Ultrahigh-Q Topological Mirror Heterostructure for High-Resolution Thermal Sensing in One-Dimensional Photonic Crystals

High-resolution optical thermal sensors are attracting increasing interest due to their potential for compact integration, electromagnetic immunity, and enhanced spectral precision. In this work, a topological mirror heterostructure based on a one-dimensional photonic crystal (1DPC) is proposed for thermal sensing applications. The structure incorporates alternating silicon/glycerin photonic layers with a glycerin defect cavity, combining the large thermo-optic response of glycerin with the strong field localization of topological edge states in a topological mirror configuration. Finite element method (FEM) simulations reveal the formation of ultranarrow resonant modes with near-unity transmission inside the photonic bandgap. The proposed topological mirror heterostructure achieves exceptional thermal sensing performance through ultranarrow resonant linewidths and strong optical confinement, resulting in ultrahigh quality factors and figures of merit. The optimized design exhibits a thermal sensitivity of −0.1177 nm/°C, a quality factor approaching 1.8 × 108, and a figure of merit of 1.53 × 104 °C−1. The proposed platform offers a promising approach to compact photonic thermal sensors that require high spectral resolution and enhanced sensing efficiency.