Near-perfect nonreciprocal radiation for extremely small incident angle based on cascaded grating structure

Abstract

The recent review (Phys. Rev. Appl. 18, 027,001 (2022)) has remarked that the nonreciprocal emitters of existing schemes are greatly limited by the small angular range since they typically occurred at rather large angles. Here, to address the key challenge, a novel scheme, based on the cascaded dielectric-magneto-optical (MO) material grating structure, is proposed and investigated. It is shown that near-unity emission and little absorption can be achieved simultaneously at the same wavelength, leading to near-perfect nonreciprocal radiation for an angle of only 1°. The underlying physical mechanism is revealed through illustrating the distributions of magnetic field amplitude. Besides, the possibility to realize strong nonreciprocity with the magnetic field as small as possible is investigated. Last, the angular ranges which can be realized by the proposed scheme are also investigated. The results should be interesting for the developing of solar cells and photovoltaics with improving efficiency and the thermal devices.