add (up position)

Press to take data

Adjust focus, intensity, horizontal expand

and position, and vertical size and position

as needed

14
5.17 APD Transfer Standard Shutter System

A shutter system (see diagram 6) for eliminating reflection from an APD

TS during measurements in a lower-level beam of the precision beamsplitter

attenuator is set as follows:

5.17.1 Pulse Generator for Shutter System

Control Setting or Connection

PWR OFF/FREQ. Hz

Main dial

30 V P-P max

Freq * 10

symmetry

DC offset

Output atten (dB)

50 n out

X.01

5 (above line), max

Off

Off

-10

Input of operation indicator switch

5.17.2 Operation Indicator Switch

Control Setting or Connection

Input

Off/on

Red light

Output

50 n out of pulse generator

On

On when shutter closed blocking APD TS

Pulse driver circuit ( PD- 5

)

5.17.3 Pulse Driver Circuit (PD-5)

Control

On/off

Shutter manual

open/cl osed

Manual /automati

c

timer

Output

Setting or Connection

On

Cl osed

Automatic timer

Shutter relays

5.18 Amplifier and Light Sensor for Shutter Timing Measurement

(See diagram 7.)

1. The SC-2 amplifier is set as follows:

Control Setting or Connection

Off/on

+ Gate output

Sensor

Zero set/±100 meter

Gain/±100 meter

On

Timer/counter, A input, 1 ms Light sensor

Adjust to zero Adjust gain to drive the timer/counter

15
2. Light sensor is set as follows:

Control

Input

Output

5.19

Pulser for Test Pulses

The pulser (see diagram 5) is set as follows:

Setting or Connection

Main beam of precision beamsplitter attenuator

SC-2 amplifier, sensor

Control Setting or Connection

Pulse height

Relay on/off

Cal

Pol +/-

A di rect output 50 n

B direct output/ext atten input

Output

5 V/0.4 ms

1 V/2.0 ms Attenuati on 2, 2, 5 10 , 10 , 10

C output 50 n

Clockwise increases height

On

To calibrate pulse height

Minus

5 V/0.4 ms

Use with C output

Use with attenuation switches.

Connect to the linear amplifier signal input

mi nus

.

Connect to the test terminal of the charge

amplifier.

Connect the charge amplifier to the linear

ampl i fier.

5.20 Charge Amplifier

The charge amplifier operation (see diagram 5) is described in section 6.

5.21 Linear (Shaping) Amplifier

The linear (shaping) amplifier operation (see diagram 5) is described in

section 6.

5.22

Wideband Amplifier

The wideband amplifier operation (see diagram 4) is described in sec- tion 6.

16
6.

Procedures for the Modulated cw Measurement System and

for the Transfer Standards

The modulated cw Nd:YAG laser measurement system produces low-level cw and pulsed beams of known peak power and energy. See figure 6-1, low-level

modulated cw measurement system. These beams provide the means for calibrating low-level transfer standards.

6.1 The Modulated cw Measurement System

6.1.1 Laser Alignment* and Operation Procedures

1. Align HeNe laser beam through the front and rear faces of the Nd:Yag

rod alone.

2. Insert and align rear mirror with HeNe beam returning on itself

through the rod.

3. Insert and align front mirror with HeNe beam returning back on itself

through the rod.

4. Insert the cavity aperture, with about a 1.5 mm diameter hole, midway

between the rod and rear mirror with HeNe beam passing through it.

5. Remove the HeNe laser.

6. Open water valves on each side of the water filter.

7. Open the outlet water valve and then the inlet water valve for cooling the distilled water pumped through the laser head.

8. Maintain distilled water level within a couple of centimeters of the

top of the stainless steel tank inside the power supply cabinet.

9. Raise the wall power switch to the on position.

10. Turn on the laser console.

11. Turn the current dial to about 0.55.

12. In about 30 s, fire laser.

13. Adjust the laser current between 15 and 17 A depending on age of the

flash lamp.

14. Set the power meter at the highest power scale.

15. Tune the laser for maximum output without the aperture by adjusting

the rear and the front mirrors.

16. Insert the aperture between the rear mirror and the laser rod and

adjust the position of the aperture with the micrometer adjustments

for maximum laser output using an available detector.

17. Insert the collimator with the large knob side next to the laser output mi rror.

18. Assuming the collimator has been preset, align the laser beam through

the center of the collimator by adjusting the large knobs of the collimator.

19. The position of the laser beam may be changed slightly by adjusting

the large knobs of the collimator while someone observes the orientation of the beam in the measurement system.

20. If the laser head and water tank feel cool, the laser may continue

operation.

21. If the laser head and the water tank feel warm, the laser is turned

off as described below.

22. If the laser is operating at a warm temperature, the water valve in

the power supply cabinet may need replacement.

*An available autocollimator may easily be used to also align the laser.

17
Figure 6-1. Low-level modulated cw measurement system.
23. If the laser output is unstable after 1 to 2 h at 15 to 17 A, the

laser current may be increased to 17 to 19 A for relatively short

peri ods

.

24. The laser current may be increased from 19 to 22 A, but the laser

output may actually decrease.

25. To turn off the laser , turn laser console dial to zero.

26. After 10 to 30 min cooling time, turn off the laser power supply

switch on the console when the laser head is cool.

27. Close the inlet water valve and then the outlet water valve.

28. Lower the wall power switch to the off position.

6.1.2 Laser to the Modulator Alignment and Operation Procedures

1. Open the shutter between the rooms.

2. Adjust the first aperture to pass only the main portion of the beam.

3. Close the shutter between the rooms.

4. Open the C-series shutter.

5. Remove the C-series lens following the C-series shutter.

6. Insert the first mirror to direct the laser beam at a right angle to

the left.

7. Open the shutter between the rooms.

8. Adjust the first mi rror to direct the laser beam to the second and

third mirrors that lower the height of the beam and convey the laser

beam at a horizontal angle through the optical components that follow

in the system.

9. Since the first mirror is removed whenever the C-series system is

used, it may need slight adjustment of its micrometer knobs when put

back into position or when the system is slightly out of alignment.

10. When the system is initially set up, the second and third mirrors are adjusted angularly to direct the be^im into the first lens and rarely

will need changing thereafter.

11. When the system is initially set up, the first lens is adjusted to

direct the beam through the modulator and rarely will need changing

thereafter.

12. When the system is initially set up, the modulator is permanently

placed at a fixed distance from the first lens at the neck of the

beam to yield fast rise and fall times of the modulator pulses.

13. Close the shutter between the rooms at the end of these procedures.

6.1.3 Modulator Alignment and Operation Procedures

1. Turn on the modulator power supply.

2. Connect the rf output of the modulator power supply to the acoustooptic light modulator.

3. Turn the carrier level of the modulator power supply to 6.

4. Turn on the dc power supply to +3 V.

5. Open the shutter between the rooms.

6. Connect the dc power supply to the video input of the modulator power

supply to generate a cw first diffracted beam on the right of the

main beam.

7. Remove the main beam absorber that follows the second lens.

8. Place a black absorbing surface in front of the aperture (iris) that

follows the beam absorber.

19
9.

10

11

12

13

14

15

16

17

18

19

20

21

22

23

6.1.4

1

2

Adjust the horizontal and vertical angles of the modulator for maxi- mum brightness of the first diffracted beam on the right of the main

beam (about 11 mrad separation).

Approximately center the beam in the modulator.

Replace and adjust the absorber that follows the second lens to

absorb the main beam and to pass the first diffracted beam on the

ri ght.

Control the modulator output by adjusting the laser current and/or

the modulator power supply carrier level.

Generate modulator pulses by applying pulses with amplitudes about

3 to 5 V from the pulse generator to the video input of the modulator

power supply (carrier level input >2 V is "on" and <0.8 V is "off").

Pulses with carrier levels above six are distorted but may be used

for energy measurements.

Determine the pulse duration [full duration half maximum (FDHM)] from

oscilloscope-observed APD pulses synchronized by pulse generator

pulses or from oscilloscope-observed pulse generator pulses corrected

by substracting 10 ns. Use 100 to 180 ns FDHM laser pulses for PIN transfer standard calibrations.

Use about 200 ns FDHM laser pulses for APD transfer standard calibrations.

The modulator may generate pulses from 1 to 107 pps.

Use laser pulse rates from ~100 to ~105 -106 pps for PIN calibrations.

Use laser pulse rates about 500 pps for APD calibrations.

Use the cw first diffracted beam to align the system following the

modulator and to align detectors with alignment mirror and iris or target in front.

Use the pulsed beam to align detectors more precisely.

Use the cw and pulsed beams to generate beams or pulses of known

energy and peak power.

Procedures for Generating the Diameter and Collimation of the Beams

at about 1 m Distance after Interacting with the Precision Beamsplitter

Attenuator

To generate ~3 mm diameter, ~3 mrad divergence, laser beams at about

1 m distance after interacting with the precision beamsplitter

attenuator, we inserted a second lens, the lens after the modulator,

and calculated and/or measured the lens and beam properties.

The focal length and position of the second lens were calculated from

the formula

where

f = 0.51 m (FL of the second lens)

d

1 = 0.64 m (distance between the modulator and the second lens)

d = 2.55 m (distance between the second lens and the detectors

for calibration)

20
3. The diameter of the beam where the detectors are calibrated was calculated from the magnification formula and measurement of the diameter of the beam passing through the modulator as follows:

where

M = ~3 nm (diameter of the beam at the detectors for calibrati on)

Dm

= ~0.6-0.8 mm (diameter of the beam through the modulator)

4.

The formulas for the diameter (Du) of the beam through the modulator

were compared to the measured value above

D.. = — — = 0.24 rrm (Gaussian beam)

M TT

and

[> M

= 2.44 — = 0.46 mm (Airy disk)

where

ji = 0.89 m (measured FL of the first lens)

X = 1.064 ym (wavelength of beam)

D

i = 5 mm (diameter of the beam at the first lens)

5.

Since calibrations of transfer standards with ~3 mm and ~6 mm diameter generated beams were similar, the ~3 mm beam was adopted for its

convenience in aligning beams and in evaluating the uniformity of the

responsivity of the transfer standard detectors.

6.1.5 Modulator to Detector Alignment and Operation Procedures

1. Generate a cw, first-order diffracted modulator beam (see 6.1.3,

above).

2. Open the shutter that allows the modulator first-order beam to enter

the precision beamsplitter attenuator system for specified times.

3. At a specific distance from the modulator, the second lens allows the

beam to pass through it with the desired orientation of the beam in

the precision beamsplitter attenuator system and rarely needs changing thereafter.

4. Orient the absorber following the second lens to absorb the main beam

and to pass the first diffracted one on the right without striking

the outside surface of the absorber.

5. Adjust the apertures to allow only the first diffracted beam to pass

through them.

6. The precision beamsplitter wedge should have the thicker portion on the left of the incoming beam.

21
7. The beam should pass through approximately the center of the precision beamsplitter attenuator parallel to the top of the optical table

at about 20 cm.

8. Slightly adjust the first mirror as needed to orient the beam through

the center of the aperture in front of the Redw 3 transfer standard.

9. To align the precision beamsplitter attenuator, a mi rror is permanently placed in the (m = 2) beam about 1.1 m from the beamsplitter.

10. A white card is temporarily placed in the (m = 3) beam about 1.1 m from the beamsplitter.

11. A white card with a hole is temporarily placed in the (m = 2) beam.

12. The (m =.2) beam and the reflected (m = 2) beam are aligned through

the hole in the card.

