The purpose of this thesis is to develop a high power, compact all solid-state blue laser, which is applicable in micro machining, LIDA, underwater ranging, biochemical techniques and so forth. The passive Q-switching technique, which is known to be a low-cost and simple method to raise the laser peak power was employed in this thesis. In the mean time, the intracavity-doubling technique was integrated to achieve the non-linear frequency conversion for generating blue laser at low cost. Based on our research finding, the reabsorption loss due to thermal effect and a paucity of suppression at wavelength of 1064 nm on laser mirrors could cause the four-level oscillation at 1064 nm instead of three-level oscillation at 914nm. Improvement in heat dissipating system, and suppression at wavelength of 1064 nm on mirror coating has led to a success in developing a quasi-three-level blue laser with peak power of 114W at wavelength 473 nm. A modified rate equation model of the quasi-three level passively Q-switched blue lasers was developed as well, in which the influence of the re-absorption loss in the gain medium and its intracavity frequency doubling were both considered. The influence of reabsorption loss upon the laser power deduction was studied by numerical simulation in order to optimize the laser performance.

Though Nd:YAG has been widely used as the traditional high power solid-state laser gain medium, Yb:YAG has more advantages such as lower quantum defect, wider absorption and emission bandwidth, and longer fluorescence lifetime, which can be used in Q-switched lasers to storage more energy. In addition, a higher doping concentration Yb:YAG with thinner thickness reduces the shift of optical path, which reduces the ring cavity stability. Therefore Yb:YAG is an eminently suitable gain medium for the two-mirror ring laser. Due to the quasi-three-level characteristic of Yb:YAG, the thermal effect influences the re-absorption loss and deteriorates the laser performance, i.e. lower slope efficiency of laser. In this thesis, we improve the laser efficiency by using Yb:YAG crystal with proper thickness, and various round-trip transmittances with different output couplers were tried. The slope efficiency with 50.3 % has been achieved. We also tried to reduce the thermal loading of Yb:YAG by crystal fiber with Cu-Al alloy package. The fabrication process of Yb:YAG crystal fiber, including sample preparation, and coating design, and the experiment result of Yb:YAG crystal fiber ring laser will be presented in detail. Furthermore, we use numerical analysis to modify the passively Q-switched Yb:YAG ring laser rate equation with FDTD (finite difference time domain) method. The simulated repetition rate, pulse width and peak power were compared to the experimental results in order to optimaize laser performance.

The purpose of this study is to develop a solid-state blue laser which has advantages of high power, short wavelength, and compact. It can be applied in micromaching, LIDAR, underwater ranging, biochemical techniques, and so forth. We increased the peak power of the laser effectively by a low-cost, small, and easy-use passive Q-switching technique. In addition, intracavity frequency-doubling is an economic way to achieve non-linear frequency conversion for blue generation. By integrating of these two techniques, we develop a compact all solid-state high-power blue laser with 83 W peak power at 473 nm. Restricted to reabsorption loss, the optical to optical conversion efficiency of 4F3/2 ¡÷ 4I9/2 quasi-three-level laser is lower than 4F3/2 ¡÷ 4I11/2 four-level laser for Nd:YAG crystal. The reabsorption loss will change with the temperature variation of the gain medium, it enormously affects to the performance and stability of quasi-three-level lasers. Therefore, in addition to make systematic studies of the conversion efficiency of KNbO3, BBO, LBO as the intracavity SHG crystals for generation of high-power blue laser, we use the numerical analysis to investigate the influence of reabsorption loss to quasi-three-level passive Q-switching laser. At present, blue laser with peak power of 83 W and pulse width of 10.6 ns was generated as a result. To our knowledge, the compact all solid-state high-power pulsed blue laser is demonstrated for the first time by integrating of passive Q-switching and intracavity frequency-doubling simultaneously.