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NBS TECHNICAL NOTE 665

U. S. DEPARTMENT OF COMMERCE /National Bureau of Standards
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology,

the Institute for Computer Sciences and Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United

States of a complete and consistent system of physical measurement; coordinates that system

with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Nuclear

Sciences " — Applied Radiation " — Quantum Electronics ' — Electromagnetics 3 — Time

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Radiation — Physical Chemistry.

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the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of

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Environment ' — Technical Evaluation and Application * — Fire Technology.

THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides technical services designed to aid Government agencies in improving cost effec- tiveness in the conduct of their programs through the selection, acquisition, and effective

utilization of automatic data processing equipment; and serves as the principal focus within

the executive branch for the development of Federal standards for automatic data processing

equipment, techniques, and computer languages. The Institute consists of the following

divisions: Computer Services — Systems and Software — Computer Systems Engineering — Information Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and

accessibility of scientific information generated within NBS and other agencies of the Federal Government; promotes the development of the National Standard Reference Data System and

a system of information analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services to ensure that the NBS staff has optimum

accessibility to the scientific information of the world. The Office consists of the following

organizational units: Office of Standard Reference Data — Office of Information Activities — Office of Technical

Publications — Library — Office of International Relations.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

3 Part of the Center for Radiation Research.

3 Located at Boulder, Colorado 80302.

« Part of the Center for Building Technology.
IR 2 4 1975 *t CXJtd

%Ts, A Pyroelectric Power Meter for the

I

s Measurement of Low Level Laser Radiation

C. A. Hamilton

G. W. Day

^'TeakniCuoJ no+e no. k&5"

Electromagnetics Division

Institute for Basic Standards

U.S. National Bureau of Standards

Boulder, Colorado 80302

» ?sg=arj o

US. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS Richard W Roberts Director

Issued February 1975
National Bureau of Standards Technical Note 665

Nat. Bur. Stand. (U.S.), Tech Note 665, 41 pages (Feb. 1975)

CODEN: NBTNAE

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC. 20402

(Order by SD Catalog No. C13. 46:665) $1.00
FOREWORD

The decision to develop the laser power meter described here

resulted from need with the laser industry for a rapid, convenient

means of low level measuring laser power. It was originally

encouraged by T. W. Russell who was responsible for the Laser

Measurement Assurance Program. The work was performed under the

supervision of R. J. Phelan, Jr., Optical Electronics Program

Leader. Others who gave substantial assistance to the project were

L. 0. Mullen, K. W. Pyatt , C, . P. Klein, Y. Beers, and Debra Deichman,

111
CONTENTS

Page

1. Introduction 1

2. Detector Design and Fabrication 2

3. Instrument Design 4 3.1 Preamplifier 8 3.2 Chopper and Speed Control 9 3.3 Readout Circuitry 12

4. Evaluation 12

4.1 Precision 14

4.2 Corroboration 26

4.3 Uniformity 26

4.4 Spectral Response 26

4.5 Linearity 28

4.6 Power Limits 30

4.7 Conclusions 30

5. References 33

List of Figures

Figure 1. Pyroelectric detector design 3

Figure 2. System block diagram 5 Figure 3. Pyroelectric Laser Power Meter being used to 6 measure the power from a He-Ne laser

Figure 4. Preamplifier converts low level detector

output into a dc voltage

Figure 5. A thermister in the preamplifier compensates 10

for the detector temperature coefficient

Figure 6. Chopper speed control and delayed reference 11

square wave

Figure 7. Readout circuit sets decimal point and calibrates ... 13

the four ranges

Figure 8. The ratio P1/P2 (divided by its mean) vs. the 15

date on which the measurement was made

iv
List of Figures (continued) Page

Figure 9. The ratio P2/P3 (divided by its mean) vs. the , date on which the measurement was made

Figure 10. The ratio P3/P1 (divided by its mean) vs. the , date on which the measurement was made

