Fano resonance-boosted topological sensor for next-generation sensing

The rapidly developing field of topological photonics has the potential to revolutionize the design and operation of optical systems. This study presents a novel approach for constructing a resilient sensor based on topological resonance. The coupling of the photonic crystal waveguide (PCW) with the topological corner state (TCS) within the structure forms the proposed sensor. The PCW provides a well-defined propagating mode, while the TCS is a localized mode that is topologically protected against perturbations. The coupling between the two modes contributes growth to a Fano resonance and results in a sharp and narrow spectral feature sensitive to the refractive index variation of the surrounding medium. The proposed sensor possesses a high sensitivity of ∼461.96 nm/RIU with a high Q-factor \(\:(\:>{10}^{6})\), high figure of merit \(\:\:(\:>{10}^{6}\:{\text{R}\text{I}\text{U}}^{-1})\), and has an ideal detection limit value of\(\:\:{10}^{-7}\:\text{R}\text{I}\text{U}\). The present study gives a new platform for a more productive way of creating highly efficient topological Fano resonance sensors. The proposed sensor is resistant, sensitive, and highly versatile, making it beneficial for different applications.