Ultra-large FSR filter based on Bragg grating-subwavelength grating slot microring resonator

Abstract

Microring resonators (MRRs) are widely used in optical filters due to their compact size, high Q, and narrow linewidth. However, traditional MRR-based high sensitivity sensors suffer from narrow free spectral range (FSR), which limits the number of channels for detecting substances and causes interference with the identification of the center wavelength when the refractive index of analytes changes significantly. In this paper, we propose an ultra-large FSR and high sensitivity filter utilizing subwavelength grating slot microring resonator with inner silicon blocks with different widths, achieving FSR of 95.5 nm and refractive index sensitivity of 743 nm/RIU. And a lab-on-chip system comprised of eight channels-based filters is presented, promoting the development of silicon photonics in the detecting resolution of small refractive index changes of analytes to 3.60×10^-4 RIU and multiple analytes simultaneously.