Lasers and Optoelectronics – Fundamentals, Devices and Applications

Dr. Anil Kumar Maini, Director, Laser Science & Technology Centre (DRDO) Metcalfe House, LASTEC, Delhi 110054 (INDIA)E-mail: maini-anil1@rediffmail.com Dr. Anil K. Maini is presently Director of Laser science and technology centre, Delhi, a premier R&D Laser Laboratory of Defence Research and Development Organization under Ministry of Defence, Govt. of India. He has more than 35 years of R&D experience as a Scientist, Team Leader, Project Director and Director in diverse disciplines related to Electronics, Lasers and Optoelectronics technologies and systems. His contributions have led to number of innovations in the development of different types of Electronics systems, Optronic sensors and Directed energy laser systems for Indian Defence forces. The key products and technologies developed under his guidance include Power Electronics Systems, family of Laser Dazzling Systems for Homeland security applications, Laser Systems for Electro Optic Counter Measures (EOCM) applications and Optoelectronic Simulators & Sensors for electro optically guided precision strike munitions. Dr. Anil K. Maini is Life Fellow of Institution of Electronics and Telecommunication Engineers (IETE) and a senior life member of Indian Laser Association. He has written extensively on a wide range of subjects in Electronics and Optoelectronics. He has authored and co-authored twelve books, 6 of the twelve books being international publications. He has delivered numerous invited talks at various universities and research centres. He has worked with several international universities under different collaborative research programmes. He has to his credit five patents and more than 125 publications in National and International journals.

Preface xix Part I LASER FUNDAMENTALS 1 1 Laser Basics 3 1.1 Introduction 3 1.2 Laser Operation 3 1.3 Rules of Quantum Mechanics 3 1.4 Absorption, Spontaneous Emission and Stimulated Emission 4 1.5 Population Inversion 10 1.6 Two-, Three- and Four-Level Laser Systems 11 1.7 Gain of Laser Medium 16 1.8 Laser Resonator 17 1.9 Longitudinal and Transverse Modes 18 1.10 Types of Laser Resonators 21 1.11 Pumping Mechanisms 23 1.12 Summary 29 2 Laser Characteristics 34 2.1 Introduction 34 2.2 Laser Characteristics 34 2.3 Important Laser Parameters 41 2.4 Measurement of Laser Parameters 49 2.5 Laser Beam Diagnostic Equipment 56 2.6 Summary 59 Part II TYPES OF LASERS 65 3 Solid-state Lasers 67 3.1 Introduction: Types of Laser 67 3.2 Importance of Host Material 67 3.3 Operational Modes 68 3.4 Ruby Lasers 76 3.5 Neodymium-doped Lasers 78 3.6 Erbium-doped Lasers 85 3.7 Vibronic Lasers 88 3.8 Colour Centre Lasers 90 3.9 Fibre Lasers 91 3.10 Summary 101 4 Gas Lasers 105 4.1 Introduction to Gas Lasers 105 4.2 Helium-neon Lasers 107 4.3 Carbon Dioxide Lasers 111 4.4 Metal Vapour Lasers 115 4.5 Rare Gas Ion Lasers 118 4.6 Excimer Lasers 120 4.7 Chemical Lasers 121 4.8 Carbon Dioxide Gas Dynamic Lasers 125 4.9 Dye Laser 125 4.10 Free-electron Lasers 127 4.11 X-Ray Lasers 129 4.12 Summary 129 5 Semiconductor Lasers 132 5.1 Introduction 132 5.2 Operational Basics 132 5.3 Semiconductor Laser Materials 135 5.4 Types of Semiconductor Lasers 136 5.5 Characteristic Parameters 148 5.6 Gain- and Index-guided Diode Lasers 152 5.7 Handling Semiconductor Diode Lasers 152 5.8 Semiconductor Diode Lasers: