Phase control of stimulated Brillouin scattering wave for a high power/energy beam combination laser with high repetition rate

Abstract

Phase control of stimulated Brillouin scattering (SBS) wave is investigated in order to develop a high power/energy beam combination laser with high repetition rate using SBS phase conjugate mirrors (PCMs). A novel phase control technique by a self-generated density modulation is proposed and its potential is demonstrated. Through this phase control technique, the relative phase difference between two SBS waves is contained within a quarter wave for all the laser pulses. This technique is expected to be very useful to develop highly repetitively operating high power/energy laser systems using a beam combination with the SBS-PCMs. In addition, stimulated Brillouin scattering and its applications is investigated. Through the measurement of the SBS reflectivity for the various liquids and for the different pumping conditions, it has been found that the reflectivity for the multi-mode pump, with large number of longitudinal modes, is significantly affected by the nonlinear effects due to the intensity spikes, so that the reflectivity is lower than that of the single mode pump. In addition, it has been demonstrated that the optical isolator composed of the SBS-PCM and the quarter wave plate can perfectly cut off the leak beam from the post stage if the distance between the SBS-PCM and the post stage is long enough compared to the pump pulse width. The works in this thesis will contribute to advancing the laser technology and its applications.