Figure 11. The ratio Pl/PSI (divided by its mean) vs. the

date on which the measurement was made

Figure 12. The ratio P2/PSI (divided by its mean) vs. the

date on which the measurement was made

Figure 13. The ratio P3/PSI (divided by its mean) vs. the

date on which the measurement was made

Figure 14. The ratio Pl/PSI (divided by its mean) vs. the room temperature at the time of measurement

Figure 15. The ratio P2/PSI (divided by its mean) vs. the room temperature at the time of measurement

Figure 16. The ratio P3/PSI (divided by its mean) vs. the room temperature at the time of measurement

Figure 17. Analysis of the data from figs. 8-16 . . . . , Figure 18. Response map of the detector from instrument 1 Figure 19. Detector linearity vs. power level

Figure 20. Uniformity maps of a detector before and after

exposure to a 55 mW beam (3.2 W/cm^ at center)

Page

16

17

19

20

21

22

23

24

27

29

31

V

A Pyroelectric Power Meter for the Measurement

of Low Level Laser Radiation

C. A. Hamilton and G. W. Day

2 s A 1 cm plastic (PVF-J Pyroelectric

detector, developed in this laboratory, has

been applied to measure low level laser

power. The result is a compact instrument

which has a low noise equivalent power

- 8 J' (10 ' W/Hz 2 ), and fast response (1 s aver- aging time), and which is precise (a ~ ± 1%) , uniform (~ ± 1%) , and inherently free from

short term drift. This note describes the

fabrication of the detector, the design of

the instrument, and the results of an ex- tensive evaluation of three such instruments.

Key words: Laser; power; pyroelectric.

1. Introduction

As a part of research program to develop high detectivity, large area pyroelectric detectors required by certain problems in laser

metrology, we have designed, constructed and evaluated a transfer

standard type of Laser Power Meter. This instrument is fast, precise

and operates at low power levels. In this note we present the design

details and evaluation results on three of these instruments.

The detector utilized in these instruments is based on the pyroelectric effect in PVF„ (polyvinylidene fluoride) and has been under
development in this laboratory for several years. The devices have an

2 active area of 1 cm . They are inherently uniform (~ ± II) over their

surface and have a large dynamic range. Because they are thermal detectors,

their spectral response is determined entirely by the absorptivity of their

surfaces (typically gold black). For their size, these plastic pyroelectric

detectors have a noise equivalent power which is unmatched by any other

thermal detector (1-2 nW/Hz 2 at low frequencies).

2. Detector Design and Fabrication

Figure 1 shows the details of the detector assembly. The plastic

used is 6 urn thick PVF

2 (polyvinylidene fluoride). " ^ Nickel films, 0.01 ym

thick, are vacuum deposited on each side of the PVF2 so that circular

2 overlapping electrode areas of 1 cm are formed.

The circular area is then coated with a highly absorbing gold black

r f\ 71 layer. ' J This is accomplished by mounting the detector 7 cm above a gold

filled tungsten filament in a sorption pumped vacuum system. The system is

-3 2 pumped to about 10 torr (1 torr = 133.3 N/m ) and back filled to 1.5 torr

with high purity nitrogen. Gold is then evaporated until a resistance monitor

in the vicinity of the detector reads about 100 ohms/square.

Contact to the nickel electrodes is made through conducting epoxy

to metal rings on either side of the plastic. Since the epoxy tends to

weaken the dielectric strength of the plastic, the front contact points

o are rotated 90 from the back contact points. This keeps the weakened

areas of the plastic well separated and prevents breakdown during the poling

process

.

The detectors are poled ' in a three step process: (i) the device

o is placed in an oven at 100 C and allowed 5 minutes to reach the oven temperature, (ii) a voltage of 800-1000 volts (1.3 - 1.6 x 10 V/cm) is applied across

the nickel electrodes for another 5 minutes, (iii) the device is removed

from the oven and allowed to cool for 5 minutes with the field still applied,

after which the voltage is reduced to zero.

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Finally, the detector is mounted in a sealed case with a glass window.

