VCSEL Industry Communication and Sensing

In VCSEL Industry: Communication and Sensing, a team of distinguished researchers and manufacturing professionals deliver a thorough and practical reference guide to vertical-cavity surface-emitting lasers (VCSELs) for young entrepreneurs, investors, venture capitalists, and researchers. The authors offer comprehensive descriptions of the technology involved, as well as a robust exploration of the industry and commercial landscape in which VCSELs exist.

The book contains numerous illustrations and schematics of the anatomy of VCSEL product developments and an insightful discussion of the proliferation of VCSELs in photonics and optics. There is also a dedicated section on photoreceivers used for VCSEL-based data communications and sensing.

VCSEL Industry: Communication and Sensing provides readers with an accessible, commercial perspective of an important technology while offering just enough technical detail to make sense of the subject. The book also includes:

• A thorough introduction to VCSELs, including discussions of semiconductor lasers, materials, wavelengths, and why VCSELs are attractive for photonics applications
• Comprehensive explorations of the VCSEL industry, including market demands, an industry landscape, descriptions of commercial products based on VCSELs, and business models
• Practical discussions of VCSELs for data communication, including high-speed VCSELs, gain and parasitic effects on bandwidth and speed, and form factors and standards
• In-depth examinations of VCSEL arrays for sensing, including high-power VCSELs in consumer electronics

Perfect for early-career researchers, engineers, entrepreneurs, investors, and managers, VCSEL Industry: Communication and Sensing will also prove to be an invaluable addition to the libraries of executives from across the semiconductor industry.

Padullaparthi Babu Dayal, PhD, is Vice President and Chief Technology Officer of Photonic Components DFM Ltd. in Hong Kong. He has over 15 years of experience in research, development, and manufacturing in academic and industrial facilities producing photonic devices for communication and sensing.

