Vertical External Cavity Surface Emitting Lasers VECSEL Technology and Applications

Provides comprehensive coverage of the advancement of vertical-external-cavity surface-emitting lasers

Vertical-external-cavity surface-emitting lasers (VECSELs) emit coherent light from the infrared to the visible spectral range with high power output. Recent years have seen new device developments ? such as the mode-locked integrated (MIXSEL) and the membrane external-cavity surface emitting laser (MECSEL) ? expand the application of VECSELs to include laser cooling, spectroscopy, telecommunications, biophotonics, and laser-based displays and projectors.

In Vertical External Cavity Surface Emitting Lasers: VECSEL Technology and Applications, leading international research groups provide a comprehensive, fully up-to-date account of all fundamental and technological aspects of vertical external cavity surface emitting lasers. This unique book reviews the physics and technology of optically-pumped disk lasers and discusses the latest developments of VECSEL devices in different wavelength ranges. Topics include OP-VECSEL physics, continuous wave (CW) lasers, frequency doubling, carrier dynamics in SESAMs, and characterization of nonlinear lensing in VECSEL gain samples. This authoritative volume:

• Summarizes new concepts of DBR-free and MECSEL lasers for the first time
• Covers the mode-locking concept and its application
• Provides an overview of the emerging concept of self-mode locking
• Describes the development of next-generation OPS laser products

Vertical External Cavity Surface Emitting Lasers: VECSEL Technology and Applications is an invaluable resource for laser specialists, semiconductor physicists, optical industry professionals, spectroscopists, telecommunications engineers and industrial physicists.

