1. April 2004 DiMarzio & McKnight, Northeastern University 10464-19-1 ECEG287 Optical Detection Course Notes Part 19: Conclusion Profs. Charles A. DiMarzio and Stephen W. McKnight Northeastern University, Spring 2004

2. April 2004 DiMarzio & McKnight, Northeastern University 10464-19-2 Electromagnetic Spectrum (by λ) 1 μ10 μ100 μ = 0.1mm 0.1 μ10 nm =100Å VIS= 0.40-0.75μ 1 mm1 cm0.1 m IR= Near: 0.75-2.5μ Mid: 2.5-30μ Far: 30-1000μ UV= Near-UV: 0.3-.4 μ Vacuum-UV: 100-300 nm Extreme-UV: 1-100 nm MicrowavesX-RayMm-waves 10 Å1 Å0.1 Å Soft X-RayRFγ-Ray (300 THz)

3. April 2004 DiMarzio & McKnight, Northeastern University 10464-19-3 What is Optical Detection? The goal is to get information from light. –Usually we look for variations in the amount of light over space... or time... or spectrum... or some combination of these. Generally the output is an electrical signal. –It may be digitized for use in a computer. –We need to measure this signal in the presence of noise.

4. April 2004 DiMarzio & McKnight, Northeastern University 10464-19-4 Course Overview 2. Sources and Radiometry 2-5. Detectors 3. Noise 6. Circuits 7. Coherent Detection 8. Signal Statistics 9. Array Detectors

5. April 2004 DiMarzio & McKnight, Northeastern University 10464-19-5 Some Detection Issues Optics –Radiometry, Beam Shaping, and Filters Detector Physics –Converting Optical Energy to Electrical Receiver Circuit – Matching to Detector, Proper Biasing Interpretation of Data –Dealing with Noise and Signal Statistics

6. April 2004 DiMarzio & McKnight, Northeastern University 10464-19-6 General Detector Issues Spectral Response Modulation Response Responsivity Noise (NEP) Damage Level Sensitive Area Circuit Considerations Device-Specific Issues Filtering –Angle, Position, Wavelength Packaging –Window Transmission, Position Power Requirements Cooling/Vacuum Requirements

7. April 2004 DiMarzio & McKnight, Northeastern University 10464-19-7 Square-Law Detector

8. April 2004 DiMarzio & McKnight, Northeastern University 10464-19-8 Noise Signal + Noise PsPs PsPs PnPn

9. April 2004 DiMarzio & McKnight, Northeastern University 10464-19-9 Noise Issues Optical Signal Power (Watts) –Normally Related to Some Desired Quantity (Reflectivity, Temperature, Distance, Magnetic Field, Scattering, Absorption, etc.) NEP (Watts per root Hertz) –Can be Related to “NEX” Example: NE  T

10. April 2004 DiMarzio & McKnight, Northeastern University 10464-19-10 Two Basic Detection Concepts Thermal DetectorsPhoton Detectors 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: en e /t=(  q e/h )P Absorber Heat Sink Power: P Heating: (dT/dt) H = CP Cooling:  (dT/dt) C =(T-T s ) Steady State: (T-T s )/  C = P i/P Stopped Mon 5 Jan 04

11. April 2004 DiMarzio & McKnight, Northeastern University 10464-19-11 Detector Types Thermal –Characteristics Wide Bandwidth Accuracy –Examples Thermocouple Thermopile Pyroelectric Photon –Characteristics Speed Sensitivity –Examples Photoemissive Photoconductive - intrinsic & extrinsic Photovoltaic - intrinsic & extrinsic

12. April 2004 DiMarzio & McKnight, Northeastern University 10464-19-12 Course Overview (1) 3 - Noise and Photon Detectors - Materials Considertations –(4) in Photoemissive Detectors –(5,6) in Semiconductor Detectors 7 - Types of Semiconductor Detectors 8 - P-N Junction Effects & Other Detectors 9,10 - Detectors as Circuit Elements

13. April 2004 DiMarzio & McKnight, Northeastern University 10464-19-13 Course Overview (2) 11,12 - Coherent Detection 13 - Semiconductor Photoconductive Detectors 14 - Signals and Noise 15 - Intro to Arrays & a bit about color 16 - Gain & BW in Semiconductor Dets. 17 - Array Detectors 18 - Odds and Ends

14. April 2004 DiMarzio & McKnight, Northeastern University 10464-19-14 SNR Layout for Coherent Detection PsPs P BKG BPF Preamp Amp P LO Filter?