20 Sep 2011, Newrad 2011

Fiber-Coupled Cryogenic Radiometer

with Carbon Nanotube Absorber

J.H. Lehman

National Institute of Standards and Technology

325 Broadway, Boulder, Colorado 80305-3228

lehman@boulder.nist.gov

David Livigni, Nathan Tomlin, Christopher L. Cromer

National Institute of Standards and Technology, Boulder, Colorado, U.S.A.

Chris Chunnilall, Theo Theocharous

National Physical Laboratory, Teddington, Middlesex, U.K.

Acknowledgments

Where

Physical Measurement Laboratory

Quantum Electronics and Photonics Division

Sources and Detectors Group

Laser Radiometry Project (11 people)

Laser Power Meter Calibration Services (10 % of NIST by income)

Wavelength m

0.1 1 10

lithography

communications

night vision systems

space - based sensors

industrial mfg. processes

medical systems

Pow

er

(W)

The next generation of detectors for laser power and energy

measurements traceable to NIST E

nerg

y (J

)

10-9

105 106

10-12

misc. military

chem/bio

Why

quantum candle

Motivation

1. C-series

2. LOCR

3. Fiber-based responsivity

with FC connector

4. Spectral responsivity

Detector

Nearly collimated

Diverging from fiber

Diverging from

monochromator

(6 nm bandwidth)

Beam geometry Measurement system

“Relative”

Absolute

(The customer)

Motivation

J. H. Lehman, C. M. Wang, M. L. Dowell, and J. A.

Hadler, Journal of Research of the National Institute of

Standards and Technology, 114, 287-291, 2009.

Absolute and Spectral Responsivity

(laser)

(f/4 monochromator and bulb)

Transfer Standards

4x Trap detectors

J. H. Lehman and C. L. Cromer, Appl. Opt., 41, 6531-6536, 2002.

Cryogenic Radiometer

fiber in??

Ideal scenario

fiber in

standard

Test

Goal: all-fiber coupling to test and standard detectors

Dilution fridge, micromachining and carbon nanotubes

centering ring

for fiber

1.4 mm

Micromachined components

1 cm

cavity ends and witness

Deep Reactive Ion Etch (DRIE)

Reflectance Results

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

5 10 15 20 25 30 35 40 45 50

Wavelength (m)

Hem

ispherical r

efle

cta

nce

VA40VA150

BSiCNnCylSi

See also OPM_OR_001

1300 1400 1500 1600Wavelength / nm

0

100

200

300

400

500

600H

emis

ph

eric

al r

efle

ctan

ce /

10

-6 Reflectance

Standard Deviation(ppm

)

tubular heat link

fiber

cavity

absorber heater

thermometer

centering ring

Cavity assembly

~ 5mm

Measurement setup

dilution

refrigerator

4 K stage

attenuators

laser

power meter manual

switch

T, R (out)

I in

optical in

fiber

assembled

fiber/cavity 70 mm

T, R (out)

Results

0 200 400 600 800 1000Time / minutes

3.6

3.8

4

4.2

4.4

Th

erm

isto

r T

emper

ature

/ K

Electrical Power

Optical Power

1 nW 3 nW

10 nW

30 nW

100 nW

Example

measurement at ~ 10 nW

1/e time constant

~ 12 minutes

(Values of power shown are nominal)

Optical/Electricial Results Summary

(U ~ 4.6 %)

10-7 1 10 100

Power (nW)

Optical/Electricial Results Summary

(U ~ 4.6 %)

1 10 100

Power (nW)

Optical/Electricial Results Summary

Power law fits for conductance modes and inequivalence

T3 insulator (phonon) - no

T1 metal (electron) -yes

Demonstrated first nanoWatt Radiometer for Fiber

Measurements

Micromachining and carbon nanotubes

Electrical is slightly more efficient linear

(but uncertainties are high)

Next iteration, shorter time constant

Reduce inequivalence, evaluate uncertainties, improve

optical coupling

Summary and Future

Results

new

(ne

w)

dilut

ion

refri

ger

ator

tubular heat link

fiber spacer

cavity

absorber

heater

thermometer

CNTs on detectors laser radiometry

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

5 10 15 20 25 30 35 40 45 50

Wavelength (m)

Hem

ispherical r

efle

cta

nce

VA40VA150

BSiCNnCylSi

1 cm

Topology: sparse, rough, long, repeatable

Behavior: 100 % black, uniform

On something useful!!

‘darkest detector’

390 µm absorber

Thermopile

Pyroelectric

w/ E. Grossman

w/ NIST-G w/ NPL

Optical/Electricial Results Summary

Approximate

Power

(nW)

Optical Power Electrical Power

Responsivity

(nW/K)

1/e Time

Constant

(minutes)

Responsivity

(nW/K)

1/e Time

Constant

(minutes)

1 n/a n/a 149 12.4

3 154 12.7 149 13.3

10 160 12.1 153 12.9

30 160 13.9 150 13.8

100 164 15 152 15.4

Measured responsivity and time constant for optical and electrical power

injections. (n/a – not available due to bad curve fit. )

U = 4.55 % (k=2)

(OFPM type B) U = 3 % (k=2)

(thermistor type B)