LASER IN BIOSCIENCE, INDUSTRY, AND DEFENCE

LASER IN BIOSCIENCE, INDUSTRY, AND DEFENCE

Narain MansharamaniFormer Scientist F

Instruments Research and Development Establishment (IRDE)Dehradun

Defence Research and Development OrganisationMinistry of Defence, New Delhi – 110 011

2012

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DRDO MONOGRAPHS/SPECIAL PUBLICATIONS SERIES

LASER IN BIOSCIENCE, INDUSTRY, AND DEFENCE

NARAIN MANSHARAMANI

Series EditorsEditor-in-Chief Associate Editor-in-Chief Editor Asst. EditorSK Jindal Dr GS Mukherjee Anita A Kavita NarwalEditorial Assistant Printing Marketing Gunjan Bakshi SK Gupta Rajpal Singh

Cataloguing in Publication

Mansharamani, NarainLaser in Bioscience, Industry, and Defence

DRDO Monographs/Special Publications Series.Includes glossary.1. Lasers 2. Laser Applications 3. Laser Safety I. Title II. Series621:366

© 2012, Defence Research & Development Organisation, New Delhi - 110 011.

ISBN 978-81-86514-35-1

All rights reserved. Except as permitted under the Indian Copyright Act 1957, no part of this publication may be reproduced, distributed or transmitted, stored in a database or a retrieval system, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the Publisher.

The views expressed in the book are those of the author only. The Editors or Publisher do not assume responsibility for the statements/opinions expressed by the author.

Designed, produced, and printed by Director, DESIDOC, Metcalfe House, Delhi - 110 054.

Contents

Preface ix

CHAPTER 1: FUNDAMENTALS OF LIGHT AND LASER BASICS1.1 History of Theory of Light 11.2 Lorentz Theory of Light Sources 21.3 Black Body 21.4 Quantum Theory of Light 31.5 Bohr’s Hypothesis 41.6 Matter Waves 61.7 Boltzmann’s Statistics 71.8 Einstein Theory 71.9 Atomic Line Shape Function 81.10 Elementary Consideration regarding Laser Action 91.11 Active Materials 111.12 Optical Resonator 161.13 Q-switching Techniques 181.14 Properties of Laser Beam 181.15 Interaction of Intense Coherent Optical Radiation 19

CHAPTER 2: PROPAGATION OF LASER BEAM IN ATMOSPHERE2.1 Introduction 232.2 Atmospheric Composition and Structure 242.3 Particles in Atmosphere 262.4 Fog, Clouds, and Rain 262.5 Scattering of Laser Beam 272.6 Absorption Spectroscopy of Atmospheric Gases 302.7 Transmission of Laser Beam 342.8 Visibility 352.9 Random Refraction 382.10 Dispersion 392.11 Propagation of Light Beam under Temperature Inversion Condition 39

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CHAPTER 3: LASER SOURCES3.1 Introduction 433.2 Medical Lasers 433.3 Industrial Lasers 503.4 Defence Lasers 53

CHAPTER 4: SYSTEMS, DEVICES, AND COMPONENTS4.1 Introduction 634.2 Laser Delivery Systems 634.3 Photodetectors 644.4 Terminology 654.5 Photomultiplier Tubes 664.6 Photoelectric Effect – Semiconductor 694.7 Avalanche Photodiodes 714.8 Indium Antimonide Detector 754.9 Mercury Cadmium Telluride Detectors 774.10 Viewing and Imaging Devices 774.11 Beam Shaping and Focusing Optics 784.12 Eye Wears, Gloves, and Clothes 80

CHAPTER 5: LASER IN BIOSCIENCE5.1 Introduction 835.2 Laser for General Surgery 835.3 Laser for Eye Surgery 845.4 Photocoagulation 875.5 Sealing of Cuts 875.6 Biosimulation with Laser 875.7 Photodynamic Therapy 885.8 Laser for Tuberculosis and Burns 885.9 Laser for Medical Diagnosis 89

CHAPTER 6: LASER IN INDUSTRY6.1 Introduction 916.2 Cutting 916.3 Drilling 926.4 Welding 936.5 Marking/Engraving 936.6 Cladding 946.7 Laser Processors for Diamonds 956.8 Micro-machining 966.9 Paint Removal 966.10 Heat Treatment 97

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6.11 Laser for Semiconductors 976.12 Laser for Thin Film Technology 97