(For infrared measurements the window is usually hot pressed zinc sulfide.)

o The window is ground to a 1 wedge to eliminate transmission variations due

to interference between front and back faces. A good hermetic seal on the case is crucial in eliminating detector response to acoustic sources. Before one of these detectors is accepted for use in a power meter, it

must pass three tests: (i) its responsivity must be between 1.3 and 2.2 x

10 A/W, (ii) its response must be uniform to ± \% over its receiving area,

-q ^ and (iii) its NEP must be less than 5 x 10 W/Hz 2 at 10 Hz. Detectors

meeting this last condition allow the power meter to meet its designed

_ Q resolution of 1 x 10 watts with a one second averaging time.

Measurements on a number of detectors have shown a typical respono sivity temperature coefficient of + 0.5%/ C. Thus, there is a calibration

change with room temperature as well as nonlinear behavior when the applied

radiation begins to warm the detector more than a few degrees. Both of these

problems are discussed in more detail in the following sections.

3. Instrument Design

r o I Almost all radiometric instruments 1 J are calibrated at one or more power levels against some standard optical source. Thus, if the detector

and its associated electronics are linear, the radiometer will be calibrated

for any input power. Figure 2 shows how this method is used in our power

meter.

Since the pyroelectric detector responds only to changes in its

temperature, the input radiation must be chopped. This is accomplished by a motor driven mechanical chopper with a 1.25 cm diameter aperture. The detector

output is amplified and synchronously demodulated to produce a dc output proportional to the chopped radiation. Since the chopper is a separate unit, the

field of view may be arbitrarily narrowed by increasing the distance between

chopper and detector. This feature is particularly useful in discriminating

against background radiation.
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The angular width of the chopper aperture relative to the blade is 20 . Thus the output wave form of the detector is dependent on the intensity distribution over the aperture. Since the preamplifier responds only to the

fundamental component and the instrument is calibrated for a narrow beam at

the aperture center, two types of error may occur. (1) If a narrow beam passes

through the aperture 6 degrees off center, the error is 1-cos 6 with the worst

case being 1.5%. (2) If the aperture is uniformly illuminated the error is

1 - —5— or a worst case of 0.5%.

yThe dc preamplifier output goes through a variable gain amplifier to a

1>\ digit display. Calibration is achieved by applying a known amount of power

and adjusting the gain to obtain the correct reading. Figure 3 is a photo

of the complete instrument as it might be used to measure the power of a He-Ne

laser beam.

The following paragraphs describe in more detail how each part of the

instrument operates.

3.1 Preamplifier

The preamplifier circuit shown in figure 4 converts the square wave

current output of the detector into a dc level. The designed dynamic range -8-2 -14-8

is 10 to 10 watts corresponding to detector outputs of 10 to 10

amperes. Because of noise considerations, it is impractical to build a

single gain amplifier with six decades of dynamic range. Thus, the first

stage is a FET input, current mode, operational amplifier whose gain is

determined by one of four feedback resistors. These resistors have a

o temperature coefficient of 0.2%/C and partially compensate for the detector

temperature coefficient. The switch which selects the resistor also provides logic signals to indicate the range setting to the display part of the

instrument. The feedback capacitors on the upper three ranges match the

amplifier time constant caused by parasitic capacitance on the lowest range.

The next stage is a narrow band amplifier which is tuned to the chopper

frequency. The sine wave output of stage 2 is synchronously rectified in
stage 3. This is accomplished by switching the gain between +1 and -1 with

the FET switch. The square wave gate for the switch is synchronized with

the chopper and has an adjustable phase delay. The next stage provides a zero adjust for the demodulated detector output, and it compensates for the

remaining temperature dependence of the detector by adding a temperature

o coefficient of -0.3%/ C. Figure 5 shows how the thermister in the feedback

network performs this task. Since the thermister is thermally tied to the

preamp case, measurements of the highest accuracy require that sufficient

time be allowed for the detector-preamp assembly to reach the same temperature. The final stage is a sharp cut-off low pass filter which

removes the ripple from the demodulated signal.