About the Book and Authors Biographies xv

Foreword xvii

Preface xix

Introduction xxi

Acknowledgments xxiii

List of Image Contributions xxv

1 Semiconductor Lasers and VCSEL History 1
Kenichi Iga

1.1 History and Basics of Semiconductor Lasers 1

1.1.1 Categorization of Semiconductor Lasers 1

1.1.2 Light Emission and Absorption in Semiconductors 3

1.1.3 Birth of Semiconductor Lasers 3

1.1.3.1 Homostructure and Double Heterostructure Lasers 3

1.1.3.2 Quantum Well Lasers 4

1.1.4 Amplification of Light in Semiconductors 5

1.1.5 Oscillation Conditions in Semiconductor Lasers 6

1.1.5.1 Laser Resonators 6

1.1.5.2 Resonant Wavelength 7

1.1.5.3 Cavity Formation 8

1.2 Semiconductor Lasers and Manufacturing 9

1.2.1 Manufacturing Process of Edge-Emitting Lasers 9

1.2.2 Vertical-Cavity Surface-Emitting Laser 9

1.3 VCSEL History and Development 11

1.3.1 Stage I: Initial Concept and Invention 11

1.3.1.1 Stage Ia: Invention and Initial Demonstration 11

1.3.1.2 Stage Ib: First Room-Temperature Continuous-Wave Operation 12

1.3.2 Stage-II: Spread of Worldwide R&D 13

1.3.3 Stage III: Extension of Applications and Initial Commercialization 13

1.3.3.1 LAN for Internet 14

1.3.3.2 Computer Mouse 14

1.3.3.3 Laser Printers 14

1.3.4 Stage IV: Spread of VCSEL Photonics 15

1.3.5 Stage V: VCSEL Industry 15

1.4 Timeline and Milestones 15

1.4.1 Milestones of VCSEL Research and Development 15

1.4.2 Single-Mode and Multi-Mode Behavior 15

1.4.3 Major Features of VCSELs 17

1.4.4 VCSELs as Major Optical Components 17

1.4.5 VCSELs in Optical Communication and Sensing 17

1.4.5.1 The Concept of VCSEL Communication and Sensing 17

1.4.5.2 VCSELs in Optical Communications 17

1.4.5.3 VCSELs in Optical Sensing 19

1.5 State of VCSEL Development 21

1.5.1 Published Papers 21

1.5.2 Toward VCSEL Photonics 21

1.5.3 Toward VCSEL High-Volume Manufacturing 22

1.5.4 Prospects of VCSEL Market 23

References 24

2 VCSEL Fundamentals 29
Jim Tatum

2.1 Introduction to Lasers 29

2.2 Basic VCSEL Structure 29

2.3 Quantum Well Gain Region (Active Region) 30

2.4 Distributed Bragg Reflector Mirrors 30

2.5 Light Output Characteristic 33

2.6 Forward Voltage Characteristic 33

2.7 Optical Modes 34

2.8 Beam Divergence 36

2.9 Modulation Characteristics 37

2.10 Temperature Characteristics 39

2.11 Thermal Transient Behavior and Short-Pulse Operation 40

2.12 Other VCSEL Structures 41

2.13 VCSEL Materials 44

2.14 Summary 44

References 45

3 VCSEL Industry: Prospects and Products 47
Babu Dayal Padullaparthi

3.1 Industry Background 47

3.1.1 VCSEL Market 48

3.1.2 VCSEL Chip Demands 48

3.1.3 VCSEL Attractiveness 51

3.1.4 VCSEL Die Cost and Foundry Economics 52

3.2 VCSEL Industry Landscape 55

3.2.1 The Key “Abilities” of VCSELs 55

3.2.2 High-Volume Manufacturing Challenges 55

3.2.2.1 Epi-Wafer Growth and F-P and PL Uniformities 56

3.2.2.2 Wafer-Fab (Processing) Specifications 57

3.2.2.3 Dry Etch Depth Uniformity 57

3.2.2.4 Wet Thermal Oxidation, Aperture Control and Uniformity 60

3.2.2.5 Chip Qualification and Reliability Tests 60

3.2.3 Industry Players 62

3.2.3.1 Epi-Houses 62

3.2.3.2 Process Foundries 62

3.2.4 Business Models 62

3.2.5 Supply Chain 64

3.2.6 Yield Improvements 65

3.2.7 Cycle Times 67

3.2.8 COVID-19 Effects 67

3.3 VCSEL Commercial Products 68

3.4 Summary 68

References 69

Bibliography 71

4 Data Communications Applications 73
Jim Tatum

4.1 Introduction 73

4.2 Growing Data 74

4.3 Data Centers and High-Performance Computing 75

4.3.1 Data Centers 76

4.3.2 High-Performance Computing 76

4.3.3 Structure of Data Centers and HPC Centers 77

4.4 Optical Interconnects 78

4.4.1 Introduction 78

4.4.2 Networking Communications Standards 79

4.4.3 Optical Transceiver Types 79

4.4.4 Consumer Connectivity 81

4.4.5 Techno-Economic Comparison of Transceiver Technology 82

4.5 Data Encoding and Multiplexing 84

4.5.1 Introduction 84

4.5.2 Spatial and Wavelength Multiplexing 84

4.5.3 Pulse-Amplitude Modulation (PAM-n) 85

4.5.4 Discrete Multi-Tone Modulation (DMT) 86

4.5.5 Other Modulation Formats 86

4.5.6 Analog and Radio Access Modulation 86

4.5.7 Modulation Format Conclusion 86

4.6 High-Speed VCSELs 87

4.6.1 Current Industry Capability 87

4.6.2 VCSEL Bandwidth Improvement 88

4.6.3 Photonic Resonance VCSELs 90

4.6.4 Laser Driver Compensation 92

4.6.5 Forward Error Correction 94

4.6.6 Some Record Results 94

4.7 Optical Link Impairments 95

4.7.1 Transmitter Impairments 95

4.7.2 Fiber Impairments 97

4.7.3 Receiver Impairments 100

4.8 Energy Efficient VCSELs 101

4.9 Datacom Market 102

4.10 Summary 102

References 102

5 VCSELs for 3D Sensing and Computer Vision 105
Babu Dayal Padullaparthi

5.1 Optical Sensors in Consumer Electronics 105

5.1.1 3D Imaging Technologies 105

5.1.1.1 Stereo Vision 106

5.1.1.2 Time-of-Flight (TOF) 106

5.1.1.3 Triangulation Technique and Structured Light 109

