Tunable small-angle nonreciprocal radiation and broadband absorption in a GST–Weyl semimetal resonant structure

Abstract

Nonreciprocal radiation is essential for advanced thermal photonics but is constrained by static performance and large incident angle requirements in current Weyl semimetal (WSM)-based devices. Here, we propose a WSM–Ge2Sb2Te5 (GST) hybrid resonant structure to achieve thermally tunable dual functionality. When GST is amorphous, the structure exhibits strong small-angle (5°) nonreciprocal radiation at 14.09 μm, with a nonreciprocity coefficient of up to 0.95, driven by coupled guided-mode and Fabry–Pérot resonances. Upon annealing, GST transforms to the crystalline state, enabling broadband high absorption across 12–15 μm with reciprocal behavior. Structural parameters modulate the resonant wavelength by adjusting the effective refractive index or optical path, while GST crystallinity significantly regulates nonreciprocal performance. This non-volatile design overcomes key limitations of static nonreciprocal devices, holding promise for adaptive energy harvesting and intelligent electromagnetic protection.