| Summary: | 碩士 === 淡江大學 === 物理學系 === 92 === In this thesis we investigate single-mode operations of diode-pumped Nd:YVO4 lasers, including a new design and experiment. Theoretically, we consider steady-state operation of a four-level laser system, derive condition for single-mode operation, and investigate how to realize single-mode laser operation with a birefringent filter. In experiment, we found that when a Nd:YVO4 laser crystal is placed inside the laser cavity many longitudinal modes with closely spaced wavelengths (a few tenths of an angstrom) appear simultaneously, and it is very difficult to achieve single-mode operation by using an etalon. In contrast, when a Nd:YVO4 laser crystal is employed as an end mirror, single-mode operation can be achieved by introducing either an etalon or a KTP crystal into the cavity, and when both were introduced, we obtained single-mode output of 198 mW at 1-W pumping. Finally, we built a new single-mode laser by using a KTP crystal and a thin-film polarizer. We may select a single mode from the laser, and single-mode operation can be easily achieved even when the cavity is 10-cm long. The polarization ratio of the laser output was greater than 100:1.
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