OUTPUT POWER AND NOISE IN A UNIDIRECTIONAL RING LASER WITH A PARTIALLY HOMOGENEOUS HIGH-GAIN MEDIUM.

摘要

In this dissertation we develop theoretical and experimental studies of a CW unidirectional ring laser with a partially homogeneously broadened high-gain medium. The procedure used for the theoretical development is the semiclassical approach in the laser theory, i.e., the optical field is treated classically and the atomic system quantum mechanically. The oscillation output and spontaneous emission noise powers from the laser are formulated by using the analysis of the spatial distributions of the radiation intensity, the gain and the population inversion in the medium. As the extension of the theory we propose new methods to determine the gain parameter, the degree of homogeneity, the saturation irradiance, the Doppler and Lorentz linewidths of the medium and the spectral linewidth of the hole burning. By applying the methods to the actual system, we determine the above-mentioned laser parameters of the He-Xe 3.5 (mu)m line. We also analyze experimentally the intensity fluctuation of a CW 3.5 (mu)m He-Xe unidirectional ring laser.; To begin, the laser equation, i.e., the space and time-dependent differential equation is formulated for the complex wave amplitude of the laser field in a partially homogeneous medium from the Maxwell and the density matrix equations. The laser equation is solved at the steady state to analyze the spatial distributions of the radiation intensity, the gain and the population inversion in the medium. By applying the theory to a unidirectional ring laser with a lossy (low-Q) resonator, the output power of the laser system is calculated and successively a new method for determining the gain parameter, the degree of homogeneity and the saturation irradiance of the medium is proposed. Taking advantage of the theory, we perform the experiment and determine the above-mentioned parameters for a He-Xe 3.5 (mu)m line.; A similar analysis is given for the spontaneous emission noise from a partially homogeneous laser system. The spontaneous emission power output is calculated in the presence of the unidirectional ring laser oscillation. As an application of the analysis of the spontaneous emissions, a method to determine the gain parameter, the Doppler and Lorentz linewidths, and the spectral linewidth of the hole burned due to the saturation is presented. Comparison of the experimental results on the He-Xe 3.5 (mu)m at the atomic linecenter to the theory determines the above laser parameters.; The intensity fluctuation of the laser oscillation is experimentally studied with a CW 3.5 (mu)m unidirectional ring laser. The digital data acquisition system is used to analyze the histograms of the laser field intensity and the analog technique is used for the power spectrum measurements.; The following subjects are given in the four appendices at the end of the dissertation: The calculation of the complex gain constant for a partially homogeneous laser medium, the mode pulling (self-stabilization of the oscillation frequency), the dispersion mode-splitting and a statistical model of the laser intensity fluctuation.