Computational study of slot photonic crystal ring-resonator for refractive index sensing

We perform simulations of slot photonic crystal ring-resonators in dielectric media. The structure comprises two concentric photonic crystal ring waveguides. A slot of width of a few tens of nm is inserted between the inner and outer ring waveguides. By individually modifying the geometric parameters of inner and outer waveguides, the ring-resonator structure generates slow-light whispering-gallery resonance with an optical field concentrating within the slot area. As a sensing element, the structure exhibits advantages of both slow-light and ring-resonator devices. The estimated sensitivity is about 250 nm/refractive index unit and the minimum detectable refractive index variation is about 0.008.