Astronomical Observational Techniques and Instrumentation

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Nov 15, 2013 (3 years and 9 months ago)

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1

Astronomical Observational Techniques
and Instrumentation

RIT Course Number 1060
-
771

Professor Don Figer

Quantum
-
Limited Detectors

2

Aims for this lecture


Motivate the need for future detectors


Describe physical principles of future detectors


Review some promising technologies for future detectors


3

Motivation for Future Detectors

4

Improving Detectors


Detector properties limit sensitivity in most applications.


For instance, dark current and read noise are important in low
flux applications.


Detectivity is a measure of system effectiveness.


.
)
(
4
1
1
2
y
Detectivit
1
y
sensitivit
1
y
Detectivit
)
(
2
)
(
)
(
4
)
(
)
(
1
1
SNR
at which
flux

y
Sensitivit
2
,
1
,
2
2
,
2
2
1
,
2
1
,
2
,
1
,
2
,
1
,
1
,
2
,
2
,
N
n
t
i
n
tQE
N
tQE
N
tQE
N
n
t
i
n
tQE
N
tQE
tQE
tQE
N
tQE
N
N
n
t
i
n
tQE
N
tQE
N
N
n
t
i
n
tQE
N
tQE
N
tQE
N
SNR
N
n
t
i
n
tQE
N
tQE
N
tQE
N
SNR
N
t
i
tQE
F
h
A
tQE
F
h
A
tQE
F
h
A
N
S
SNR
read
pix
dark
pix
background
SNR
read
pix
dark
pix
background
SNR
SNR
read
pix
dark
pix
background
SNR
read
pix
dark
pix
background
SNR
SNR
read
pix
dark
pix
background
read
dark
back
inst
inst
inst

















































































5

Detectivity in Broadband Applications

10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
1.5


2.5


3.2


3.9


4.4


4.9


5.4


5.8


6.2


6.6


1
1.5


2.5


3.2


3.9


4.4


4.9


5.4


5.8


6.2


6.5


3
1.5


2.4


3.2


3.8


4.4


4.9


5.3


5.7


6.1


6.5


4
1.4


2.4


3.1


3.8


4.3


4.8


5.3


5.7


6.1


6.5


5
1.4


2.3


3.1


3.7


4.3


4.8


5.2


5.7


6.1


6.4


6
1.3


2.3


3.0


3.7


4.2


4.7


5.2


5.6


6.0


6.4


7
1.3


2.2


3.0


3.6


4.2


4.7


5.1


5.5


5.9


6.3


8
1.2


2.1


2.9


3.5


4.1


4.6


5.0


5.5


5.9


6.3


9
1.2


2.1


2.8


3.4


4.0


4.5


5.0


5.4


5.8


6.2


10
1.1


2.0


2.7


3.4


3.9


4.4


4.9


5.3


5.7


6.1


11
1.1


1.9


2.7


3.3


3.8


4.3


4.8


5.2


5.6


6.0


12
1.0


1.9


2.6


3.2


3.7


4.3


4.7


5.1


5.6


5.9


13
1.0


1.8


2.5


3.1


3.7


4.2


4.6


5.1


5.5


5.8


14
0.9


1.7


2.4


3.0


3.6


4.1


4.5


5.0


5.4


5.8


15
0.9


1.7


2.3


2.9


3.5


4.0


4.4


4.9


5.3


5.7


16
0.9


1.6


2.3


2.9


3.4


3.9


4.3


4.8


5.2


5.6


17
0.8


1.6


2.2


2.8


3.3


3.8


4.3


4.7


5.1


5.5


18
0.8


1.5


2.1


2.7


3.2


3.7


4.2


4.6


5.0


5.4


19
0.8


1.4


2.1


2.6


3.1


3.6


4.1


4.5


4.9


5.3


read noise
green=detectivity greater than that for baseline (QE=70%, read noise=5e-)
pink=detectivity less than that for baseline
Detectivity Metric
FOM
Quantum Efficiency
Figure 3. Detectivity as a function of quantum efficiency and read noise for
broadband astrophysics applications.

