Theoretical And Experimental Study On Output Characteristics Of LD End-pumped 1.5?m Q-switched Laser

The LD end-pumped 1.5?m passive Q-switched laser has outstanding advantages such as high peak power,small size,light weight,and low power consumption.It has broad application prospects in the laser ranging and lidar fields.Taking the development of miniature human eye safety band lidar as the requirement background,the thesis conducts theoretical and experimental research on the output characteristics of LD end-pumped 1.5?m Q-switched lasers,and completes the design of the key parameters of the laser and the experimental testing of the output characteristics.Based on in-depth data research,the paper combed the implementation method of 1.5?m laser output and the corresponding domestic and foreign research status,expounded the energy level structure criteria,physical property criteria,and luminescence characteristics of Er³⁺/Yb³⁺co-doped phosphate glass,Er³⁺/Yb³⁺co-doped phosphate glass and Co²⁺:Mg Al₂O₄crystal were selected as the laser's gain medium and Q-switched crystal;the rate equations of the 1.5?m Q-switched laser were given and derived.The formula of the energy and pulse width of the laser output single pulse was studied.Based on this,the output characteristics of the 1.5?m Q-switched laser and its influencing factors were studied,and the computer simulation of the oscillation process and output waveform of the 1.5?m Q-switched laser was realized.In the end,we determined the optimal gain medium length to be 2.5 mm according to the laser design requirements,the optimal transmittance of the Q-switched crystal is 90%,and the optimal value of the output coupling mirror reflectance R is 85%.On the basis of satisfying the above conditions,try to reduce the cavity length and the round-trip loss of the oscillating light as much as possible;use the mode matching theory of the laser cavity,and consider the heat transmission of the gain medium Mirror effect,flat-flat-cavity mode oscillation theory,and spatial light field distribution of the pump source.The mode matching problem of the LD end-pumped 1.5?m laser resonator was studied.The spatial overlap factors of the oscillating mode and pump mode were calculated.And analysis,it is obtained that the optimal beam waist position of the pump light is near the end face of the gain medium at a distance of1 mm.In addition,the output characteristics of the LD end-pumped 1.5?m Q-switched laser are also experimentally tested.The average single pulse energy is 113.5?J,the energy instability is 8.48%,the average pulse width is 4.4 ns,and the pulse width fluctuation is5.79%,peak power is 25.8 KW,far field divergence angle is 10.74 mrad,energy conversion efficiency under rated operating conditions is 0.59%,and stable operating temperature range is-30??50?.The research results of this paper have certain reference value for the optimal design of the LD end-pumped 1.5?m passive Q-switched laser and its application in laser ranging and lidar systems.