3.2 Chopper and Speed Control

Since the preamplifier is tuned to a specific frequency, it is

important that the chopper run at a precise speed. This is accomplished

by the speed control circuit shown in figure 6. In addition to intersecting the laser beam, the chopper wheel also passes through an LEDphototransistor pair. The square wave output of the phototransistor is

amplified and used to trigger a pulsing circuit. This circuit creates a stable 3 ms pulse whose height and width are independent of frequency.

Thus, when the pulses are averaged, the resulting dc level is proportional

to the chopper speed. This level is compared to a reference and the

amplified difference signal drives the motor. The servo loop described

above controls the chopper speed to better than 0.1 Hz.

A second part of the circuit provides the delayed reference square wave used in the preamplifier synchronous rectifier. The rising edge

of the phototransistor output triggers a one-shot with adjustable

pulse length. The falling edge of the one-shot output triggers a second one-shot also with adjustable pulse length. The first pulse

length is set to the desired delay time and the second is set to one half the

chopper period. Thus, the output of the second one-shot is a delayed

reference square wave.
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11
3.3 Readout Circuitry

As shown in figure 7, the readout circuitry begins with the

analog and digital outputs of the preamplifier. The four digital lines

give the range setting and are decoded to drive the display decimal

point and a mW or uW indicator. The analog output of the preamp

passes through the readout amplifier to the digital panel meter.

Reed relays select a different feedback resistor for each range. These

resistors are adjusted to make the system gain switch in exact decade

increments. This compensates for any inaccuracy contributed by the

switched preamp resistors. The input resistor to the readout amplifier is then adjusted to calibrate the whole system for a specific

detector.

The output of the readout amplifier also passes through a voltage follower to an analog output connector. This allows the instru

ment to be used with a recorder.

4. Evaluation

Three Laser Power Meters of the type described in the preceding

sections have been studied for a period of several months to assess their performance and limitations and to indicate their general utility

for the measurement of low level laser power.

The accuracy of these instruments is principally dependent on extensive and careful initial calibration. We deal here only with

relative measurements and hence obtain information about the precision of the instruments rather than the accuracy. Among the

parameters affecting the overall precision are the alignment of the

chopper and detector, detector uniformity, detector noise, temperature

coefficient, linearity, and drift in detector responsivity

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12
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the four ranges

13
Most of the measurements were made on range 2 (200 yW F.S.).

Based on design and experience with the instruments, it is expected

that similar performance should be expected on range 3 (2 mW F.S.)

and within the limits of detector linearity on range 4 (20 mW F.S.).

Range 1 (20 pW F.S.) performance may not be quite as good as the

upper ranges due to detector noise and limitations of background

light.

4.1 Precision

The principal measurements were made with a commercial 2 . 4 mW

(1/e radius = 0.45 mm, divergence = 1 m rad) unpolarized He-Ne laser

operating at 632.8 nm. The laser illuminated a wedged glass beam

splitter at a distance of 1.6 m from the laser. The first surface

o reflection (angle of incidence = 3 ) had a power level of about

100 uW. The chopper and detector of each instrument were alternately

inserted into this reflected beam at distances from the beam splitter

of 0.5 and 1.5 meters respectively. Alignment was achieved by visually

centering the beam in both the chopper aperture and detector active

area. Power transmitted through the beam splitter was measured with a silicon diode power meter; The latter power meter was fixed in position

to eliminate problems of detector nonuniformity and zero adjusted to

compensate for room temperature fluctuations.

Data were normally taken daily and consisted of measurements

of the reflected power by the three pyroelectric Laser Power Meters

(PI, P2, P3) , a measurement of the transmitted power (PSI), the date

and temperature. Several people (some of them unfamiliar with the

instruments) participated in the data taking to insert some human

factors into the evaluation.

