Optimization Of Laser Conversion Efficiency Of LD End-pumped Quasi-Three-Level Laser

Since the advent of the first laser,the development of solid-state lasers has become more and more mature.The use of laser diode end-pumped solid-state lasers has become the focus of research with its unique advantages.The crystal parameters are the first considerations in designing a laser.The length of the crystal has a significant influence on the performance and efficiency of the laser.The crystal length of the laser has a large influence on the self-absorption loss,thermal diffraction loss and output power of the three-level laser.Therefore,based on the research done in the laboratory,based on the rate equation,the relationship between the crystal length of the LD end-pumped solid-state laser and the reabsorption loss,the thermally induced diffraction loss and the output power was theoretically calculated.The main work is as follows:Firstly,Nd:GdVO₄ was selected as the laser crystal.The basic description of the laser crystal was carried out.The parameters of the laser crystal were analyzed to establish a quasi-three-level system model.The theoretical analysis of the R₁ to Z₅ energy level at 912 nm laser transition.Then,the thermal effect of the laser crystal was analyzed.The heat conduction equation was analyzed in detail.Then the thermally induced diffraction loss effect was theoretically deduced and numerically calculated to obtain the relationship between crystal length and thermal diffraction loss.Finally,considering the effect of the thermally induced diffraction loss,the output power of the laser was theoretically analyzed and calculated,and the relationship between crystal length and laser output power was obtained.Finally,the basic theory of the cavity was introduced.By comparing the advantages and disadvantages of the flat-flat cavity and the flat-concave cavity,the experimental study of the912 nm laser with a flat-concave cavity was selected.Based on the theoretical calculation,different crystal lengths were selected for experimental research,and the output power of the laser was obtained for different crystal lengths.By analyzing and comparing with the theoretical calculation results,the optimal crystal length corresponding to the laser with the highest output power is 6 mm.