| Laser-diode (LD) pumped all solid-state laser has the advantages of high pump efficiency, a compact structure, high stability, etc. Due to these advantages, this kind of laser has wide applications in the fields such as materials processing, military, medical and so on.In this dissertation, by using the fiber-coupled laser-diode as the pump source, a-cut Nd:Lu0.15Y0.85VO4crystal as the gain medium, we have studied the performance of the passively Q-switched mode-locked laser with GaAs saturable absorber. Using c-cut Nd:GdVO4crystal as the gain medium, we have studied the optimization of the output pulse characteristics and the pulse width characteristics in the passively Q-switched mode-locked laser by using GaAs saturable absorber as the intracavity mode-locker, and in the both actively and passively Q-switched mode-locked laser with acousto-optic (AO)—GaAs saturable absorber, respectively. And under the optimal conditions of obtaining the largest output pulse energy or the narrowest output pulse-width, the optimal parameters of the small-signal transmission of GaAs saturable absorber and the reflectivity of the output mirror were obtained, respectively. Besides, these parameters have been verified in the experiment, and the experimental results were consistent with the theoretical simulation. The optimum parameters obtained above have a certain reference value in the design of these solid-state Q-switched mode-locked lasers. The main contents of this dissertation include:(I) Considering the single-photon absorption (SPA) and two-photon absorption (TPA) processes in the GaAs saturable absorber, also taking the Guassian spatial distribution of the intracavity photon density into account, a couple of rate equations for a diode-pumped passively QML laser with GaAs saturable absorber were given under Guassian distribution approximation, and theoretically studied the optimal output pulse energy and the optimal output pulse-width of the singly Q-switched envelope of the passively QML laser with GaAs saturable absorber. The dependence of the optimum output pulse energy and the optimum pulse-width on the small-signal transmission of GaAs saturable absorber and the reflectivity of the output mirror have been obtained, respectively. Using a three-mirror-folded cavity, diode-pumped passively Q-switched mode-locked c-cut Nd:GdVO41.06μm laser with GaAs saturable absorber has been realized. At a given pump power with different reflectivities of the output mirror and different small-signal transmissions of GaAs, the average output power, the pulse-width of the Q-switched envelope and the pulse energy have been measured. The optimal theoretical results are in agreement with the experimental results.(Ⅱ) The theoretical and experimental studies on the characteristics of a LD-pumped doubly Q-switched mode-locked (QML) c-cut Nd:GdVO4laser with AO modulator and GaAs saturable absorber have been presented. By considering the SPA and TPA processes of GaAs saturable absorber, the Guassian spatial distribution of the intracavity photon density, and the influence of the turnoff time of the AO Q-switch, the coupled rate equations for a LD-pumped doubly Q-switched mode-locked laser with acousto-optic (AO) modulator and GaAs saturable absorber have been provided. The optimal output pulse energy of the diode-pumped doubly Q-switched and mode-locked c-cut Nd:GdVO4laser with AO and GaAs saturable absorber was theoretically studied. For a given pump level, the dependence of the optimum output pulse energy on the small-signal transmission of GaAs saturable absorber and the reflectivity of the output mirror have been carried out. Sample calculations for a LD-pumped doubly QML c-cut Nd:GdVO4laser with AO modulator and GaAs saturable absorber are presented. For a given pump power with different reflectivities of the output mirror and a determinate small-signal transmission of GaAs, the average output power, the pulse-width of the Q-switched envelope and the pulse energy have been measured. The optimal theoretical results are in agreement with the experimental results.(Ⅲ) Using a three-mirror-folded cavity, diode-pumped passively Q-switched mode-locked Nd:Lu0.15Y0.85VO41.06μm laser with GaAs saturable absorber has been realized. The dependences of the pulse width, pulse repetition rate, average output power and single pulse energy on the incident pump power have been measured. The experimental results show that Nd:Lu0.15Y0.85VO4mixed crystal is an excellent laser gain medium for generating QML laser pulses.The main innovations of this dissertation are as follows:(Ⅰ) We have firstly studied the optimization of the output characteristics of LD-pumped passively Q-switched mode-locked c-cut Nd:GdVO4laser with GaAs saturable absorber. The theoretical analysis is consistent with the experimental results. (Ⅱ) We have firstly studied the optimization of the output characteristics of LD-pumped doubly Q-switched mode-locked c-cut Nd:GdVO4laser with AO modulator and GaAs saturable absorber. The theoretical analysis is consistent with the experimental results.(Ⅲ) We have firstly realized the operation of a LD-pumped Q-switched and mode-locked Nd:Lu0.15Y0.85VO4mixed crystal1.06μm laser with GaAs saturable absorber. |
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