Preface xiii

Part I Continuous wave VECSEL 1

1 History of Optically Pumped Semiconductor Lasers – VECSELs 3
Mark E. Kuznetsov

1.1 Introduction 3

1.2 OPS-VECSELs: Concept and History 4

1.3 Micracor 8

1.4 OPSL Development at Micracor: First Steps 11

1.5 OPS Development at Micracor: Pushing Forward 14

1.6 OPS Development at Micracor: Final Chapter 16

1.7 VECSELs beyond Micracor 20

References 22

2 VECSELs in the Wavelength Range 1.18–1.55 𝛍m 27
Antti Rantamäki and Mircea Guina

2.1 Introduction 27

2.2 Overview of GaAs-based Gain Mirror Technologies for Long-wavelength Infrared VECSELs 28

2.2.1 InGaAs QWs 28

2.2.2 GaInNAs QWs 28

2.2.3 InAs QDs 30

2.2.4 GaAsSb QWs 31

2.3 Overview of InP-based Gain Mirror Technologies for Long-wavelength Infrared VECSELs 32

2.3.1 Monolithic InP-based DBRs 32

2.3.2 Dielectric and Metamorphic DBRs 33

2.3.3 Semiconductor-dielectric-metal Compound Mirrors 34

2.3.4 Wafer-bonded GaAs-based DBRs 37

2.3.4.1 DirectWafer Bonding 39

2.3.4.2 Low Temperature Bonding 44

2.3.5 Gain Structures in Transmission 47

2.4 Conclusion 50

References 50

3 Single-frequency and High Power Operation of 2–3 Micron VECSEL 63
Marcel Rattunde, Peter Holl, and Joachim Wagner

3.1 Introduction 63

3.2 Semiconductor Lasers for the MIR Range 64

3.3 III-Sb Material System 66

3.4 2–3 μm VECSEL Design 68

3.4.1 Standard Barrier Pumped Structures 68

3.4.2 In-well Pumping 69

3.4.3 Low Quantum Deficit Barrier Pumping 70

3.5 Mounting Technologies 72

3.5.1 Intracavity Heatspreader 74

3.5.2 Thin Device 76

3.5.3 Double-sided Heatspreader 77

3.6 Single-frequency Operation (SFO) of 2–3 μm VECSEL 78

3.6.1 Key Parameters for Single-Frequency Operation 79

3.6.2 SFO with Intracavity Heatspreader 81

3.6.2.1 Laser Cavity Setup 82

3.6.2.2 Wavelength Tuning 83

3.6.2.3 Emission Linewidth 85

3.6.2.4 Active Stabilization and Influence of Sampling Time 88

3.6.2.5 Conclusion 90

3.6.3 SFO withWedged Heatspreader 91

3.6.4 SFO with Microcavity VECSELs 92

3.6.5 SFO without Intracavity Heatspreader 94

3.7 Conclusion 99

References 101

4 Highly Coherent Single-Frequency Tunable VeCSELs: Concept, Technology, and Physical Study 109
Mikhael Myara

4.1 Introduction: Lasers for Applications 109

4.2 The “Ideal” Laser 111

4.3 Toward Single-Mode Operation 113

4.4 Toward High Coherence 118

4.5 The VeCSEL in the State of the Art 121

4.6 Highly Coherent, Tunable VeCSEL Design 122

4.7 Limits and Solutions 125

4.8 Highly Coherent, Tunable VeCSEL: Main Characteristics 127

4.9 Ultrahigh-Purity Single-mode Operation 129

4.10 Spatial Coherence 131

4.11 Time Domain Coherence and Noise 131

4.11.1 Noise in Photonics: Basics 131

4.11.2 Intensity Noise of a VeCSEL 135

4.11.3 Phase Noise, Frequency Noise, and Linewidth of a VeCSEL 136

4.12 Conclusion 139

Acknowledgements 140

References 140

5 Terahertz Metasurface Quantum Cascade VECSELs 145
Benjamin S. Williams and Luyao Xu

5.1 Introduction 145

5.1.1 Waveguides for THz QC-Lasers 146

5.1.2 Overview of Metasurface QC-VECSEL Concept 148

5.2 Metasurface Design 149

5.3 QC-VECSEL Model 152

5.3.1 Confinement Factor 156

5.3.2 Metasurface and Cavity Optimization 157

5.4 THz QC-VECSEL Performance: Power, Efficiency, and Beam Quality 159

5.4.1 Effect of Metasurface on Spectrum 160

5.4.2 Effect of Output Coupler 161

5.4.3 Focusing Metasurface VECSEL 162

5.4.4 Intra-cryostat Cavity QC-VECSEL 165

5.5 Polarization Control in QC-VECSELs 166

5.6 Conclusion 169

References 170

6 DBR-free Optically Pumped Semiconductor Disk Lasers 175
Alexander R. Albrecht, Zhou Yang, and Mansoor Sheik-Bahae

6.1 Introduction 175

6.2 DBR-free Semiconductor Disk Lasers 176

6.2.1 Opportunities and Advantages 177

6.2.2 Thermal Analysis 178

6.2.3 Longitudinal Mode Structure and Broadband Tunability 180

6.3 Device Fabrication 182

6.4 DBR-free SDL Implementation 185

6.4.1 High Power Operation 185

6.4.2 Broad Tunability 187

6.4.3 Wafer-scale Processing 189

6.5 Novel Concepts 189

6.6 Conclusions 192

References 193

7 Optically Pumped Red-Emitting AlGaInP-VECSELs and the MECSEL Concept 197
Hermann Kahle, Michael Jetter, and Peter Michler

