1. 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

2. 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

3. 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

4. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-4 Classical Noise Model Add Field Amplitudes Re U Im U UsUs UnUn 10464-3.tex:2

5. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-5 Photon Noise 10464-3.tex:4 10464-3.tex:5 nn nn RMS eiei eiei nn 

6. 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

7. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-7 Photon Detector Responsivity e-e- h Photon Energy: E=h =hc/ Total Energy: Pt Photon Count: n p =Pt/h Electron Count: n e =  q Pt/h Electron Rate: n e /t=  q P/h Current: i = en e /t=(  q e/h )P w    q e/h hWhW

8. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-8 Photon Detector Gain 10464-3.tex:6 qq G Signal Noise

9. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-9 Photon Counting (1) 05 Clock Gate Counter t Clock Signal t Photon Arrival t Photon Count 312 Probability Density n Experimental Setup to measure the probability distribution of photon number.

10. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-10 Photon Counting (2) t Photon Arrival t Anode Electrons t and 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 Count 1 2 0 t True Count 1 2 0 1 1 2

11. 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

12. 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 (?)

13. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-13 Other Noise Sources Johnson Noise G-R Noise Background Noise Electronic Noise

14. 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

15. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-15 NEP Example 10464-3.tex:9 10464-3.tex:10

16. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-16 Detectivity, D* 10464-3.tex:11 10464-3.tex:12

17. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-17 Background Noise 10464-3.tex:1310464-3.tex:14 Signal Bkg

18. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-18 Some Simplified Backgrounds 10464-3.tex:1610464-3.tex:15

19. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-19 Background Noise 10464-3.tex:17 Signal Bkg with Fluctuations

20. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-20 Background NEP 10464-3.tex:1810464-3.tex:19

21. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-21 Detectivity Limits and Example 10464-3.tex:2010464-3.tex:21

22. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-22 Detector Examples: Spectral Photon Radiance 10464-3-32

23. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-23 Detector Examples: Detectivity, D* 10464-3-34

24. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-24 Detector Examples: Total Background Power 10464-3-31

25. Jan 2004 Chuck DiMarzio, Northeastern University 10464-3b-25 Detector Examples: NEP 10464-3-3