Asymmetric and nonreciprocal thermal radiation with tailored angular range in width-perturbation nonlocal gratings

Precise manipulation of directional thermal emission is crucial for advanced thermal management and energy conversion systems. However, traditional periodic structures suffer from inherent symmetry limitations, restricting the spatial freedom of thermal emission control in both reciprocal and nonreciprocal systems. Herein, we extend the asymmetric thermal emission from reciprocal to nonreciprocal systems using magneto-optical asymmetric (nonlocal) nano-gratings to further decouple the correlation between absorptivity and emissivity. In reciprocal systems, designed supercell with gradient grating width achieve asymmetric thermal emission and the dispersion can be flexibly tuned through coupled mode theory. Extended to nonreciprocal system, a novel unidirectional nonreciprocal effect is further induced by the asymmetric supercell. A highly responsive unidirectional nonreciprocal thermal radiation with a tunable and quantitative angular range through high-order diffraction can be achieved. This work provides a viable strategy for novel and high-precision directional nonreciprocal thermal emission control, promising applications in advanced energy harvesting.