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T3 •H • • • . <JH o o o o o o c ao o + 1 + 1 + 1 + 1 + 1 + 1 o LO vD o o r> H &-? • • • • • . CO in CN1

1—1 + O+

CN1 o1 rH1

e~5 6-? &-S 6-S &-? e~5 00 LO CN rH 1—

m

D ON CN o> 00 o o o H O o rH rH

co

QJ rH

Pu

H COH

H 00 00 6 m Is". m m vD vO

to co

=Sfe

•rH •rH •H CN ro rH CO CO CO Ph Ph Ph Ph Ph Ph _| CN CO i-l CN co

Ph Ph Ph Ph Ph Ph

vO

CO

CO

bfl •Hmeo

rH

<+H

03 t3

<u M

<HHo

L0 •H

COXi—

a)

rHP

•H

PL.

24
Reduced data consisted of the ratios P1/P2, P2/P3, P3/P1, Pl/PSI , P2/PSI and P3/PSI. There are plotted vs. date and temperature in figures

8 to 16 and the results are summarized in figure 17.

Analysis of this data for precision gives a typical standard

deviation of 1% . Because the measurements are made sequentially, the

results are dependent on the stability of the laser. The extent to

which this increases the scatter in the data is not readily measurable.

In a separate experiment, with instruments 2 and 3 in fixed alignment,

simultaneously measuring the reflected power from two nearly identical

beam splitters, the ratio P2/P3 showed a standard deviation of 0.25%.

The difference between this number and the 1.251 from figure 17 is a measure of the scatter due to the combined effects of detector non- uniformity and laser fluctuations. We thus believe that the standard

deviation numbers presented in figure 17 are conservative as a measure

of system performance. Uniformity is discussed further below.

Linear regression analysis for temperature coefficient gives a statistically significant slope only for the ratio P3/PSI. As noted

previously, the electronics of all three instruments were designed to

compensate for a temperature coefficient of the detector responsivity

of + 0.51/ C, even though some variation in the temperature coefficient

of the responsivity from detector to detector was known to exist. The

detector of instrument 3 evidently has an inherently low temperature co- efficient. A better approach would be to match the compensation of the

detector.

Analysis for long term drift shows a statistically significant

slope for two of the instruments (1 and 3) relative to the silicon

diode power meter, of 1-2 parts in 10 per day. Power meter number 2

does not show this drift. A drift of this magnitude is not of extreme

concern in an instrument which is used as a transfer standard but needs

to be considered. The source of this drift has not yet been isolated

but most likely relates to aging of either the detector itself or of

the high value feedback resistors used in the preamp. Measurements of

25
typical feedback resistors ranging over 45 days indicate that these components are probably not responsible for the drift. Long term experiments,

now in progress, are expected to further illuminate this matter.

4.2 Corroboration

Approximately 20 calibrations of a similar instrument against

the NBS C-series calorimeter have been made by the Laser Parameter

Measurements Group of NBS, Boulder. Analysis of this data shows a standard deviation of 1.27%. This data was taken on range 3 (2 mW F.S.).

It should be pointed out that this instrument was not one of the three

evaluated above and had not had as thorough a check out as the other

three

.

4.3 Uniformity

A response map of the detector from instrument 1 using a beam

diameter of ~ 0.3 mm is shown in figure 18. It is typical of the

uniformity of these plastic pyroelectric detectors. Quantitative

measurements yield uniformities (standard deviation for any array of

168 points covering roughly the central 2/3 of the area) of between

1.3 and 1.8% for these three instruments.

4.4 Spectral Response

As mentioned above, the spectral response of these instruments

is determined by the absorptivity of the gold black on the detector

and by the window transmittance . The absorptivity of the gold black

is process dependent but based on comparisons with detectors having

a known spectral response, it appears that the gold black is typically

flat and highly absorbing in the visible and becomes less absorbing at

26
Figure 18. Response map of the detector from

instrument 1.

27
wavelengths beyond 1 ym . A monotonic decrease in absorptivity between

1 ym and 25 ym of 50% is probably typical.

