| Summary: | 碩士 === 國立臺灣大學 === 光電工程學研究所 === 99 === This thesis is composed of three parts：(1) the theory of quasi-phase- matching(QPM) and the QPM optical parametric oscillator(OPO), (2) the fabrication technique of one-dimensional periodically poled congruent grown lithium tantalite(LiTaO3) for cascade OPO-SHG 465nm blue laser chip, (3) the measurement and analysis of OPO-SHG blue light generators.
First of all, I will introduce the mechanism of nonlinear frequency conversion and QPM theory, and its application to the optical parametric and second harmonic generation. By using Sellmeier equation, I design the QPM period of periodically poled LiTaO3 (PPLT) for the above application. By taking advantage of the nickel-diffusion assisted electric poling process, I fabricated cascaded OPO-SHG devices on 0.75mm-thick congruent LiTaO3 substrate. For cascaded OPO-SHG PPLT device, I design multi- SHG segment composed of 3 QPM periods with 4.9514 um, 4.9865 um, and 5.0218 um. Another SHG design is composed of 5 QPM periods with 4.9514 um, 4.9689 um, 4.9865 um, 5.0041 um and 5.0281 um. By this design, we achieve OPO-SHG blue laser with high slope efficiency and broad spectrum.
Using a 532nm, bean of 5ns pulse width as the pump source, a 13mm long cascaded OPO-SHG chip in a concave laser cavity of 15mm length is shown to generate a 465nm high efficiency broadband blue laser. The spectrum is shown to have a 1.4 nm bandwidth and 21% slope efficiency. By this process, an average output power of 54mW blue light laser has been achieved under a 350mW input green pump, which corresponds to a conversion efficiency of 15.4%.
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