13. The (m = 3) beam and the reflected (m = 2) beam are made to coincide

on the card in the (m = 3) beam by adjusting the micrometers of the

beamsplitter.

14. Repeat step 12.

15. Remove the card in the (m = 2) beam.

16. Repeat step 13.

17. Repeat the above steps until no further adjustments are needed.

18. The peak power or energy of each beam emerging from the beamsplitter

depends upon the number of reflections and passes the original beam

undergoes in the precision beamsplitter attenuator.

19. Place the detector in the beam to be used about 1 m from the beamsplitter.

20. Place absorbers in front of the beams not being used.

6.1.6 Procedures for Realignment of the Modulated cw Measurement System

1. Turn on the laser and other equipment as described elsewhere.

2. Quickly check the alignment of the beam into the apertures, the modulator and the stop to absorb the main beam. ; 3. If necessary, adjust the position of the first aperture to allow the

main portion of the beam to pass.

4. If necessary, adjust the position of the first mirror to center the

beam in the aperture in front of the Redw 3 transfer standard.

5. If necessary, adjust the other apertures and occasionally the horizontal and vertical angles and translators of the modulator to pass

the beam and to generate the first diffracted beam on the right.

6. If necessary, adjust the stop to absorb the main beam and pass the

first diffracted one on the right.

7. If necessary, align the beamsplitter attenuator as described in 6.1.5

steps 9 through 17 above.

6.1.7 Shutter Timing Measurement Procedures

1. Align the light sensor attached to the SC2 amplifier in the (m = 0)

beam.

2. Attach the SC2 amplifier gate output to the timer/counter and read

the shutter timing.

6.2 Redw 3 (TC15) Transfer Standard Alignment and Operation Procedures

1. Center the (m = 0) cw first diffracted beam in the entrance of

Redw 3.

22
2. Absorb the three reflections from the window of Redw 3 in a high

absorption black surface a few millimeters below the incoming beam

and ~30 cm away.

3. Orient the center reflection just below the incoming beam.

4. Turn on Redw 3 TS and allow it to warm up 24 h before measurements.

5. Set the upper right hand switch to Power or Energy.

6. Set to the 0.1 J, the 1 J, or the 10 J and the laser, 100 s scales.

7. Temporarily turn the measurement selector switch to laser power, not

timed.

8. Adjust the calorimeter baseline to give plus or minus zero readout.

9. Return the measurement selector switch to laser 100 s. 10. With its switch up, adjust the integrator baseline knob for no change

in readout.

11. Limit the Redw 3 measurements on the 0.1 J, 1 J, and 10 J scales to

0.0100 to 0.1000, 0.100 to 1.000, and 1.00 to 10.00 readouts, respectively.

12. Set and clear the dual preset controller for 20 s on and 120 s off

(see 5.3.2 above).

13. Start time generator.

14. Press the Redw 3 start measurement button at 18 s (1 or 2 s before

shutter is to open).

15. At about 218 s, the red light by the restart meter button will go on and the meter can be read.

16. Press the Redw 3 restart meter button.

17. For the usual calibration sequence, make measurements without the

video input of the modulator power supply, with the video input twice

at the same carrier level, and without the video input.

18. Energy into Redw 3 is computed by subtracting the average readout

without video input of the modulator power supply from each readout

with the video input of the modulator supply and dividing the results

by the calibration value.

19. cw power into Redw 3 is computed from the energy computed in step 18

divided by the input time.

6.3 APD Transfer Standard (APD TS) Procedures

6.3.1 APD TS Alignment and General Operating Procedures

1. Attach the alignment mi rror and iris to the entrance of APD TS.

2. Attach the APD TS to the tilt table and the heavy-duty translating

system in the (m = 2) or the (m = 3) cw first diffracted laser beam.

3. Align the APD TS with the (m = 2) or the (m = 3) cw laser beam in the

center of the iris and reflected from the alignment mirror back on itself through a hole in a card in the beam and/or by superimposing

the reflected (m = 2) beam on to the (m = 3) beam or the reflected

(m = 3) beam on to the (m = 2) beam.

4. Align the APD TS precisely in the (m = 2) or the (m = 3) pulsed laser

beam by observing the pulse height (oscilloscope 50 n amplifier plugin unit) and varying the iris size.

5. To make APD TS calibrations, the relay switch (see 5.5) is connected

to give alternately for about 10 s each equivalent levels of pulsed

peak power and cw power of the laser beam into the system.

6. Adjust the pulse generator (see 5.13) for about 200 ns (FDHM) laser

pulses, as observed by the APD TS, for peak power closely approximating cw power.

23
7 . Set pulse rate ~500 pps for the pu^ed energy to be negligible com- pared to the cw energy.

8. A square-wave generator operates the relay switch that alternately

connects 3 V peak pulsed and 3 V dc signals for about 10 s each, or any other time selected, to the video input of the modulator power

supply (see 5.4 and 5.5).

9. The order for the signals during a 100 s laser input is about 5 s pulsed input for the first and last 5 s and alternately 10 s cw and

10 s pulsed inputs.

10. APD TS measurements are made without the wideband amplifier (0 dB)

and with the wideband amplifier (20 and 40 dB) attached to the output

of the preamplifier (signal output connection).

11. APD measurements are from ~10" 7 W to ~10" 4 W peak power.

6.3.2 APD TS System Parts

1. APD TS.

2. Temperature controller and preamplifier power supply.

3. Bias power supply.

4. Wideband amplifier (20 dB and 40 dB gain).

5. Temperature meter.

6. Cables marked for connections.

7. Voltmeter with 0.1 percent accuracy or better (furnished by the user when the APD transfer standard is at the customer's site).

8. Alignment mirror and iris.

9. Aperture in a universal lens mount.

6.3.3 APD TS System Setup Procedures

1. Use cables as marked to make APD TS connections.

2. Before attaching the bias power supply to the APD TS, test it for

correct output voltage and polarity as given on the APD TS.

3. The voltmeter to measure the bias power supply must be ungrounded . 4. Connect the temperature controller and preamplifier power supply to

the APD TS.

5. Connect the bias power supply to the APD TS and the voltmeter.

6. Connect the APD TS signal output to the oscilloscope 50 ft input.

7. When a signal needs amplification, attach the APD TS to the wideband

amplifier at 20 or 40 dB.

8. Connect the output of the wideband amplifier to the oscilloscope 50 ft

i nput

.

9. Connect the temperature meter to the APD TS.

10. Run the temperature controller and preamplifier power supply at least

1 h before making measurements.

11. Begin measurement after temperature meter is steady.

12. Gradually apply the bias power supply voltage to the APD TS and gradually return it to zero voltage when shutting equipment down.

13. Align the APD TS (see 6.3.1) in the (m = 2) or the (m = 3) beam of

the precision beamsplitter attenuator.

14. In the modulated cw measurement system, place the tube, with the

black paper aperture, in front of the APD TS without clipping the

beam or moving the aligned APD TS.

24
15. In the modulated cw measurement system, set the pulse duration to

200 ns (FDHM) reading the APD TS output using the center four divisions of the oscilloscope read to one quarter division.

6.3.4 APD TS Calibration Procedures —cw Interval, Pulse Rate, and Background

Measurements

1. Follow 6.3.5 steps 1 to 8 to preset pulse levels.

2. Connect the pulse generator to the timer/counter or the electronic

counter (see 5.6 and 5.7).

3. Connect the dc PS at +3 V and the square wave generator 50 ft output

to the +3 V dc and input square wave connections of the relay switch,

respectively (see 5.5).

4. Connect the analyzer cable of the relay switch to the timer/counter

(see 5.6).

5. From previous peak power measurements, select the 0.1 J, the 1 J, or the 10 J and the laser, 100 s scales of Redw 3 for both background

and APD TS measurements.

6. Open the shutter between the rooms.

7. With the dual preset controller at 20 s on and 120 s off, start the

time generator (see 5.3).

8. Press the start measurement button of Redw 3 transfer standard at

about 18 s. 9. Measure five cw input time intervals at the analyzer cable (see sec- tion 5.6).

10. Measure five pulse rates at the input frequency cable after setting

the pulse rate to <500 pps (see 5.13).

11. Read Redw 3 when the ready light goes on at about 218 s. 12. Press the restart meter button of Redw 3 to clear the reading.

13. Repeat these measurements after 6.3.5 peak power measurements below.

6.3.5 APD TS Calibration Procedures--Peak Power Measurements

1. Block the entrance of Redw 3.

2. Attach the pulse generator to the video input of the modulator power

supply.

3. Manually open the shutter.

4. To set the vertical deflection of the APD TS oscilloscope readout at

a given level, adjust the carrier level of the modulator power supply

between 0.5 to 6 and the laser current between 15 to 17 or 17 to

19 A; and if needed for very low levels, place and adjust the flat

coated glass, variable attenuator in front of the iris following the

second lens.

5. For no wideband amplifier (0 dB) following the preamplifier, use the

50 ft unit plug-in unit oscillocope scales from 5 mV to 50 mV or 0.5 V per division in step 4.

6. For the 20 dB gain of the wideband amplifier, use the 50 ft plug-in

unit oscilloscope scales from 10 mV to 100 mV per division in step 4.

7. For the 40 dB gain of the wideband amplifier, use the 50 ft plug-in

unit oscillosope scales from 20 mV or 50 mV to 100 mV per division in

step 4.

8. Adjust the pulse duration to 200 ns (FDHM).

9. Close the timed shutter following the modulator.

25
10. Close the shutter between rooms to allow modulator surfaces to cool

for a few minutes.

11. Open the shutters between the rooms.

12. Remove the block in front of Redw 3.

13. Connect the analyzer cable of the relay switch to the video input of

the modulator power supply.

14. Connect the pulse generator output to the input frequency connection

of the relay switch with the 50 n termination attached.

15. Connect the square wave generator output to the square wave input of

the relay switch and to the vertical input of channel A of the oscilloscope or to the red light indicator.

16. Use the positive output of the oscilloscope or the red light indicator to determine pulsed beam operation.

17. After pulsed beam operation for a few seconds, start the dual preset

controller (see 5.3).

18. At about 18 s, press start measurement button of Redw 3.

19. Read the mean height of the middle of the APD TS pulses for the six

periods between five cw inputs.

20. Read Redw 3 at about 218 s when the ready light goes on.

21. Press the restart meter button of Redw 3 to clear the reading.

22. Repeat these measurements a second time at the same input.

23. Record the temperature near the detector, the laser amperes, and the

modulator carrier level.

24. Repeat 6.3.4 cw time interval, pulse rate and background measurements.

6.3.6 APD TS Calibration Computation

1.

The calibration factor (K in V/W) using Redw 3 transfer standard is

R/(C3 T N3 S)

for oscilloscope readout where

AS1 = average voltage reading of APD TS where A is the average

deflection reading and SI is the volts/division setting of

the oscilloscope.

R = Redw 3 reading less the average background reading

C3 = Redw 3 calibration (reading/J)

T = average duration of cw inputs (seconds)

N3 = number of T inputs

S = beamsplitter ratio

2.

The calibration factor (K0 in V cm2 /W) using area L2 is

K0 = K L2.

3.

The peak power (W) is

W = R/(C3 T N3 S).

26
4. The peak power density (WO in W/cm2

) is

WO = W/L2.

6.3.7 APD TS Uniformity Measurement Procedures

1. Attach the alignment mirror and iris to the collector of the APD TS.

2. Attach the APD TS to the tilt table and the heavy-duty or other

transl ator.

