Table Of ContentTopics in Applied Physics Volume 19
Topics in Applied Physics
Founded by Helmut K.V.Lotsch
Volume 1 Dye Lasers Editor: F.P.Schiifer
Volume 2 Laser Spectroscopy of Atoms and Molecules
Editor: H. Walter
Volume 3 Numerical and Asymptotic Techniques in Electromagnetics
Editor: R. Mittra
Volume 4 Interactions on Metal Surfaces Editor: R.Gomer
Volume 5 Mossbauer Spectroscopy Editor: U.Gonser
Volume 6 Picture Processing and Digital Filtering Editor: T.S.Huang
Volume 7 Integrated Optics Editor: T. Tamir
Volume 8 Light Scattering in Solids Editor: M. Cardona
Volume 9 Laser Speckle and Related Phenomena Editor: J. C. Dainty
Volume 10 Transient Electromagnetic Fields Editor: L. B. Felsen
Volume 11 Digital Picture Analysis Editor: A. Rosenfeld
Volume 12 Turbulence Editor: P. Bradshaw
Volume 13 High-Resolution Laser Spectroscopy Editor: K.Shimoda
Volume 14 Laser Monitoring of the Atmosphere Editor: E. D. Hinkley
Volume 15 Radiationless Processes in Molecules and Condensed Phases
Editor: F.K.Fong
Volume 16 Nonlinear Infrared Generation Editor: Y.-R.Shen
Volume 17 Electroluminescence Editor: J .I. Pank ove
Volume 18 Ultrashort Light Pulses, Picosecond Techniques and Applications
Editor: S. L. Shapiro
Volume 19 Optical and Infrared Detectors Editor: R.J. Keyes
Volume 20 Holographic Recording Materials Editor: H. M.Smith
Volume 21 Solid Electrolytes Editor: S. Geller
Volume 22 X-Ray Optics, Applications To Solids
Editor: H.J.Queisser
Volume 23 Optical Data Processing, Applications Editor: D.Casasent
Optical and
Infrared Detectors
Edited by R. J. Keyes
With Contributions by
R.J.Keyes P.W.Kruse D.Long A.F.Milton
E.H.Putley M.C.Teich H.R.Zwicker
With 115 Figures
Springer-Verlag Berlin Heidelberg GmbH 1977
Robert J. Keyes
Lincoln Laboratory, Massachusetts Institute of Technology,
Lexington, MA 02173, USA
ISBN 978-3-662-22261-4 ISBN 978-3-540-37378-0 (eBook)
DOI 10.1007/978-3-540-37378-0
Library of Conar011 CataiOJiiq ill Publication DatL Kc:ra, Robert J. 1927-. Optical and infrared dctccton. (Topies in
app!ied physic:s; v. 19). Includes biblioaraphies. I. Infra-red detectors. I. Title. TAIS70.K48. 681'.2. 77-7309
This work is subjoc:t to copyriahL AU l"iJhll arc I"IIICIYcd, whether the whole or part of the material is coneerncd, speeific:ally
those of translation. reprintina. ro-11111 of UluatratiDIII. broadcutina. reproduction by photocopying machine or similar mcano,
and storage in data bankL UDder §54 of the German Copyriabt Law, where copies arc made for other than private usc,
a fee is payable to the publisher, the amount of the recto he determined by agreement with the publisher.
Cl Springer-Verlag BerliDHeidclberg 1977
Originally published by Sprioga"-Verlag Berlin Heiclclbo:Jg New Yod< ill 1977
Softcover reprint of the banlcover lsi edition 1977
The use of registered nameo, trademarko. etc. in this publication does Dot imply, even in the abaenc:e of a specific statement, that
such names are exempt from the relevant protoc:tive laws and ....,.lations and therefore free for llCDeral use
215.1/3 Ll0-S43211l
Preface
This volume is written for those who desire a comprehensive analysis of the
latest developments in infrared detector technology and a basic insight
into the fundamental processes which are important to evolving detection
techniques. Each of the most salient infrared detector types is treated in
detail by authors who are recognized as leading authorities in the specific
areas addressed. In order to concentrate on pertinent aspects of the present
state of the detector art and the unique point of view of each author, extensive
tutorials of a background nature are avoided in the text but are readily
available to the reader through the many references given.
