Nonreciprocal wide-angle and narrowband thermal emitter

Abstract

Nonreciprocal thermal radiation allows the violation of Kirchhoff's law, as the spectral directional emissivity and absorptivity at the same angle can be different. Prior research has elucidated that certain optical resonance modes facilitate amplification of nonreciprocity at specific angles or wavelengths. However, achieving nonreciprocal thermal radiation with both wide-angle coverage and narrowband characteristics poses a fundamental yet challenging problem. In this work, we demonstrate a nonreciprocal thermal emitter that achieves both wide-angle and narrowband through a periodic structure composed of magneto-optical materials. With an external magnetic field (B = 3 T or 1 T), the pronounced nonreciprocity arising from the magneto-optical localized resonance mode at 6.52 μm or 7.18 μm facilitates a distinct difference between the emissivity and absorptivity across a wide angular range from near 0°–89°. The robustness of the wide-angle and narrowband nonreciprocal thermal radiation is demonstrated with ±5 % fluctuations in structural parameters. The performance of the nonreciprocity with azimuthal angle ϕ ranging from 0° to 360° is also investigated. This work holds promising potential for applications in thermal management, directional thermal camouflage, high-efficiency thermophotovoltaic systems, and more.