Extremely wide-angle nonreciprocal thermal emitters based on Weyl semimetals with dielectric grating structure

Although various nonreciprocal thermal emitters have been suggested to break the balance between absorption and emission, the majority can only achieve nonreciprocal effect at one certain angle, and the angular range in which these structures exhibit nonreciprocal effect is heavily restricted. In this work, the scheme to realize extremely wide-angle nonreciprocal thermal radiation effect is proposed and investigated. It is achieved by placing a dielectric grating atop a Weyl semimetal film backed with a metal mirror. The results show that the emitter exhibits strong nonreciprocal radiation at the wavelength of 15.98 μm when the incident angle is 30°. What's more, the strong nonreciprocal radiation can be achieved in a wide angular range. Such behavior results from the guided mode resonance, which is revealed by investigating the distribution of electromagnetic field at the resonant wavelength and is also confirmed by the dispersion relation of guided mode. This work provides a new approach to the design of novel nonreciprocal thermal emitters.