3. Align the APD TS with the reflected beam from the alignment mi rror returning on the path of the incoming beam.

4. Calibrate the APD TS in the center of the APD collector and in at

least four other areas in the four cardinal directions next to the

perimeter of about a central 1 cm2 circular area to determine the

uniformity of the responsi vity

.

5. Compute the average responsivity at the 95 percent confidence interval (Cl) and use these data in the uncertainty statement of the calibration .

6.3.8 APD TS Field of View Measurement Procedures

1. Attach the alignment mirror and iris to the collector of the APD TS.

2. Align the APD TS with the reflected beam from the alignment mi rror through the center of the attached iris at angles of reflection ^e R

) of 0, 5, 7.5, 10, 12.5, 15, 17.5, and 20 mrad in the four cardinal

directions, and calibrate the APD TS at 0 mrad and at some of the

angles in the four cardinal directions.

3. Compute the calibration for each angle selected.

4. Define beam divergence in mrad as

D = 20

R + 3

where the divergence of the beam in the system is approximately

3 mrad.

5.

Prepare a table of the beam divergence (D) versus correction factor

for the calibration, (CF)q = Kq/K where

K

d

= calibration at divergence D K = calibration at e R

= 0

6.3.9

APD TS Impulse Response Correction Procedures

1. Place the APD TS into operation at the bias voltage indicated on the

i nstrument

.

2. Attach the output of the APD TS to a 350 MHz to 500 MHz bandwidth,

50 ft input impedance, oscilloscope plug-in unit.

3. Collimate a 300 ps duration, 0.9 ym LED pulsed beam with a converging

lens and align the APD TS about a half meter from the LED pulsed

beam.

4. Attenuate as needed the 300 ps, 0.9 ym LED pulsed beam with a variable transmission flat coated attenuator.

27
5. Feed the 300 ps, 0.9 pm LED pulsed beam into the APD TS in its linear

region without the wideband amplifier (0 dB) and with the wideband

amplifier (20 dB and 40 dB) attached.

6. Photograph the impulse response and ringing portions of the curve on the oscilloscope.

7. Read values at every subdivision from the impulse response curves.

8. Convolute from ~10 ns to ~100 ns duration, Gaussian and skewed

Gaussian pulse data (1 V peak) and impulse response data (unity area)

using the convolution computer program.

9. Compute and plot correction factors for peak voltage versus the

observed pulse duration to get the original pulses for the 0 dB and

the 20 dB and 40 dB gain settings of each APD TS.

6.3.10 Procedures for Measuring the Inequivalence of Pulsed and cw Power

1. Observe the height variation of pulses of the APD transfer standards

as the laser pulses are stretched and compressed between 200 ns and

600 ns (average pulse height variation was within 2.5 percent).

2. Compare calibrations using (1) pulsed peak power measurements and

(2) cw power measurements (calibrations using (1) and (2) were within

1 percent of each other).

3. We concluded (1) that the pulse height, if it could be measured to

cw, would not vary significantly and (2) that the pulsed peak power

and the cw power inequivalence has a 2.5 percent uncertainty.

6.3.11 APD Transfer Standard Optics

1. The sequence of the optics in the APD transfer standards from the

outside to the inside are aperture, collector lens, diffuser, and

silicon avalanche photodiode (APD).

2. The aperture is about 1.1 cm diameter.

3. The lens is a B270 crown glass, biconvex lens that has about a 2.5 cm diameter and a 2.5 cm focal length and a 1.064 ym anti refl ecti on coati ng.

4. The lens is about 2.13 cm from the diffuser and about 2.54 cm from

the APD.

5. The diffuser is about 0.16 cm thick Suprasil-1 glass with the front

surface ground with a 400 grit abrasive (about 40 • 10“ 4 cm size).

6. The APD is about 0.3 cm diameter and about 0.07 cm

2

area, and is hermetically sealed behind a flat glass window.

7. APD 5-5 has an APD with a hybrid preamplifier in a single modified 12

lead TO-8 package.

6.4 PIN Transfer Standard (PIN TS) Procedures

6.4.1 PIN TS Alignment and General Operation Procedures

1. Attach the alignment mi rror and iris to the entrance of the PIN TS.

2. Attach the PIN TS to the tilt table and the heavy-duty or other

translating system in the (m = 2) or the (m = 3) cw first diffracted

laser beam.

3. Align the PIN TS with the (m = 2) or the (m = 3) cw laser beam in the

center of the iris and reflected back on itself through a hole in a card in the beam or with the superposition of either the (m = 2) and

28
the reflected (m = 3) beam from the PIN TS mirror or the (m = 3) and

the reflected (m = 2) beam from the PIN TS mirror.

4. Align the PIN TS precisely in the (m = 2) or the (m = 3) pulsed laser

beam by observing the pulse height on an oscilloscope with a megohm

amplifier plug-in unit and varying the iris size.

5. Place the tube, with a black paper aperture, in front of the PIN TS

without clipping the beam or moving the aligned PIN TS.

6. Compute laser energy/pulse from the total energy in a beam divided by

the number of pulses.

7. Use Redw 3 in the (m = 0) beam or a PIN TS in the (m = 2) beam as a reference standard.

8. Use pulses from 100 to 180 ns duration (FDHM) (laser pulses <100 ns are unsteady and above 200 ns may be distorted in the linear amplifier).

9. Use about 105 to 3 105 pps with the reference Redw 3 TS and 10 3 pps

maximum with the reference PIN TS (the 3 105 pps limit is necessary

with a pulse height analyzer readout).

10. Integrate and amplify PIN pulses with the charge amplifier and the

linear amplifier at the specified external and internal settings.

11. Calibrate the average joules per pulse versus the average peak

voltage per pulse.

12. Calibrations are independent of pulse duration to 200 ns.

13. Determine pulse duration (FDHM) from APD TS or by subtracting 10 ns from pulse generator pulses.

14. Adjust the carrier level of the modulator power supply and the laser

current to control pulse energy.

15. The PIN TS measures ~10" 14 J to ~10-11 J/pulse.

6.4.2 PIN TS System Parts

1. PIN transfer standard.

2. Temperature controller power supply.

3. Temperature meter.

4. Charge amplifier.

5. Portable NIM BIN with power supply for NIM BIN components.

6. Linear amplifier NIM BIN component.

7. Pulser NIM BIN component.

8. Bias power supply NIM BIN component.

9. Voltmeter with 0.1 percent or better accuracy (furnished by the user

when the PIN TS is at the customer's site).

6.4.3 PIN TS System Setup Procedures

1. Use cables as marked to make PIN TS connections.

2. Connect the bias power supply by itself to an ungrounded voltmeter

and gradually increase output to -180 V.

3. If it is functioning properly, connect the bias power supply to the

PIN TS and to the ungrounded voltmeter.

4. Connect the charge amplifier directly to the signal output terminal

of the PIN TS using a double male type N connector and to the back of

the linear amplifier.

5. Connect the temperature controller to the PIN TS.

6. Connect the temperature meter to the PIN TS.

29
7. Turn on the temperature controller and other equipment for at least one hour before measurements.

8. Check the readout of the temperature meter to know the temperature

controller is functioning.

9. Gradually apply bias voltage and gradually return it to zero voltage

when shutting equipment down.

10. Align the PIN TS (see 6.4.1, steps 1 through 5).

11. From ~10-14 J/pulse to ~10" n J/pulse, use pulse durations (FDHM)

from 100 ns to 200 ns with the longest pulses used with the

Redw 3 TS.

12. Set and measure the pulse duration (FDHM) by an APD TS or by subtracting 10 ns from measurements of pulse generator pulses.

13. The linear amplifier is set internally at time constant (TC) 2 ys,

multiplier X 0.2, and delay out.

14. The linear amplifier is set externally at

BLR ASYM 1 RATE OUT

Bipolar positive peak

Coarse gain 5 and fine gain 0.500 (set by turning potentiometer

courvtercl ockwi se)

Coarse gain 10, 50, 100, and 200 (when calibrated or needed) and

fine gain 1.000 (set by turning potentiometer clockwise)

15. Use oscilloscope as follows

Bandwidth: >200 MHz

Input: 1 Mft Sweep: 0.2 ys

Vertical deflection: 5 to 100 mV/div to 2V/div

Baseline: 2 divisions

Pulse height: 3 to 5 divisions

16. Other PIN transfer standards than the ones described here have been

calibrated with a pulse height analyzer (PHA) readout (600 n input)

and an oscilloscope readout (1 Mn input) in parallel (see 5.16).

17. The PHA readout may be read alone with the same calibration as when

read in parallel with the oscilloscope, but the oscilloscope readout

must be read in parallel.

18. The PHA readout gives both accurate averages and individual measurements of pulse height.

6.4.4 PIN TS Calibration Procedures— Preparation Procedures and Pulse Rate

and Background Measurements

1. Select a pulse rate from 10 5 to 3 • 10 5 pps of the pulse generator

when using the Redw 3 TS as a reference standard.

2. Select a pulse rate of <10

3

pps of the pulse generator when using a PIN TS as a reference standard.

3. Set and measure the FDHM pulse duration between 100 and 200 ns by an APD TS or by subtracting 10 ns from measurements of pulse generator

pulses.

4. Align the PIN TS with the (m = 2) or (m = 3) cw laser beam in the

center of the iris and reflected from the alignment mirror back on itself through a hole in a card in the beam or with the superposition

of either the (m = 2) and the reflected (m = 3) from the PIN TS mirror or the (m = 3) and the reflected (m = 2) beam from the PIN TS

mi rror.

30
5. Place the tube, with a black paper aperture, in front of the PIN TS

without clipping the beam or moving the aligned PIN TS.

6. When a PIN TS is used in the (m = 2) beam as a reference standard,

use the procedures of steps 4 and 5 above except orient the PIN TS at

a slight angle from the incoming beam and open and close the (m = 2)

beam shutter to verify that no reflected (m = 2) beam enters a detector in the (m = 3) beam.

7. With the pulse generator attached to the video input of the modulator

power supply, adjust the carrier level (0.5 to about 9) and the laser

current (15 to 17 A or 17 to 19 A for relatively short periods) to

get the desired pulse amplitudes.

8. Select the pulse amplitude of the PIN TS from 20 mV/division to

2 V/division, a two division baseline, and a three to five division

peak of the oscilloscope megohm amplifier plug-in unit (see 5.14).

9. Connect the pulse generator to the electronic counter or the timer/

counter.

10. Press the stop button of the time generator, close the timed shutter,

and clear the dual preset controller to zero readout.

11. Close the shutter between rooms for a few minutes to cool the modulator surfaces after being heated by the laser beam.

12. Set the dual preset controller to open the shutter at 20 s and close

it at 120 s. 13. Press the start button of the time generator if the Redw 3 TS is used

as a reference standard, otherwise, perform step 16 only.

14. Open the shutter between rooms.

15. Press the start meter button of Redw 3 at 18 s. 16. Measure the pulse rate.

17. Read the Redw 3 meter when the ready light goes on at about 218 s. 18. Press the restart meter button of Redw 3.

19. Go to 6.4.5 energy measurements, ^top, or start at step 7 again.

6.4.5 PIN TS Calibration Procedures--Energy Measurements

1. Perform PIN TS calibration procedures (see 6.4.4) before proceeding

with these steps.

2. Attach the pulse generator to the video input of the modulator power

supply.

3. Reset the dual preset controller.

4. Press the start button of the time generator.

5. Press the start meter button of Redw 3 at 18 s if Redw 3 is used as a reference standard, otherwise omit steps 5, 7, and 8.

6. Read each PIN TS peak every 10 s during the 100 s the timed shutter

is open.

