Coupling condition engineered subwavelength grating waveguide ring resonator for sensitivity enhancement

Abstract

In this paper, we propose a new type of subwavelength grating (SWG) racetrack resonator with engineered coupling condition and waveguide nanostructure. Highly dispersive coupling condition between bus waveguide and SWG ring is achieved, which has a V-shape envelope of resonance spectrum, through adjusting the SWG unit shape, dimension and the length of directional coupling region. When top cladding refractive index changes, instead of indicated in single resonant wavelength shift, which is the case for conventional SWG ring resonator, the movement of the spectrum envelope peak actually represents the sensitivity of our device. SWG racetrack resonators with two different widths are investigated, showing much bigger spectrum shift compared with the conventional one. The results may provide a new approach for further improve device sensitivity and hold great promise for potential applications in integrated optical sensor.