| Summary: | 碩士 === 國立中央大學 === 電機工程學系 === 102 === In recent years, photonic crystal (PhC) nanocavities have inspired great interest in on-chip interconnection or single photon source because of small mode volume, high Purcell effect, low threshold power, and high structure controllability. However, the low output power of PhC nanocavity limits the application for fiber communication, and the PhC array has been proposed to overcome this bottleneck. Moreover, the coupling effect is an important factor for array output power. In this research, the effects of cavity separation and permutation angle on coupling effect and resonant modes of quasi-L2 cavity were investigated.
According to simulation results, the fundamental mode would split into bonding mode and anti-bonding mode in double cavity. The mode splitting of 30o direction coupling is less dependent on cavity separation, because the evanescent wave of fundamental mode propagates along 30o direction. In triple cavity cases, the light would be confined at the strongest coupling cavities. As the cavity arranged at same permutation angle, all cavities would couple to each other. The PhC array separates from square array and rhombus array. In the square array, light would only be confined in the strongest cavities. In the rhombus array, all cavities would couple to each other. According to momentum analysis, the rhombus array has better vertical confinement than square array. So the rhombus array could achieve strong coupling between cavities and keep good confinement.
According to experimental results, we observed the mode splitting fits with simulation results. As increasing cavity separation, we still could observe mode splitting at 30o coupling direction. And the PhC array mode splitting measurement results also fits with simulation result. So the coupling effect is fits with simulation analysis. The best permutation of PhC nanocavity array is 30o direction, which could keep all cavities coupling, in-phase resonating, and high output power mode operation. These results could provide a design standard of PhC array geometry structure.
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