7. Read the Redw 3 meter when the ready light goes on at about 218 s. 8. Press the restart meter button of Redw 3.

9. Repeat steps 3 through 8 a second time, otherwise go to step 10.

10. Record the temperature near the transfer standard, the laser amperes,

and the modulator carrier level.

11. Repeat 6.4.4 steps 12 through 17.

31
6.4.6 PIN TS Calibration Computation

1. Calibrations J1 (J/V) and K1 (J/V cm2

) for oscilloscope readout and

J2 (J/PHA reading) and K2 (J/PHA reading cm2

) for PHA readout of a PIN TS in the (m = 2) or (m = 3) beam using a Redw 3 TS in the

(m = 0) beam are

C3 S F T AS1 * '

K1 = J1/L2, J/V cm2

02 = C3 S F T PI

* J/PHA read1ng

K2 = J2/L2, J/PHA reading cm2

where

J = R/(C3 S F T), joules/pulse

R = Redw 3 reading minus the average background reading

C3 = Redw 3 calibration, reading/ joule

S = beamsplitter ratio

F = average pulse rate

T = input time, 100 s AS1 = average pulse height of A divisions times the volts

per division SI of the oscilloscope

PI = av PHA reading of the pulses

L2 = apertured area of the PIN TS

2. Calibration J3 (J/V) and K3 (J/V cm2

) for oscilloscope readout and J4

(J/PHA reading) and K4 (J/PHA reading cm2

) for PHA readout of a PIN

TS in the (m = 3) beam using another PIN TS in the (m = 2) beam as a reference standard are

J3

C2 BS2

S AS1*

J/V

K3 = J3/L2, J/V cm2

J4 = > J/PHA reading

K4 = J4/L2, J/PHA reading cm2

where

C2 = calibration, J/V of PIN TS as a reference standard

BS2 = average pulse height of the reference PIN TS of B divisions

times the volts per division S2 of the oscilloscope

32
6.4.7 PIN TS Uniformity Measurement Procedures

1. Attach the alignment mirror and iris to the PIN TS.

2. Attach the PIN TS to the tilt table and the heavy-duty or other

translator.

3. Align the PIN TS with the reflected beam from the alignment mirror

returning on the path of the incoming beam.

4. Calibrate the PIN TS in the center and in at least four different

areas next to the edge of the aperture of the PIN diode to determine

the uniformity of the responsivity over the approximately 1 cm2 PIN

area.

5. Compute the average responsivity at the 95 percent confidence interval and use these data in the uncertainty statement of the calibration.

6.4.8 PIN TS Scan Procedures for Uniformity Measurement

1. Use a cw Nd:YAG laser source with very stable output.

2. Attenuate the beam with a coated glass attenuator that is raised or lowered to vary the attenuation.

3. Attenuate the beam with the (m = 2) beam of a wedge.

4. Change the beam direction 90 deg with a wedge.

5. Attenuate the beam with a coated glass attenuator that is rotated to

change attenuation.

6. Focus the beam on the detector with a 1 m FL lens.

7. Position the beam with a horizontal and a vertical scanning mirror.

8. Attach the PIN TS detector output to a 50 ft plug-in of an oscilloscope.

9. Scan the whole detector with a less than 1 mm diameter, ultrastable

laser beam with 12 or more horizontal sweeps.

10. Photograph the scan image on the oscilloscope.

11. Use the detector with the most uniform scan image as a PIN TS.

6.5 Temperature Controllers for APD and PIN Transfer Standards

1. The temperature controllers for the APD and PIN transfer standards

operate on dc power to reduce noise.

2. The temperature controllers maintain the transfer standards at a temperature in the 30°C to the 35°C range using an IC temperature

transducer.

3. A milliammeter or other readout instrument indicates the relative

temperature of the transfer standard.

4. The temperature controller is operated about one hour before the

transfer standard to which it is attached is used.

5. Figure 6.5-1 shows the dc temperature controller circuit.

6.6 Procedures for Calibration of Customer's Instrument at NBS

1. The APD or PIN transfer standard is aligned in the (m = 2) beam of

the precision beamsplitter attenuator (BA-1) with a tube in front for

reducing the field of view.

2. The customer's instrument is aligned in the (m = 3) beam of BA-1 with

a tube in front of the instrument.

3. A pulse rate <10 3 is used.

33
D.C.

Temperature

Controller

.2 ^ b

DO + O

34

Figure

6.5-1.

DC

temperature

controller

circuit.
4. A shutter in the (m = 2) beam of BA-1 is used to eliminate a small

amount of reflection from the APD TS when the customer's instrument

is read.

5. During a 100 s input, the APD and the customer's instrument are alternately read for 10 s each.

6. The APD TS is read when the shutter in the (m = 2) beam is open and

the customer's instrument when the shutter is closed.

7. The PIN TS is used with the shutter in the (m = 2) beam open, and it

is aligned without a reflection into the customer's instrument.

8. The PIN TS and the customer's instrument are read every 10 s for a 100 s input.

9. For APD TS measurements, the peak power density (W/L2) into the cus- tomer's instrument is

W/L2 = V/K

29.7 L2

where

W/L2 = peak power density in W/cm2 into the customer's instrument

V = average oscilloscope readout in V

K = APD TS calibration in V/W

29.7

= beamsplitter attenuation ratio

L2 = area of the customer's instrument in cm2

10.

For PIN TS measurements, the energy density (E/L2) into the cus- tomer's instrument is

E/L2 = V J3

29.7 L2

where

E/L2 = energy density in J/cm2 into the customer's instrument

V = average oscilloscope readout in V

J3 = PIN TS calibration in J/V

29.7

= beamsplitter attenuation ratio

L2 = area of the customer's instrument in cm2 11. Calibration of the customer's instrument may be performed in any beam

except (m > 4) of the precision beamsplitter attenuator, using an APD

TS, a PIN TS, or a Redw 3 TS and using the appropriate equations.

12. If the customer's instrument is calibrated at pulse durations around

100 to 200 ns and is to be used at pulse durations around 10 ta

20 ns, then the instrument must have sufficient bandwidth for calibrations to apply at 10 to 20 ns.

6.7

APD TS Measurement Instructions for the Customer's Site

6.7.1 General Instructions

1. When you receive our transfer standard system, please carefully read

the enclosed operating instructions. Note the way the equipment is

packed so that you can repack it that way.

2. After completing measurements, please send the transfer standard system with all original parts to N3S.

a. Send by UPS Blue Label.

35
b. Sender must prepay shipping charges. You cannot send UPS collect.

c. Ship to:

U.S. Department of Commerce - NBS

Alvin L. Rasmussen, 724.02

325 Broadway

Boulder, CO 80303

3. Before shipping back to NBS, be sure that the instrument is packed in

the manner it was sent.

4. Please call Alvin L. Rasmussen at NBS at 303-497-5367 (FTS 320-5367)

and advise when the instrument will be or was shipped.

6.7.2 APD Transfer Standard Operating Instructions

A. Warning to stay within the limits of the APD TS

1. This system is for pulsed peak power between about 10” 1 and

102 P W.

2. Stay within the ranges in the table of the APD TS system.

3. Exceeding these limits can burn out components in the APD TS and

cost considerable expense and time to repair and recalibrate.

4. Disassembling the APD TS can ruin its calibration.

5. Operate the APD TS in a darkened room to prevent instrument

damage and erroneous measurements.

B. System Parts

1. APD TS with aperture below.

2. APD TS temperature controller and preamplifier power supply.

3. Temperature meter.

4. P for positive and N for negative bias power supply.

5. Wideband amplifier.

6. Marked cables.

7. Alignment mirror and iris.

8. Aperture in a universal lens mount.

9. Ungrounded precision voltmeter (provided by the user).

C. Bias Power Supply Check

1. Attach B- VM cable to rear of the bias power supply and to the

ungrounded precision voltmeter.

2. Turn on the bias power supply, gradually turn the 10-turn potentiometer clockwise to read exactly the bias voltage on the voltmeter, gradually return potentiometer to 0 V, and turn off the

power supply.

3. If the voltmeter read the bias voltage, proceed to the next step.

D. Setup

1. Attach the APD temperature controller and the preamplifier power

supply to the APD TS.

2. Attach the temperature meter to the APD TS.

3. Attach the bias power supply to the APD TS and to the ungrounded

precision voltmeter.

4. Attach the signal (output) of the APD TS to an oscilloscope 50 ft plug-in unit with a BW of 350 to 500 MHz.

5. Attach the 20 dB or 40 dB input of the wideband amplifier to the

APD TS and the output to the oscilloscope (see step 4) when lower

peak power levels are to be measured.

6. Yellow wires from APD 5-1 TS and APD 5-5 TS are attached to a Wheatstone bridge set at low sensitivity to minimize heating from

36
the bridge current. Resistance readings of about 691 and 684 n,

respectively, indicate proper temperature of each APD and its

preampl i fi er.

E. Operation

1. Turn on the temperature controller and the preamplifier power

supply, run them for at least one hour, and check the temperature

meter or ribbon thermometer for a steady reading.

2. Turn on the bias power supply, gradually turn the 10-turn potentiometer clockwise to read exactly the bias voltage on the voltmeter, and gradually return it to zero and off when shutting down

the equipment.

3. A1 i gn the APD TS.

a. Blow dust off the APD collector surface with a squeeze-type

air blower ONLY (other types such as those in spray cans may

spray liquid and damage the surface).

b. Reattach the aperture, the alignment mirror and the iris.

c. Align the APD TS in a visible light or 1.064 ym beam with the

beam returning on itself, or

d. Align the APD TS without the alignment mi rror and the iris by

positioning the APD diode for maximum pulses at one gain and

range in the calibration table. See APD 5-5 calibration

table for the difference in calibration using maximum pulses.

4. Make APD TS measurements.

a. Set a baseline of two divisions and a pulse height of three

to five divisions.

b. Refer to the table for gain, calibration, range and uncertai nty

.

c. Read the peak voltage and the observed pulse duration (FDHM)

to one quarter division each.

d. Find the corrected peak voltage by multiplying the observed

values by the correction factors in the figures.

e. Divide the corrected peak voltage by the calibration (corrected for beam divergence when given) in the table to get

the power density (W/cm2 ).

f. Acquire sufficient data for significant statistical informati on.

F. Shutdown.

1. Gradually turn the ten-turn potentiometer of the bias power

supply counterclockwise to zero and turn off the power supply.

2. Turn off the temperature controller and preamplifier power

supply.

3. Reattach the alignment mi rror to the APD TS to protect the collector.

G. APD Transfer Standard Equipment

1. APD bias power supplies, Bertan Assoc. Inc., Model 602B-15N (APD

5-1) and Model 602B-15P (APD 5-5).

2. Digital voltmeter for bias voltage measurement, Dana 4600 (used

at NBS)

.

3. AP 462A wideband amplifier, S/N 551-01053.

4. Oscilloscope readout, Tektronix 7904, NBS 145935 (used at NBS).

a. APD readout, dual trace amplifier, 7A24, 50 n.

b. Dual time base, 7B92A.

37
TEMP.

CONTROLLER

AND AMPL TEMP.

PS+15V MTR.

i

i _ j

APD DETECTOR AND PREAMPL

1.064 /im

LASER

PULSES

WIDEBAND AMPL

(LOWEST LEVELS)

OSCILLOSCOPE

Figure 6.7-1. APD transfer standard system.

38
a dO IV sao

o o

cq

o

C\l o o

o

o dO d A

o o

0) 00

6 6

o

N6

COc

<

CO

CD

O

39

Kiyure

6.7-2.

