Mode-coupling and Competition Phenomenon within InGaN-based Microcavity Laser

• Main Authors: Tai, Tzu-Ying, 戴慈映
• Other Authors: Kuo, Hao-Chung
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/9pfd9j

碩士 === 國立交通大學 === 光電工程研究所 === 107 === Nowadays, semiconductor lasers are important optoelectronic active components for many applications. Nitride-based laser is an ideal light source because of its short wavelengths, high robustness and high speed. For the emerging applications in photonic chip, the low threshold pumping density and high speed are essential. Therefore, nitride-based microcavity or nanocavity are one of the topics with great research potential. In part one of this thesis, excitation area dependent photoluminescence and temperature dependent photoluminescence were conducted to explored the modal competition between the InGaN-based core-shell nanorods array. In the monolithic rod lattice, the photons leaking out of one rod would be re-harvested by adjacent ones with the coupling effect. As the excitation area increased, we found that the positive feedback among the excitation rods enhanced the Q-factor of long-wavelength mode much more significantly, so that the long-wavelength mode dominated the lasing behavior under a sufficiently large excitation area. Moreover, the bandgap of InGaN and GaN evolved in an opposite way due to the temperature effects and band gap renormalization effect. We observed that the dominant mode switched from 3.29eV to 3.41 eV when temperature decreased from 255K to 240K. In part two of this thesis, we built a two-dimensional model of the InGaN-GaN core-shell by COMSOL Multiphysics and investigated the influence of different number of rods and spacing on Q-factor enhancement and resonant wavelength shift. With an optimized spacing, the Q-factor of a photonic molecule consisting of six rods was enhanced 8 times and the threshold gain was reduced 87% than single microcavity. Based on this result, we believe that by designing the arrangement of the photonic molecules, it is possible to achieve high quality and low threshold microcavity laser devices with a small area, which has great potential for integration of optoelectronic components in monolithic process.