Research On High-brightness All-solid-state Laser And Continuous-wave Intracavity Mid-infrared Optical Parametric Oscillator Based On PPLN

High-power and high-brightness all-solid-state lasers, which have a lot of advantages, such as high power output, compact and high beam quality and so on, have been widely used in military and industry as the laser source. But the thermal effect is the bottleneck of high-power and high-brightness lasers, which has been further researched by many scientists. Mid-infrared source at 3～5μm has many application in detection, air monitoring, optical spectrum analysis and laser radar and so on because of its unique predominance. Recently, with the development of the nonlinear crystal, such as PPLN crystal, and the pumping source, utilizing optical parameter oscillator to generate Mid-infrared at 3～5μm has attracted many experts. This dissertation is based on the researches of two fields: one is the thermal effect, which is the bottleneck of high-power high-brightness laser, the other is the continuous-wave mid-infrared source at 3.66～4.41μm, which is generated by opical parametric oscillator. The main contents and key creation points are as follows:1. Generation, influences on laser system, measurement, mitigation and compensation of thermal effects in LD side-pumped and end-pumped solid-state lasers are theoretically researched and numberically analyzed in detail, which offer the theoretical basis for high-power high-brightness laser design;2. We have measured the thermal focal length of the LD-side-pumped Nd:YAG laser and drawn the two U curves based on the radius and tangential components with different cavity length. The characteristics of the two U curves are analyzed and researched. When the laser operates at the boundary of the tangential component, the output power and beam quality are both high, then the high-power and high-brightness laser is achieved;3. A new theoretical model of continuous-wave intracavity single resonant parametric oscillators, accommodating a multi-frequency pump laser field, is presented. The characteristics of the idler wave and the signal wave is described, which is the theoretical basis of high power density in the resonator and high energy conversion efficiency;4. A continuous-wave intracavity OPO which can generate continuous-wave at 3.66～4.41μm has been designed. For the first time, we have realized the continuous-wave at 3.66～4.41μm in the dominant by adopting a LD end-pumpede Nd:YVO4 laser as the pumping source and a PPLN crystal placed into an oven as the nonlinear crystal and the introcavity technology. At the PPLN's grating period of 28.5μm and the temperature of 140°C , the SRO threshold is only 2.1W (the diode-laser power) and the maximum idler output power of 155mW at 3.86μm has been achieved when the 808nm pump power is 8.5W, leading to an optical-to-optical conversion efficiency of 1.82%.