APD

5-1

correction

factors

(

without

HP

amplifier)

for

peak

voltage

(Vp

CF)

and

for

observed

pulse

duration

(OBS

At

CF)

versus

the

observed

pulse

duration

(OBS

At).
o do dA

(0

c

<3

CO

GO

O

40

Figure

6.7-3.

APD

5-1

correction

factors

(with

HP

462A

amplifier

20

dB

and

40

dB)

for

peak

voltage

(Vp

CF)

and

for

observed

pulse

duration

(OBS

At

CF)

versus

the

observed

pulse

duration

(OBS

At).
Ei jo tv sao

41

APD

5-5

correction

factors

(

without

HP

amplifier)

for

peak

voltage

(Vp

CF)

and

for

observed

pulse

duration

(OBS

At

CF)

versus

the

observed

pulse

duration

(OBS

At).
o do iv sao

o O o o o o o o

Tl; CO CM o O) co Nr_

’ rJ I- o o 0*0

o o

CO

o

CM

o o

o

o JO dA

o

0) o

o

co6

o

o

42

Figure

6.7-5.

APD

5-5

correction

factors

(with

HP

462A

amplifier

20

dB

and

40

dB)

for

peak

voltage

(

Vp

CF)

and

for

observed

pulse

duration

(OBS

At

CF)

versus

the

observed

pulse,

duration

(OBS

At).
Table

1.

APD

5-1

system

calibration

CM CO LO

LO «0- 4-> • • • 3 CL) rH o o o cn 1 1 1 -o c > 03 o

CO (T3 rH 03

CD (- o o «”H oc • • • o o o

CD CO

cn CO rH LO C CM LO • • co E rH LO o t- O * | 1 1 <3- CM

£- 3 o CM

CD 3. • • • 2 CM o o o

Q_

>3 to +->

—«

0) c o •— 4-> -r- 03 •O' CO CO <0 *0. • • • 4-> E +-> LO a* o CO CO O -r— t- 03 r~ ~c r-H rH hD 01

</)

O +-> CD C CO 3 • to o C 4- H-> CO

•rO

C £_

0) E

>1 0J E f—< -M cn 0) O LO c co t- LO CO CM

•I- t- 3 VS. • • • (O 0) to LO o o o +-> 4-> > CO 03 to

S- CO 01 (O • • CD E +J 0) C • • O 0) CO r— •r- CO CO c r oi 1 TO TO

=3 +-> -C +-> cn

+-> CO 3 O

O r— CM ^a- 5 OL

CD c_ c_ i— G 0) CD > •«— !— O 4-4-

to 4- LO -i- -r- c O r— r— 4— O Q. Q. O *r— o CM EE M <C CO cO

C- CO r—C

CM • Id

CD CC 00 nj- CO to r— < «£

-Q .Q »—h

C U_ * CM CM E -r- +-> CM LO LO 3 i— — •o- <o- Z CO Q • sz o E CM C_3 CL. Q_ E X X

LO

O

A

'O' OJ * r> r-« CL >> >3

-O •O’ o •+->*-> o 03 CJ >>•»-•«— c CO LO •r— • 1/1 D L L o 3 CO o o £_ o O •!“ cO (O

•r* \ rH T—H

rH 0) r—

L f i—

4-> CM CL CO <— CO

OO

CO E * X

X

X CD •r- i— Q. CL

tO * * -tC £_ o o

X3 00 (T> r~- o CO 00 Q.4-) +-> •i— • • • • *r* O s- L_ r— 03 00 00 H-> 0) to 0) CD

CO > f0 C_ •O' 3 > >

C_> C_ 3 O rC

C

JO +-> 03 CL'i- -r-

•f— t_ r— CD .—. ,—,

CO Q.

X rH CM CO

-H +»

H

O < h—

r^-~*s

— i—C —

CVJ CO * v— '

* 4-

43
Table

2.

APD

5-5

system

calibration

CO 1 1 <y\ CM o • • • 3 a) o o o 4— o 03 1 1 1 (—<

TO c > 03

<0 <o rH "O 00 +-> <13 c_ o o o • c

az • • • 4- 03 o o o r— O

03 c_ m 03

4-> CL

•t— CM

<v 03 c • cn I—c

03 o rH c CM o • • CO E 00 o TO "O

t_ o * 1 1 1 03 T3 \* CO LO +-> (O

c_ 3 CO r^ 1—< o

a) 3- • • • 0) o 5 CO o o r— c o 4- (X3 CL 03£_ LOO E • cO rH

03 >3 JO >>

-a -t-> »—

H

JO

0)

C

O XI

r—•

+-> •r— LO LO LO +J c

CO CO cO a* • • • •r o

4-> E 4-> tn a« o CO CO 5 i— O •r— £_ 03 1—1

rH r-H +-> 1— 4-> <u T3 cxj

If)

a -t-> O) t_

03 c 1X3

C J0 3 03 •r—

•i

r

i— CX3 <c U

>3 • r—

If) o Q.

C 4— 4-> 1X3 •r- • r— O C c_ +J

03 »—< E r—

>3 o> E O 3

+-> o> <u LO E c co «- a* LO LO r-~- r-H •r— 3 LO a* • • • r

CO <u If) 03 o o o +-> +->

4-> > co CO 3

£_ co -*-> co Cl • • 03 £ (X3 03 4-> C • • u aj r“ 3 •1- CO CO c jo a> O 1 TO TO

+-> sz 4-> 03

+j CX3 E 3 O

O 3 r- CM * E CL

Cl) •1

C_ £_

*i

X

G O) 03 > (T3 i— •i

E O 4- 4-

in 4- LO -r- r— c O £_ i

r—

4- o O ^ CL CL O '1

TO 4- CM E E

+-> r— <£ <0 CO

t_ CO 'O' <—1 o • 03 C_

a; c o co LO If) •r— o < <C

JO -Q t c sz LJ_ +-> « CM CM E •r— +-> o CM LO LO 5

r—> c 0) '3' *0" CO o • 4-> J= o E CM 0) O o- o. E T3 • zc IC CO u >3

"3- Q3+-> Q) 9) #3 r--. C c CL >3 >»

TO •f— •r—

O • 4-> +-> o 03 -*-> (O o >»•>— •i

c: CO O' LO •r— • CO +-> </)+->£- £_ o 3 o o o o 3 L, O -1- CO CO

•r—

—^ 1 ( T 1 rH <D 03

rL r—r CM Cl CX3 "O O l CO O o

03 E ¥

X

X

X O) (X3 e •r- i— Q. CL

t_

aK

¥ 4- c u 3 O

O

JO LO I—i

03 o <o C/3 CL 4-> +-> •f— • • • m -r-* JO TO O £— (_ r— LO LO +-> 03 03 </) 03 0)

CO > CO C_ o +-> «0- 3 > > o 5_ 3 0) CO O i— C c

JO +-> c E 03 CL-r- •t— 1— C_ 03 •r* r— 03 r— / S rr \ — 1 « co Q. CO

cl t X

H CM t — s ^ CO 4— T C—3

IW Ur" , — rH CM CO tc '

— — * * +-

44
Table 3. Error budget APD 5-1 system.

Source of error Uncertainty %*

Redw 3 transfer standard 1.9

Beamsplitter attenuator 2.5

Equivalence of pulsed and cw power 2.5

Oscilloscope readout 3.0

Amplitude response of HP 462A amplifier 2.5

Precision, uniformity, and field of view

Total error budget

1.0

(1) Without HP 462A amplifier 10.9

(2) With HP 462A amplifier at 20 and 40 dB 13.4

*At the 95 percent Cl.

45
Table 4. Error budget APD 5-5 system.

Source of error Uncertainty %*

Redw 3 transfer standard 1.9

Beamsplitter attenuator

(1) Without HP 462A amplifier

(2) With HP 462A amplifier at 20 and 40 dB

1.9

2.5

Equivalence of pulsed and cw power 2.5

Oscilloscope readout 3.0

Amplitude response of HP 462A amplifier 2.5

Precision, uniformity, and field of view 1.1

If aligned for maximum output, use a 1.05

correction factor and add to error budget 1.2

Total error budget

(1) Without HP 462A amplifier

(2) With HP 462A amplifier at 20 and 40 dB

10.4

13.5

*At the 95 percent Cl.

46
H. APD System Description

The APD has inherently small size and nonuniform responsi vi ty

.

To overcome these problems, the largest APD available at 3 mm diameter was used with a focusing lens (collector) and etched glass

diffuser in front of it. Still, the responsivity in volts/watt

varied over the portion of the collector area apertured. Consequently, the uniformity of the responsivity and the field of view were

statistically determined.*

Since the APD systems designed have <100 MHz bandwidth, corrections to the peak voltage of the fastest pulses are necessary for

dependable calibrations as a function of pulse duration. These

corrections are calculated from the convolution of Gaussian pulses

with the impulse response of the system.

Because of the temperature coefficients of components, the APD

and its preamplifier were placed in a temperature-controlled environment. It consists of a thermally insulated box containing the com- ponents and a dc temperature controller circuit operating around 30°

to 35°C. The silicon photodiode lies in the center of a hole inside

the box. A temperature meter and a ribbon thermometer next to the

APD indicates the inside temperature.

The dc bias is rectified 20 kHz and contributes little noise to

the APD output.

6.8 PIN TS Measurement Instructions for the Customer's Site

6.8.1 General Instructions

I. When you receive our transfer standard system, please carefully read

the enclosed operating instructions. Note the way the equipment is

packed so that you can repack it that way.

2. After completing measurements, please send the transfer standard system with all original parts to NBS.

a. Send by UPS Blue Label.

b. Sender must prepay shipping charges. You cannot send UPS collect.

c. Ship to:

U.S. Department of Commerce - NBS

Alvin L. Rasmussen, 724.02

325 Broadway

Boulder, CO 80303

3. Before shipping back to NBS, be sure that the instrument is packed in

the manner it was sent.

4. Please call Alvin L. Rasmussen at NBS at 303-497-5367 (FTS 320-5367)

and advise when the instrument will be or was shipped.

*An ir-enhanced APD from the manufacturer, which became available after the

APD transfer standards were completed, can be used if the need occurs,

because they are reported to be more uniform and higher in responsivity than

the APD described here.

47
6.8.2 PIN Transfer Standard Operating Instructions

A. Warning to stay within the limits of the PIN TS.

1. This system is for pulsed energies between 10 to 104 fJ/cm2 . 2. Stay within the gains and ranges in the table of the PIN TS

system.

3. Operate the PIN TS in a darkened room to prevent instrument

damage and erroneous measurements.

B. System Parts

1. PIN transfer standard.

2. PIN temperature controller power supply.

3. Temperature meter.

4. Charge amplifier.

5. Charge amplifier cable.

6. NIMBI N with linear amplifier, pulser, and bias power supply.

7. Five marked cables.

8. Alignment mirror, iris, and two lens mount sleeves.

9. Ungrounded precision voltmeter (provided by the user).

C. Bias Power Supply Check

1. Attach the HV--NEG BIAS cable to rear of the bias power supply

and to the ungrounded precision voltmeter.

2. Turn on the bias power supply, gradually turn the 10-turn potentiometer clockwise to read -180.0 V on the voltmeter, gradually

return potentiometer to 0 V, and turn off the power supply.

3. If the voltmeter read -180.0 V, proceed to the next step.

D. Setup

1. Attach the +15 —+15 cable to the PIN TS and the PIN temperature

controller power supply.

