High-Performance Refractive Index Sensing Based on Fano Resonances in a Subwavelength Grating Waveguide Microring Resonator

High sensitivity and low detection limit are critical for refractive index (RI) sensors. This work introduces a subwavelength grating waveguide microring resonator (SWG-MRR) as a novel platform for achieving Fano resonances without relying on complex cascaded structures. By tracking the Fano resonance of the SWG-MRR, high-performance RI sensing is experimentally demonstrated with high sensitivity and low detection limit. Using the wavelength detection method, the sensitivity and detection limit are 460 nm/RIU and 4.35 × 10⁻⁵ RIU, respectively. For the intensity detection approach, the sensitivity and detection limit are 2.05 × 10⁴ dB/RIU and 4.88 × 10⁻⁸ RIU, respectively. This work presents an efficient scheme for realizing Fano resonances and highlights the SWG-MRR as a promising candidate for lab-on-chip sensing systems.