This book explores various aspects of lasers from their basic scientific principles of its operation to applications in diverse fields.The book was translated from the Russian by V. Purto and was published by Mir in 1974. ContentsIntroduction 7Chapter 1. The Nature of Light 13Particles or Waves? 13Photons—Quanta of Light 18Chapter 2. Atom as Quantum System 23Quantum Concepts on the Atomic Structure Structure of the Atom 23Quantum Numbers Radiation and Absorption 25Distribution of Particles Among Energy 36Levels Active Systems 38Chapter 3. Generators of Light 43 Ruby Laser 43Properties of Laser Beam 51 Active Materials 56Methods and Sources of Excitation 63Resonant Systems 70Continuous-Wave Lasers 74Glass Lasers 77Giant Pulses 80Gas Lasers 85Methods of Concentrating Gas Laser Radiation at One Frequency 101 Liquid Lasers 104 Semiconductor Lasers 106Chapter 4. Application of Lasers 117 Lasers in Communications 117 Light Beam Modulation Methods 120 Beam Waveguides 132 Lasers in Computers 138 Application of Lasers in Metrology 143Lasers in Chemistry 145 Lasers in Photography 147 Lasers for Treating of Materials 155 Laser Gyroscopes 159 Lasers in Detection and Ranging 163 Laser Range Finders 167 Laser Tracking of Satellites 170 Lasers in Space Equipment 177Communication with Spacecraft During Atmos­pheric Re-Entry 182 Detection and Communications Under the Sea 185Other Military Applications of Lasers 188Lasers in Medicine and Biology 194Chapter 5. Lasers and Science 200 Testing Einstein’s Theory of Relativity 200 Measuring the Drift of Continents by Means of Lasers 204 Lasers for Geodetic Studies and Atmospheric Sounding 208 Measuring of Speeds 210 Laser Space Communications 210Chapter 6. The Prospects of Lasers 225 Pipeline out of a Laser Beam 225 Lasers and Communications with Extraterrestrial Civilizations 228 Spaceship of the Future 241 Looking Ahead  243