Study On Mode Coupling In Optical Microcavities Based On Optical Waveguide

Due to their small mode volumes and high quality (Q) factors, optical microcavities have important application values in various fields, such as low threshold microcavity lasers, optical filters, sensors, optical switches and modulators. The microcavity laser coupled with waveguide can drive other optical devices by conveying energy through waveguide. In order to achieve the integration of microcavity lasers with other devices, the research of microcavity lasers coupled with waveguide become particularly important. This dissertation mainly studies the mode coupling in optical microcavities with waveguide, and the main contents and innovation achievements are summarized in the following:Bring forward a novel coupling structure. Two identical microcavities are bridged at radial direction by a waveguide, which can achieve photon exchange in a long distance. We study the influence of waveguide length, up cladding thickness and etching depth on mode wavelength and mode Q factor by using three dimensional finite-difference time-domain (FDTD) electromagnetic simulations. The results show that the strong and weak optical interactions between two microcavities and the vertical radiation losses are modulated by waveguide length, the mode Q factors oscillate with the variation of waveguide length, and high Q resonances are observed at conditions of the cancellation of the vertical leakage and weak optical interaction between two microcavities. With the increase of the thickness of up cladding layer, the Q factors first increase rapidly and then decrease rapidly. The Q factors with3μm waveguide length are always larger than2.6μm, this result is very consistent with the Q factor modulation of waveguide length. The Q factor increases from2800to5600with the increase of etching depth before the etching depth reaches3.5μm, and then the Q factor oscillate with the increase of etching depth. This result can help us to control the etching depth for realizing low threshold lasing of resonant system.We study the mode characteristics of two coupled metal-insulator confined circular resonators. We analyze the influence of the thickness of insulator on mode wavelength and Q factor. The results show the split of degenerate mode, and the split of Q factors of OE and OO modes happens when the thickness of insulator is larger than1.3μm.In addition, in order to achieve the directional output of waveguide, we propose a structure that two metal-insulator confined circular resonators couple through a waveguide. We analyze the influence of the width of waveguide on mode wavelength and Q factor. The results show that once the width of waveguide is close to the cut-off width of TE-2and TE-1guided waves, the quality factor of TM5,3and TM11.1modes decrease rapidly because the whispering gallery modes in the resonators are strongly coupled with the guided waves of waveguide.