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Theoretical And Experimental Study On Thermal Effect Of LD End-pumped Nd:KGW Laser

Posted on:2010-02-06Degree:MasterType:Thesis
Country:ChinaCandidate:S S LiuFull Text:PDF
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Diode-pumped solid-state lasers have become a focus in the field of lasers due to their many advantages such as high efficiency, compactness, high stability, and long lifetime. The characteristics of output power and thermal effect of diode-pumped Nd:KGW are studied theoretically and experimentally in this paper. The main content can be generalized as follows:1. The main properties,advantages,applications and developments of DPSSL were introduced briefly.The thermal effect of laser crystal in DPSSL were also introduced; then the background and significance of the research on the thermal effect of diode-pumped solid-state lasers are mentioned.2. The thermal effect theory of Nd:KGW crystal was analysed. The thermal conduct model of Nd:KGW crystal was firstly established based on the characteristic of end-pumped anisotropic laser crystal. The temperature fields distribution in Nd:KGW crystal has been obtained based on poisson equation with surrounding cooled thermal.The OPD induced by end-face deformation and total OPD were calculated. Based on the former calculation, we obtained the focal length of laser crystal with different pumping power. The calculating results show that the OPD induced by end-face deformation is 74% of the total OPD for Nd:KGW crystal with the incident pump power is 10w, the radis of pump beam is 350μm. This illuminates that end-face deformation is the main factor resulting in thermal effect. Besides, the tempreture distribution in laser crystal was obtained with different Nd ion concentration and pumping radius.3. Basing on the stability theory of resonators, the thermal lens in LD-end-pumped Nd:KGW was determined, which was in good agreement with that obtained theoretically; Basing on the space-dependent four-level rate equation theory, the output properties of LD end-pumped solid-state lasers were analyzied; Using the results of thermal lens to optimize cavity parameters, some experiments were made about LD-end-pumped Nd:KGW cw 1064nm. The output characteristics of Nd:KGW laser was studied with different Nd ion concentration and different pumping radius and different transmission of output mirrors. When the pump power is 3.148W, the output power of the cw laser at 1064nm is 1.24W, with the optical-optical efficiency of 38.9% and the slope efficiency of 41.8%.4. The experiment and theories of a LD end-pumped Nd:YVO4/KTP intracavity frequency-doubled laser are demonstrated. When the pump power is 3.13W, the output power of the cw laser at 532nm is 153mW, with the optical-optical efficiency of 4.9%. The threshold is 185 mW. In order to improve the optical-optical efficiency, using ABCD matrix, we choose V-shaped cavity which compress the radius of pump beam on KTP efficiently. When the pump power is 3.13W, the output power of the cw laser at 532nm is 231mW, with the optical-optical efficiency of 7.4%. The threshold is 288 mW. Comparing with the experimental results of straight cavity frequency double green laser above, we can see that the V cavity compress the radius and enhance the density on KTP which result in increasing the optical-optical efficiency of 2.5%.5. The theoretical model about the Q-switched lasers was given in this paper. The rate equations of a LD-pumped passively Q-switched Nd:KGW were also numerical solved . The theoretical pulse width, singal-pulse energy, peak power and the waveform of the1064nm laser was obtained theoretically, which was in good agreement with that obtained experimentally. When the incident pump power is 3W, repetition of 21.32Hz, pulse with of 57.6ns, peak power of 312W are obtained.
Keywords/Search Tags:All solid state laser, Nd:KGW crystal, thermal effect, end-face deformation, focal length, Intracavity frequency doubling, Passively Q-switching
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