New developments in radiometry at NRC

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New developments in radiometry at NRC

Bamber, Charles

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Recent developments in

radiometry

CORM 2012: Ottawa May 30 , 2012

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Outline

• Radiometry: the measurement of light

• Traceability chain: cryoradiometer to

routine calibrations

• Uncertainty budget

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In a semiconductor, absorption of a

photon

creates two charge carriers:

one electron

& one hole

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In a p-i-n diode, the ‘energy landscape’ is

engineered so that electrons run downhill

Wavelength / nm

200

400

600

800

1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000

Re

s

p

on

s

iv

it

y

/

a

m

p

s

p

e

r

wa

tt

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

SILICON

PHOTODIODES

GERMANIUM

PHOTODIODES

INDIUM ANTIMONIDE

PHOTODIODES

PtSi

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The cryogenic radiometer measures optical power by

substituting in an equivalent amount of electrical power

LIQUID HELIUM

LIQUID

NITROGEN

HEATSINK

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( )

( ) ( )

S

_pow

λ

=

I

λ

P

λ

Responsivity is the ratio of the amount of current that

flows out of the device for a given input optical power

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cryogenic radiometer

transfer radiometer

working standard

client detector

The calibration of every

client detector is

traceable to the cryorad

HOLOGRAPHIC

GRATINGS

ELLIPSOIDAL REFLECTOR

TURNTABLE

WORKING

STANDARD

TEST

DETECTORS

ORDER

SORTING

FILTERS

XENON ARC

LAMP

TUNGSTEN

HALOGEN

LAMP

F/9 beam

MONOCHROMATOR

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Each link in the

traceablility

chain has its

own

uncertainty

budget

cryorad

→ transfer standard

0.076 0.025 0.066 0.02 .010 .017 1000 0.032 0.015 0.002 0.02 .010 .017 950 0.038 0.002 0.010 0.03 .010 .017 900 0.047 0.008 0.011 0.04 .010 .017 850 0.047 0.006 0.012 0.04 .010 .017 800 0.032 0.006 0.013 0.02 .010 .017 750 0.032 0.006 0.015 0.02 .010 .017 700 0.033 0.006 0.015 0.02 .010 .017 650 0.033 0.003 0.016 0.02 .010 .017 600 0.034 0.000 0.018 0.02 .010 .017 550 0.035 0.004 0.021 0.02 .010 .017 500 0.041 0.016 0.024 0.02 .010 .017 450 0.045 0.001 0.027 0.03 .010 .017 400 0.054 0.021 0.034 0.03 .010 .017 380 0.049 0.027 0.020 0.03 .010 .017 360 0.051 0.025 0.025 0.03 .010 .017 340 0.059 0.042 0.020 0.03 .010 .017 320 0.049 0.026 0.021 0.03 .010 .017 300

Magnitude of uncertainty component , % Wavelengt h nm B B A B B Type Overall Uncertaint y % Monochrom. Bandwidth Effects 5 nm FWHM Monochrom. Wavelength Calibration ( ± 0.1 nm ) Measurement Repeatability Calibration Of Electronic Equipment Cryogenic radiometer effects Source Of Uncertaint y 0.076 0.025 0.066 0.02 .010 .017 1000 0.032 0.015 0.002 0.02 .010 .017 950 0.038 0.002 0.010 0.03 .010 .017 900 0.047 0.008 0.011 0.04 .010 .017 850 0.047 0.006 0.012 0.04 .010 .017 800 0.032 0.006 0.013 0.02 .010 .017 750 0.032 0.006 0.015 0.02 .010 .017 700 0.033 0.006 0.015 0.02 .010 .017 650 0.033 0.003 0.016 0.02 .010 .017 600 0.034 0.000 0.018 0.02 .010 .017 550 0.035 0.004 0.021 0.02 .010 .017 500 0.041 0.016 0.024 0.02 .010 .017 450 0.045 0.001 0.027 0.03 .010 .017 400 0.054 0.021 0.034 0.03 .010 .017 380 0.049 0.027 0.020 0.03 .010 .017 360 0.051 0.025 0.025 0.03 .010 .017 340 0.059 0.042 0.020 0.03 .010 .017 320 0.049 0.026 0.021 0.03 .010 .017 300

Magnitude of uncertainty component , % Wavelengt h nm B B A B B Type Overall Uncertaint y % Monochrom. Bandwidth Effects 5 nm FWHM Monochrom. Wavelength Calibration ( ± 0.1 nm ) Measurement Repeatability Calibration Of Electronic Equipment Cryogenic radiometer effects Source Of Uncertaint y

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Since wavelength uncertainty is often

the biggest component, address that

• upgrade monochromator

• perform in-house wavelength calibration

• generate corrections to beat manufacturer’s

spec

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A spectral source is scanned

with the monochromator

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Corrections can be

generated for the

difference between

measured

wavelength and

accepted value

547.12-546.07=1.05

scan over 546.07 line

0

0.05

0.1

0.15

0.2

0.25

0.3

540

542

544

546

548

550

552

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Each monochromator was calibrated

with Hg & He spectral sources

-3

-2.5

-2

-1.5

-1

-0.5

0

250

500

750

1000

1250

e

rro

r (

n

m)

correction=5.42e-6*

λ^2-.007919+0.371

0

1

2

3

4

5

6

250

500

750

1000

1250

e

rro

r (

n

m)

correction=3.4e-6*

λ^2-.000433λ+0.233

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Underlying contaminant peaks could skew

the centroid

Note the asymmetry

405nm line (residual .0012nm)

fit to 691nm line (residual 0.089)

0 0.0005 0.001 0.0015 0.002 0.0025 686 688 690 692 694 696 -0.00008 -0.00006 -0.00004 -0.00002 0 0.00002 0.00004 0.00006 data fit data-fit

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residuals after 2nd order correction

254 297 334 405 436 447 492 502 546 588 668 691 707 728 773 809 1083 1175

-0.1

-0.05

0

0.05

0.1

0.15

200

400

600

800

1000

1200

M1

M2

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Checking with an

independent spectrometer

White light

y = 0.9953x + 1.7323

640

660

680

700

720

740

760

655

675

695

715

735

McPherson setting

m

easu

red

b

y A

van

te

s

-0.03

-0.025

-0.02

-0.015

-0.01

-0.005

0

0.005

0.01

re

s

idua

l f

rom

s

tr

a

ight

l

ine

(

nm

)

White light

McPherson

monochromator

Avantes

spectrometer

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Some spectral lines will be

eliminated from the calibration

residual error (error bars = stdev)

-0.1 -0.05 0 0.05 0.1 0.15 200 400 600 800 1000 1200 390.64 nm 0 0.0002 0.0004 0.0006 0.0008 0.001 0.0012 384 386 388 390 392 394 396 398 435.83nm 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 430 432 434 436 438 440 442

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Lessons learned

• Work on the largest sources of uncertainty

• Know your equipment

• Know the physics

• Be cautious