For the specific instruments tested, which had glass windows, the

calibration should be independent of wavelength over essentially all of

the transparent range of the window. At longer wavelengths, using a different window material, calibrations must be made at the wavelength

of interest.

4.5 Linearity

Measurements of responsivity vs. temperature show that PVF_

pyroelectric detectors may have a temperature coefficient of as much

o as 0.51/ C at room temperature. Thus, when the applied power level is

sufficient to raise the PVF

? temperature more than a few degrees, the

response will become nonlinear. This nonlinearity was measured as follows

.

A nominal 10% transmitting neutral density filter was placed in

front of one of the power meters. The filter was mounted on a swival

base in such a way that it could be moved in and out of the beam in a re2 producible fashion. Using a 2.0 mm diameter (1/e points) 632. 8 nm laser

beam, a number of power measurements were made with and without the 10%

filter. Figure 19 shows the filter input/output ratio as a function of

the input power level. In order to avoid range to range errors, the

measurement of each ratio was made without changing ranges on the power

meter. This resulted in a rather poor resolution in the low power reading

The error bars are an indication of this resolution problem.

Assuming that the filter transmission is independent of power,

the upward curve of the data is a measure of the nonlinearity in the

2 detector. The threshold of nonlinearity is about 50 mW/cm . For

the beam diameter of typical He-Ne lasers (~ 1.5 mm) nonlinearity

begins at about 1 mW. At a power of 3mW, the error is about 4% and

at 10 mW the error is 10%.

28
<

Ujo

Q.

10.4

10.2

10.0

9.8

9.6

9.4

9.2-

0.1

0.01 POWER (mW)

0.1

xr

£

6

V

10 POWER DENSITY (mW/cm2

) 100 10 00

Figure 19. Linearity was determined by using the pyroelectric

detector to measure a neutral density filter transmission ratio as a function of max power density (lower

axis) and total power (upper axis). The source was

2 a He-Ne laser with a Gaussian beam and a 1/e intensity

diameter of 2.0 mm. Each ratio was obtained on a single

range of the power meter, eliminating possible range to

range calibration errors, but increasing the scatter of

the data. The curve is a subjective estimate based on the data points

.

29
The results of figure 19 are undoubtedly a function of beam

diameter. It is expected that with larger beams the nonlinearity threshold will be a larger total power and a smaller power density.

4.6 Power Limits

Three rather mediocre detectors were chosen for damage studies

and a uniformity scan of each was made. The detectors were then

exposed for 60 seconds to successively higher beam powers from the

laser described in section 4.5. After each exposure a uniformity

scan was made. At a power level of 12 mW total and a maximum irradiance

2 of 700 mW/cm , all of the detectors survived without damage. A power

2 level of 27 mW and 1.2 W/cm caused about a 151 depression in the uni2 formity scan. Exposure to the unattenuated 55 mW (3.2 W/cm ) beam

resulted in about a 401 depression. Uniformity maps of a detector before

and after exposure to the 55 mW beam are shown in figure 20.

Based on these results, a safe maximum irradiance for these

2 detectors is 500 mW/cm". This conclusion was tested by putting a high responsivity (1.6 uA/W) , very uniform (± IS) detector in a 9 mW,

2 500 mW/cm beam for one hour. A uniformity scan made after this expo- sure showed no damage. Although the detectors are not damaged at these

high power densities, their response is highly nonlinear, and accurate

measurements cannot be made. (See section 4.5).

4 . 7 Conclusions

The goal of this effort was to exploit certain properties of

plastic pyroelectric detectors (viz. high detectivity, uniform response,

broad spectral range) for the development of a laser power meter which

was fast and could make meaningful measurements at low power levels. The

resulting instrument meets these conditions, has good precision, and is

simple to use.

30
Figure 20. Uniformity maps of a detector before and after

exposure to a 55 mW beam (3.2 W/cm^ at center)

Detector was of inferior quality prior to

exposure

31
At the present there are no other instruments with comparable

performance in this power range and with broad spectral response.

