Rainfall-Induced Optical Phase Fluctuations in the Atmosphere

Abstract

The effective use of coherent optical systems in the field, such as lasers, depends strongly on maintaining a relatively high degree of lateral phase coherence over mutual separations that correspond to aperture sizes of practical concern. It is anticipated that such systems, to be of any general utility, will operate under a wide variety of environmental conditions such as clear-air turbulence, rain, fog, snow, etc. In this paper we investigate, theoretically, the effect of rain-induced optical phase fluctuations of an initially coherent wave propagating through the lower atmosphere. In this regard it should be mentioned that clear-air turbulence-induced phase fluctuations have been thoroughly investigated and are well documented in the literature(1). Although rain-induced irradiance fluctuation has been considered previously,(2) this paper, to the best of our knowledge, is the first treatment of rain-induced phase fluctuations and their associated effects on coherent optical systems.