Study The Couple Between Waveguide And Cavity In Two Dimensional Photonic Crystal

The micro-cavity, the waveguide and the coupling of them is thebasis of the various types of optical devices in photonic crystal. By theFDTD method, we simulate the transmission spectra of waveguide andcavity optimized. And the coupling problem between them is alsoinvestigated. The main works are as follows:We first research the waveguide characteristics in thetwo-dimensional square lattice photonic crystal. Two types of waveguides,such as line defect waveguide and coupled resonator waveguide, areintroduced in two dimensional photonic crystals. We systematicallyanalyzed their transmission spectra when the parameters of cylinderschange. The results showed that there are always two pass bands in thephotonic band gap and the first pass band increase widen when thediameter and the dielectric constant of the cylinders close to thewaveguide decreased continuously. Moreover, the transmittance was alsoimproved. For the coupled-cavity waveguides, we consider mostly thechanging diameter of the dielectric cylinders for different locations closeto the cavity. The results showed that the defect modes move the highfrequency when the diameter increases continuously. Then, we studied the characteristics of micro-cavity in a triangularlattice photonic crystal. After adding the dielectric cylinders into the fournearest neighbor hole of micro-cavity, the results showed that the defectmodes of micro-cavity moved to longer wavelength when the dielectriccylinders’diameter increased.After that, we researched the coupling between the waveguide andmicro-cavity. Summarize the results obtained above, we optimized thestructure of the direct-coupled waveguide and the side coupledwaveguide. After analysis, we obtained the results of propagationcharacteristics of these two kinds of coupling structures.In addition, by the FDTD method, we also investigate amulti-terminal filter based on two-dimensional photonic crystals. Werecord the light transmission spectra for each out port. Then byoptimizing the structure of the multi-terminal filter, we improve itscharacteristic of filtering.At the last, used FDTD method, we calculate transmission spectra inwoodpile structure based on the different section cylinders. We find thatthe woodpile structure had a complete band gap, and the band gap couldbe modulated by the dielectric cylinders with different sections.