| Diode-pumped solid-state laser is widely used in material processing, military, medical therapeutics, basic research, etc for their advantages, such as high efficiency, compactness, stability, long lifetime and all solid-state construction, now it has become the researching emphasis because unique merits. In the research area of laser diode end-pumped all-solid state lasers,a temperature gradient is formed in the laser crystal because of the absorption of the pump power. Because the temperature at the center of the laser crystal is higher comparing with the edge, a deformation of the surface appeared 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 and make the designing of the laser cavity more difficult.We developed the composite crystal of Nd:YVO4/ YVO4 using the diffusion bonding method, tested its basic optical property,and finded that the composite crystal has much longer thermal focus length under the same pump condition comparing with the single crystal.The laser with output wavelength at 1570nm is widely used in range finding because they are relatively safe to people's eyes. Optical Parametric Oscillator (OPO) pumped by 1064nm Nd:YAG laser at 1570nm is one of the most effective way to get the eye-safe laser.A LD pumped Nd:YVO4/ YVO4 composite crystal laser and a acousto-optically (AO)Q-Switched Nd:YAG intracavity optical parametric oscillator(OPO) are researched theoretically and experimentally.The content of this dissertation is listed as below:1. The history and development of all solid state lasers and Nd:YVO4/ YVO4 composite crystal are reviewed; the research statue of frequency-doubling laser and 1570nm wavelength eye-safe laser are summarized.2. The developing method of Nd:YVO4/ YVO4 composite crystal is introduced, the optical properties of Nd:YVO4/YVO4 composite crystal and Nd:YVO4 single crystal are studied contrastedly . It is demonstrated that the composite crystal can effectively recede the temperature of crystal, relieve the thermal lens and get higher output power. 3. The frequency-doubling property of Nd:YVO4/YVO4 composite crystal with KTP is studied in a"V/Z-shaped"folded cavity, giving an optical conversion efficiency of 31.3% and 37%.4. The characters of Cr4+:YAG and GaAs crystal on Q-switching are introducing, get the Q-switching laser output using Nd:YVO4/YVO4 composite crystal for the first time,and find that comparing with the single crystal , the refraction loss caused by the thermal effect is little ,the thermal lens effect is improved, the laser efficiency of the composite crystal is much higher.5. 1570nm quasi-continuous laser is realized by putting non-critical-phase-matched KTA into LDA side-pumped Nd:YAG AO Q-switched laser which constructed an intra-cavity OPO; The output power of 563.3mW at 1570nm is produced with the frequency of 4kHz at the incident current of 14.5A, the output coupler transmission is 30%, and the peak power achieves 5. 6×104W.The innovative points:1. Comparing with the former diffusion bonding method, which use high pressure 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 was put in an even temperature field and was 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.2.The optical properties of Nd:YVO4/YVO4 composite crystal were systemicly studied for the first time Because the research work of the technique of thermal bonding is difficult, there is little study on the technique of thermal bonding in our country.3. The output properties of 1570nm laser were researched for the first time by putting a non-critical-phase-matched KTA into LDA side-pumped Nd:YAG AO Q-switched laser to construct an intra-cavity OPO. |
PDF Full Text Request