6

Detectivity in Low Flux Broadband Applications

10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
0.1


0.2


0.3


0.3


0.4


0.4


0.5


0.5


0.5


0.6


1
0.1


0.2


0.2


0.3


0.3


0.4


0.4


0.5


0.5


0.5


3
0.0


0.1


0.1


0.2


0.2


0.2


0.3


0.3


0.3


0.4


4
0.0


0.1


0.1


0.1


0.2


0.2


0.2


0.2


0.3


0.3


5
0.0


0.1


0.1


0.1


0.1


0.2


0.2


0.2


0.2


0.2


6
0.0


0.0


0.1


0.1


0.1


0.1


0.2


0.2


0.2


0.2


7
0.0


0.0


0.1


0.1


0.1


0.1


0.1


0.2


0.2


0.2


8
0.0


0.0


0.1


0.1


0.1


0.1


0.1


0.1


0.2


0.2


9
0.0


0.0


0.0


0.1


0.1


0.1


0.1


0.1


0.1


0.1


10
0.0


0.0


0.0


0.1


0.1


0.1


0.1


0.1


0.1


0.1


11
0.0


0.0


0.0


0.1


0.1


0.1


0.1


0.1


0.1


0.1


12
0.0


0.0


0.0


0.0


0.1


0.1


0.1


0.1


0.1


0.1


13
0.0


0.0


0.0


0.0


0.1


0.1


0.1


0.1


0.1


0.1


14
0.0


0.0


0.0


0.0


0.0


0.1


0.1


0.1


0.1


0.1


15
0.0


0.0


0.0


0.0


0.0


0.1


0.1


0.1


0.1


0.1


16
0.0


0.0


0.0


0.0


0.0


0.1


0.1


0.1


0.1


0.1


17
0.0


0.0


0.0


0.0


0.0


0.0


0.1


0.1


0.1


0.1


18
0.0


0.0


0.0


0.0


0.0


0.0


0.1


0.1


0.1


0.1


19
0.0


0.0


0.0


0.0


0.0


0.0


0.1


0.1


0.1


0.1


read noise
green=detectivity greater than that for baseline (QE=70%, read noise=5e-)
pink=detectivity less than that for baseline
Detectivity Metric
FOM
Quantum Efficiency
Figure 4. Same parameters as used to generate Figure 3, except the exposure
time is only 5 seconds, instead of 10 minutes. It is apparent that read noise
becomes a dominant factor in detectivity for this case.

7

Detectivity in Narrowband Applications

10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
0.1


0.2


0.3


0.4


0.5


0.6


0.7


0.8


1.0


1.1


1
0.1


0.2


0.3


0.4


0.5


0.6


0.7


0.8


0.9


1.1


3
0.1


0.2


0.3


0.4


0.5


0.6


0.7


0.8


0.9


1.0


4
0.1


0.2


0.3


0.4


0.5


0.6


0.7


0.8


0.9


0.9


5
0.1


0.2


0.3


0.4


0.5


0.5


0.6


0.7


0.8


0.9


6
0.1


0.2


0.3


0.3


0.4


0.5


0.6


0.7


0.8


0.8


7
0.1


0.2


0.2


0.3


0.4


0.5


0.6


0.6


0.7


0.8


8
0.1


0.1


0.2


0.3


0.4


0.4


0.5


0.6


0.7


0.7


9
0.1


0.1


0.2


0.3


0.4


0.4


0.5


0.6


0.6


0.7


10
0.1


0.1


0.2


0.3


0.3


0.4


0.5


0.5


0.6


0.7


11
0.1


0.1


0.2


0.2


0.3


0.4


0.4


0.5


0.6


0.6


12
0.1


0.1


0.2


0.2


0.3


0.4


0.4


0.5


0.5


0.6


13
0.1


0.1


0.2


0.2


0.3


0.3


0.4


0.4


0.5


0.6


14
0.1


0.1


0.2


0.2


0.3


0.3


0.4


0.4


0.5


0.5


15
0.0


0.1


0.1


0.2


0.2


0.3


0.3


0.4


0.4


0.5


16
0.0


0.1


0.1


0.2


0.2


0.3


0.3


0.4


0.4


0.5


17
0.0


0.1


0.1


0.2


0.2


0.3


0.3


0.4


0.4


0.4


18
0.0


0.1


0.1


0.2


0.2


0.3


0.3


0.3


0.4


0.4


19
0.0


0.1


0.1


0.2


0.2


0.2


0.3


0.3


0.4


0.4


read noise
green=detectivity greater than that for baseline (QE=70%, read noise=5e-)
pink=detectivity less than that for baseline
Detectivity Metric
FOM
Quantum Efficiency
Figure 5. Detectivity as a function of quantum efficiency and read noise for
narrowband astrophysics applications.

