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

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 nonrecipmcal lithography-free thermal emitter is achieved. The emitter exhibits near-complete dualchannel nonrecipmcal thermal radiation at the wavelengths of 15.337 mu m and 15.731 mu m for an external magnetic field of 3 T and an incident angle of 56 degrees. Besides, the magnetic field distribution is also calculated to confirm that the dual-band nonrecipmcal radiation originates from the coupling effect between two OTSs. Our work may pave the way for constructing dual-band and multi-band nonrecipmcal thermal emitters.