Effects of turbulent flows in a resonator cavity on ring laser outputs

Abstract

It has been found that turbulent flows may exist in the gain media of liquid and gas lasers. With the existence of turbulences in the gain medium, not only the propagation constant but also the gain becomes a spatially and temporally random function because of the random distributions of the number density of active molecules. In this research, the statistical properties, including the average intensity and contrast, of the output intensity of a ring laser are investigated. The gain medium is assumed to be partially homogeneously broadened and slightly saturated. For simplicity, a plane wave is considered. Combined with the perturbation approach, the method of phase screen is used. In this method, the turbulences are assumed to be concentrated within a thin screen which causes random phase modulation. Therefore, the stimulated wave is randomly modulated in phase and randomly amplified in intensity by the gain cell in each passage in a ring cavity. The number of passages is decided by the photon lifetime in this cavity. A Gaussian correlation function is used for describing the random structure. Effects of the turbulence characteristic length and fluctuation strength on the laser output are discussed. Several numerical examples for dye lasers are presented.