2. Attach the TEMP MTR—TEMP MTR cable to the PIN TS and the temperature meter.

3. Attach the charge amplifier cable to the rear of the linear

amplifier and to the charge amplifier using the pair of screws on the device.

4. Attach the charge amplifier directly to the signal (output) terminal of the PIN TS using the double male connector.

5. Attach the T connector to the NEG BIAS terminal of the PIN TS.

6. Attach the HV--NEG BIAS cable to the rear of the bias power supply and to the NEG BIAS terminal of the PIN TS.

7. Attach the B- --VM cable to the NEG BIAS terminal of the PIN TS

and the ungrounded precision voltmeter.

8. Attach the linear ampl ifier--SCOPE cable to the bipolar output of

the linear amplifier and to an oscilloscope meghom plug-in unit

with BW > 200 MHz and 0.2 ys sweep.

9. Set the linear amplifier at BLR: ASYM.l, RATE OUT and the gain at one of the ranges of the calibration table (see step 10).

10.

Set the fine gain at 0.500 by turning the potentiometer counter

clockwise and at 1.000 by turning the potentiometer clockwise.

E. Operation

1. Turn on the temperature controller power supply, run it for at

least one hour, and check the temperature meter for a steady

readi ng.

2. Turn on the NIMBIN and run it for at least one hour.

48
3. Turn on the bias power supply, gradually turn the potentiometer

clockwise to read -180.0 V, and gradually return it to zero and

off when shutting down the equipment.

4. Align the PIN TS.

a. Blow dust off the PIN collector surface with a squeeze-type

air blower ONLY (other types may spray liquid and damage the

surface)

.

b. Reattach the two lens mount sleeve, the alignment mirror, and

the iris.

c. Align the PIN TS in a visible or 1.064 ym beam with the beam

almost returning on itself, or

d. Align the PIN TS without the two lens mount sleeves, the

alignment mirror, and the iris by positioning the PIN diode

for maximum pulses at one gain pair and range of the calibration table.

5. Make PIN TS measurements.

a. Set a baseline at two divisions and a positive pulse height

from three to five divisions.

b. Refer to the table for gain, calibration, range and uncertainty.

c. Read the pulse height to one quarter division and determine

the peak voltage.

d. To determine energy multiply the peak voltage by the calibration.

e. Acquire sufficient data for significant statistical information.

f. If the area of the beam is less than the area of the PIN TS,

either multiply the calibration by the area of the PIN TS for

a new calibration in J/V, or multiply the calibration by the

area of the PIN TS divided by the area of the beam for a new calibration in J/V cm2 . F. Shutdown.

1. Gradually turn the ten-turn potentiometer of the bias power supply counterclockwise to zero and turn off the power supply.

2. Turn off the N I MB IN.

3. Turn off the temperature controller.

4. Reattach the two lens mount sleeves and the alignment mirror to

the PIN TS to protect the diode.

G. PIN Transfer Standard Equipment

1. PIN bias power supply, Bertan Assoc. Inc., Model 342.

2. Digital voltmeter for bias voltage measurement, Dana 4600 (used

at NBS)

.

3. Charge amplifier, Tennelec, TC 162, S/N 326 (PIN 4-1) and S/N 293

(PIN 4-3).

4. Linear (shaping) amplifier, Tennelec, TC 222, S/N 386 (PIN 4-1)

and S/N 230 (PIN 4-3).

5. Pulser, Tennelec, TC 812.

6. Oscilloscope readout, Tektronix 7904, NBS 145935 (used at NBS).

a. PIN 4-3 readout, dual trace amplifier, 7A12, 1 mn.

b. PIN 4-1 readout, dual trace amplifier, 7A26, 1 mn NBS 146251.

c. Dual time base, 7B92A.

49
H. PIN System Description

The charge and linear amplifiers of the PIN system integrate the

current and shape of the pulse. A pulse emerges whose peak voltage

is proportional to the energy in the original PIN pulse. Peak voltages of pulses are read out on an oscilloscope and/or a pulse height

analyzer (PHA). The latter records the occurrence and amplitudes of

pulses from which one can determine the average amplitude and the

stability of the laser output.

Because of the temperature coefficients of components, the PIN

was placed in a temperature-controlled environment. It consists of a thermally insulated box containing the components and a dc temperature controller circuit operating around 30° to 35°C. The silicon

photodiode lies in the center of a hole inside the box. A temperature meter indicates the inside temperature.

The dc bias is rectified 20 kHz and contributes little noise to

the PIN output.

TEMP.

CONTROLLER

PS +15V

TEMP.

MTR.

PIN DETECTOR

1.064 /im

LASER

PULSES

CHARGE

AMPL

PULSER*

D- LINEAR

AMPL*

PULSE HEIGHT

ANALYZER (PHA)

OSCILLOSCOPE

*IN NIM BIN

Figure 6.8-1. PIN transfer standard system.

50
Figure 6.8-2. Typical output of PIN transfer standard system.

7. Analysis of the Systematic and Random Errors [1-8]

The NBS measuring system generates low-level beams of known peak power

and energy for calibrations. Peak power or energy is determined from the

known splitting ratios of a precision beamsplitter attenuator, Model 1 (BA-1),

and transfer standard measurements in a higher level beam. Measurement uncer- tainties are calculated at the 95 percent Cl. Error budgets of each transfer

standard are given in reference 1.

Comparing low-level transfer standards in the modulated cw system, the

pulse energy from APD and from PIN TS measurements were with 1 to 2 percent of

each other (February 1984).

51
Table

5.

PIN

4-1

system

calibration. *

CO CM CM CO • • • •

4-> 00 LO CO oo

=> <u o CD 1 1 1 1 o c > •H- tO "3 o LO 'd" <v c_ CM r-~ to

cc • # . . o o o o V

cn o o o o c "0- CM

to cn r-> CM

t- CM oo r-H E i 1 1 1 rO o o LO CM

<U 4— CM 1—1

CO »-H

C CM CM

LxJ

•O -M i—t

0)C o 1 +->•!—

to tO tO »« cn

O CM CO

+-> E -m lo ** . • . . o t- CTJ 00 CM CM 1— -»-> <3J i—1

r-H to O 4-> <u c lO 3

t/)

C <4- 4-> •r- O C

OJ t—t

>, 0) E O p o) a) C tO t» •d- VO LO LO

•I— l_ 3 • • • • ID D Vt OJ o o o o

-t-> > tO I- tO

M • tv E CO tO U QJ ZL c r flj =>+->-!= CM

+J • O

a.

0)

0J5

to in c • 4- O oo A O -r- -M § c

•r— t- tO LO 00 5S- LO 1 O) t_ c r^» CO CO CO -L> cn

JD JO to 3 E -r- 2: to

+-> a» CL o t/> G

s:

+-> 3 r-H o • LO c CM 00 j- J- >> CM o ^ H r*H rH i—H « tO tO <C

•r- CM | e i 1 tO OJ r—

M E o o o o .c CL a; <0 O r-H r-H r-H r-H -*-> -a • £_ -t- •H- c V 00 CM

JO > • • • • o > * i

• -C F— E r— CM Z CM o *— * r-i CM • +-> • LxJ E

tO -3 o i-*- CO rx

O 1— •F— o s:

a

A

O • • • . zo lO i

OJ

r-H CM LO CM o o X 00 <n CL a CL CO r-H o o QJ *' r"0 00 o

•i— (— (_ tO

Q • to «c to a< o o

oj ac r— 1 t_ CL o cm ac to 1

V Q. LxJ a> v— • r— QJ c o O o O c r-H •r— <_) oc t_ a

4-

C •r— o O o o o CO 1— 1— to to

•r- * •itO LO o o o •r— z: o o

>— * 4- CT> • • . * 4-> >- <D CL CM o r-H (—1 1 1 tO 00 • • .. Q <d- E C\J C_ < 1— LxJ 2 3 O IO CM JO Z3 Q 4-> cn

•r— • • CL r-H LxJ t_ r^. t- O 0) r—

cc 1

OO oj to t— to C tO _l CO Z <C CL

X

<u £_ •r— LO o o o <_> CO o —i 2T < l— c tO to rH LO o •I— o OJ rH * * 4- -tf

52
Table

6.

PIN

4-3

system

calibration

CD CO «—

H • • • •

4-> CD lO oo oo

i3 a) O cn 1 1 1 i O C > -H- T5 <C3 CM CD

aj tO LO CM <3- OC • • • • o o o o

a)03 o o o o c 00 <T)

<TJ CM CO «-H t_ CM CD I—i E >>0 4- 1 1 1 I cn\

t- o 00 o rH o 03 4- r—4

LO 1—1

f—l c i—1

>>

O 4-> i—<

03

C

O •— 4-> •!—

(T3 CO <a s* o o *3"

4-3 E LO • • • • o •I— CD 00 00 CsJ CVJ 1— -M ai r-H r-H

t/> o +-> <U c (O • 3

LO

3.

C\J

CO

C 4- 4-> •r- O C

03 t—i

>, 03 E O p Ol D C I.

•i— £_ 3 Ifl it

«3 0) LO CD

+-> > fO

t- ro gj

p CL) E <0 o 03 c x= 0) zi pr+->

n <j- • • • • o o o o o

CL

a>

o>s

</)

00c

r-I CT> 3

CL

10

cr

<4-

O

O -r- 4-> C— fO

ai l c

-Q jD I—l *3" CO O) in co co

00§

LOCM<I"-

+-> "

to cm

4-> c_> <u

«/) -oc

4-3 (O 3O CM c CO CO J- Jt >> ct o N #—i

rHH rH • fO to C-

•r— CM l 1 1 I </> 0) t—

4-3 E O o o o x: CL <13 r> to O r-H rH rH »—)

4-3

O • f-H (_ 4- •H- e: 03 OO

-O > • • • • o > * tz zz

•r—

—

r E • 1— CM Z • 0 r— CO LO • 4-3 • LU Csl

<T3 -3 CO CO CO CD t— •1“

O 21 E O • • • • LO zd L0 1

a 03 03 CM •3- CM o O X 00 CL

-a CL :z> 0 O o LU * rD 0 O

•r— 1— C_ L0 CD • L0 < to rH O

03 oc t r—

CL

O CM QC <a r—

ai * CL LU 03 • r— r— aj c o o o o c r-H •r— 0 in £_ O

4- c •i— o o o o o CO 1— 1— <o L0 r— 4c •1

LO o o o •r— 2: 0 O

r— 4c 4- CD • • • • 4-3 >- 03 CL CM o rH «-H rH CO 00 • • .. 0 c_ E CM (_ < (— LU Z 3 O <T3 CM X2 ZD Q 4-3 CD r— • • CL h LU (_ cc_ O a> r— ac 1— OO 03

ns 1— 00

C <T3 __i ZD 2= < CL

X 03 L, •r— LO o o o C_> CO O •— S <C 1— c to CO t—1

LO o •r— o cn rH 4c 4c 4- 44 _J o 4c

53
Table 7. Error budget PIN 4-1 system

Source of error Uncertainty %*

Redw 3 TS for linear amplifier gain

of 5, 0.500 and 10, 1.000 1.9

PIN 4-3 TS for linear amplifier gain

of 50, 1.000 and 100, 1.000 of PIN 4-1:

Redw 3 TS 1.9% + Beamsplitter 2.5% +

+ Oscilloscope 3.0%

Precision 0.6%

8.0

Beamsplitter attenuator

(1) Linear amplifier gain of 5, 0.500

and 10, 1.000 and beam ratios of

(m=0)/(m=2) and (m=Q)/(m=3) 2.5

(2) Linear amplifier gain of 50, 1.000

and 100, 1.000 and beam ratio of

(m=2)/(m=3) 0.7

Oscilloscope readout

Precision and uniformity for linear amplifier gain

3.0

5, 0.500 0.5

10, 1.000 0.6

50, 1.000 0.5

100, 1.000 0.6

Total error budget for linear amplifier gain

5, 0.500 7.9

10, 1.000 8.0

50, 1.000 12.2

100, 1.000 12.3

*At the 95 percent Cl.