8

Detectivity in Narrowband Applications with Low
Dark Current

10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
1.4


2.2


2.9


3.5


4.0


4.5


4.9


5.3


5.7


6.1


1
0.7


1.3


1.8


2.4


2.8


3.3


3.7


4.1


4.5


4.8


3
0.3


0.5


0.8


1.0


1.3


1.5


1.8


2.0


2.3


2.5


4
0.2


0.4


0.6


0.8


1.0


1.2


1.4


1.6


1.8


2.0


5
0.2


0.3


0.5


0.6


0.8


1.0


1.1


1.3


1.4


1.6


6
0.1


0.3


0.4


0.5


0.7


0.8


1.0


1.1


1.2


1.3


7
0.1


0.2


0.4


0.5


0.6


0.7


0.8


0.9


1.1


1.2


8
0.1


0.2


0.3


0.4


0.5


0.6


0.7


0.8


0.9


1.0


9
0.1


0.2


0.3


0.4


0.5


0.6


0.6


0.7


0.8


0.9


10
0.1


0.2


0.2


0.3


0.4


0.5


0.6


0.7


0.7


0.8


11
0.1


0.2


0.2


0.3


0.4


0.5


0.5


0.6


0.7


0.8


12
0.1


0.1


0.2


0.3


0.3


0.4


0.5


0.6


0.6


0.7


13
0.1


0.1


0.2


0.3


0.3


0.4


0.4


0.5


0.6


0.6


14
0.1


0.1


0.2


0.2


0.3


0.4


0.4


0.5


0.5


0.6


15
0.1


0.1


0.2


0.2


0.3


0.3


0.4


0.4


0.5


0.6


16
0.1


0.1


0.2


0.2


0.3


0.3


0.4


0.4


0.5


0.5


17
0.0


0.1


0.1


0.2


0.2


0.3


0.3


0.4


0.4


0.5


18
0.0


0.1


0.1


0.2


0.2


0.3


0.3


0.4


0.4


0.5


19
0.0


0.1


0.1


0.2


0.2


0.3


0.3


0.4


0.4


0.4


read noise
green=detectivity greater than that for baseline (QE=70%, read noise=5e-)
pink=detectivity less than that for baseline
Detectivity Metric
FOM
Quantum Efficiency
Figure 6. Same parameters as used to generate Figure 5, except the dark
current is 0.0001 electrons/second/pixel, instead of 0.1 electrons/second/pixel. It
is apparent that read noise becomes a dominant factor in detectivity for this
case. Also, note that the detectivity is comparable to that for the broadband
imaging case modeled in Figure 3.

