Gas sensing with a high-quality-factor photonic crystal ring resonator

A design for a high Q factor photonic crystal ring resonator (PCRR) is presented. The PCRR is based on 2D pillar type photonic crystals, which consist of a hexagonal array of silicon rods. The cavity is created by removing elements from the regular PhC grid. Achieving strong confinement of light intensity in the low index region (filled with the gaseous analyte) is the advantage of this PCRR. In that manner, the interaction of light and analyte, which can be a liquid or a gas, will be enhanced. The high quality factor of the cavity (Q=1.2×104 ), along with strong overlap between the field of the resonant mode and the analyte as well as the low group velocity of PCRR modes yield enhanced light-matter interaction. An enhancement factor of 1.149×105 compared to the bulk light absorption in a homogenous material provides the potential for highly sensitive gas detection with a photonic crystal ring resonator.