5.1.2 Apple’s 3D Sensing Technology Breakthrough and its Impact 110

5.2 Why VCSELs for Smart Optical Sensors? 112

5.2.1 Key Features of High-Power VCSEL Arrays 112

5.2.2 Figures of Merit of 2D VCSEL Arrays 113

5.2.2.1 Optimizing Losses: Slope Efficiency and Wall Plug Efficiency 113

5.2.2.2 Fill Factor and Power Scaling 114

5.2.3 Key Challenges 114

5.2.3.1 Thermal Dissipation (Heat Sinking) and Packaging 114

5.2.3.2 Spectral Width, Wavelength Uniformity, and Beam Quality 115

5.2.3.3 Field-of-View (FOV) and Micro-Optic Illuminators 115

5.2.3.4 Thermal Limits and Pulse Switching Times 116

5.3 3D Sensing (Mobile) Products 118

5.3.1 Smartphones: iOS vs Android 118

5.3.2 TOF-Based Proximity Sensors 119

5.3.3 TOF-Based Illumination Sensors 119

5.3.4 Structured-Light-Based Face Recognition Sensors 120

5.3.5 Other Short-Range 3D Sensors 121

5.4 Computer Vision and Virtual Reality 121

5.4.1 Key Aspects of XR (AR, MR, VR) 123

5.4.2 Augmented Reality (AR) 124

5.5 3D Sensing Mobile and Camera Industry Prospects (until 2025) 125

5.6 Summary 126

References 126

6 Automotive LiDARs 129
Babu Dayal Padullaparthi

6.1 Introduction to LiDARs 129

6.1.1 Classification of LiDARs 129

6.1.2 Technologies and Sensor Fusion 130

6.1.3 Advanced Driver Assistance Systems (ADAS) 132

6.2 Operating Principle of LiDARs 134

6.2.1 Time-Delay and Phase-Shift-Based Pulsed Light Detection 134

6.2.2 Frequency-Based Continuous Light Detection 135

6.2.3 Light Transmitters in LiDARs 135

6.2.4 Light Detectors in LiDARs 136

6.2.5 Lidar Module with Integrated System-on-Chip (SOC) 136

6.3 VCSELs in LiDAR Industry: Landscape and Direction 137

6.3.1 Autonomous Shuttles: MaaS/ASaaS 139

6.3.2 LiDARs in Drones, Robotics, etc. 140

6.4 Key Aspects of LiDARs 140

6.4.1 Measurement Techniques 141

6.4.2 Wavelength 142

6.4.3 Eye Safety 143

6.4.4 Laser Radiance and Perception 143

6.4.5 Challenges 144

6.4.5.1 Background Light Rejection 145

6.4.5.2 Single Photon Counting Using SPAD Arrays 145

6.4.5.3 Range Aliasing 145

6.4.5.4 Power Consumption and System Integration 146

6.5 Examples of VCSEL-and EEL-Based LiDARs 146

6.5.1 Solid-State Flash LiDAR 147

6.5.2 Solid-State Addressable-Flash LiDARs 148

6.5.3 MEMS Scanning LiDAR 148

6.5.4 Mechanical Scanning LiDAR 150

6.5.5 FMCW LiDARs 150

6.5.6 Optical Phased Array (OPA) and Si-Photonics-Based LiDARs 151

6.5.7 VCSELs for in-Cabin Sensing 151

6.6 Automotive Communication: IVE (Infotainment) and C-V2X 152

6.7 Market Summary 153

References 154

7 Illumination, Night Vision, and Industrial Heating 159
Jim Tatum

7.1 Introduction 159

7.2 Optical Properties of Illumination Sources 159

7.3 Commercial Examples of VCSEL Illuminators 161

7.4 VCSEL-Based Industrial Heating 164

7.5 Summary 167

References 168

8 Single-Mode VCSELs for Sensing Applications 169
Kenichi Iga and Jim Tatum

8.1 Introduction 169

8.2 Single-Mode VCSELs 169

8.2.1 Spatial Mode Control 170

8.2.2 Polarization Control 172

8.2.3 Wavelength Tuning Principles 174

8.3 Single-Mode VCSEL Application Examples 176

8.3.1 Laser Mouse and Finger Navigation 176

8.3.2 Optical Encoders 178

8.3.3 Laser Printers 178

8.3.4 Gas Sensors 179

8.3.5 Atomic Clocks and Magnetometers 181

8.3.6 Optical Coherence Tomography 182

8.3.7 Other Emerging Applications 184

8.4 Summary 185

References 185

9 Single-Mode VCSELs for Communications Applications 189
Kenichi Iga and Jim Tatum

9.1 Introduction 189

9.2 LW-VCSEL Design and Manufacturing 190

9.2.1 LW-VCSEL Structures 190

9.2.2 1310 nm VCSEL 191

9.2.3 VCSELs in the 1550 nm Band 191

9.2.4 Other Wavelengths for Data Communications 192

9.3 Quantum Communications 193

9.4 Summary 195

References 195

10 Future Prospects 199
Babu Dayal Padullaparthi, Kenichi Iga, and Jim Tatum

10.1 VCSEL Industry 199

10.2 Datacom VCSELs 200

10.3 VCSEL Arrays for 3D Sensing (Short Distance) 200

10.4 VCSEL Arrays for 3D Sensing and Imaging (Long Distance) 201

10.5 kW-Level VCSEL Arrays for Industrial and Night Vision 201

10.6 Single-Mode VCSELs for Communication and Sensing 202

10.7 Quantum Technologies 202

10.8 Neuromorphic/Neurophotonic Technologies 202

10.9 Biomedical/Bio-Photonic Applications 203

10.10 New Directions of VCSEL Technologies (as of March 2021) 203

10.11 Concluding Remarks 204

References 205

Appendix A VCSELs Design Engineering 207
Babu Dayal Padullaparthi

Appendix B Epitaxial Growth Engineering 221
Babu Dayal Padullaparthi

Appendix C Wafer Process Engineering 235
Babu Dayal Padullaparthi

Appendix D Wafer Level Testing 245
Jim Tatum

Appendix E Reliability and Product Qualification 255
Jim Tatum

Appendix F Eye Safety Considerations 273
Jim Tatum

Appendix G Laser Displays and TV 277
Kenichi Iga

Appendix H Red VCSELs 287
Jim Tatum

Appendix I GaN-Based VCSELs 291
Kenichi Iga

Appendix J Photodetectors 297
Babu Dayal Padullaparthi

Image Gallery 311

Index 313

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