Beam quality improvement in an end-pumped Nd:YAG slab amplifier by the increase of the super-Gaussian order of laser diode beam profile

Abstract

This work focuses on a new estimation to pave the way for an easier optical design of a slab amplifier according to optical path difference (OPD) distribution via laser diode (LD) as a pump source. In general, the output of LD consists of super-Gaussian beams with order 1 in the fast axis and order 3 in the slow axis. The thermal lens (TL) effect is the most important challenge in the optical design of the slab amplifier chain for transferring light from one single-module slab to the next. The formed TL in the slab volume is compensated via the zigzag path of the seed laser in the slab thickness direction. Aforementioned, to improve the output beam quality (BQ) of the slab amplifier, TL effect must be covered by using external optical elements in the slab width direction. In the present paper, the OPD spatial distribution of LD pumped Nd:YAG slab (0.6% Nd3+ dopant) is estimated by using math functions that can be matched. It follows both aspheric and super-Gaussian functions in the slab width direction. Our results show that the super-Gaussian estimation could portray a better understanding of OPD changes and create the conditions for optimizing the slab amplifier output BQ which relates to the super-Gaussian parameter of LD beam in the slow axis. Experimental measurement of TL-diopter in the slab thickness direction proves our simulation results.