The most nearly comparable instruments are those based on high quality

silicon photodiodes. These instruments have a substantial variation

of response with wavelength and do not respond at all to radiation at

wavelengths longer than 1 urn. The problem of long term drift is significant but should not

materially detract from the usefulness of the instrument when used

as a transfer standard with regular calibrations.

32
5. References

[!•] Nakamnra, K. , and Wada, Y., "Piezoelectricity, Pyroelectricity,

and the Electrostriction Constant of Poly (vinylidene fluoride)",

J. Polymer Sci . A2, 161-173 (1971).

[2.] Bergman, J. G. , Jr., McFee, J.. H. , and Crane, G. R., "Pyroelectricity

and Optical Second Harmonic Generation in Polyvinylidene Fluoride

Films", Appl . Phys . Lett . , 18_, 203-205 (1971).

[3.] Glass, A. M. , McFee, J. H. , and Bergman, J. G., "Pyroelectric

Properties of Polyvinylidene Fluoride and Its Use for Infrared

Detection", J. Appl . Phys . 42_, 5219-5222 (1971).

[4.] Phelan, R. J., Jr., Peterson, R. L., Hamilton, C. A., and Day, G. W.

,

"The Polarization of PVF and PVF

2 ", Proc. Int. Conf. on Ferroelectricity , Ferroelectrics 7_, 375-377 (1974).

[5.] Day, G. W. , Hamilton, C. A., Peterson, R. L., Phelan, R. J., Jr.,

and Mullen, L. 0., "Effects of Poling Conditions on Responsivity and

Uniformity of Polarization of PVF- Pyroelectric Detectors", Appl . Phys . Lett . 24, 456-458 (1974).

[6.] Harris, Louis, McGinnies , Rosemary, and Siegel, Benjamin, "The

Preparation and Optical Properties of Gold Blacks", J. Opt . Soc . Am. 38_, 582-589 (1948).

[7.] Harris, Louis, and Cuff, Kermit, "Reflectance of Goldblack Deposits,

and Some other Materials of Low Reflectance from 250 my to

1100 my. The Scattering-Unit-Size in Goldblack Deposits", J.

Opt . Soc . Am. 46_, 160-163 (1956).

[8.] In addition to the instrument described in this note, we have

developed a laser power meter which makes a continuous electrical

calibration of the pyroelectric detector. See: Phelan, R. J., Jr.

and Cook, A. R., "Electrically Calibrated Pyroelectric Optical-Radiation

Detector", Appl . Optics 12, 2494-2500 (1973).

[9.] The use of a silicon diode power meter in these evaluations should in no way be construed as an endorsement. It is simply appropriate to insert

a device with a presumably different set of characteristics into the

evaluation. 33
NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBS Technical Note 665

2. Gov't Accession

No.

4. TITLE AND SUBTITLE

A Pyroelectric Power Meter for the Measurement

of Low Level Laser Radiation

7. AUTHOR(S)

C. A. Hamilton and G. W. Day

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Same as Item 9

.

3. Recipient's Accession Nc

5. Publication Date February, 1975

6. Performing Organization (-ode

8. Performing Organ. Report No.

10. Project/Task/Work Unit No. 2764152

11. Contract /Grant No.

13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200- word or less [actual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

A 1 cm

2 plastic (PVF

2

) pyroelectric detector, developed in

this laboratory, has been applied to measure low level laser power.

The result is a compact instrument which has a low noise equivalent

power (10~ 8 W/Hz*5

) , and fast response (1 s averaging time) , and

which is precise (o - ± 1%), uniform (~ ± 1%), and inherently free

from short term drift. This note describes the fabrication of the

detector, the design of the instrument, and the results of an extensive evaluation of three such instruments.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper

name; separated by semicolons)

Laser; power; pyroelectric.

18. AVAILABILITY [X^ Unlimited

|

' For Official Distribution. Do Not Release to NTIS

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