CHAPTER 7: LASER IN DEFENCE 7.1 Introduction 997.2 Laser Simulator 997.3 Laser Ranging and Designation 1017.4 Laser Gyroscope 1057.5 Laser Isotope Separation-Uranium Enrichment 1097.6 Laser Range Gated Imaging 1107.7 Underwater Applications 1127.8 Differential Absorption Lidar 1137.9 Detection of Explosives, Hazardous Gases, and Biological Warfare Agents 1227.10 Beam Weapon Lasers 123

CHAPTER 8: FUTURISTIC DEVELOPMENT/APPLICATIONS8.1 Introduction 1318.2 Lasers for Bioscience 1318.3 Lasers for Industry 1338.4 Lasers for Defence 1338.5 Protection against Disasters 134

CHAPTER 9: LASER SAFETY9.1 Introduction 1379.2 Structure and Function of Eye 1379.3 Skin Hazards 1399.4 Hazards due to Air-borne Contamination 1409.5 Electrical Hazards 1409.6 Cryogenic Hazards 1449.7 Fire Hazards 1449.8 Explosive Hazards 1459.9 Chemical Hazards 1459.10 Laser Classification and Safety Guidelines 1459.11 Maximum Permissible Exposure and Hazardous Range 1499.12 Do’s and Don’ts 1529.13 Responsibilities of a Laser Safety Officer 152Appendixes 155Symbols 159Glossary 163Index 171

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Preface

The objective of writing this monograph is to highlight laser in bioscience, industry, and defence and its futuristic development and uses exclusively for scientists, engineers, and students. The applications of laser in bioscience are diagnosis, testing, biosimulation, photocoagulation, photodynamic therapy, and surgery. The applications of laser in industry are in various materials processing starting with testing, cutting, marking, polishing, welding, drilling, annealing, aligning, and measurement. The applications of laser in semiconductors are lithography, repair, and manufacturing processes like sputtering and cladding. In defence, starting with training aids, laser is used for ranging, viewing, imaging, guidance, navigation, communication, and safety; and as weapon and for countermeasure. Lasers are widely used in entertainment, computer, consumer equipment, construction, atmospheric study, meteorology, agriculture, forestry, basic science, sensors for pollution control, early warning against land slide or earthquake, and communication. It is very difficult to cover all applications of laser, however, this monograph covers most important and cost-effective applications where other tools or methods are not as effective as lasers. For more details, references of books, journals, and conference proceedings are given.

This monograph comprises nine chapters. Fundamental of Light and Laser Basics provides a historical account of lasers starting from Newton’s Corpuscular’s theory of light and interaction of light with matter to how Charles Townes arrived in developing theory of lasers. Propagation of Laser Beam in Atmosphere describes scattering, molecular absorption, and various optical effects of lasers that are useful for ranging and remote detections. Laser Sources dwells upon various types of laser sources useful in the field of bioscience, industry, and defence. Systems, Devices, and Components provides an account of components like detectors, focusing, and beam delivery devices. Laser in Bioscience describes the use of lasers in eye surgery, photocoagulation, photodynamic for early cancer diagnosis, distorting cancerous cells, tuberculosis and burn, and bioscience study. Laser in Industry explains various applications like welding, cutting, polishing annealing, etc.; and different manufacture procedures, diamond cutting and polishing, semiconductors manufacturing, ultraviolet laser lithography, engraving and testing, and quality assurance. Laser in Defence describes various applications like weapon simulation, ranging remote detection of explosive and biological warfare agents, etc. Futuristic Developments/Applications provides an overview of future of diode-pumped ceramic disc laser, high power laser diode, and quantum cascade lasers in bioscience, industry, and defence.

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Laser Safety provides an account of possible laser hazard/laser beam hazards and gives a comprehensive account of precautions against laser and first-aid.

Good source of information for lasers and applications are Applied Optics (USA), IEEE Journal of Quantum Electronics, Laser Focus World, Photonics Spectra, Optics Letters, Photonics News, Proceedings of SPIE, and Applied Physics Letters.

I am grateful to Shri SS Sundaram, Director, IRDE for giving permission to use the library facilities at IRDE.

In the end, I would like to thank my son Shri Rohit Mansharamani, for presenting a laptop to me on father’s day. This has made my writing work easier. This book could not have been written without the encouragement, patience, and support of my wife Smt Sarla.

