Study On 1.9μm Laser Pumped Ho:YAP Q-Switched Dual Pulse Laser

The 2μs band is located in the atmospheric window,the strong absorption band of water and the safety zone of human eye.It has important applications in laser medicine,laser ranging,photoelectric countermeasure,lidar and so on.Especially 2μm double-pulse laser has great application requirements in the fields of atmospheric environment monitoring,fine processing,dynamic holographic imaging and so on.In this paper,the main objective is to obtain a stable 2μm Ho:YAP Q-switched double-pulse laser output.The main contents include:Theoretically,based on the energy level transition theory of Ho ions,and based on the rate equation model of 1.9μm laser-pumped Ho:YAP Q-switched pulse laser,a two-step loss term is introduced into the cavity loss term,and a rate equation model of Ho:YAP Q-switched double-pulse laser is established.The influence of the amplitude and duration of the two-step loss on the output performance of the Q-switched double-pulse laser is simulated,which provides a theoretical basis for the experiment.Experimentally,Tm:YAP continuous laser 0-24.92W output is obtained based on the double-end pumping technology of a semiconductor laser.The measured central wavelength is kept at 1989.01 nm.Secondly,a Ho:YAP acousto-optic Q-switched double-pulse laser cavity is built,with repetition rate 500 Hz,Ua=4.5V,Ub=3.25V,Tb=2μs,Tc=2μs and pump power 24.92W,the maximum average output power of Ho:YAP double-pulse laser is 3.62W,the center wavelength is 2117.64 nm,the line width is 0.64 nm,the double-pulse laser is stable,the average width of two pulses is 68.80ns,and the pulse interval is 2μs,the beam quality is M_x~2=1.39,M_y~2=1.48.Thirdly,by adjusting the ratio of Ub to Ua,it is shown that when the value of Ub/Ua increases gradually,the energy of the first pulse decreases and the width of the pulse widens gradually.The energy of the second pulse increases gradually and the pulse width is compressed.When Tb is adjusted between 0 and 8μs,it is found that Tb plays a decisive role in the interval between the two pulses,but it has little effect on the pulse width and energy of the double-pulse laser when it is established.Finally,the effects of high loss state Ua,low loss state Ub,low loss state duration Tb and non-loss state duration Tc on laser output performance are obtained through repeated experiments,which verifies the correctness of the theoretical simulation model and lays a foundation for achieving stable Ho:YAP acousto-optic Q-switched double-pulse laser output.