Azimuth-Incidence-Angle Tuned Near-Unity Nonreciprocity via Weyl Semimetal Hetero-Stack

Nonreciprocal thermal radiation (NTR) has attracted much attention because of the great potentials in various aspects ranging from renewable energy, molecular sensing, to thermal circuitry and camouflage. To manipulate the magnitude and sign of nonreciprocity simultaneously, a trilayer fashion of Weyl semimetal (WSM)-dielectric-WSM terminated by a metallic substrate is proposed. By engineering the structural parameters, a surprising result of spectrally selective as well as azimuth-incidence-angle tuned NTR is realized. It is demonstrated that the mediated thermal emitter presents a near-unity nonreciprocity of 0.99 at the resonance of
$9.24~\mu m$
, and a wide emission angle up to 85°. By changing the azimuthal angle of incidence (
$\phi $
), nonreciprocity spectra can also be effectively manipulated, which is symmetrical with
$\phi $
= 90°. The presented configuration works for a broad incidence and azimuthal angles range, consisting highly advantageous properties to diverse NTR applications.