The The Yvo <sub> 4 </ Sub> / Of Nd: The Yvo <sub> 4 </ Sub> The Hotkey Co-crystal Preparation And Laser Characteristics Of Study

In recent several years, there has been an increasing interest in laser-diode pumped all-solid-state lasers because such lasers can be widely used in the fields of military affairs, industry, medicines and so on.In the research area of laser-diode end-pumped Nd:YVO₄ all-solid-state lasers, a temperature gradient is formed in the laser crystal because of the absorption of the pump power. Because the temperature of the center of the laser crystal is higher comparing with the edge of it, a deformation of the surface is happened and a thin convex is formed, in addition, the change of refractive index of the laser crystal can also devote to the thermal lens effect. The thermal effect affects the laser quality and makes the designing of the laser cavity more difficult.In this paper, the diffusion bonding (deep optical contacting) method is used to make a Nd:YVO₄/YVO₄ composite crystal. The wave-front interference method isused to test the quality of the interface and the P-V value is 0.082 λ ( λ=0.6328μm),this value indicates that the quality is excellent. A press is put on the interface area from the side to test the bonding strength, and find that a firm bond is formed. In order to test the excellent thermal effect of the diffusion bonded crystal, the focal length is tested comparing with the single crystal with the same volume and dope concentration. And find that the composite crystal have much longer thermal length under the same pump condition comparing with the single crystal.In order to analyze the thermal effect of the composite crystal, the mathematical software MATLAB is used to calculate the temperature distribution in the laser crystal, displayed the excellent thermal effect vividly comparing with the single crystal.In this paper, the application fields of the composite crystal are suggested, the excellent effects of the diffusion bonding method have been analyzed, and the idea of the development of the diffusion bonding method is given.In this paper, LD end-pumped YVO₄/Nd:YVO₄ all-solid-state laser is researched. The transform efficiency from pump power to fundamental power is 60%, especially when the pump power is high, the diffraction loss caused by the thermal effect is little and the thermal lens effect is improved, the laser efficiency of the composite crystal is much higher comparing with the single crystal.In this paper, LD end-pumped YVO₄/Nd:YVO₄/KTP intra-cavity double frequency laser using a V-cavity is researched. By analyzing the factors that effect the second-harmonic-generation (SHG) process, a suitable laser cavity is designed and a steady 3.1W continuous-wave (CW) green laser with the transform efficiency 17.2% (from pump power to green laser power) is generated. The SHG process is simulated according to the laser theories.In this paper, LD end-pumped Cr⁴⁺:YAG , GaAs passively Q-switched YVO₄/Nd:YVO₄ laser is researched. In the same condition, output laser pulses with narrower pulse width, higher repetition rate, single pulse energy and peak power are generated comparing with the single crystal. The process of pulse generation is simulated by calculating the rate equation obtained under plane wave approximation. The theoretical predictions are in agreement with the experimental results.The innovative points of this dissertation:1: Comparing with the cooling method of the laser crystal before, which emphasized in the side-cooling using water and optical face cooling using cold air, in this paper, a transparent thermal absorber is diffusion bonded to the doped laser crystal. The heat which is generated at the pump face of the laser crystal is transmitted effectively from the diffusion interface, so the thermal effect of the laser crystal is improved effectively.2: Comparing with the former diffusion bonding method, which use high press and high temperature in the diffusion bonding process, in this paper, a deep optical contacting method is used. In this process, the diffusion bonding surface is precisely polished and contacted by the intra-molecular strength (H-bond), and then it is put in an even temperature field and heat-treated by a suitable temperature. In the process of heat treatment, the molecular bond is rearranged and a steady and strong bond is formed. 3: In this paper, the mathematical software MATLAB is used to analyze the heat distribution in the composite crystal and single crystal. The thermal effect of the composite crystal is displayed vividly.