7.1 Introduction 197

7.2 Direct Red-Emitting AlGaInP-VECSELs and Second-Harmonic Generation 199

7.2.1 GaInP QuantumWells and the AlGaInP Material System 199

7.2.2 GaInP QuantumWell VECSELs: A Comparison 201

7.2.2.1 Architecture of the Semiconductor Structures 202

7.2.2.2 Experimental Setup 203

7.2.2.3 Characterization Results 204

7.2.2.4 Internal Efficiency 204

7.2.3 Power Scaling via QuantumWell and Multi-Pass Pumping 208

7.2.3.1 QuantumWell Pumping 208

7.2.3.2 Multi-Pass Pumping 210

7.2.4 Second-Harmonic Generation into the UV-A Spectral Range 211

7.3 The Membrane External-Cavity Surface-Emitting Laser (MECSEL) 212

7.3.1 The Semiconductor Active Region Membrane 213

7.3.2 MECSEL Setup 215

7.3.3 MECSEL Characterization 216

7.3.3.1 Output Power Measurements 216

7.3.3.2 Beam Profile and Beam Quality Factor 218

7.3.3.3 Spectra 218

7.4 Conclusions 221

References 221

Part II Mode-Locked VECSEL 229

8 Recent Advances in Mode-Locked Vertical-External-Cavity Surface-Emitting Lasers 231
Anne C. Tropper

8.1 Introduction 231

8.1.1 Ultrafast Lasers 232

8.1.2 Ultrafast Semiconductor Lasers; Diodes, VECSELs, and MIXSELs 233

8.2 Ultrafast Pulse Formation in a Surface-Emitting Semiconductor Laser 235

8.2.1 Surface-Emitting Gain Chip Design 235

8.2.2 Gain Filtering 238

8.2.3 Gain Saturation and Recovery 239

8.2.4 Saturable Absorbers for ML-VECSELs and MIXSELs 241

8.3 Performance of Passively Mode-Locked Semiconductor Lasers 244

8.3.1 Pulse Duration 244

8.3.2 Pulse Repetition Rate 246

8.3.3 Mode-Locked VECSELs: Visible to Mid-Infrared 248

8.3.4 Simulation and Modeling 249

8.3.5 Noise 251

8.4 Applications 252

8.4.1 Biological Imaging 252

8.4.2 Quantum Optics 253

8.4.3 Supercontinuum Generation and Frequency Combs 253

8.4.4 Terahertz Imaging and Spectroscopy 254

8.5 Summary and Outlook 255

References 256

9 Ultrafast Nonequilibrium Carrier Dynamics in Semiconductor Laser Mode-Locking 267
I. Kilen, J. Hader, S.W. Koch, and J.V. Moloney

