Design and analysis of a thermally and structurally tunable one-dimensional topological photonic crystal-based multichannel filter

In this study, we present a thermally tunable one-dimensional topological photonic crystal (PC)-based multichannel filter that leverages the unique properties of topological edge states (TESs) for robust optical filtering. The filter is constructed by alternating two distinct one-dimensional PCs, each comprising thermally responsive PbTe layers and structurally robust GaN layers. This arrangement creates multiple interfaces that support localized TESs. Using the transfer matrix method, our analysis demonstrates that increasing the number of interfaces (channels) leads to significantly sharper resonant peaks, characterized by a reduced full width at half maximum (FWHM), enhanced quality factors (QFs), and decreased spectral spacing between adjacent channels. Moreover, thermal tuning, enabled by the temperature-dependent refractive index of the PbTe layers, induces a linear blue shift in the resonant wavelengths and a simultaneous linear decrease in FWHM over the temperature range of 20 °C to 80 °C. Key performance metrics show a reduction in the FWHM from 38.4 nm to 0.4 nm and an increase in the QF from 400 to 3597 as the number of channels increases from 1 to 9. Compared to conventional filters, our design offers superior spectral confinement, lower optical losses due to topological protection, and higher scalability in integration, thereby providing enhanced performance in dynamic, real-time applications. Furthermore, variations in layer thickness provide an additional degree of freedom to shift the operating wavelength. This innovative approach is particularly suitable for optical communications, high-resolution spectroscopy, and sensing. Future experimental validation is planned to verify these simulation predictions.