Detection: chapter 3 Statistical detection theory I Example of detection
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-1 ECEG287 Optical Detection Course Notes...
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Transcript of Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-1 ECEG287 Optical Detection Course Notes...
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-1
ECEG287 Optical Detection Course Notes
Part 3: Noise and Photon Detection
Profs. Charles A. DiMarzio
and
Stephen W. McKnight
Northeastern University, Spring 2004
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-2
Topic Outline
• Noise Sources– Overview of Noise Sources– A Simple Noise Model
• Photon Noise - Fundamental Limit• Photon Detectors
– Quantum Efficiency– Gain– Types and Examples
• Other Noise Sources
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-3
10464-3.tex:1
Noise Sources
• Photon Noise - Fundamental Limit
• Johnson Noise• G-R Noise • Background Noise• Electronic Noise
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-4
Classical Noise Model
Add Field Amplitudes
Re U
Im U
Us
Un
10464-3.tex:2
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-5
Photon Noise
10464-3.tex:4 10464-3.tex:5
n
n
RMS
RMS
RMS
ei
ei
RMSn RMS
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-6
Photon Detector Concepts
• Quantum Efficiency (spectral dependence)• Gain• Responsivity
– Current or Voltage
• Noise– Current or Voltage
• Mechanisms of Detection– Later, for Specific Devices
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-7
Photon Detector Responsivity
e-
h
Photon Energy: E=h=hc/Total Energy: PtPhoton Count: np=Pt/hElectron Count: ne=qPt/hElectron Rate: ne /t=qP/hCurrent: i = ene /t=(qe/h)P
wqe/h
hW
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-8
Photon Detector Gain
10464-3.tex:6
qG
Signal
Noise
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-9
Photon Counting (1)
0 5
Clock
GateCounter
tClock Signal
t
Photon Arrival
t
Photon Count3 1 2
Probability Density
n
Experimental Setup to measure the probability distribution of photon number.
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-10
Photon Counting (2)
t
Photon Arrival
t
Anode Electrons
t
Anode Electronsand Threshold
Photon counting threshold removes gain fluctuations but misses multiple counts. It does not reduce dark counts.
t
Photocathode Electrons
Error 1: Dark Count: Counted an electron when no photon was present.
Error 2: Missed Count: Counted one electron when two photons were present.
t
Photocathode Electron Count1
2
0
t
True Count1
2
0
1
1 2
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-11
Photon Detector Types
• Photoemissive– Vacuum Photodiodes
– Photomultipliers
– Low Quantum Efficiency, High Gain
• Semiconductor– Photoconductive
• Intrinsic and Extrinsic
• High Quantum Efficiency
• High Gain
• Example: Avalanche Photodiode
– Photovoltaic• Intrinsic and Extrinsic
• High Quantum Efficiency
• No Gain
• Low Noise
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-12
Photon Detector Characteristics
• Advantages– Sensitivity– Low Noise– Speed– Small Size
• Disadvantages– Difficult Calibration– Damage Susceptibility
• Other– Ruggedness (?)– Narrow Spectral Range– Cooling Requirement (?)
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-13
Other Noise Sources
• Johnson Noise
• G-R Noise
• Background Noise
• Electronic Noise
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-14
Thermal Noise
10464-3.tex:7 10464-3.tex:8
Stopped here Wed 14 Jan 04
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-15
NEP Example
10464-3.tex:9 10464-3.tex:10
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-16
Detectivity, D*
10464-3.tex:11 10464-3.tex:12
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-17
Background Noise
10464-3.tex:13 10464-3.tex:14
Signal
Bkg
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-18
Some Simplified Backgrounds
10464-3.tex:1610464-3.tex:15
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-19
Background Noise
10464-3.tex:17
Signal
Bkg withFluctuations
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-20
Background NEP
10464-3.tex:18 10464-3.tex:19
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-21
Detectivity Limits and Example
10464-3.tex:20 10464-3.tex:21
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-22
Detector Examples: Spectral Photon Radiance
10464-3-32
Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-23
Detector Examples: Detectivity, D*
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Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-24
Detector Examples: Total Background Power
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Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-25
Detector Examples: NEP
10464-3-3