Research On Laser Diode Side-Pumped Nd:YAG Laser Based On Gain Distribution Control

It is of great significance to develop advanced solid-state lasers with excellent output performance and to solve the problem of optical component damage at high power output.The paper studies the theory of gain distribution management.By optimizing the relevant structural parameters of the LD side-pumped module,a new 5-way LD side-pumped module with uniform gain distribution is designed.The thermal performance of the new LD side-pumped module was tested,and it was found that the thermal focal lens of the new side pump module under the same experimental conditions was 2 times thermal focal lens of the commercial side-pumped module,which preliminarily verified Correctness and feasibility of the gain distribution management.Then,a continuous output experiment was carried out based on the new 5-way LD side-pumped module equipped with 0.3 at.%Nd:YAG crystal rods,and the maximum output power was 71 W,the light-light efficiency was 29%,and the slope efficiency was 43%.When the 1.1 at.% Nd:YAG crystal rod is used as the working crystal of the new side-pumped module,the continuous output power is up to 78 W,the maximum light-to-light efficiency is 31%,the slope efficiency reaches47%.The Q-switching output characteristics of the new 5-way LD side-pumped module under low doping concentration gain medium and high doping concentration gain medium are compared and studied.When the gain medium is 0.3 at.% Nd:YAG crystal rod,the shortest pulse width is 33 ns,the maximum single pulse energy is 14 m J,and the maximum peak power is 415 k W.Compared with the Q-switching output characteristics of the commercial side-pumped module equipped with the same doping concentration working crystal,the new side pump module is superior in output indicators such as Qswitching average output power and single pulse energy.And there is no large-area highpower spot at the center of the cross-section of output laser spot.Based on the new sidepumped module(equipped with 1.1 at.% Nd:YAG crystal rod),the Q-switching output experiment was carried out,the shortest pulse width was 36 ns,the maximum single pulse energy was 9 m J,and the maximum peak power was 237 k W.Based on the experimental device of the oscillation level,the damage threshold calculation of the end face of the working crystal rod is completed.The damage threshold of the coating on both sides of the crystal rod is 0.44 GW/cm2 at ?30 ns,which provides a reference for subsequent experiments.Based on the theory of gain distribution management,a new 7-way LD side-pumped module with loop gain distribution is designed,and the new 7-way side-pumped module is used as the amplifier stage to carry out the first-stage amplification experiment.The average output power,pulse width,single pulse energy,and peak power are 9.4 W,19 m J,and 674 k W respectively,and the spatial intensity distribution of the output spot after double-pass amplification tends to be uniform,as Near-flat-top Gaussian distribution.