9

Detectivity in Spectroscopic Applications

10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
0.0004


0.0009


0.0013


0.0017


0.0021


0.0026


0.0030


0.0034


0.0039


0.0043


1
0.0004


0.0009


0.0013


0.0017


0.0021


0.0026


0.0030


0.0034


0.0038


0.0043


3
0.0004


0.0008


0.0012


0.0016


0.0020


0.0024


0.0028


0.0032


0.0036


0.0040


4
0.0004


0.0008


0.0011


0.0015


0.0019


0.0023


0.0027


0.0031


0.0034


0.0038


5
0.0004


0.0007


0.0011


0.0014


0.0018


0.0022


0.0025


0.0029


0.0033


0.0036


6
0.0003


0.0007


0.0010


0.0014


0.0017


0.0020


0.0024


0.0027


0.0031


0.0034


7
0.0003


0.0006


0.0010


0.0013


0.0016


0.0019


0.0022


0.0026


0.0029


0.0032


8
0.0003


0.0006


0.0009


0.0012


0.0015


0.0018


0.0021


0.0024


0.0027


0.0030


9
0.0003


0.0006


0.0008


0.0011


0.0014


0.0017


0.0020


0.0023


0.0025


0.0028


10
0.0003


0.0005


0.0008


0.0011


0.0013


0.0016


0.0019


0.0021


0.0024


0.0026


11
0.0002


0.0005


0.0007


0.0010


0.0012


0.0015


0.0017


0.0020


0.0022


0.0025


12
0.0002


0.0005


0.0007


0.0009


0.0012


0.0014


0.0016


0.0019


0.0021


0.0023


13
0.0002


0.0004


0.0007


0.0009


0.0011


0.0013


0.0016


0.0018


0.0020


0.0022


14
0.0002


0.0004


0.0006


0.0008


0.0010


0.0013


0.0015


0.0017


0.0019


0.0021


15
0.0002


0.0004


0.0006


0.0008


0.0010


0.0012


0.0014


0.0016


0.0018


0.0020


16
0.0002


0.0004


0.0006


0.0008


0.0009


0.0011


0.0013


0.0015


0.0017


0.0019


17
0.0002


0.0004


0.0005


0.0007


0.0009


0.0011


0.0013


0.0014


0.0016


0.0018


18
0.0002


0.0003


0.0005


0.0007


0.0009


0.0010


0.0012


0.0014


0.0015


0.0017


19
0.0002


0.0003


0.0005


0.0007


0.0008


0.0010


0.0011


0.0013


0.0015


0.0016


read noise
green=detectivity greater than that for baseline (QE=70%, read noise=5e-)
pink=detectivity less than that for baseline
Detectivity Metric
FOM
Quantum Efficiency
Figure 7. Detectivity as a function of quantum efficiency and read noise for high
resolution spectroscopy astrophysics applications.

10

Detectivity in Spectroscopic Applications with
Low Dark Current

10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
0.0036


0.0073


0.0109


0.0146


0.0182


0.0219


0.0255


0.0292


0.0328


0.0365


1
0.0024


0.0048


0.0072


0.0096


0.0120


0.0144


0.0168


0.0192


0.0215


0.0239


3
0.0010


0.0021


0.0031


0.0042


0.0052


0.0063


0.0073


0.0084


0.0094


0.0104


4
0.0008


0.0016


0.0024


0.0032


0.0040


0.0048


0.0056


0.0064


0.0072


0.0080


5
0.0007


0.0013


0.0020


0.0026


0.0033


0.0039


0.0046


0.0052


0.0059


0.0065


6
0.0005


0.0011


0.0016


0.0022


0.0027


0.0033


0.0038


0.0044


0.0049


0.0055


7
0.0005


0.0009


0.0014


0.0019


0.0024


0.0028


0.0033


0.0038


0.0042


0.0047


8
0.0004


0.0008


0.0012


0.0017


0.0021


0.0025


0.0029


0.0033


0.0037


0.0041


9
0.0004


0.0007


0.0011


0.0015


0.0018


0.0022


0.0026


0.0030


0.0033


0.0037


10
0.0003


0.0007


0.0010


0.0013


0.0017


0.0020


0.0023


0.0027


0.0030


0.0033


11
0.0003


0.0006


0.0009


0.0012


0.0015


0.0018


0.0021


0.0024


0.0027


0.0030


12
0.0003


0.0006


0.0008


0.0011


0.0014


0.0017


0.0019


0.0022


0.0025


0.0028


13
0.0003


0.0005


0.0008


0.0010


0.0013


0.0015


0.0018


0.0021


0.0023


0.0026


14
0.0002


0.0005


0.0007


0.0010


0.0012


0.0014


0.0017


0.0019


0.0022


0.0024


15
0.0002


0.0004


0.0007


0.0009


0.0011


0.0013


0.0016


0.0018


0.0020


0.0022


16
0.0002


0.0004


0.0006


0.0008


0.0010


0.0013


0.0015


0.0017


0.0019


0.0021


17
0.0002


0.0004


0.0006


0.0008


0.0010


0.0012


0.0014


0.0016


0.0018


0.0020


18
0.0002


0.0004


0.0006


0.0007


0.0009


0.0011


0.0013


0.0015


0.0017


0.0019


19
0.0002


0.0004


0.0005


0.0007


0.0009


0.0011


0.0012


0.0014


0.0016


0.0018


read noise
green=detectivity greater than that for baseline (QE=70%, read noise=5e-)
pink=detectivity less than that for baseline
Detectivity Metric
FOM
Quantum Efficiency
Figure 8. Same parameters as used to generate Figure 7, except the dark
current is 0.001 electrons/second/pixel, instead of 0.1 electrons/second/pixel. It
is apparent that read noise becomes a dominant factor in detectivity for this
case.

11

Read Noise

The Importance of Read Noise
in Imaging





Images of the Arches cluster near the Galactic center, base
d on real data obtained with
Keck/LGSAO. Each image has synthetic shot noise and increasing read noise (left to right and
top to bottom: 0, 5, 10, 100 electrons).


