High-Q coupled topological edge state in 1D photonic crystal mirror heterostructure for ultrasensitive thermal sensing

Abstract

This work explores a novel 1D topological photonic crystal (PC) mirror heterostructure for high-performance thermal sensing. The design leverages a unique coupled topological edge state mode (CTES) exhibiting exceptional light confinement at the interface, characterized by a record-high quality ($Q$) factor. The study investigates the effects of nematic liquid crystal (NLC) integration and temperature variations to enhance functionality. Two NLC defect configurations are explored: complete replacement of silica layers and localized replacement within one topological PC. In both scenarios, the CTES mode exhibits tunability in frequency and $Q$ factor due to the thermo-optic properties of the NLC. This dynamic control offers advantages for various applications beyond thermal sensing, including filtering and switching. The first NLC configuration achieves an outstanding $Q$ factor of ${10}^7$, surpassing the intrinsic value. Additionally, it demonstrates exceptional thermal sensitivity (−0.12317 nm/°C) and a remarkable figure of merit (1002.48 ${°C}^{-1}$). These superior sensing characteristics are attributed to the strong light localization at the interface and the intensified light-matter interaction facilitated by the NLC. The second configuration offers a trade-off between sensitivity and tunability, exhibiting a $Q$ factor in the ${10}^6$ range, a sensitivity of −0.05853 nm/°C, and a figure of merit of 86.53 ${°C}^{-1}$. This study presents a groundbreaking design for 1D topological PC mirror heterostructures with integrated NLC. This platform holds immense promise for developing high-performance, tunable narrowband filters and ultrasensitive thermal sensors, paving the way for advancements in diverse photonic applications.