Dispersion-engineered subwavelength grating microring resonator for high-sensitivity and wide-range on-chip sensing

Silicon-based microring resonator sensors are promising components for lab-on-chip sensing systems. However, developing a microring resonator sensor with both high sensitivity and wide detectable range has remained challenging. Here, we experimentally demonstrate a high-sensitivity and wide-range subwavelength grating microring resonator sensor by leveraging its dispersion properties. These properties enable the formation of an envelope spectrum. By tracking this envelope spectrum for sensing, the detectable range is liberated from the limitation of the free spectral range. Moreover, the dispersion properties are crucial for the improvement of sensitivity. Through dispersion engineering, the subwavelength grating microring resonator achieves a refractive index sensitivity of 791 nm/RIU, with the detectable range no longer limited by the free spectral range. This work advances the design principles for microring resonator sensors and paves the way for high-performance on-chip optical sensing platforms.