Fluorescence as a source of noise in Q-switched ruby laser atmospheric backscattering experiments

Abstract

Interpretation of the results of atmospheric baekscattering experiments, when using a Q-switched ruby laser as the source of photons, requires consideration of several sources of noise in the statistical analysis. This paper discusses the effects of directly backscattered ruby fluorescence in detail. It is found that, for an unshuttered system, fluorescense noise will be equal to the signal expected from altitudes above about 50-60 km (assuming only a molecular atmosphere). The "crossover" altitude is lowered if aerosols are present. When a shutter is used as a fluorescence block, it is found that a spurious "layer" structure may be produced--but only for shutter cutoff times of greater than about 375 [mu]sec. It is concluded that, for a properly designed optical radar system, ruby fluorescence will not be a significant source of spurious returns. In particular, it is concluded that this source will not explain the enhanced returns from about 80 km observed by et al. (1967).