| Diode pumped solid state lasers(DPSSL)have become the central focus of the field of lasers due to their many advantages such as high efficiency, stability, good quality of light beam, compactness, long time and etc. Diode-pumped passively Q-switched laser is much efficient to obtain narrow pulse width and high peak power. So, today, they are widely used in fields of photoelectrics industry, military, medical treatment, scientific research, and etc.Nd:GdVO4 is a new laser crystal which is reported in 1992 for the first time. It will be a good replacement of Nd:YVO4 and Nd:YAG because of its high emission cross section and thermal conductivity. Cr4+:YAG is reported in 1988 as a laser crystal, but much attention is paid to its saturable absorption near 1.06 u m from 1992. Cr +:YAG as absorber is a very small device, so it is very simple and convenient, which suits to small-sized passively Q-switched lasers. We have realized 1.06u m and 532nm lasers with short pulse, high peak and high repetition, by using Nd:GdVO4 as laser crystal, using Cr4+:YAG as saturable absorber, using KTP as frequency doubling crystal. The main continents of the dissertation are as follows:1. The history, development and present conditions of diode pumped solid state lasers are reviewed, some laser crystals in common use are introduced and some import parameters of theirs are given. The Q-switched technology is summarized from all round, and the major researches we have made and the present conditions about overseas and domestic of our country are summarized as well.2. Characteristics of Nd:GdVO4 is researched and its important parameters are given at the meantime. Some experiments are made about LD-end-pumped Nd:GdVO4 cw 1.06u m. Some conclusions are drawn, when the incident pump power is 8W, the output power is 3.85W. We have realized c-cut Nd:GdVO4 laser for the first time. When the incident pump power is 8W, the output power 2.85W is obtained. Nd:GdVO4 and Nd:YVO4 have the same laser properties, so we compared laser properties of Nd:GdVO4 with Nd: YVO4.3. The fundamental properties of Cr4+:YAG is researched, and rate equation is given when the Gauss's distribution is considered. Theoretical analyses about pulse width, peak power, pulse energy are presented. Some experiments are made about LD end-pumped a-cut and c-cut Nd:GdVO4 by using Cr4+:YAG as saturable absorber, pulse width of 9ns and peakpower of 6.64kW are obtained with c-cut Nd:GdVO4. And some comparisons with a-cut Nd:YVO4 using Cr4+:YAG as passive Q-switching are made.4. Some researches about frequency doubling are made, and two methods to improve intensity of second frequency generation are given. We realized Q-switched 532 nm laser, by using Nd:GdVO4 as laser crystal ,using Cr4+:YAG as saturable absorber, using KTP as intra-cavity frequency doubling crystal. Average power of 109mW, repetition of 40kHz, pulse width of 30ns, pulse energy of 2.6uJ, peak power of 91W are obtained.
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