Table Of ContentDiode Lasers
Series in Optics and Optoelectronics
Series Editors: R G W Brown, Queens University Belfast, UK
E R Pike, Kings College, London, UK
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Department of Physics
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First published 2005 by Institute of Physics Publishing
Published 2018 by Routledge
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ISBN 13: 978-0-7503-0726-0 (pbk)
To Tomomi, without whose support I would not have been able to
spend so much time at my computer, and to Taro and Chibi, without
whose attention I would have had no excuse to leave my computer.
Contents
Preface xi
1 Introduction 1
References 5
2 Essential semiconductor physics 6
2.1 Free electrons in semiconductors 6
2.2 Formation of bands in semiconductors 7
2.3 Band theory and conduction 9
2.4 Electron and hole statistics 11
2.5 Doping 14
2.6 Heavy doping 15
2.7 Recombination and generation 19
2.8 Energy bands in real semiconductors 20
2.9 Minority carrier lifetime 23
2.10 Minority carrier diffusion 24
2.11 Current continuity 25
2.12 Non-equilibrium carrier statistics 26
2.13 Summary 26
2.14 References 26
3 Laser fundamentals 28
3.1 Stimulated emission 31
3.2 Population inversion in semiconductors 34
3.3 The p-n homojunction laser 35
3.4 The active region and threshold current 40
3.5 Optical properties of the junction 43
3.6 Output characteristics of the homojunction laser 47
3.7 Summary 51
3.8 References 52
vii
viii Contents
4 Optical properties of semiconductor materials 54
4.1 A model of the refractive index 54
4.2 The refractive index of a semiconductor laser cavity 61
4.3 Gain in semiconductors 66
4.3.1 The vector potential and the interaction Hamiltonian 70
4.3.2 Fermi’s golden rule 71
4.3.2 The matrix element and densities of states 75
4.4 Summary 76
4.5 References 77
5 The double heterostructure laser 79
5.1 Introduction 79
5.2 Materials and epitaxy 81
5.2.1 Molecular beam epitaxy 88
5.2.1.1 MBE of aluminium gallium arsenide 90
5.2.1.2 MBE of indium gallium arsenide phosphide 92
5.2.2 Chemical vapour phase epitaxy 92
5.2.2.1 Hydride chemical vapour deposition 93
5.2.2.2 The trichloride process 94
5.2.2.3 MOCVD 94
5.3 Electronic properties of heterojunctions 96
5.3.1 Band bending at heterojunctions 99
5.4 The double heterostructure under forward bias 102
5.4.1 Recombination at interfaces 106
5.5 Optical properties of heterojunctions; transverse mode control
and optical confinement 108
5.6 Materials and lasers 115
5.6.1 InP systems: InGaAs, InGaAsP, AlGalnP 116
5.6.2 InAs-InSb lasers 125
5.7 Lateral mode control 126
5.8 Summary 128
5.9 References 128
6 Quantum well lasers 132
6.1 Classical and quantum potential wells 132
6.2 Semiconductor quantum wells 139
6.3 Quantised states in finite wells 147
6.4 The density of states in two-dimensional systems 150
6.5 Optical transitions in semiconductor quantum wells 153
6.5.1 Gain in quantum wells 157
6.6 Strained quantum wells 163
6.7 Optical and electrical confinement 167
6.8 Optimised laser structures 177
6.9 Summary 180
6.10 References 181
Contents ix
7 The vertical cavity surface emitting laser 185
7.1 Fabry-Perot and waveguide modes 199
7.2 Practical VCSEL cavity confinement 202
7.3 Oxide confined devices 207
7.4 Long wavelength VCSELs 213
7.5 Visible VCSELs 216
7.6 Summary 218
7.7 References 219
8 Diode laser modelling 222
8.1 Rate equations; the idealised DH laser 222
8.2 Gain compression 224
8.3 Small signal rate equations 228
8.4 Modelling real laser diodes 232
8.4.1 InGaAsP/InP quantum well lasers 232
8.4.2 Separate confinement heterostructure quantum well
laser 235
8.4.3 Three level rate equation models for quantum well
SCH lasers 245
8.5 Electrical modelling 249
8.6 Circuit level modelling 253
8.7 Summary 258
8.8 References 258
9 Lightwave technology and fibre communications 260
9.1 An overview of fibre communications and its history 260
9.2 Materials and laser structures 268
9.3 Laser performance 272
9.3.1 Mode selectivity 272
9.3.2 Modulation response 273
9.3.3 Gain switching 275
9.3.4 Linewidth 277
9.4 Single wavelength sources 281
9.4.1 DBR lasers 285
9.4.2 DFB lasers 287
9.5 High bandwidth sources 288
9.6 Summary 290
9.7 References 291
10 High power diode lasers 293
10.1 Geometry of high power diode lasers 294
10.2 Single emitter broad area diode lasers 297
10.3 Lateral modes in broad area lasers 298
10.4 Controlling filamentation 305
