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

Abstract

Bound states in continuum (BIC) have been proposed as a means to efficiently improve light-matter interactions in metasurfaces. 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 the infrared (NIR) region comprising a silicon metasurface with chiral quasi-BIC, a silver layer, and a thermoelectric layer. A chiral quasi-BIC supported by a silicon metasurface can be realized under normal incidence. Based on finite element method simulations, a silicon metasurface with a silver layer shows a high Q-factor of 958.6 with a giant absorption circular dichroism of 0.83. Subsequently, we study the thermal performance of the chiral absorbers by using the heat transfer module of COMSOL. Combined with the thermoelectric material bismuth telluride, we calculate the differential photothermoelectric effects of the system under circular-polarized light irradiation. When the incident flux is 100 W cm−2, the output voltage under right-circular-polarization (left-circular-polarization) light reaches 0.59 mV (0.08 mV), which can be used for polarization detection. Therefore, our designed structure incorporating thermoelectricity broadens the applications of chiral BIC in sensors and detectors.