12

Aperture vs. Read Noise


Effective Telescope Size vs. Read Noise

20
30
40
50
60
70
80
0
1
2
3
4
5
6
Read Noise (electrons)
Telescope Diameter (m)

This plot shows a curve of constant sensitivity for a range
of telescope diameters and detector read nois
e values
in
low
-
light applications
.
A 30 meter telescope
and
zero read
noise detector would deliver the same signal
-
to
-
noise ratio
as a 60 meter telescope with current detectors
.

13

Very Low Light Level
-

ExoPlanet Imaging


The exposure time required to achieve SNR=1 is dramatically
reduced for a zero read noise detector, as compared to
detectors with state of the art read noise.

10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0
6,600


2,300


1,311


900


680


544


453


388


338


300


1
7,159


2,674


1,591


1,123


865


703


591


510


448


400


2
8,486


3,457


2,141


1,547


1,209


992


841


730


645


577


3
10,148


4,363


2,760


2,016


1,587


1,309


1,113


968


857


768


4
11,954


5,312


3,402


2,500


1,976


1,633


1,392


1,212


1,074


964


5
13,830


6,281


4,053


2,990


2,369


1,961


1,673


1,459


1,293


1,161


6
15,745


7,259


4,709


3,484


2,764


2,291


1,956


1,706


1,513


1,359


7
17,684


8,244


5,368


3,979


3,161


2,621


2,239


1,954


1,734


1,558


read noise
mag_star=5, mag_planet=30, R=100, i_dark=0.0010
Exposure Time (seconds) for SNR = 1
FOM
Quantum Efficiency
14

Principles of Quantum Limited Detectors

15

Key Capabilities for Future Improvement


photon
-
counting (zero read noise)


wavelength
-
resolving


polarization
-
measuring


low power


large area


in
-
pixel processing


high dynamic range


high speed


time resolution

16

QLID Technology Contenders

Table 1. Quantum
-
limited Detector Technologies.

Superconductors

Semiconductors

Transition Edge Sensor (TES)

energy resolution

operating temperature of tens of mK

Electron Multiplying CCD (EMCCD)

commercially available

excess noise factor

Superconducting Tunnel Junction (STJ)

energy resolution

operating temperature of mK, leakage
current

Linear Mode Avalance Photodiode
(LM
-
APD)

ns time constant

excess noise factor (although MCT
has ~no excess noise)

Kinetic Inductance Detector (KID)

energy resolution

ms time constant

Geiger Mode Avalance Photodiode
(GM
-
APD)

large pulse per photon

afterpulsing

Superconducting Single Photon Detectors
(SSPD)

ns time constant

low fill
-
factor, polarized, few K

17

Key to Single
-
Photon Counting


A photon
-
counting system requires that the ratio of signal
from a single photon to the noise of the system be big enough
to detect.


enough

big
system

of

noise
signal

generated
-
photo


This can be achieved by:


increasing numerator (e.g., charge gain)


decreasing denominator (e.g., cooling, better circuits)


decreasing what is “big enough” (e.g., better processing)


combination of all

18

Superconductors


Most metals have descreased resistance with lower
temperature, but they still have finite resistance at T=0 K.


Superconductors lose all resistance to electrical current at
some temperature, T
c
. Examples include: Pb, Al, Sn, and Nb.


Electrons in superconductors bond as “Cooper pairs” that do
not interact with the ion lattice below T
c

because the required
interaction energy exceeds the thermal energy in the crystal.


In general, T
c
<4.2 K.


Recent developments have produced “high” temperature
superconductors, for which T
c
>77 K (temperature of liquid
nitrogen).


