High-Power Laser Radiation in Atmospheric Aerosols

Unique properties of laser radiation including its monochromatic properties, polarization, high spectral intensity, coherence, narrow beam divergence, the possibility of controlling the pulse duration and radiation spectrum and, finally, the fact that extremely high power and energy create very favorable conditions for the extensive application of lasers to communi­ cation systems, systems for the lidar sensing and ultra-high-precision ranging, navigation, remote monitoring of the environment, and many other systems operating in the atmosphere. The operative efficiency of the above systems depends significantly on the state of the atmosphere and the corresponding behavior of laser radia­ tion propagating through it. This circumstance has stimulated the studies of the above regularities during the passt 10-15 years. For the investiga­ tions to be carried out the scientists were forced to develop new theories and methods for studying the problem experimentally. Moreover, during such investigations some previously unknown phenomena were observed, among them the nonlinear effects accompanying high-power laser radiation propagating through the atmosphere are of paramount importance. Among the nonlinear effects caused by high-power laser radiation inter­ action with the atmosphere, the effects accompanying the propagation of high-power radiation through the atmospheric aerosols are of particular interest. Aerosols always occur in the atmosphere. It should be noted that the microphysical and optical characteristics of atmospheric aerosols vary widely, this fact causes a great variety in the features of their inter­ action with radiation.

