Numerical Investigation of Dual-Mode Angular Grating Sub-Wavelength Microring Resonator for Concurrent Refractive-Index and Temperature Sensing

Advancements in fabrication technology have enabled the development of various waveguide structures for integrated optical sensors, including subwavelength-based designs. This study introduces a subwavelength-based design for optical sensing applications. To extend the sensing range, side-mode suppression techniques based on angular grating subwavelength microring resonators have been implemented. These angular gratings employ silicon pillars of distinct widths, facilitating effective index modulation along the optical path of microring resonator. For refractive index (RI) based sensing, ambient temperature variations significantly impact the RI. To address this challenge, we propose a dual-polarization angular grating subwavelength microring resonator (DP AG-SWGMRR) capable of simultaneously measuring RI and temperature. A comprehensive analysis of the effects of key structural parameters on the center wavelength, side-mode suppression ratio and quality factor is presented. Simulation results for bulk sensing applications indicate that the proposed device achieves a high sensitivity of 1222 nm/RIU for the TM 0 mode and 850 nm/RIU for the TE 0 mode. Furthermore, under ambient temperature variations, the sensor provides sensitivities of 208 pm/°C for the TM 0 mode and 286 pm/°C for the TE 0 mode. The side-mode suppression capability achieves a free spectral range of approximately 47.8 nm for the TE 0 mode. The proposed structure demonstrates excellent performance, accuracy, compact size, and compatibility with other subwavelength grating waveguide-based devices, underscoring its significant potential for applications in compact biomedical sensing.