19

Slide Title

20

Avalanche Photodiodes (APDs)

21

Geiger
-
Mode Imager:

Photon
-
to
-
Digital Conversion

Quantum
-
limited sensitivity

Noiseless readout

Photon counting or timing


APD

Digital

timing

circuit

Digitally

encoded

photon

flight time

photon

Lenslet

array

APD/CMOS array

Focal
-
plane
concept

Pixel circuit

22

Geiger
-
Mode Operation

23

Gain of an APD

1

10

100

M

Breakdown

0

Ordinary
photodiode

Linear
-
mode
APD

Geiger
-
mode
APD

Response
to a photon

M

1




I(t)

24

Current

Voltage

Current

Linear

mode

Geiger

mode

V

br

on

off

Current

Voltage

Current

Linear

mode

Geiger

mode

V

br

on

avalanche

off

quench

arm

V
dc

+

V

Operation of Avalanche Diode

25

Avalanche Diode Architecture

10
µ
m
0.5
µ
m
metal
metal
p
+
implant (collects holes)
p
+
implant
n
+
implant (collects electrons)
low E
-
field
high E
-
field
-
V
h
ν
ROIC
metal
bump bond
Quartz substrate
+V
10
µ
m
0.5
µ
m
metal
metal
p
+
implant (collects holes)
p
+
implant
n
+
implant (collects electrons)
low E
-
field
high E
-
field
-
V
h
ν
ROIC
metal
bump bond
Quartz substrate
+V
26

Performance Parameters


Photon detection efficiency
(PDE)


The probability that a single
incident photon initiates a
current pulse that registers in a
digital counter



Dark count Rate
(DCR)/Probability (DCP)



The probability that a count is
triggered by dark current
instead of incident photons

time

time

time

time

time

Single photon input

APD output

Discriminator

level

Digital comparator output

Successful

single photon

detection

Photon absorbed
but insufficient
gain


missed
count

Dark count


from dark
current

27

APD Charge Gain


Show animation with thumping euro
-
techno disco music

http://techresearch.intel.com/spaw2/uploads/files/SiliconPhotonics.html


28

32x32 Timing Circuit Array

0.35
-
m
m CMOS process
fabricated through MOSIS

1.2 GHz on
-
chip clock

Two vernier bits

0.2
-
ns timing quantization

100
-
m
m spacing to match the
32x32 APD array


Timing image/histogram measuring propagation of
electronic trigger signal

Vernier bits

Counter

Time bin

Pixels

29

32x32 APD/CMOS Array with
Integrated GaP Microlenses

30

Shortcomings of Conventional Imaging


When the 3D world is projected
into a flat intensity image, there is
a huge information loss.


Image processing algorithms
attempt to use intensity edges to
infer properties of 3D objects.


Consequences of lost information
for automated image segmentation
and target detection/recognition:


Depth ambiguity


Sensitivity to lighting, reflectivity
patterns, and point of observation


Obscuration and camouflage

31

Ladar Imaging System



Imaging system photon starved


Each detector must
precisely time

a
weak

optical pulse


Sub
-
ns timing, single photons


Microchip laser

Geiger
-
mode
APD array

Color
-
coded

range image

32

Laser Radar Brassboard System (Gen I)


4


4 APD array


External rack
-
mounted timing circuits


Doubled Nd:YAG passively Q
-
switched microchip laser


(produces 30 µJ, 250 ps pulses at


= 532 nm)


Transmit/receive field of view scanned to generate 128


128 images

Taken at noontime on a sunny day

33

Conventional vs Ladar Image

Conventional image

3D image

34

Foliage Penetration Experiment

Laser radar


on tower

elevator

View from

100 m tower

Objects

under trees

35


Foliage Penetration Imagery

36

Transition Edge Sensors (TESs)

37

Transition Edge Sensors (TES)


A TES is similar to a bolometer, in that photon energy is
detected when it is absorbed in a material that changes
resistance with temperature.


The difference is that a TES is held at a temperature just below
the transition temperature at which the material becomes
supconducting.


The effective change in resistance when photons are absorbed
is very large (and easy to detect).


One of the disadvantages of using TES’s is that the transition
temperature is usually very low, requiring exotic cooling
techniques.



38

TES Schematic

39

Slide Title


xxxxxx



40

TES Wavelength Resolution

41

Slide Title

42

Prototype TES Device

43

Superconducting Tunneling Junctions
(STJs)

44

Superconducting Tunneling Junctions (STJs)


An STJ uses the current response of a Josephson junction (aka
STJ) when struck by a photon to detect light.


The junction is similar to semiconducting junction and is
composed of superconductor
-
insulator
-
superconductor.


The gap energy is generally much less than for silicon, so
optical photons induce charge gain that depends on photon
energy.

45

TES vs. STJ

46

Superconducting Single Photon Detectors
(SSPDs)

47

Slide Title

48

Slide Title

49

Slide Title

50

Slide Title

51

Slide Title

52

Slide Title


xxxxxx



53

Slide Title