Experimental Measuring of Beam Phase Aberrations for a Side-Pump Passive Q-Switched Laser

Many factors of intracavity perturbation will degrade the output power and beam quality for high power passive Q-switched slab laser. We propose and demonstrate the measurement of output laser beam quality with a side-pump Q-switched zig-zag slab YAG configuration by adopting Hartmann-Shack (H-S) wavefront sensor and Zernike mode reconstruction method. Experiment shows that wavefront properties can be comprehensively obtained by processing the image of intensity dot matrix. by this means, PV and RMS values of wavefront aberration, every order zernike aberrations can be acquired accurately, and point spread function (PSF) of laser beam and distribution of circle energy can also be obtained by further calculation, so the beam-quality can be understood completely. Experimental results show that the wavefront aberration of output mode is mainly concentrated in the frontal 10 ranks of Zernike aberration, mainly including the defocus A3, the low-order astigmatism A4 and A5, the coma aberration A6 and the spherical aberration A10 because of the crystal thermal effect and intracavity aberrated perturbation.