Chiral photothermoelectric effect driven by high-Q quasi-bound states in the continuum

Bound states in continuum (BIC) have been proposed as a means to efficiently improve the light-matter interaction of metasurface. While breaking the mirror symmetry of structure and developing BIC into a reachable and observable quasi-BIC, it is usually accompanied by the chiral phenomenon with high quality (Q) factor. Here, we report a spin-sensitive photodetector in infrared (NIR) region, which is composed of a silicon metasurface with chiral quasi-BIC, a silver layer, and a thermoelectric layer. A chiral quasi- BIC supported by a silicon metsurface can be realized under normal incidence. Based on Finite element method (FEM) simulation, a silicon metsurface with a silver layer shows a high Q-factor of 958.6 with a giant absorption circular dichroism (CD) of 0.83. Subsequently, we study the thermal performance of the chiral absorbers by using Heat Transfer module of Comsol. Combining with the thermoelectric material bismuth telluride, we calculate the differential photothermoelectric effects of the system under circular-polarized light (CPL) irradiation. When the incident flux is 100 W/cm2, the output voltage under RCP (LCP) light reaches 0.59 mV (0.08 mV), which can be used for polarization detecting. Therefore, our designed structure incorporating thermoelectricity broadens the applications of chiral BIC in sensors and detectors.