Electromagnetic wave confinement and optimization based on strip-shaped photoresist cavities

A SU-8 cavity fabrication process was proposed, by which SU-8 photoresist microstrips could be precisely written onto the surface of photonic crystal waveguides. It was shown by simulation results that the bandgap range of the waveguide could be shifted from 0.269c/a to 0.266c/a (where c is the speed of light and a is the lattice constant) by covering the photonic crystal surface with a SU-8 strip cavity with a refractive index of 1.57 and a thickness of 0.1 μm. The relationship between the SU-8 strip width and the quality factor (Q factor) of the photonic crystal cavity was investigated. It was indicated by the results that when the strip width exceeded 2 μm, the ratio of the total Q value to the mode volume V₀ of the system was significantly increased compared with that when the width was less than 2 μm. An effective route for the optimization of the Q factor is provided by this finding, by which a foundation is laid for enhancing the potential performance of optical cavity modes.