端面抽运板条介质抽运光束不均匀性及改善方法研究

Nonhomogeneity of end-pumped slab pumping beam and its improvement

基于Zemax软件下的非序列模式(non-sequential mode)光线追迹法,分别模拟复合结构板条介质抽运端面和掺杂介质区工作端面上的光强度分布。由追迹结果可知,经过整形,在抽运面强度分布均匀的抽运光束经过非掺杂介质区传播到掺杂介质工作端面后光束分布均匀性大大降低。研究表明复合结构板条介质中非掺杂介质区影响了抽运光束,即抽运光在非掺杂介质区传播过程中发生全内反射,导致部分光束在实际工作端面的部分区域发生叠加,从而致使实际工作端面抽运光束分布不均匀。最后,依据平面波导匀化理论,从改变非掺杂介质区长度和入射光束发散角大小角度出发,提出改善抽运光束均匀性的思路,并进行了模拟验证。

Based on the non-sequential mode ray tracing of Zemax,light intensity distributions of pumped face and end surface in composite slab were simulated respectively.The tracing results showed that the light intensity distribution was homogeneous when the pumping beam was on the pumped face,however,the light intensity distribution was non-homogeneous when it was on the end surface after transmitting through the undoped crystal.The investigation results indicated that the propagation of pumping beam in the undoped crystal caused total internal reflection,which induced the overlap of pumping beam in partial region of end surface,and then induced the non-homogeneity of pumping beam distribution on the end surface.Finally,according to the planar waveguide homogenization theory,we put forward feasible techniques based on changing the length of undoped crystal and the divergence of incident beam to improve the pumping beam homogeneity,and carried out the simulation validation.