Lasing dynamics of photonic-crystal single-cell cavity is studied by Lorentz-dispersive Gain FDTD method. From hexapole mode of a photonic-crystal single-cell cavity, the generation of laser modes and the relaxation oscillation are observed.
We have designed channel-drop filters with two line defects and a resonance system based on the two-dimensional triangular-lattice-hole photonic-crystal structure by two-dimensional and three-dimensional finite-difference time-domain simulations. The quality factors have been calculated to be around 3,500 of a two-dimensional channel-drop filter and to be around 300 of a resonance system based on the triangular-lattice hole-based photonic-crystal slab structure.
Using the finite-difference time-domain calculations, we study whispering-gallery-like modes in photonic crystal air-bridge slab hexagonal defect cavities as good candidates for high quality-factor (Q) and small mode-volume (V) resonant modes. In the hexapole mode of a modified single-defect cavity, structural parameters are optimized to obtain very large Qs of even higher than 2 x 106 with small effective V of the order of cubic wavelength in material, the record value of theoretical Q/V. In addition, the H2-cavity whispering-gallery mode (WGM) is investigated and the defect geometry is modified to increase the Q of the WGM. By symmetrically distributing 12 nearest neighbor holes around the defect and controlling size of holes, it is possible to drastically increase the Q of >105 while preserving effective mode volume of the order of the cubic wavelength in material. We expect the WGMs in photonic crystal cavities are quite promising for low-loss photonic integrated circuit elements and high-efficiency quantum optical devices.
We design a 1 X 4 optical splitter made of photonic crystal waveguides and analyze the properties of the optical splitter using the finite-difference time-domain method. Our simulation results show that the transmission properties vary with bend geometries and wave frequencies. Additionally we perform numerical simulations of T-shaped waveguide branches in the splitter to reduce the reflections at the T- branches. The improvement of transmission is achieved by placing the defects of extra rods in the branching region.
We design a micro-scale wavelength-division-demultiplexing device based on the anomalous dispersion and band gaps in photonic crystals. We first calculate the band structures needed for the analysis of the anomalous dispersion, using the finite-difference time-domain method with periodic boundary conditions. Then a simple wavelength demultiplexer is designed and simulated by use of these results. The designed demultiplexer is composed of two photonic crystal structures that have different cylinder radii and are in close contact with each other. From the computed results, the possibility of micro-scale photonic crystal demultiplexers is demonstrated.
We have developed an finite-difference time-domain program that can analyze photonic devices with gain and/or dispersion. As an example, a two-dimensional photonic-crystal laser is simulated. The simulation can show the relaxation oscillation behavior at extremely high current injection.