Operating Characteristics of Photonic Crystal Filters Based on Micro Resonators

In order to design a wideband bandwidth-tunable filter, we design four kinds of filters with two types of micro cavities through different coupling structures between the waveguide and the micro resonator in the two-dimensional photonic crystal structure. By means of the coupled mode theory (CMT), we qualitatively analyze the influences of phase detuning factor and ratio of coupling quality factors on the fiber performances. We use finite-difference time-domain (FDTD) method to study the transmission spectra of the filter by adjusting rod radii of the 5 x 5 micro resonators. The simulated results show that the three symmetrical filters have high normalized transmission (85. 3 %-99. 9%), narrow bandwidth (1. 8-5. 6 nm) , and broad tunable range for extracting peak wavelength (1308. 0-1582.3 nm) at each peak wavelength. Compared with the asymmetrical filter, symmetrical filters have higher normalized transmission at peak wavelength. The symmetrical structures have potential value in the designs of optical signal extraction interfaces, optical sensing, and optical interconnection networks.