| Summary: | 碩士 === 淡江大學 === 物理學系 === 91 === The main purpose of the thesis is to investigate and compare the performance of diode-pumped Nd-YVO4 and Nd-LSB lasers, both in continuous-wave and Q-switched operations. Our experiments show that thermal effects of the pump beam on the Nd-LSB crystal are very significant: the laser cavity is difficult to align, especially at longer cavity length (> 4 cm, for our experiment); increase of the pump power may change laser alignment, it may also destroy the stability of the laser cavity. However, the situations can be improved with shorter cavity lengths. Comparing the transmission spectra and laser polarization of these two media, we found Nd-YVO4 is more sensitive to variations in pump polarization, and the extinction ratio of the Nd-YVO4 laser output is higher than that of the other. In the same CW laser cavity configuration, the slope efficiencies of both lasers are about the same; however, the threshold power of Nd-YVO4 is lower, so its overall conversion efficiency is better. In the same Q-switched laser cavity configuration, the pulse energy of Nd-LSB laser is significantly higher than that of Nd-YVO4; this is in good agreement with theory. With a shorter cavity and a lower pump power (<1 watt), the output quality of Nd-LSB lasers could be improved if the size of the pump beam can be properly adjusted.
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