Contenu

1: Microphysical and Optical Characteristics of Atmospheric Aerosols.- 1.1. Introduction.- 1.2. Preliminary Discussion.- 1.2.1. Light Scattering by a Single Aerosol Particle.- 1.2.2. Light Scattering by a System of Particles.- 1.2.3. Scattering Phase Matrix.- 1.3. Light Scattering by Clouds and Fogs.- 1.3.1. Microphysical Parameters of Clouds and Fogs.- 1.3.2. Volume Extinction Coefficients.- 1.4. Light Scattering by Hazes.- 1.4.1. Microphysical Parameters of Hazes.- 1.4.2. Volume Extinction Coefficients.- 1.5. Microphysical and Optical Characteristics of Precipitation.- 1.6. Scattering Phase Functions of Polydispersed Aerosols.- References: Chapter 1.- 2: Low-Energy (Subexplosive) Effects of Radiation on Individual Particles.- 2.1. Regular Regimes of Droplet Vaporization in the Radiation Field.- 2.2. Vaporization of Haze Particles Consisting of a Solid Nucleus and a Shell of Salt in Solution.- 2.2.1. The Equation describing Particle Vaporization.- 2.2.2. The Heat Problem.- 2.2.3. Variation of Salt Concentration in the Process of Particle Vaporization.- 2.2.4. Growth of the Solid Nucleus.- 2.3. Some Peculiarities in the Vaporization of Solid Aerosol Particles by High-Power Radiation.- 2.3.1. The Diffusion Regime of Vaporization of Solid Spherical Particles.- 2.3.2. The Pre-Explosion Gas-Dynamic Regime of Vaporization.- 2.4. Burning of Carbon Aerosol Particles in a Laser Beam.- 2.5. Initiation of Droplet Surface Vibrations by Laser Radiation.- 2.5.1. Basic Relationships.- 2.5.2. Resonance Excitation of the Capillary Waves.- 2.5.3. The Parametric Excitation of the Capillary Waves.- 2.5.4. Experiments on the Excitation of the Oscillations of Transparent Droplets using Laser Radiation.- References: Chapter 2.- 3: The Formation of Clear Zones in Clouds and Fogs Due to the Vaporization of Droplets under Regular Regimes.- 3.1. Basic Characteristics of the Process of Clearing a 'Frozen' Cloud.- 3.2. Stationary Cleared Channels in Moving Clouds.- 3.3. The Unstable Regime of Moving Cloud Clearance.- 3.4. The Determination of the Parameters of the Cleared Zone Taking into Account the Angular Beam Width and Wind Speed.- 3.5. The Generalized Formula Describing the Beam Intensity in the Process of Beam-Induced Clearing.- 3.6. The Cleared Channel under Conditions of Turbulent Aerosol Transport.- 3.7. Nonlinear Extinction Coefficient of Aerosols.- 3.8. The Investigation of Beam-Induced Clearing of Natural Fogs.- References: Chapter 3.- 4: Self-Action of a Wave Beam in a Water Aerosol under Conditions of Regular Droplet Vaporization.- 4.1. Basic Equations of Wave Beam Self-action in a Discrete Scattering Medium.- 4.2. The Field of the Effective Complex Dielectric Constant of the Aerosol (within the Beam).- 4.2.1. Components of the Effective Complex Dielectric Constant.- 4.2.2. The Fluctuation Characteristics of the Field of the Complex Effective Dielectric Constant.- 4.3. Description of the Mean Intensity of a Beam.- 4.3.1. The Method of Transfer Equation.- 4.3.2. The Parabolic Equation Method.- 4.4. The Influence of Thermal Distortions of Wave Beams and Fluctuations of the Medium on the Beam-Induced Dissipation of Water Aerosols.- 4.4.1. The Influence of Nonstationary Thermal Defocusing on the Beam-Induced Dissipation of Water Aerosols.- 4.4.2. The Influence of Stationary Thermal Distortions of the Beam on the Process of Water Aerosol Dissipation.- 4.4.3. The Influence of the Turbulent Motion of the Medium on the Dissipation of Water Aerosols by Laser Beams.- References: Chapter 4.- 5: Laser Beam Propagation through an Explosively Evaporating Water-Droplet Aerosol.- 5.1. Droplet Explosion Initiated by High-Power Laser Radiation.- 5.1.1. Droplet Explosion as an Optothermodynamic Process.- 5.1.2. Experiments.- 5.2. Droplet Explosion Regimes.- 5.2.1. Fragmentation.- 5.2.2. Gas-Dynamic Explosion.- 5.3. Attenuation of Light by an Exploding Droplet.- 5.3.1. Extinction Coefficient of a Droplet Exploding in the Supercritical Regime.- 5.3.2. The Extinction Coefficient in the case of a Two-Phase Explosion.- 5.4. Experimental Investigations of Laser Beam Propagation through Explosively Evaporating Aerosols.- References: Chapter 5.- 6: Propagation of High-Power Laser Radiation through Hazes.- 6.1. Nonlinear Optical Effects in Hazes: Classification and Features.- 6.1.1. Characteristic Relaxation Times in Hazes Irradiated with High-Power Lasers.- 6.1.2. Propagation Equations for High-Power Radiation in Media Composed of Randomly-Distributed Centers.- 6.2. Nonlinear Scattering of Light by Thermal Aureoles around Light-Absorbing Particles.- 6.2.1. Introduction.- 6.2.2. An Analysis of Thermohydrodynamic Perturbations of the Medium due to the Absorption of Radiation by Solid Aerosol Particles.- 6.2.3. The Influence of Turbulent Heat Transfer and Particle Motion relative to the Medium on the Optical Characteristics of Thermal Aureoles.- 6.3. Thermal Self-Action of a High-Power Laser Pulse Propagating through Dusty Hazes.- 6.3.1. A Theoretical Analysis of the Effects of Light Scattering by Thermal Aureoles and the Defocusing of the Laser Pulse in the Light-Absorbing Hazes.- 6.3.2. Calculation of Laser Beam Self-broadening in a Light-Absorbing Aerosol by the Method of Statistical Modeling.- 6.3.3. Experimental Investigations of Pulsed Laser Self-broadening due to Scattering by Thermal Aureoles.- 6.4. Laser Radiation Transfer in Combustible Aerosols.- 6.5. Thermal Blooming of the cw and Quasi-cw Laser Beams due to Light Absorption by Atmospheric Aerosols and Gases.- 6.5.1. General Discussion of the Problem.- 6.5.2. The Effects of Laser Beam Interaction with a Conservative Light-Absorbing Component.- 6.5.3. Thermal Self-Action of Laser Beams in Water-Droplet Hazes.- References: Chapter 6.- 7: Ionization and Optical Breakdown in Aerosol Media.- 7.1. Physical and Mathematical Formulations of the Problem.- 7.2. Theoretical Analysis of Pulsed Optical Breakdown on Solid Aerosol Particles.- 7.2.1. Evaluations of the Order of Magnitude.- 7.2.2. The Analysis of Avalanche Ionization Processes in the Vapor Aureoles of Light-Absorbing Particles.- 7.3. The Influence of Atmospheric Turbulence on the Concentration of Optical Breakdown Centers.- 7.4. Laboratory Experiments on Laser Sparking.- 7.5. Optical Breakdown of Water Aerosols.- 7.5.1. Optical Bre…