June 2012 Narain MansharamaniDehradun

Chapter 1

Fundamentals of Light and Laser Basics

1.1 HISTORY OF THEORY OF LIGHTIn 1666, Sir Isaac Newton, after his famous experiment on prismatic decomposition

of white light into its component colours, elaborated on what is known as Corpuscular theory of light. According to Corpuscular theory, light is regarded as flight of material particles emitted by a source, the sensation of light being produced by their mechanical action upon the retina. The rectilinear propagation followed once from the second law of motion. He explained reflection, refraction, and colour in thin film by putting rays of light into fits, i.e., corpuscles being supposed to arrive at the surface in different phase, i.e., fits of easy reflection and easy transmission. Small bodies have attractive powers or some other force by which they stir up vibrations in which they act, vibration being swifter than the rays, overtakes successfully, and agitate them, increase and decrease their velocities thereby put them into these fits.

In 1676, Romer demonstrated that light requires a finite time for its propagation, travelling across space with a velocity, which he estimated at 3,08,995 km/s. The impact of corpuscles moving at such high speed might well expect to exert a pressure. Although, optical pressure could not be detected at that time, due to corpuscular striking surface. Huygens considering Wave theory, explained reflection, refraction, and double refraction in unaxial crystal by Wave theory. But Newton clung to the idea of corpuscles, presumably, as he could not visualise strong medium, which could be defined, if Wave theory was given. Later, discovery of polarisation of light was a blow to Huygens Longitudinal Wave theory. Frensel gave concept for transverse wave and explained interference of light. He had to define elastic solid medium ether, which can sustain waves at high speed with no obstruction to material bodies, but millions of times rigid than steel. Although no evidence of longitudinal disturbance was observed in ether, since transverse one in elastic ether medium must be associated with longitudinal disturbances.

In 1821, HC Osterd observed magnetic effect of current, and Michael Faraday’s conception of electric and magnetic force and their interrelation expressed in terms of lines of force were founded. Faradays laws of electromagnetic induction were established in 1831. From this, James Clerk Maxwell developed the equation that underlines all modern theories of electromagnetic waves.

Laser in Bioscience, Industry, and Defence

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In 1860, Maxwell showed that the propagation of light could be regarded as an electromagnetic phenomenon; the wave consists of an advance of coupled electric and magnetic forces. If an electric field is varied periodically, a periodical magnetic field is obtained, which in turn generates a varying electric field and the disturbance is passed on in the form of a wave which is called as electromagnetic wave. Maxwell's theory predicated the speed at which these electromagnetic waves would travel from measurements of the magnetic field of electric current, the velocity of propagation being the ratio of the electromagnetic to the electrostatic unit. This ratio, determined, from electric and magnetic measurements, turned out to be the velocity of light, and indicated that light was essentially an electromagnetic phenomenon. Hertz discovered the wave predicated by Maxwell in 1892, which produced electric oscillation in a pair of conductors between which sparks were passed. The conductor radiates waves that could be detected by another pair of similar conductors, which oscillates in resonance with the first pair, causing the passage of minute's sparks between these conductors. Maxwell theory, like the electric solid theory requires ether, but not a mechanical one in which material displacement took place but, an electromagnetic one, in which displacement of current and magnetic field could occur. The periodic disturbances, which are supposed to constitute these waves, were called displaced current by Maxwell. These displaced currents can occur in free ether, or in a dielectric, i.e., in non-conductor of electricity. Maxwell theory told nothing about the nature of this electric displacement, so that in one sense, about the real nature of luminous disturbances were much vaguer than the wave 50 years earlier, when the elastic solid theory was generally accepted. For in the motion of a solid, we are dealing with perfectly definite physical process. As Schusler remark in the preface of his work on Optics ‘So long as the character of the displacement, which constitute the waves, remain undefined, we cannot pretend to have established a theory of light1-3.

1.2 LORENTZ THEORY OF LIGHT SOURCESMaxwell theory identified light as an electromagnetic disturbance, HA Lorentz

advanced this idea that the atoms and molecules contained electrons, but are capable of vibration under the influence of a restoring force, when displaced. The bound electrons execute damped vibration under the influence of a restoring force, when displaced. The bound electrons, executing damped vibration were supposed to be the source of the luminous disturbances, or it might act as an absorber of radiation energy, when its natural frequency of vibration was in agreement with that of the radiation2,3,4. This theory accounted for many of the newly discovered effects of magnetism on light, as well as the older phenomena of refraction, dispersion, etc.

