Wide-angle and broadband nonreciprocal thermal emitter with cascaded dielectric and Weyl semimetal grating structure

The recent review [Phys. Rev. Appl. 18, 027001 (2022)] has considered that the existing schemes of nonreciprocal radiation are greatly limited by the narrow-operated bandwidth and small angular range. To address these key challenges, here, the wide-angle and broadband nonreciprocal radiation based on cascaded dielectric and Weyl semimetal (WS) grating atop a thick continuous metal film is investigated. It is shown that strong nonreciprocal radiation with nonreciprocity larger than 0.9 is achieved in the spectral range of 14.77-16.175lm for the angle of 59 degrees. The physical origin behind this broadband nonreciprocal radiation is revealed through investigating the magnetic field distributions at several selected wavelengths and is also confirmed by the impedance matching theory. In addition, the broadband nonreciprocal radiation performance remains stably in a wide parameter space. Furthermore, it is found that the broadband spectral nonreciprocity can be maintained well in a wide angular range, in particular, above 0.7 nonreciprocity can be realized in the wavelength range of 14.5-16.5lm for the angle between 36 degrees and 64.5 degrees. Both features make the proposed scheme very attractive for real production. Finally, the broadband spectral nonreciprocity can be flexibly controlled through change in the axial vector of the WS. We believe that the conclusions will pave the way for designing energy harvesting and conversion devices with improved efficiency.

Automated summary

The recent review points out that existing schemes of nonreciprocal radiation are limited by narrow-operated bandwidth and small angular range. In this study, a wide-angle and broadband nonreciprocal radiation based on cascaded dielectric and Weyl semimetal grating is investigated. The broadband nonreciprocal radiation performance remains stable in a wide parameter space and can be flexibly controlled through changes in the axial vector of the Weyl semimetal. The conclusions of this study could pave the way for designing energy harvesting and conversion devices with improved efficiency.