Numerical Simulation Of Solid-state Laser Coherent Combiners And Laser Phase Detection Method Research

The development of high power solid state laser is limited by heat problem of laser medium. The waste heat stored in the laser medium causes ununiformity of the temperature distribution in the medium, which will result in the power and the beam quality degradation. Multiple-beam laser combination can solve this problem effectively. The methods disperse the waste heat in each way, which not only increase the output power, but also improve the beam quality. Coherent combination, compared with incoherent combination, is one of the most effective methods, which has a higher output power and a better beam quality, and of which controlling phase is a key technology. The multi-beam coherent combination was studied by theoretical analysis, numerical simulation and experiment. We got the intensity distribution of coherent combination in near and far field, and the main factors which influence effect of coherent combination were discussed. Meanwhile we studied solid state laser phase detection by experiment. These results will provide references for MOPA system used in the coherent combination.The interference fringe contrast model for the coherent lights was established. The influence of laser linewidth and polarization on interference fringe contrast were calculated, then we analysed the varying regular of the interference fringe contrast.The theoretical model for analyzing coherent combination of Gaussian beams was established. The factors which influence coherent combination were discussed. We got the intensity distribution of coherent combination of far field, the combined efficiency and the encircled-power ratio in different array fashions, and we got the combined efficiency with a different beams numbers and a different array fashions, at the same time we got the encircled-power ratio in different random phasic difference.The mathematical model of coherent combination of super-Gaussian beams was established. The intensity distribution of 25 super-Gaussian beams was contrasted in far field as that of incoherent combination in square array fashion, and the intensity distribution in various conditions was analyzed, then the encircled-power ratio in different propagation distance was also obtained.The method of phase detecting for solid-state laser was studied. We got beat frequency signal by heterodyne method when the laser works in continuous mode and quasi-continuous mode, and in order to filter high-order harmonic wave we developed a proper filter, then we got the clear beat frequency signal. At the same time we developed a circuit system to detect phase, by which we detected the phase difference of two signals successfully when the laser worked in continuous mode, and presented the change of phase versus time, then the velocity of phase difference change was calculated. The experimental study on phase detection of laser amplifier has carried out, in which we inserted an amplifier in the oscillator stage output light path, got the change of phase versus time in different pumping power indensity and the speed rate of change of phasic difference and so on. And these results will provide support for further phase active closed-loop control.