Research On LD End Pumped Tm: YAG Pulse Single Longitudinal Mode Laser

The 2μm laser produced by laser diode pumping Tm³⁺doped crystal is widely used in the mid-infrared laser field because of its simple structure and high efficiency.In the implementation of pulsed single longitudinal mode lasers,the hybrid mode of pre-laser+Fabry-Perot（F-P）etalon has the advantages of low voltage of Q-switch,simple system structure,low price,easy realization of high frequency,and active control of synchronization with external signal.This paper is based on the pre-laser technology,combined with the F-P etalon technology to realize the Tm:YAG laser 2μm Q-switched pulse single longitudinal mode output.The main research contents are as follows:In theory,based on the Tm:YAG continuous laser rate equation and the Tm:YAG acousto-optic Q-switched laser rate equation,determine the optimal doping concentration and length of the crystal,and simulate the output characteristics of the Tm:YAG continuous and acousto-optic Q-switched laser.On the basis of these,the Tm:YAG Q-switched laser rate equation model based on the pre-laser theory is established for the first time,and we analyze the variation of the number of energy-level inversion particles on the working substance and the number of oscillating photons in the cavity with time.In order to achieve the effect of the pre-laser technology,we simulate and determine the parameter information inserted into the Fabry-Perot（FP）etalon,and bring the loss formula with the angle and thickness of the etalon into the laser gain loop formula,and finally obtain the prediction Single longitudinal mode establishment and output time under laser technology.Based on the thermal model of LD-pumped double-ended bonding Tm:YAG crystal,the internal temperature distribution of the crystal and the focal length range of the crystal thermal lens are simulated.On the basis of these,we design a laser resonator with good optical and thermal stability,which lays the foundation for the development of subsequent experiments.In the experiments,the experimental studies of LD end-pumped Tm:YAG continuous laser,LD end-pumped Tm:YAG acousto-optic Q-switched laser,LD end-pumped pre-laser Tm:YAG acousto-optic Q-switched laser and LD end-pumped pre-laser Tm:YAG acousto-optic Q-switched single longitudinal mode pulse laser have been carried out successively.And we explore the variation law of the amplitude,width and line width of the laser output Q-switched pulse with the amplitudeU_b and duration_bT of the second step signal on the Q switch.Finally,when the pumping power is 12.84W and the Q-switching repetition frequency is 100Hz,we achieve a single longitudinal mode laser output with a single pulse energy of 3.52m J and a pulse width of 184.01ns.Its center wavelength is 2013.6nm.The beam quality isM_x²=.109,M_y²=1.03.