The volume opens with a broad-brush introduction to the various types
of infrared detectors that have evolved since Sir William Herschel's discovery
of infrared radiation 175 years ago. The second chapter presents an overall
perspective of the infrared detector art and serves as the cohesive cement
for the more in-depth presentation of subsequent chapters. Those detector
types which, for one reason or other have not attained wide use today,
are also discussed in Chapter 2.
The more notable and widely used infrared detectors can be divided
into three basic classes which are indicative of the primary effect produced
by the photon-detector interaction, i.e., thermal, photoconductive, photo
voltaic, and photoemissive. Chapters 3, 4, and 5 offer a detailed treatment
of each of these important processes.
The objectives of an infrared detector are to find a signal, measure it,
and extract some vital information for subsequent use. Charge-coupled
devices (CCD) and nonlinear photon interactions are new techniques for
extracting more information from weak infrared signals. These devices, when
directly or indirectly coupled to basic detector types, place a tremendous
amount of low noise, compact, inexpensive logic at the disposal of infrared
sensor designers. The marriage of CCD concepts to detector technology is
young, moving fast, and portends great strides in the ability to retrieve
small signal information from complex radiation environments. Chapter 5
presents some of the latest developments and concepts in this unique area.
Methods of measuring the phase and frequency of coherent infrared signals
have become important in order to extract the maximum information from
laser signals. The efficient nonlinear mixing of coherent infrared radiation in
standard detector materials has achieved sensitivities approaching the
theoretical limit (a few photons per measurement interval) and has stimulated
VI Preface
new applications for lasers in the communication, radar, and spectroscopy
fields. A volume concerned with infrared detectors would be incomplete
without addressing some of the salient aspects of heterodyne or nonlinear
detection-hence Chapter 7.
I would like to thank the contributors to this volume, P. Kruse, E. Putley,
D.Long, H.Zwicker, F.Milton, and M.Teich, for giving of their time,
energy, and expertise in preparation of their chapters; I also thank my wife,
Gladys, for her assistance.
Lexington, Mass. Robert J. Keyes
March, 1977
Contents
1. Introduction. By R.J. Keyes
2. The Photon Detection Process. By P. W. Kruse (With 22 Figures) . . . 5
2.1 Classification and Phenomenological Descriptions of Selected
Photon Detection Mechanisms 7
2.1.1 Photon Effects . . . . . 8
2.1.2 Thermal Effects . . . . 26
2.1.3 Wave Interaction Effects 33
2.2 Noise in Radiation Detectors . 36
2.2.1 Noise in Semiconductor Detectors 37
2.2.2 Noise in Photoemissive Devices 41
2.3 Figures of Merit . . . 42
2.3.1 Spectral Response 42
2.3.2 Responsivity 43
2.3.3 D* ...... . 44
2.3.4 D** . . . . . . 45
2.3.5 Noise Equivalent Power 45
2.3.6 Detectivity . . . . . . 46
2.3. 7 Frequency Response, Response Time, Time Constant, f* . 46
2.3.8 Noise Spectrum . . . . . . . . . . . . . . . . . . 47
2.4 The Signal Fluctuation and Background Fluctuation Limits . 47
2.4.1 Signal Fluctuation Limit . . . . . . . . . . . . . . 48
2.4.2 Background Fluctuation Limit . . . . . . . . . . . . 50
2.4.3 Composite Signal Fluctuation and Background Fluctuation
Limits . . . . . . . . . . . . . . .. 56
2.5 State-of-the-Art of Infrared and Optical Detectors 59
References . . . . . . . . . . . . . . . . . . 65
3. Thermal Detectors. By E.H.Putley (With 14 Figures) 71
3.1 Basic Principles . 72
3.2 The Thermopile 79
3.3 The Bolometer . 82
3.4 The Golay Cell and Related Detectors. 89
3.5 Pyroelectric Detector . . . . . . . 90
