Laser Beam Propagation and Path Characterization

Abstract

AbstractThis chapter deals with laser beam propagation through the atmosphere. Applications include laser communication systems and High Energy Laser (HEL) weapon systems. Collimated beams are treated as well as beams that converge to a focus in the atmosphere. For terrestrial laser communication systems, laser beam quality is influenced by atmospheric turbulence and the aberrations of the beam-projection telescope. For HEL beams, other influences include thermal blooming and AO beam correction. For aircraft-mounted HEL systems, boundary layer turbulence arises, as does point-ahead angle for moving targets. Definitive beam path characterization techniques are described. Once values have been obtained for the key characterization parameters, an optimum wavelength region can be identified at which HEL beams (of the same beam power) concentrate maximum possible irradiance flux at target center, thereby maximizing system lethality and lethality range. Choice of outrider HEL wavelengths lying far from the optimum region can catastrophically reduce system performance, potentially dooming the system to failure from the outset.