| Summary: | 碩士 === 國立中山大學 === 光電工程學研究所 === 86 === Longtudinal-pumped solid-state lasers are easier to make the pumping modeand the cavity mode match to each other than flash lamp pumped laser. With this kind of pumping, it's easier to get TEM00 transverse mode and higher optical-tooptical conversion efficiency. The heat generated in the gain medium is also reduced. But, when pumpung power is scaled up,excess heat still needs to be removedNot all thermal effect is so affective to the design of laser cavity as thermal-lens effect. It had been proposed in papers that when thermal-lens effect is produced in the gain medium, it's possible to consider the gain medium as a focusing lens. Anda formula is developed to describe the effective focal length. In this thesis, we developed a new way to measure the thermal lens effect.It's not only accurate but also makes it possible to observe the longtudinal temperature distribution. Essentially, this is to scan the gain medium when working by low-coherent light and analyze the ahange on the index of reflection. We found that the averaged temperature at the center of Nd:YVO4 crystal is between 160-182 degree when pumped at an intensity of 3.4KW/cm2. We may desigh an optimal cavity after accurate measurement on thermal lenseffect. The IR laser we designed had a 59.4% total efficiency and 68% slope efficiency. The intracavity frequency doubled green laser reaches an outputpower 1.8W with a beam quality factor better than 1.9.
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