Vlll Contents
3.6 Other Types of Thermal Detectors . . . . . . . . . . . 95
3.7 The Use of Thermal Detectors in Infrared Imaging Systems . 96
References . . . . . . . . . . . . . . . . . . . . . . . 98
4. Photovoltaic and Photoconductive Infrared Detectors
By D. Long (With 15 Figures) 101
4.1 Basic Theory . . . . . . . . . . . . . . 102
4.1.1 Direct Photon Detection . . . . . . 102
4.1.2 Photocurrent, Gain, and Responsivity . 103
4.1.3 Noise Mechanisms . . . . 104
4.1.4 Detectivity . . . . . . . 106
4.1.5 Other Detector Parameters 107
4.2 Photovoltaic Detectors 109
4.2.1 Theory . . . . . . . . . 109
4.2.2 Materials . . . . . . . . 114
4.3 Intrinsic Photoconductive Detectors 120
4.3.1 Theory . . . . . . . . . . 120
4.3.2 Materials . . . . . . . . . 124
4.4 Extrinsic Photoconductive Detectors 129
4.4.1 Theory . . . . . . 129
4.4.2 Materials . . . . . 132
4.5 Summary and Conclusions 133
References . . . . . . . . 145
5. Photoemissive Detectors. By H.R.Zwicker (With 22 Figures) . . 149
5.1 Introduction . . . . . . . . . . 149
5.1.1 Applications and Advantages . . . . . . . . . . 149
5.1.2 Limitations . . . . . . . . . . . . . . . . . . 150
5.1.3 Types of Photoemissive Surfaces: Classical and NEA . 150
5.1.4 RMandTMModes . 151
5.1.5 OutlineofChapter. . . . . . . . . . . 152
5.2 The Photoemission Process . . . . . . . . . 152
5.2.1 Fundamentals of Electron Escape Energy . 152
5.2.2 Escape-Energy Parameters for Metals and Semiconductors . 154
5.2.3 Thresholds of Various Materials and Choice of Photo-
emissive Substances 155
5.3 Classical Photoemissive Surfaces 159
5.3.1 The (CsSb) Photoemitter . 159
5.3.2 The S-1 (AgCsO) Photocathode 161
5.4 Negative Electron Affinity (NEA) Devices 163
5.4.1 Introduction and Advantages . 164
5.4.2 Basic Physics of NEA Operation 165
5.4.3 NEA GaAs . . . . . . . . . 167
Contents IX
5.4.4 Modeling the NEA Surface . . . . . . . . . . . . . 169
5.4.5 Fabrication and Optimization of RM and TM NEA GaAs . 172
5.4.6 Other NEA IR Photocathodes . . . . 177
5.4. 7 N EA Silicon . . . . . . . . . . . 181
5.5 Photoemissive Devices: The Photomultiplier 182
5.5.1 Introduction . . . . . . . 182
5.5.2 Photocathode Dark Current . 182
5.5.3 The Electron Multiplier . . . 184
5.5.4 Spectral Response Data . . . 188
5.5.5 Specialized NEA Analysis Tools 191
References . . . . . . . . . . . . .- . 192
6. Charge Transfer Devices for Infrared Imaging. By A.F.Milton
(With 18 Figures) . . . . . . . 197
6.1 Historical . . . . . . . . . . . 197
6.2 Charge Coupled Devices . . . . . 200
6.2.1 Basic Operating Principles . 200
6.2.2 Limitations . . . . . . . . 203
6.3 Time Delay and Integration (TDI) and IR Sensitive CCD . . 213
6.4 Direct Injection: Hybrid and Extrinsic Silicon . 216
6.5 Accumulation Mode: Extrinsic Silicon . . 219
6.6 IR CID . . . 220
6.7 Conclusions . 227
References . 228
7. Nonlinear Heterodyne Detection. By M. C. Teich (With 24 Figures) . 229
7.1 Two-Frequency Single-Photon Heterodyne Detection 231
7.2 Two-Frequency Multiphoton Heterodyne Detection 232
7.2.1 Multiple-Quantum Direct Detection . . . . . 232
7.2.2 Theory of Multiphoton Photomixing. . . . . 234
7.2.3 Signal-to-Noise Ratio and Minimum Detectable Number
of Photons . 237
7.2.4 Experiment . . . . . . . . . . . . . . . . . . . . 239
7.2.5 Discussion . . . . . . . . . . . . . . . . . . . . . 242
7.3 Three-Frequency Single-Photon Heterodyne Detection Using a
Nonlinear Device . . . . . . . . . . . . . . . . . . 243
7.3.1 System Configuration . . . . . . . . . . . . . . . . 244
7.3.2 Application to cw Radar with Sinewave Input Signals . . 249
7.3.3 Application to cw Radar with Gaussian Input Signals
(Gaussian Spectra) . . . . . . . . . . . . . . 257
7.3.4 Application to cw Radar with Gaussian Input Signals
(Lorentzian Spectra) . . . . . . . . 263
7.3.5 Application to an Analog Communications System . . . 266
