Research On Q-switched And Q-switched Mode-locking Laser Characteristics Of LD-pumped Nd-doped Vanadatemixed-crystals

Laser-diode (LD) pumped solid-state laser has wide applications such as optical communication, industry, information processing, laser measuring and medicine, due to its simple structure, high pump efficiency, high stability and high beam quality, and has been paid much attention on.In this dissertation, by using a commercial fiber-coupled laser-diode array as the pump source, Nd:YV04, Nd:Lu0.15Y0.85VO4, Nd:Lu0.5Y0.5VO4and Nd:Luo.33Yo.37Gdo.3V04crystals as the gain mediums, we have investigated the I performance of the actively Q-switched lasers with acoustic-optic (AO) modulator, and passively Q-switched lasers with GaAs saturable absorber, respectively; using GaAs as the intercavity mode-locker, the passively Q-switched and mode-locked lasers have been realized; we also have studied the output performances of the diode-pumped dual-loss-modulated QML lasers with AO-GaAs. Meanwhile, the coupling wave rate equations under Gaussian distribution approximation are given to analyze the properties of the above-mentioned Q-switched lasers and the simultaneously Q-switched and mode-locked lasers. The main content of this dissertation is generalized as follows:I Diode-pumped actively Q-switched Nd:Lu0.15Y0.85VO4and Nd:Lu0.33Y0.37Gd0.3VO4lasers with AO modulator have been realized, respectively. The dependences of the output power, pulse width, pulse energy and peak power on the pump power have been measured at different repetition rates of AO modulator. The actively Q-switched Nd:Lu0.33Y0.37Gd0.3VO4laser with AO modulator can generate shorter pulse width of Q-switched envelope,larger pulse energy and higher average peak power.(Chapter2.1)ⅡA diode-pumped passively Q-switched Nd:Lu0.15Y0.8sVO4、Nd:Lu0.5Y0.5VO4and Nd:Lu0.33Y0.37Gd0.3VO4lasers with GaAs have been realized. The dependences of output power, pulse width, single pulse energy and peak power on incident pump power are measured. The passively Q-switched Nd:Lu0.33Y0.37Gd0.3V04laser with GaAs can obtain shorter pulse width of Q-switched envelope, larger pulse energy and higher average peak power. Considering the single photon and two-photon absorptions of GaAs saturable absorber, a couple of rate equations describing the passively Q-switched lasers with GaAs have been built up. These coupled rate equations are solved numerically and the numerical solutions of the rate equations reproduce the laser characteristics well.(Chapter2.2)Ⅲ A diode-pumped passively Q-switched and mode-locked (QML) Nd:Lu0.15Y0.85VO4NNd:Lu0.5Y0.5VO4and Nd:Lu0.33Y0.37Gd0.3VO4lasers with GaAs have been realized. The QML Nd:Lu0.33Y0.37Gd0.3VO4laser can obtain shorter pulse width of Q-switched envelope, larger pulse energy and higher average peak power. By considering the Gaussian transversal distribution of intracavity photon density and the longitudinal distribution of photon density along the cavity axis, a couple of rate equations describing the QML lasers have been built up.These coupled rate equations are solved numerically and the theoretical results are in agreement with the experimental results.(Chapter3.1)IVUsing Nd:YVO4、Nd:Lu0.5Y0.5VO4and Nd:Lu0.33Y0.37Gd0.3VO4crystals as laser media, the dual-loss-modulated QML lasers with AO and GaAs are realized.For Nd:Lu0.33Y0.37Gd0.3VO4laser cavity, the pulse width is compressed significantly and the peak power increases. Considering the influence of the AO modulator, the rate equations for a diode-pumped dual-loss-modulated QML laser can be obtained, the numerical solutions of the rate equations reproduce the laser characteristics well.(Chapter3.2)The main innovations are generalized as follows:I By using Nd:Lu0.15Y0.85VO4, Nd:Lu0.5Y0.5VO4and Nd:Luo.33Y0.37Gd0.3VO4crystals as the laser gain medium for the first time, diode-pumped actively Q-switched lasers with AO modulator, passively Q-switched lasers with GaAs, QML lasers with GaAs and dual-loss-modulated QML lasers with AO and GaAs have been realized, respectively. Meanwhile, the coupling wave rate equations under Gaussian distribution approximation are given to analyze the properties of the above-mentioned Q-switched lasers and the simultaneously Q-switched and mode-locked lasers, and the numerical simulations agree well with the experimental results.Ⅱ Comparison for the performance of Nd:YVO4, Nd:Lu0.15Y0.85VO4, Nd:Lu0.5Y0.5VO4and Nd:Lu0.33Y0.37Gd0.3VO4lasers are realized for the first time. The experimental results show that larger pulse energy and shorter pulse width can be obtained in the Nd:Lu0.33Y0.37Gd0.3VO4lasers than those obtained in Nd:YVO4, Nd:Lu0.15Y0.85VO4and Nd:Lu0.5Y0.5VO4crystal lasers because of the inhomogeneous broadening of the fluorescence line widths and reduction of the stimulated emission cross-section.