Six-band strong nonreciprocal radiation at small angle of incidence 5.9° by toroidal cylinder arrays

Abstract

Nonreciprocal thermal radiation overcomes Kirchhoff's law which requires spectral absorptivity to equal emissivity, establishing a distinct radiative heat transfer mechanism. However, among the previously reported nonreciprocal thermal radiators, research on dual-polarized multi-band systems remains relatively scarce and is limited to large incidence angles, which limits the practical application of nonreciprocal thermal radiators. To address these challenges, we propose a six-band, dual-polarized strong nonreciprocal thermal radiator comprising a silicon-based void ring cylinder periodic array, a magneto-optical material layer (InAs), and a silver (Ag) metal reflector. When the applied magnetic field strength is 2.5 T and the incidence angle is 5.9°, six strong nonreciprocal peaks can be shown with nonreciprocity of more than 80% under transverse electric (TE) polarization and transverse magnetic (TM) polarization. Through the study of coupled mode theory and electromagnetic field distribution, the physical mechanism of the strong nonreciprocity of the device structure in this work is revealed. It is believed that this study of six-band, dual-polarized strong nonreciprocal thermal radiation at small angles of incidence has the practicability of energy harvesting control and thermal radiation.