Application Areas 153 5.9 Summary 154 Part III LASER ELECTRONICS AND OPTOELECTRONICS 159 6 Building Blocks of Laser Electronics 161 6.1 Introduction 161 6.2 Linear Power Supplies 161 6.3 Switched-mode Power Supplies 173 6.4 Constant Current Sources 186 6.5 Integrated-circuit Timer Circuits 191 6.6 Current-to-voltage Converter 197 6.7 Peak Detector 199 6.8 High-voltage Trigger Circuit 200 6.9 Summary 202 7 Solid-state Laser Electronics 208 7.1 Introduction 208 7.2 Spectrum of Laser Electronics 208 7.3 Electronics for Solid-state Lasers 213 7.4 Electronics for Pulsed Solid-state Lasers 214 7.5 Electronics for CW Solid-state Lasers 233 7.6 Solid-state Laser Designators and Rangefinders 237 7.7 Summary 238 8 Gas Laser Electronics 242 8.1 Introduction 242 8.2 Gas Discharge Characteristics 242 8.3 Gas Laser Power Supplies 242 8.4 Helium-Neon Laser Power Supply 244 8.5 Carbon Dioxide Laser Power Supplies 257 8.6 Power Supplies for Metal Vapour Lasers 260 8.7 Power Supplies for Excimer Lasers 261 8.8 Power Supplies for Ion Lasers 262 8.9 Frequency Stabilization of Gas Lasers 263 8.10 Summary 267 9 Laser Diode Electronics 271 9.1 Introduction 271 9.2 Laser Diode Protection 271 9.3 Operational Modes 276 9.4 Laser Diode Driver Circuits 278 9.5 Laser Diode Temperature Control 291 9.6 Summary 308 10 Optoelectronic Devices and Circuits 315 10.1 Introduction 315 10.2 Classification of Photosensors 315 10.3 Radiometry and Photometry 316 10.4 Characteristic Parameters 318 10.5 Photoconductors 324 10.6 Photodiodes 329 10.7 Phototransistors 340 10.8 Photo- FET, SCR and TRIAC 343 10.9 Photoemissive Sensors 345 10.10 Thermal Sensors 347 10.11 Displays 349 10.12 Light-emitting Diodes 351 10.13 Liquid-crystal Displays 356 10.14 Cathode Ray Tube Displays 361 10.15 Emerging Display Technologies 362 10.16 Optocouplers 363 10.17 Summary 370 Part IV LASER APPLICATIONS 379 11 Lasers in Industry 381 11.1 Introduction 381 11.2 Material-processing Applications 381 11.3 Laser Cutting 385 11.4 Laser Welding 390 11.5 Laser Drilling 393 11.6 Laser Marking and Engraving 396 11.7 Laser Micromachining 401 11.8 Photolithography 407 11.9 Rapid Manufacturing 411 11.10 Lasers in Printing 414 11.11 Summary 418 12 Lasers in Medicine 422 12.1 Introduction 422 12.2 Light tissue Interaction 422 12.3 Laser Diagnostics 430 12.4 Therapeutic Techniques: Application Areas 442 12.5 Ophthalmology 443 12.6 Dermatology 449 12.7 Laser Dentistry 453 12.8 Vascular Surgery 455 12.9 Photodynamic Therapy 456 12.10 Thermal Therapy 459 12.11 Summary 460 13 Lasers in Science and Technology 466 13.1 Introduction 466 13.2 Optical Metrology 466 13.3 Laser Velocimetry 478 13.4 Laser Vibrometry 482 13.5 Electronic Speckle Pattern Interferometry 484 13.6 Satellite Laser Ranging 490 13.7 Lasers in Astronomy 494 13.8 Holography 496 13.9 Summary 503 14 Military Applications: Laser Instrumentation 508 14.1 Introduction 508 14.2 Military Applications of Lasers 508 14.3 Laser-based Instrumentation 512 14.4 Guided Munitions 532 14.5 Laser Communication 556 14.6 Summary 561 15 Military Applications: Directed-energy Laser Systems 566 15.1 Introduction 566 15.2 Laser Technology for Low-intensity Conflict (LIC) Applications 566 15.3 Electro-optic Countermeasures 580 15.4 Directed-energy Laser Weapons 585 15.5 Summary 592 Review Questions 595 Self-evaluation Exercise 596 Bibliography 598 Appendix A: Laser Safety 597 Index 603