Roland Diehl (Ed.) High-Power Diode Lasers Fundamentals, Technology, Applications With Contributions by Numerous Experts With 260 Figures and 20 Tables K@f Springer
Contents Introduction to Power Diode Lasers Peter Unger 1 1. Fundamental Aspects of Diode Lasers 1 1.1. Emission and Absorption in Semiconductors 1 1.2. Basic Elements of Semiconductor Diode Lasers 8 1.3. Optical Gain and Threshold Condition 10 1.4. Edge- and Surfacc-Emitting Lasers 13 1.5. Lateral Confinemcnt 15 1.6. Quantum-Well Structures 18 2. Fabrication Technology 20 3. Optical Waveguides and Resonators 24 3.1. Effective Refractive Index 24 3.2. Normalized Propagation Diagrams 26 3.3. Optical Near- and Far-Field Patterns 28 3.4. Fabry-Perot Resonator 31 3.5. Diode Laser Spectrum 33 3.6. Mirror Coatings 34 4. Rate Equations and High-Power Operation 37 4.1. Rate Equations for Electronic Carriers and Photons 37 4.2. Electrical and Optical Characteristics of Power Diode Lasers... 41 4.3. Design Considerations for High-Power Operation 46 List of Symbols 50 List of Constants 51 Abbreviations for Indices 51 References 52
X Contents Dynamics of High-Power Diode Lasers Edeltraud Gehrig and Ortwin Hess 55 1. Microscopic Spatio-Temporal Properties of Diode Lasers 56 1.1. Role of Microscopic Spatio-Temporal Properties in Macroscopic Laser Characteristics 57 1.2. Optical-Field Dynamics 59 1.3. Physics of the Active Semiconductor Medium 63 2. Spatio-Temporal Dynamics of High-Power Diode Lasers 67 2.1. Optical Injection 67 2.2. Influence of Laser Geometry and Facet Reflectivitics 68 2.3. Dynamics of Optical Emission Characteristics 71 2.4. Spatial and Spcctral Carrier Dynamics 73 2.5. Spatial and Spcctral Refractive-Index and Gain Dynamics 76 3. Conclusion 78 List of Symbols 79 References 80 Epitaxy of High-Power Diode-Laser Structures Markus Weyers, Arnab Bhattacharya, Frank Bugge and Arne Knauer... 83 1. Growth Methods 86 1.1. Molecular-Beam Epitaxy and Its Variants 87 1.2. Metalorganic Vapor-Phase Epitaxy 91 1.3. Comparison of MBE and MOVPE 94 2. Materials for High-Power Diode Lasers 96 2.1. GaAs and AlGaAs 96 2.2. GalnP and AlGalnP 98 2.3. GalnAsP on GaAs 101 2.4. hip, GalnAs(P) and AlGalnAs 102 3. Doping 103 3.1. N-Type Doping 103 3.2. P-Type Doping 103 4. Heterostructures 106 5. Straincd Quantum Wells 107 5.1. Pseudomorphic Growth and Strain Relaxation 107 5.2. Strain Compensation 109 6. Device Results 110 List of Acronyms 113 References 114
Contents XI GaAs Substrates for High-Power Diode Lasers Georg Müller, Patrick Berwian, Eberhard Buhrig and Berndt Weinert 121 1. Selection of the Growth Mcthod 122 1.1. Important Features of GaAs Crystal-Growth Methods 122 1.2. Liquid-Encapsulated Czochralski (LEC) and Vapor-Controlled Czochralski (VCZ) Techniques 124 1.3. Thermal Stress and Dislocation Density 124 1.4. Methods of Directional Solidification: Gradient Freeze and Bridgman Variants 126 2. Physico-Chemical Features of the VGF Technology for the Growth of Si-Doped Low-EPD GaAs Single Crystals 129 2.1. Discussion of VGF Variants 129 2.2. Important Chemical Reactions in the VGF Growth of Si-Doped GaAs 132 2.3. VGF Furnace Concepts 139 2.4. Preparation of Starting Materials and Procedure of VGF Growth 140 3. Numerical Modeling for VGF-Process Optimization 141 3.1. Principles and Strategy of the Numerical Modeling 142 3.2. Optimization of VGF-Growth Equipment 146 3.3. Optimization of Growth Runs by Inverse Modeling 146 4. Crystal and Wafer Propcrtics 154 4.1. Wafering 156 4.2. Elcctrical Characterization and Silicon Doping 156 4.3. Optical Characterization by Infrared and Photoluminescence Mapping 156 4.4. Residual Dislocations 158 5. Conclusion 166 List of Symbols 167 List of Acronyms 168 References 169 High-Power Broad-Area Diode Lasers and Laser Bars Götz Erbcrt, Arthur Bärwolff, Jürgen Sebastian and Jens Tomm 173 1. Epitaxial Waveguide Structures for High-Power Diode Lasers 175 1.1. The Large Optical Cavity (LOC) Concept 175 2. Technology for Broad-Area Diode Lasers and Laser Bars 184 2.1. Processing of Contact Windows 185 2.2. Processing of Mesa Structures 187 2.3. Metallization 190 2.4. Laser-Bar Preparation 192 2.5. Facet Coating 194
