Research On Beam Shaping System Design Of Slab Lasers

In recent years, with continuous research, slab laser has been greatly developed both in high average power and high beam quality. The geometric symmetry of slab and the Zigzag propagation path which are designed for the slab laser solve the thermal depolarization, thermal focus and other thermal effects theoretically, but the result in experiments and industrial applications is far from the expectations. Multimode output, misalignment, dynamic distortion, different gain ability of the slab led to the output power and beam quality have not reached the results of theoretical calculations. In addition, the output beam has a rectangular shape with high aspect ratio, which brings great difficulties in many applications. At the same time, the wavefront of slab laser has lager defocus and astigmatism, the divergence angels in horizontal and vertical direction are different, showing a typical astigmatic beam characteristics, reducing energy concentration of far-field beam quality, which results in significantly reduce of beam qualities. To solve these problems, this paper presents a method of designing and optimizing a beam shaping and aberration compensation system for slab laser, and the simulation analysis and experiment have been done under different conditions.The energy distribution of narrow direction is Gaussian-like, while the energy distribution of the other direction is super-Gaussian-top-hat, which lay the foundation for the simulation of the output beam of the slab laser in Zemax. Comparison for some typical beam shaping system is made, after analyzing the advantages and disadvantages of those systems, here we put forward a method that combine cylinder lens with spherical lens to design the shaping system for slab laser.This system between passive shaping system which is designed according to single beam parameter and adaptive optics system.The initial structural parameters is calculated by matrix optics, and using Zemax to optimize it. The simulation and experimental results show that By changing the distance between each lens, we can shape the rectangular beam into square collimated beam, whose size varies in the range of to with low phase aberrations, while the size of the input beam is. After shaping, the wavefront aberration of the slab laser beam has great improvement, the far-field energy concentration increase greatly.