Study On Output Characteristics And Thermal Effects Of Compact Nd:YAG Pulsed Lasers

With the breakthrough of laser diode(LD)pumped all-solid-state laser(DPSSL),it has been widely used in laser radar,precision machining,range finder,medicine,etc.It also has served as the pumping source for the OPO(optical parametric oscillator)to generate mid-infared lasers.Because its excellent performance such as good beam quality,high efficiency and high stability.We developed a water-free Q-switched Nd:YAG laser with high temperature LDAs pumping.By calculation of Boltzmann distribution with temperature,the results indicated Nd:YAG was suitable to work at 1064 nm in high temperature environments.By studying the physical and optical characteristics of Nd: YAG laser crystal and comparing it with other gain media,the advantages of this crystal as a gain medium were analyzed.The Boltzmann distribution of the energy level in the crystal at different operating temperatures was calculated,and it was proved that it can achieve stable and efficient laser output in high temperature pumped solid-state lasers.By using Ansys software,the temperature field distribution in the crystal under different pumping conditions and the thermal lens effect of the crystal were simulated.According to the rate equation of the four-level system,different factors affecting the output characteristics of the laser were analyzed.High-temperature LDAs end-pumped and side-pumped Nd: YAG electro-optic Q-switched lasers were designed respectively.In the end-pumped Nd: YAG electro-optic Q-switched laser,high temperature LDAs were used as the pump source,and the Nd: YAG crystal sliced ??at the Brewster angle was pumped through a specially designed light guide cone beam coupling system.Using the DKDP electro-optic Q switch for Q-switching operation,a single-pulse output of 44.1mJ and 50.2mJ of single-pulse energy was obtained at the repetition frequency of 20 Hz and the pump voltage pulse width of 250?s and 300?s.Corresponding pulse widths were 18.3ns and 21.3ns and the slope efficiency was 12.35%and 12.24%.In a side-pumped Nd: YAG electro-optic Q-switched laser,in order to make the pump light in the laser crystal more uniform,the Nd: YAG crystal was pumped by a pumping method around the circle,and a polarization beam splitter prism was inserted in the cavity.The quarter-wave plate and DKDP electro-optic Q-switch performed Q-switching operation on a side-pumped Nd: YAG laser.At the repetition frequency of 20 Hz,the pump voltage pulse width of 300 ?s and the working temperature of 60°C,a single pulse energy of 102 mJ was obtained and the corresponding pulse width was 26 ns.After reducing the repetition frequency to 1 Hz,a single pulse output of 124 mJ was obtained and the corresponding pulse width was 25.6 ns.It was found through experiments that the use of a high-temperature pump source can reduce the heat dissipation pressure of the laser while obtaining a high-energy laser output,so that the laser can achieve the purpose of no water cooling and miniaturization.