XII Contents 3. Behavior of High-Power CW Diode Lasers 199 3.1. Inrluence of Heat on Laser Performance 199 3.2. Simulation of Tcmperature Distribution 201 3.3. Recent Results 213 List of Symbols 216 References 218 Properties and Prequency Conversion of High-Brightness Diode-Laser Systems Klaus-Jochen Boller, Bernard Beier and Richard Wallenstein 225 1. Beam Quality 228 1.1. The Diffraction Parameter M 2 230 1.2. Measurement of the Wavefront 232 2. Single-Stripe Diode Lasers 235 3. High-Power Diode Lasers 238 4. Diode Amplifiers 239 5. AlGaAs Diode-MOPA Systems 241 6. Diode-MOPA Systems Based on InGaAs 245 7. Nonlinear Prequency Conversion with High-Brightness Diode-MOPA Systems 249 7.1. Second-Harmonic Generation 249 7.2. Diode-Pumped Optical Parametric Oscillators 253 8. Summary 256 List of Symbols and Abbreviations 257 References 259 Tapered High-Power, High-Brightness Diode Lasers: Design and Performance Michael Mikulla 265 1. Introduction 266 2. Theoretical Background 267 3. BPM Simulations 269 4. Epitaxial Layer Structures 270 4.1. Comparison of LMG and LOC Structures 271 5. Broad-Area Diode Lasers with LMG Layer Structures 272 6. Fabrication of Tapered Devices 273 7. Experimental Results 274 7.1. Tapered Laser Oscillators 274 7.2. Tapered Laser Amplifiers 276 7.3. Tunable High-Brightness Diode-Laser Systems 279 7.4. Tapered Diode-Laser Arrays 282 8. Manufacturability 284
Contents XIII 9. Conclusion 285 List of Symbols 287 References 287 Cooling and Packaging of High-Power Diode Lasers Peter Loosen 289 1. Basic Properties of Micro-Channel Coolers for High-Power Diode Lasers 291 2. Manufacturing and Flow Dynamics of Cu Micro-Channel Coolers... 295 3. Packaging of Diode-Laser Bars 297 List of Symbols 300 References 301 High-Power Diode Lasers for Direct Applications Uwe Brauch, Peter Loosen and Hans Opower 303 1. Introduction (Hans Opower) 303 2. Incoherent Bcam Combining (Peter Loosen) 309 2.1. Properties of High-Power Diode Lasers for Direct Applications. 311 2.2. Beam Quality of Incoherently Combined Beams 313 2.3. Technical Devices 316 2.4. Beam Collimation 320 2.5. Aperture Fillhig and Stacking Accuracy 325 2.6. Applications 328 2.7. Discussion and Perspectives 331 3. Coherent Beam Combining (Uwe Brauch) 331 3.1. Coherence Properties of Semiconductor Diode Lasers 334 3.2. Combining of Diffraction-Limited Beams 336 3.3. Phase Coupling and Beam Combining of Single-Longitudinal-Mode Lasers 345 3.4. Prospects and Limitations of Coherent Beam Combining 360 List of Symbols 362 References 364 New Concepts for Diode-Pumped Solid-State Lasers Andreas Tünnermann, Holger Zelhner. Wolfram Schöne, Adolf Giesen and Karsten Contag 369 1. Fundamental Concepts of Diode-Pumped Solid-State Lasers 369 1.1. Thermal Considerations 371 2. Fiber Lasers 374 2.1. Laser-Active Waveguides 375 2.2. Double-Clad Fiber Lasers 377 2.3. Pump-Radiation Absorption in Double-Clad Fibers 378
XIV Contents 2.4. High-Power Laser Operation 381 2.5. Fiber-Laser Emission in the Visible Spectral Region 384 3. Thin-Disk Laser 386 3.1. Design Considerations 387 3.2. Numerical Simulation of the Thin-Disk Laser 388 3.3. Results and Discussion 393 3.4. Conclusion 403 List of Symbols 404 Referenccs 405 Index 409