High power laser propagation

High power laser beams propagating in the atmosphere are subjected to a variety of effects, the most important of which are absorption, scattering, turbulence induced beam spreading and wander, thermal blooming, and gas breakdown. In this paper, simplified models are used to show how the various atmospheric effects interrelate and impact on the best laser choice for high power applications through their dependence on the laser wavelength and temporal mode (e.g., CW or pulsed) of operation. Results for sea level propagation at seven common laser wavelengths varying from 0.34 microns to 10.6 microns are presented that show the mid-IR wavelengths to be favored for typical turbulence and aerosol scattering conditions. At the longer 10.6-micron CO2 laser wavelength thermal blooming is dominant due to stronger molecular absorption, while at the shorter wavelengths turbulence induced beam spreading and aerosol absorption and scattering effects become important and tend to limit the increase in irradiance expected on the basis of diffraction effects alone.