1.3 BLACK BODYKirchhoff established that at a given temperature, the ratio between the emission

ε and absorption power A for a given wavelength is same for all bodies.

ε/A = constant (1.1)

For all bodies at the same temperature, the more powerfully a body absorbs, the more powerfully it will emit when heated, i.e., black body will give more light when heated. A black body absorbs all electromagnetic radiations that fall on it; such an object if heated would be a perfect radiator, producing radiation which is called black

Contents PrefaceCHAPTER 1: FUNDAMENTALS OF LIGHT AND LASER BASICS1.1 History of Theory of Light1.2 Lorentz Theory of Light Sources1.3 Black Body1.4 Quantum Theory of Light1.5 Bohr’s Hypothesis1.6 Matter Waves1.7 Boltzmann’s Statistics1.8 Einstein Theory1.9 Atomic Line Shape Function1.10 Elementary Consideration regarding Laser Action1.11 Active Materials1.12 Optical Resonator1.13 Q-switching Techniques1.14 Properties of Laser Beam1.15 Interaction of Intense Coherent Optical Radiation

CHAPTER 2: PROPAGATION OF LASER BEAM IN ATMOSPHERE2.1 Introduction2.2 Atmospheric Composition and Structure2.3 Particles in Atmosphere2.4 Fog, Clouds, and Rain2.5 Scattering of Laser Beam2.6 Absorption Spectroscopy of Atmospheric Gases2.7 Transmission of Laser Beam2.8 Visibility2.9 Random Refraction2.10 Dispersion2.11 Propagation of Light Beam under Temperature Inversion Condition

CHAPTER 3: LASER SOURCES3.1 Introduction3.2 Medical Lasers3.3 Industrial Lasers3.4 Defence Lasers

CHAPTER 4: SYSTEMS, DEVICES, AND COMPONENTS4.1 Introduction4.2 Laser Delivery Systems4.3 Photodetectors4.4 Terminology4.5 Photomultiplier Tubes4.6 Photoelectric Effect – Semiconductor4.7 Avalanche Photodiodes4.8 Indium Antimonide Detector4.9 Mercury Cadmium Telluride Detectors4.10 Viewing and Imaging Devices4.11 Beam Shaping and Focusing Optics4.12 Eye Wears, Gloves, and Clothes

CHAPTER 5: LASER IN BIOSCIENCE5.1 Introduction5.2 Laser for General Surgery5.3 Laser for Eye Surgery5.4 Photocoagulation5.5 Sealing of Cuts5.6 Biosimulation with Laser5.7 Photodynamic Therapy5.8 Laser for Tuberculosis and Burns5.9 Laser for Medical Diagnosis

CHAPTER 6: LASER IN INDUSTRY6.1 Introduction6.2 Cutting6.3 Drilling6.4 Welding6.5 Marking/Engraving6.6 Cladding6.7 Laser Processors for Diamonds6.8 Micro-machining6.9 Paint Removal6.10 Heat Treatment6.11 Laser for Semiconductors6.12 Laser for Thin Film Technology

CHAPTER 7: LASER IN DEFENCE7.1 Introduction7.2 Laser Simulator7.3 Laser Ranging and Designation7.4 Laser Gyroscope7.5 Laser Isotope Separation-Uranium Enrichment7.6 Laser Range Gated Imaging7.7 Underwater Applications7.8 Differential Absorption Lidar7.9 Detection of Explosives, Hazardous Gases, and Biological Warfare Agents7.10 Beam Weapon Lasers

CHAPTER 8: FUTURISTIC DEVELOPMENT/APPLICATIONS8.1 Introduction8.2 Lasers for Bioscience8.3 Lasers for Industry8.4 Lasers for Defence8.5 Protection against Disasters

CHAPTER 9: LASER SAFETY9.1 Introduction9.2 Structure and Function of Eye9.3 Skin Hazards9.4 Hazards due to Air-borne Contamination9.5 Electrical Hazards9.6 Cryogenic Hazards9.7 Fire Hazards9.8 Explosive Hazards9.9 Chemical Hazards9.10 Laser Classification and Safety Guidelines9.11 Maximum Permissible Exposure and Hazardous Range9.12 Do’s and Don’ts9.13 Responsibilities of a Laser Safety Officer

Appendixes SymbolsGlossaryIndex