| Summary: | 碩士 === 國立清華大學 === 光電工程研究所 === 93 === Abstract
The Nd:YCOB crystal is a new self-frequency doubling (SFD) crystal. The self-frequency doubling scheme is appealing because it simplifies the laser cavity by synthesizing both good laser performance and harmonic generation property into a single optical element, which means easier assembling and lower cost. By self-frequency doubling (SFD) method, the Nd:YCOB crystal has a great potential to produce green,red and blue lasers.
In this thesis, we derived the theoretical noise model of the Nd:YCOB crystal. A few simulation results were demonstrated. We also obtained 0.87mW cw green output with less than 1W diode pump power focused in the 13% Nd:YOCB crystal. Subsequently, we measured the number of the longitudinal modes by the Fabry-Perot interferometers. There were multi-longitudinal modes in the laser cavity. In order to suppress the green noise, single longitudinal mode operation was preferred. Therefore, we try two methods to solve problems. We improved the cooling of the Nd:YCOB crystal, and added an output coupler after the laser cavity. However, single mode operation has not yet been not achieved.
LSAT[(La,Sr)(Al,Ta)O3] crystal is a new candidate single crystal as a substrate for gallium nitride epitaxial growth. Excellent lattice matching with gallium nitride makes this material specially promising. However, small absorption observed in as-grown crystal close to 450nm seems to be connected with the existence of colour centres. Annealing removes these defects.
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