Optimum Wavelength and Power for Efficient Laser Propagation in Various Atmospheric Environments

摘要

This paper discusses the optimum laser wavelength and power for efficient propagation in maritime, desert, rural, and urban atmospheric environments. The theoretical/numerical model used in this study includes the effects of aerosol and molecular scattering, aerosol heating and vaporization, thermal blooming due to aerosol and molecular absorption, atmospheric turbulence and beam quality. These processes are modeled in a fully three- dimensional and time-dependent manner. It is found that aerosols, which consist of water, sea salt, organic matter, dust, Soot, etc., are particularly important because they result in laser scattering and enhanced thermal blooming. In the water vapor transmission windows, the total absorption coefficient driving thermal blooming can be caused mainly by aerosols and not water vapor. In certain maritime environments the deleterious effects of aerosols can be reduced by vaporization. Aerosols which cannot be vaporized, e.g., dust and soot, can significantly increase thermal blooming. The laser power, averaged over dwell time, delivered to a distant target as a function of transmitted power is obtained for a number of wavelengths and atmospheric environments. The optimum wavelength and power are found for each atmospheric environment.