Laser Beam Propagation and Path Characterization

Abstract

This chapter deals with laser beam propagation through the atmosphere, with applications that include laser beam communication systems and High Energy Laser (HEL) weapon systems. Laser beams that converge through the atmosphere as well as collimated beams are considered. With 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 can include thermal blooming, AO beam correction, and point-ahead angle (i.e., tilt anisoplanatism). For aircraft-mounted HEL systems, boundary layer turbulence and telescope vibrations also need to be taken into account. HEL beam path characterization experiments are described. Once measured values have been obtained for the path characterization parameters, an optimum wavelength can be determined at which the HEL beam achieves both maximum irradiance density at the target and maximum lethality range. Selection of a non-optimum wavelength can catastrophically undermine the HEL system performance.