| In recent 20 years, diode pumped solid-state lasers (DPSSL) have become a highlight in the laser field for the high efficiency, compactness, and long lifetime, etc. Neodymium (Nd3+) doped crystals have long been the main candidates for the gain medium and the researches are very extensive. At present, lasers for the 1.06μm four-level transitions and the following frequency doubled 0.53μm green lasers have been fruitful and productive. In contrast, the quasi-three-level 0.9μm transitions and the frequency doubled blue lasers are still stumbled for the low gain. In view of this condition and background, this dissertation intends to make efforts on the investigation of the generation mechanism and relevant technologies in quasi-three-level laser of Nd3+ doped vanadate crystals. And hopefully we can make some contribution for the development of 0.91μm lasers and the frequency doubled 0.46μm deep blue lasers.First of all, we make a comprehensive, detailed overview and analyze on the development of 0.9μm DPSSL and the frequency doubled blue lasers for different structures, different gain mediums and different operating ways. Then we conclude the main problems existing in this subject. Thermal conductivity is the most important parameter in the heat dissipating ability of laser crystal. To address the issue in the values of thermal conductivity about the real values are measured and the variation towards temperature is obtained. The results show values for Nd:GdVO4 and Nd:YVO4 are 7.3 W/m·K and 6.7 W/m·K at T=25℃, based on which we can conclude that their thermal conductivities are comparable, whereas the value for Nd:GdVO4 is little higher than that of Nd:YVO4.Based on the energy transition theory and the quasi-three-level mechanism, we introduce the space-dependent rate equations of 0.91μm line transion under thermal equilibrium, including the energy transfer upconversion (ETU) and excited state absorption (ESA) process. The influence of ETU and ESA on pump threshold, output power, spatial distribution of inversion density, and thermal effect in laser crystal are simulated and analyzed by numerical calculations. The results reveal that besides quantum defect, ETU process is another important heat-source in laser crystal during the 912 nm laser generation. From the comparison between theoretical simulation results and experimental data, equivalent cross-section of ESA in 912 nm laser is determined asσESA1.0±0.5×10-20 cm2.To alleviate the boring thermal effect in quasi-three level lasers, an efficient water-cooled micro-channel heatsink is designed and manufactured based on theories of heat transfer and fluid dynamics. By employing this type of heatsink, output power and beam quality of 0.91μm lasers are remarkably improved and 10-W class high power output with high brightness and high efficiency are aquaired.In view of the poor optical conversion efficiency and slope efficiency of 0.91μm lasers, we theoretically propose theπ-polarized light pumping scheme, which can improve the output characteristics of 0.91μm by increasing the absorption efficiency of pump light. And from the experimental results, the slope efficiency and the optical conversion efficiency has been significantly upgraded compared with the corresponding results of the traditional un-polarized pumping.We have also performed the preliminary experimental study in characteristics of high peak power laser output at 912 nm with high repetition rate and short duration realized by acousto-optical Q-switching. Furthermore, we have realized the plused 0.46μm deep blue laser in a Z-type cavity insensitive to thermal lens by acousto-optical Q-switching and intracavity frequency doubling.
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