Optical coupling characteristics between a circular defect resonator and a waveguide in a two-dimensional photonic crystal slab

To develop a wavelength division multiplexing (WDM) device using a photonic crystal (PC), we investigate coupling strength between a circular cavity resonator and a waveguide with various structural parameters. In the WDM device, light signals with various wavelengths generated in different cavity resonators travel through a single waveguide. Careful tuning of the cavity-waveguide coupling is necessary for practical operations, since the light signals must have the same intensities in the waveguide. Carrying out three-dimensional finite-differential time-domain (FDTD) calculations along with photonic bands, we search for the optimum structure for the WDM.