The Research Of Intra-cavity MgO:PPLN Mid-infrared Optical Parametric Oscillator Under LD In-band Pumping

High-power tunable mid-infrared(3-5?m)lasers have important research value and research prospects in the military and civilian fields such as military confrontation,laser radar,spectral analysis,and laser communications.The Quasi-phase-matching Optical Parametric Oscillator(QPM-OPO)based on a nonlinear optical frequency conversion technique can obtain high-power tunable laser in this band.In this dissertation,the laser diode(LD)end-pumped Nd:YVO4 laser is used as the pump source,and the crystal(MgO:PPLN)is used as the nonlinear medium to improve the output power and conversion efficiency of mid-infrared parameters.The LD resonant pumped intra-cavity OPO was developed.The specific work is summarized as follows:Theoretical aspects: The working principles and properties of quasi-phase matching techniques and optical parametric oscillation techniques were analyzed.According to the basic model of OPO dynamics in the inner cavity,the dynamic process analysis of the inner cavity OPO Q-switched state was performed.The influence of thermal effects on the threshold and the factors affecting the conversion efficiency were studied.The thermal effect in 808 nm and 880 nm LD pumped were analyzed.Design aspects: A folding-type complex structure of a fundamental frequency optical resonator and an optical parametric oscillation chamber was constructed.Numerical simulation of two cavity structures is performed to design and optimize the cavity of 1064 nm fundamental frequency light and OPO parametric light,respectively.Finally,the best overall cavity parameters were determined.Experimental aspects: An experimental study of an LD pumped cavity optical parametric oscillator was performed.The 808 nm and 880 nm LD pumped cavity OPO experiments were performed respectively.In the 808 nmLD pumped continuous state,the 2780.8~4180.5nm mid-infrared laser is achieved,and the output wavelength was consistent with the theoretical simulation results.After that,the LD pumped Q-switched OPO experiment was performed with idler light output.Intracavity Q-OPO experiments were performed in the 1.4-1.7?m band at a transmission rate of T=40% and high inverse(HR).The 1.65 W laser output at 4.1?m was finally obtained.It's single pulse energy was 55?J,and the single pulse peak power was 5.25 kW.The reverse conversion in the experiment and the pulse image under different frequencies was analyzed.Finally,comparing the light output characteristics of the 808nm/880 nm LD pumped parametric light,according to the experimental results,the advantages of resonance pumping are clearly defined.