Dual-band nonreciprocal thermal radiation by coupling optical Tamm states in magnetophotonic multilayers

Abstract

Kirchhoff's law is one of the most fundamental law in thermal radiation. The violation of traditional Kirchhoff's law provides possibilities for achieving energy conversion with higher efficiency. Various micro-structures have been designed to realize single-band nonreciprocal thermal emitters. However, dual-band nonreciprocal thermal radiations are still rarely studied. Here, we introduce magneto-optical material into a cascading one-dimensional (1-D) magnetophotonic crystal (MPC) heterostructure composed of two 1-D MPCs and a metal layer. Assisted by the nonreciprocity of the magneto-optical material and the coupling effect of two optical Tamm states (OTSs), a dual-band nonreciprocal lithography-free thermal emitter is achieved. The emitter exhibits near-complete dual-channel nonreciprocal thermal radiation at the wavelengths of 15.337 μm and 15.731 μm for an external magnetic field of 3 T and an incident angle of 56°. Besides, the magnetic field distribution is also calculated to confirm that the dual-band nonreciprocal radiation originates from the coupling effect between two OTSs. Our work may pave the way for constructing dual-band and multi-band nonreciprocal thermal emitters.