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Investigation of output phase characteristic for a passively Q-switching high-power slab YAG laser

Many factors of intracavity perturbation will degrade the output power and beam quality for high power passive Q-switched slab laser. In this paper, the experiment test on the output beam quality of a passive Q-switched zig-zag slab Nd:YAG laser has been performed by adopting Shack-Hartmann (S-H) wavefront sensor and Zernike mode reconstruction theory. In this way, the PV and RMS values of the wavefront aberration, every order zernike aberrations can be acquired accurately, distribution of circle energy in far-field and other beam evaluation factors can also be obtained by further calculation, so the beam-quality can be known fully. Experimental results show that the wavefront aberration of laser is mainly concentrated in the frontal 10 ranks of Zernike aberration, mainly including the defocus A3, the low-order astigmatism A5, the coma aberration A6 and the spherical aberration A10 because of the crystal thermal effect and the intracavity aberrated perturbation.