54
Table 8. Error budget PIN 4-3 system.

Source of error Uncertainty %*

Redw 3 TS for linear amplifier yain

of 5, 0.500 and 10, 1.000 1.9

PIN 4-1 TS for linear amplifier gain

of 50, 1.000 and 100, 1.000 of PIN 4-3:

Redw 3 TS 1.9% + Beamsplitter 2.5% +

+ Oscilloscope 3.0%

Precision 0.6%

8.0

Beamsplitter attenuator

(1) Linear amplifier gain of 5, 0.500

and 10, 1.000 and beam ratios of

(m=0)/(m=2) and (m=0)/(m=3) 2.5

(2) Linear amplifier gain of 50, 1.000

and 100, 1.000 and beam ratio of

( m=2 ) / (m=3) 0.7

Oscilloscope readout

Precision and uniformity for linear amplifier gain

3.0

5, 0.500 0.6

10, 1.000 0.6

50, 1.000 0.6

100, 1.000 0.6

Total error budget for linear amplifier gain

5, 0.500 8.0

10, 1.000 8.0

50, 1.000 12.3

100, 1.000 12.3

*At the 95 percent Cl.

55
7.1 Analysis of Errors of the APD Transfer Standards

Source of Error Analysis

1. Redw 3 transfer standard in the

(m = 0) beam (commercial calorimeter and power meter)

2. Precision beamsplitter attenuator

(unknown polarization)

3. Inequivalence of pulsed and

cw power

4. Oscilloscope

5. Amplitude response of the

wideband amplifiers

6. Precision and uniformity

7. Field of view

8. Impulse response

9. Time interval

1. Calibrated by the C and Q-series

calorimeters [2,3,6], Random and

systematic errors of calibration

are added.

2. [4]

3. Pulses should reach the level of cw power during the pulse duration.

a. Checked by measuring the variation of the pulse peak for

durations from ~200 to

~600 ns.

b. Checked by comparing pulsed

and cw power calibration meas- urements .

4. Calibrated oscilloscope deflection

factor, time base, and impulse

response [5].

5. Calibrated by measuring the

variation in the pulse peak for

durations from 10 to 200 ns of

pulse generator pulses passing

through the wideband amplifier.

6. a. Precision determined over each

gain calibrated,

b. Uniformity determined at a given input over the collector

area by measuring the responsivity at the center and in

the four cardinal directions

near the edge of the photodiode.

7. Calibrated by measuring the

responsivity at several input

angles into the APD in the four

cardinal directions.

8. Correction factors for the peak

voltage determined from the convolution of the impulse response and

Gaussian pulses and skewed Gaussian pulses.

9. Calibrated by a timer/counter.

56
7.2 Analysis of Errors of the PIN Transfer Standards

Source of Error Analysis

1. Redw 3 transfer standard in the

(m = 0) beam (commercial calorimeter and power meter)

2. Precision beamsplitter

attenuator (unknown polarization)

3. Oscilloscope

4. Precision and uniformity

5. Pulse rate

6. Time interval (shutter)

7. Pulse height analyzer readout

1. Calibrated by the C- and Q-series

calorimeters [2,3,6]. Random and

systematic errors of calibration

are added.

2. [4]

3. Calibrated oscilloscope deflection

factor, time base, and impulse

response.

4. a. Precision determined over each

gain calibrated.

b. Uniformity determined at a given input over the diode

area by measuring the responsivity at the center and in the

four cardinal directions near

the edge of the photodiode.

c. Uniformity also determined by

scanning the area of the

photodiode with an ultrastable

cw laser beam and

photographing the oscilloscope

readout.

5. Calibrated by a timer/counter or frequency counter.

6. Calibrated by a readout of a light sensor and amplifier attached to a timer/counter.

7. Linear if the pulse duration is

<200 ns and the internal settings

of the linear amplifier are TC

2 yS, mult X0.2.*

Linear amplifier settings greater than these pass excessive noise and less

than these make calibrations nonlinear.

57
7.3 Calibration of Redw 3 (TC15) Transfer Standard (Time Dependent)

Redw 3 (TC15) Date: Apr 85

Nati onal

standard

reference

used

Scales Calibration

(meter units/

joule)

n 95%

Cl

Date of latest

calibration

C-series 10 J, 100 s 1.092 21 0.13 24 Apr 85

1 J, 100 s 1.094 28 0.18 23 Apr 85

0.1 J, 100 s 1.088 20 0.40 24 Apr 85

Q-series 10 J, 100 s 1.090 20 0.22 24 Mar 82

1 J » 100 s 1.086 21 0.27 25 Mar 82

Currently, the C-series national reference standard only is used to calibrate

the Redw 3 (TC15) TS. Calibrations are independent of the reference standards. The C-series reference standard is easier to use.

58
7.4 Summaries of the Uncertainties at the 95 Percent Confidence Interval of

Calibrations of the APD and the PIN Transfer Standards

APD 5-1 Date: Aug 85

Summary of the uncertainties at the 95 percent Cl of the calibration of

APD 5-1 transfer standard (time dependent)

Source of

uncertai nty

Source of

i nformati on Date Uncertai nty

%*

Comments

Redw 3 TS Cali brati on 4/85 1.9

Precision beamsplitter attenuator

(unpolarized beam)

[4] 2.5

Inequivalence of

pulsed & cw power

Cali brati on 4/81 2.5

Osci lloscope Cal i brati on 2/85 3

(verti cal

deflecti on)

Amplitude

response of

the wideband

ampl i f i er

Cali brati on 12/81 2.5

Time interval

cw input

Calibration 8/85 0.0

Impul se response

Calibration 7/81 0.0 Correction factors

of the pulse height

between 10 ns and

100 ns Precision Calibration 5/85 0.4, 0.6,

0.6

For gains of 0, 20,

and 40 dB, resp.

Uni formity Cal i brati on 11/80 0.9

Field of

vi ew

Cal i bration 12/80 1.0 For divergence of

25 mrad

For APD 5-1 the

precision, uniformity, and field of

view uncertainty

are combined into

the largest uncertainty, 1.0%

Total 10.9, 13 .4, 13.4 For gains of 0, 20,

and 40 dB, resp.

*At the 95 percent Cl.

59
APD 5-5 Date: Aug 85

Summary of the uncertainties at the 95 percent Cl of the calibration of

APD 5-5 transfer standard (time dependent)

Source of

uncertainty

Source of

information

Date Uncertainty

%*

Comments

Redw 3 TS Cal i brati on 4/85 1.9

Precision beamsplitter attenuator

(unpolarized beam)

[4] 1.9

2.5

Without HP 462A amp.

With HP 462A amp.

Inequivalence of

pulsed & cw power

Calibration 4/81 2.5

Oscilloscope Cali brati on 2/85 3 Vertical deflection

Amplitude response

of the wideband

ampl ifier

Calibration 12/81 2.5

Time interval

cw input

Calibration 8/85 0.0

Impulse

response

Cali brat ion 7/81 0.0 Correction factors

of the pulse height

between 10 ns and

100 ns Precision Cal i brati on 6/85 0.5,0. 5,

0.7

For gains of 0, 20,

and 40 dB, resp.

Uniformity** with

alignment (1)

and (2)

Calibration 5/85 0.9 and

1.7, resp •

Field of

view

Cal i brat ion 12/81 1.1 For divergence

of 15 mrad

Correction factor

for alignment (2)t

Cal i brati on 5/85 0.6 Correction factort = 1.05

For APD 5-5 the precision, uniformity,

and field of view

uncertainty are combined into the

largest uncertainty,

alignment (1)** 1.1%

and alignment (2)**

1.7%

Alignment (1)**

Alignment (2)**

Total 10.4,

Total 11.6,

13.5, 13.5

14.7, 14.7

For gains of 0, 20,

and 40 dB, resp.

60
* At the 95 percent Cl.

**(1) Incoming beam reflected on itself from mirror attached to the detector

entrance.

(2) Maximum output with the beam entering the center of the detector and

moving the detector parallel to this position for other measurements.

t Correction factor for alignment (2)

average alignment (2) uniformity measurements

average alignment (1) uniformity measurements’

PIN 4-1 Date: Aug 85

Summary of the uncertainties at the 95 percent Cl of the calibration of PIN 4-1

transfer standard (time dependent)

Source of Source of Date Uncertai nty Comments

uncertai nty information %*

Redw 3 TS Calibration 4/85 1.9 For linear amplifier

gain of 5, 0.5; 10,

1; 50, 1; and 100, 1 PIN 4-3 TS Cali brati on 5/85 8.0 For linear amplifier

gain of 50, 1 and

100, 1.

Precision beam- [4] 2.5 and For linear amplisplitter attenuator 0.7 fier gain of 5, 0.5

and 10, 1; and 50, 1 and 100, 1; resp.

Osci 1 loscope Calibration 2/85 3.0 For vertical deflection

Pulse rate Cali brati on 4/82 0.0

Time interval

(shutter)

Cal i bration 8/85 0.0

Precision Calibration 5/85 0.4 For linear ampli0.6 fier gain of 5,

0.5 0.5; 10, 1; 50, 1;

0.6 and 100, 1; resp.

Uniformity Calibration 2/82 0.5 The uniformity is

referred to only if

it exceeds the precision.

Totals 7.9, 8.0, 12 .2, 12.3 For linear amplifier

gain of 5, 0.5; 10,

1; 50, 1; and 100, 1 resp.

*At the 95 percent Cl.

61
PIN 4-3 Date: Aug 85

Summary of the uncertainties at the 95 percent Cl of the calibration of PIN 4-3

transfer standard (time dependent)

Source of

uncertai nty

Source of

information

Date Uncertai nty

%*

Comments

Redw 3 TS Calibration 4/85 1.9 For linear amplifier

gain of 5, 0.5; 10,

1; 50, 1; and 100, 1, PIN 4-1 TS Calibration 5/85 8.0 For linear amplifier

gain of 50, 1 and

100, 1.

Precision beamsplitter attenuator

[4] 2.5 and

0.7

For linear amplifier gain of 5, 0.5

and 10, 1; and 50, 1 and 100, 1; resp.

Osci 1 loscope Calibration 2/85 3.0 For vertical

deflection.

Pulse rate Calibration 8/85 0.0

Time interval

(shutter)

Calibration 8/85 0.0

Precision Calibration 5/85 0.4

0.3

0.4

0.4

For linear amplifier gain of 5,

0.5; 10, 1; 50, 1;

and 100, 1; resp.

Uni formi ty Calibration 6/80 0.6 The uniformity is

referred to only if

it exceeds the precision.

Totals 8.0, 8.0, 12 .3, 12.3 For linear amplifier

gain of 5, 0.5; 10,

1; 50, 1; and 100, 1 resp.

*At the 95 percent Cl.

62
8. Procedures for Quality Control of the Modulated cw Measurement System and

of the APD and PIN Transfer Standards

8.1 Alignment Verification

1. Before measurements proceed each day, the modulated cw measurement

system is aligned or realigned as described elsewhere.