9.1 Introduction 267

9.2 Background Theory 269

9.2.1 Pulse Propagation 269

9.2.2 Microscopic Theory 273

9.3 Domain Setup/Modeling 277

9.3.1 The VECSEL Cavity 277

9.3.2 The Gain Region 278

9.3.3 The Relaxation Rates and the Round Trip Time 280

9.3.4 Noise Buildup to Pulse 281

9.4 Numerical Results 282

9.4.1 Single-Pass Investigation of QWs and SAMs on the Order of Second Born–Markov Approximation 282

9.4.1.1 Inverted QuantumWell 282

9.4.1.2 Saturable Absorber 285

9.4.2 Mode-Locked VECSELs 288

9.4.2.1 Gain, Absorption, and Dispersion 288

9.4.2.2 Pulse Buildup and Initial Conditions 290

9.4.2.3 Self-Phase Modulation from QWs 290

9.4.2.4 Mode-Locked Pulse Family 291

9.4.2.5 Influence of Loss on the Mode-Locked Pulse 294

9.4.2.6 Limits on the Shortest Possible Pulse and the Hysteresis Effect 296

9.5 Outlook 299

References 300

10 Mode-Locked AlGaInP VECSEL for the Red and UV Spectral Range 305
Roman Bek, Michael Jetter, and Peter Michler

10.1 Introduction 305

10.2 Epitaxial Layer Design of AlGaInP-SESAM Structures 306

10.2.1 QuantumWell SESAMs 306

10.2.2 Quantum Dot SESAMs 307

10.3 Temporal Response of AlGaInP SESAMs 307

10.4 Cavity Designs 309

10.5 Characterization Methods 310

10.6 Mode-Locking Results 311

10.6.1 QuantumWell Mode-Locked AlGaInP VECSELs 311

10.6.1.1 High Output Power 311

10.6.1.2 Femtosecond Operation 312

10.6.2 Quantum Dot Mode-Locked AlGaInP VECSELs 314

10.7 Second Harmonic Generation into the UV Spectral Range 315

10.8 Summary and Outlook 317

References 318

11 Colliding Pulse Mode-locked VECSEL 321
Alexandre Laurain

11.1 Introduction 321

11.2 Principle of Colliding Pulse Modelocking 322

11.3 Requirements for Stable Colliding Pulse Modelocking 324

11.3.1 Pulse Timing 324

11.3.2 Gain Recovery and Pumping Rate 324

11.3.3 Polarization 326

11.3.4 ModeWaist and Saturation Fluence 326

11.4 Design of an Ultrafast CPM VECSEL 327

11.4.1 The Optical Cavity 327

11.4.2 The Gain Structure 328

11.4.3 The SESAM 333

11.5 Modelocking Results 335

11.5.1 Robustness of the Modelocking Regime 335

11.5.2 Cross Correlation of the Output Beams 336

11.5.3 Pulse Duration Optimization 338

11.5.4 Multipulse Regime 340

11.6 Pulse Interactions in the Saturable Absorber 341

11.6.1 Field Intensity Distribution 341

11.6.2 Saturable Absorption Model 343

11.6.3 Dynamics of the Carrier Density Distribution 345

11.6.4 Absorption Losses and Pulse Shaping 347

11.6.5 Saturation Fluence of the Absorber 349

11.6.6 Power Balance in CPM Operation 350

11.7 Summary and Outlook 352

Acknowledgments 353

References 353

12 Self-Mode-Locked Semiconductor Disk Lasers 357
Arash Rahimi-Iman

12.1 Introduction 357

12.2 Mode-Locking Techniques for Optically Pumped SDLs at a Glance 358

12.3 History of Saturable-Absorber-Free Pulsed VECSELs 360

12.3.1 Self-Mode-Locked Optically Pumped VECSELs 360

12.3.1.1 Once Upon a Time – Beyond Magic 361

12.3.1.2 Mode Competition – A Struggle for Acceptance 363

12.3.1.3 More Than a Flash in the Pan – TriggeredWave of Results 364

12.3.2 Harmonic Self-Mode-Locking 366

12.3.3 Self-Mode-Locking Quantum-Dot VECSEL 368

12.3.4 SML Cavity Configurations 369

12.3.5 SML VECSEL at OtherWavelengths 371

12.4 Overview on SESAM-Free Mode-Locking Achievements 373

12.4.1 Spotlight on SML VECSELs 373

12.4.1.1 Pulse Duration 373

12.4.1.2 Peak Power 374

12.4.1.3 Repetition Rate 375

12.4.2 SESAM-Free Alternatives to SML VECSEL 375

12.4.2.1 Graphene or Carbon Nanotube Saturable Absorber Mode-Locked VECSELs 375

12.4.2.2 SESAM-Free VECSEL Design with Intracavity Kerr Medium 375

12.5 Investigations into the Mechanisms and Outlook 376

12.5.1 First Studies Concerning the Mechanisms Behind SML 376

12.5.2 Z-Scan Measurements of the Nonlinear Refractive Index in a VECSEL Chip 377

12.5.3 Applications and Expected Advances 380

Acknowledgments 381

References 382

Index 387 

Michael Jetter is Leader of the Epitaxy and Laser Group, Institute for Semiconductor Optics and Functional Interfaces, University of Stuttgart, Germany. He is expert in III-V semiconductor epitaxy and semiconductor lasers.

Peter Michler is Professor and Head of the Institute for Semiconductor Optics and Functional Interfaces, University of Stuttgart, Germany. His research concentrates on quantum dots, non-classical light sources and semiconductor lasers, semiconductor based quantum optics and photonic quantum technologies.