2. APD and PIN transfer standards are aligned as described elsewhere.

3. APD and PIN transfer standards previously aligned do not need re- alignment each day, if the modulated cw measurement system required

little alignment at the beginning of the day.

8.2 Optical Surface Maintenance

1. The mirrors and first lens are always covered.

2. The modulator, the second lens and the precision beamsplitter attenuator are covered between uses.

3. When uncovered, dust is blown off their surfaces with a hand-squeeze

type air blower.

4. If the surfaces appear dirty and calibration values appear out of

control, the precision beamsplitter attenuator is cleaned by passing

lens tissue containing methanol across its surfaces and letting the

alcohol evaporate.

8.3 Laser Mode and Stability Requirements

1. The laser should have single mode output.

2. If the laser shows a multimode pattern at the first mirror, the laser

should be realigned as described elsewhere.

3. If the oscilloscope readout of the APD or PIN transfer standard are too

unstable to read, the laser current is increased; or if instability

persists, the flash lamp of the laser is replaced.

8.4 Shutter for Timed Laser Input Calibration

1. The shutter time is calibrated for a 100 s input periodically as described elsewhere.

2. If the time error is greater than 0.05 percent, the time base of the

time generator in the shutter system is corrected.

8.5 Redw 3 Transfer Standard Calibration

1. The Redw 3 transfer standard to which all calibrations are referred is

calibration checked once a year.

2. Calibrations are performed on the C-series system only since C-series

and Q-series calibrations of the Redw 3 transfer standard are within

the experimental error of each other.

3. Calibrations are performed on the 0.1 J, 1 J, and 10 J and 100 s scales

for at least three settings of each J scale.

8.6 Oscilloscope Calibration

1. The vertical deflection of the oscilloscope readouts is calibrated

every 12 to 18 months using the NBS or commercial amplitude calibrator.

63
2. The time base of the oscilloscope readout is calibrated every 12 to 18

months using a time mark generator.

3. The impulse response of the oscilloscope readout for the APD transfer

standard is calibrated using a step generator (rise time <25 ps).

4. Vertical deflection and time base scales are adjusted to be within the

manufacturer's specification when necessary.

8.7

Time and Frequency Measurement Equipment Calibration

1. The timer/counter is calibrated every 12 to 18 months.

2. The electronic counter is calibrated every 12 to 18 months.

8.8

APD and PIN Transfer Standard Calibration

1. The APD and PIN transfer standards are calibrated at least six levels

for each gain setting.

2. The APD TS gain settings calibrated are 0 dB (without the wideband

amplifier) and 20 dB and 40 dB (with the wideband amplifier).

3. The PIN TS coarse and fine gain settings calibrated are 5, 0.500; 10,

1.000; 50, 1.000; 100, 1.000; and, when needed, 200, 1.000.

4. APD and PIN transfer standards are recalibrated at one or more levels

of each gain setting every 6 to 12 months and before and after their

use.

8.9

APD and PIN Transfer Standard Uniformity and Field of View Calibrations

1. APD and PIN transfer standards should be calibrated at least near the

center and the edge of approximately a 1 cm

2

area in the four cardinal

directions at one input level to determine the uniformity of the

calibration over the surface.

2. APD transfer standards should be calibrated at various angles to the

incoming beam in the four cardinal directions to determine the field of

view or the calibration correction factor versus the beam divergence.

3. Each PIN TS should be scanned with a stabilized cw NdrYAG laser, and

the surface responsivity from an oscilloscope readout should be

photographed. The most uniform responding PIN silicon photodiodes

should be selected as PIN transfer standards.

8.10

Pulse Height Corrections of APD Transfer Standards from Impulse Response

Measurements

1. These corrections and measurements are repeated if the preamplifier

and/or wideband amplifier attached to the APD are changed.

2. These measurements are made in a linear region of the APD TS.

9. Computer Programs for Computation and Treatment of APD and PIN Transfer

Standard Calibration Data

1. DMAKE is for creating a new disk data file.

2. RENAMEFILE is for changing the name of a disk data file to another

name.

3. APD is for computing APD transfer standard calibration data.

64
4 . APDSCAN sorts out specified APD calibration data for evaluating their

status and for the APDDATE and the APDPLOT program sequence.

5. APDDATE (start with APDSCAN) processes run number data for a chronological plot of APD calibration data to detect trends in the calibration.

6. APDPLOT (start with APDSCAN) plots the percent variation of each APD

calibration value from the average value versus time in months and

years on the screen. It makes available on hard copy the average APD

calibration value, the percent variation of each calibration value from

the average value, the standard deviation, and the 95 percent Cl.

These data help show the stability, scatter, and trends of the

cal i brati on.

7. EDITAPD edits APD files. It also sorts them by date and run.

8. AREA creates data files at the areas specified for peak power density

and energy density calibration data of the APD and PIN transfer standards, respectively.

9. PINSCAN sorts out specified PIN calibration data for evaluating their

status and for the PINDATE and PINPLOT program sequence.

10. PINDATE (start with PINSCAN) processes run number data for a chronological plot of PIN calibration data to detect trends in the cal i brati on.

11. PINPLOT (start with PINSCAN) plots the percent variation of each PIN

calibration value from the average value versus time in months and

years on the screen. It makes available on hard copy the average PIN

calibration value, the percent variation of each calibration value from

the average value, the standard deviation, and the 95 percent Cl.

These data help show the stability, scatter, and trends of the

calibration.

12. EDITPIN edits PIN files. It also sorts them by date and run.

13. PIN J12 is for computing PIN transfer standard data referring to a Redw

3 transfer standard.

14. PIN J34 is for computing PIN transfer standard data referring to a PIN

transfer standard.

15. DUPDISC creates a backup disc.

16. DELETEAPD generates new files from old ones and has multiline deleting

procedure.

17. AREAAPD generates data files at areas specified.

18. APDPL0T1 plots chronologically the percent variation of each APD

calibration value from the average. Otherwise it is similar to

APDPLOT.

19. PINPL0T1 plots chronologically the percent variation of each PIN

calibration value from the average. Otherwise it is similar to

PINPLOT.

20. AREAPIN generates data files at areas specified.

21. LEASTSQR sorts data to be used for a least square fit, dumps the data

into SQR and calls up program LINEAR to perform the least square fit.

10. Location of Programs and Data Files

10.1 Main Disc APD Rasmussen

Backup 1 APD for Rasmussen APD Disc

Backup 2 APD for Rasmussen APD Disc

Magnetic tape cartridge 34 with one of the above

65
10.2

Main Disc PIN Rasmussen

Backup 1 PIN for Rasmussen PIN Disc

Backup 2 PIN for Rasmussen PIN Disc

10.3 Redw 3 (TC 15)

Main Prog C Series

Main Data

10.4 Impulse Response

TAPE PAS9 Convolution of two waveforms

11. Data File Identification (e.g., 1430505, A5500, or P411010)

A. Single Letter I (unity area), A (APD area specified), or P (PIN area specified) 1 B. Double digit identifying transfer standard like 41, 43, 51, 52, etc.

C. Double digit like 00, 20, or 40 for APD amplifier gain or

D. Four or five digits like 0505, 1010, 5010, or 10010 for PIN amplifier

gain

E. Additional letters or digits for chronology like NEW, 85, etc.; for area like 20, 45, 81, etc.; for the purpose of the measurements like 2

(uniformity), 3 (field of view), et al

.

F. In programs APD, J12 and J34 for computing data, codes are explained

12. Computer Calibration Data of Redw 3 and APD and PIN Transfer Standards

A. Redw 3 TS Calibration Data (files 10 J, 100 s; 1 J, 100 s, 0.1 J, 100s)

B. APD 5-1 TS Calibration Data (files 15100, 15120, 15140, A5100, A5120,

A5140)

C. APD 5-5 TS Calibration Data (files 15500, 15520, 15540, A5500, A5520,

A5540)

D. PIN 4-1 TS Calibration Data (files 1410505, 1411010, 1415010, 14110010,

P410505, P411010, P415010, P4110010)

E. PIN 4-3 TS Calibration Data (files 1430505, 1431010, 1435010, 14310010)

13.

References

[1] Sanders, A. A.; Rasmussen, A. L. A system for measuring energy and peak

power of low-level 1.064 ym laser pulses. Nat. Bur. Stand. (U.S.) Tech.

Note 1058; 1982 November.

[2] West, E. D.; Case, W. E.; Rasmussen, A. L.; Schmidt, L. B. A reference

calorimeter for laser energy measurements. J. Res. Nat. Bur. Stand.

(U.S.) 76A( 1 ) ; 1972 January-February

.

[3] Franzen, D. L.; Schmidt, L. B. Absolute reference calorimeter for measuring high power laser pulses. Appl . Opt. 15(12); 1976 December.

[4] Danielson, B. L. Measurement procedures for the optical beam splitter

attenuation device BA-1. Nat. Bur. Stand. (U.S.) NBSIR 77-858; 1977 May.

[5] Andrews, J. R.; Baldwin, E. E. Amplitude calibrator for oscilloscopes.

Nat. Bur. Stand. (U.S.) NBSIR 81-1646; 1981 April.

66
[6] Case, W. E. Quality assurance program for the hBS C, K, and Q laser

calibration systems. Nat. Bur. Stand. (U.S.) NBSIR 79-1619; 1979 August.

[7] Case, W. E. Documentation of the NBS C, K, and Q laser calibration systems. Nat. Bur. Stand. (U.S.) NBSIR 82-1676; 1982 September.

[8] Rasmussen, A. L.; Sanders, A. A. Transfer standards for energy and peak

power of low-level 1.064 micrometer laser pulses and continuous-wave laser

power. Opt. Eng. Paper 2097; 1986 February.

67
NBS-114A (REV. 2 -80 ) U.S. DEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. Report No. 3. Publication Date BIBLIOGRAPHIC DATA

SHEET (See instructions)

REPORT NO.

NBSIR 85-3032 December 1985

4. TITLE AND SUBTITLE

Documentation of the NBS APD and PIN Calibration Systems for Measuring Peak Power

and Energy of Low-Level 1.064 urn Laser Pulses.

5. .AUTHOR/ S) . „ „

. A. L. Rasmussen and A. A. Sanders

6 . PERFORMING ORGANIZATION (If joint or other than NBS. see instructions) 7 . Contract/Grant No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9.

SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State. ZIP)

Department of Defense, Calibration Coordination Group,

Aerospace Guidance and Metrology Center, Newark Air Force Station, Ohio 43057,

Metrology Engineering Center, Department of the Navy, Pamona, CA 91769

10

.

supplementary notes

"] Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here) National Bureau of Standards APD (avalanche) and PIN silicon photodiode transfer

standards are documented for a calibration service to measure 1.064 pm laser

_ o _ 4 -Ifi -11

pulses from MO to MO W peak power and M0 to M0 J energy. A

modulated cw measurement system generating known low-level pulses is described.

Calibration support equipment, systematic and random errors, and computer programs

and calibration data are also described.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semi col qn s) APD transfer standards; beamsplitter attenuator; calibration procedures; calibration

service; low-level laser measurements; modulated cw measurement system; 1.064 pm

laser pulse measurements; PIN transfer standards; pulse energy; pulse peak power.

13. AVAILABILITY 14. NO. OF

PRINTED PAGES

|X | Uni imited

| | For Official Distribution. Do Not Release to NTIS

I n Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

74

15. Price

[X | Order From National Technical Information Service (NTIS), Springfield, VA. 22161

USCOMM-DC 6043-P80

U. S. GOVERNMENT PRINTING OFFICE: 1986-677-461/45,092 REGION NO. 8