Observation of nonvanishing optical helicity in thermal radiation from symmetry-broken metasurfaces.

Wang, Xueji; Sentz, Tyler; Bharadwaj, Sathwik; Ray, Subir Kumar; Wang, Yifan; Jiao, Dan; Qi, Limei; Jacob, Zubin · Sci Adv · 2023

basic_science · Level V

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Abstract

Spinning thermal radiation is a unique phenomenon observed in condensed astronomical objects, including the Wolf-Rayet star EZ-CMa and the red degenerate star G99-47, due to the existence of strong magnetic fields. Here, by designing symmetry-broken metasurfaces, we demonstrate that spinning thermal radiation with a nonvanishing optical helicity can be realized even without applying a magnetic field. We design nonvanishing optical helicity by engineering a dispersionless band that emits omnidirectional spinning thermal radiation, where our design reaches 39% of the fundamental limit. Our results firmly suggest that metasurfaces can impart spin coherence in the incoherent radiation excited by thermal fluctuations. The symmetry-based design strategy also provides a general pathway for controlling thermal radiation in its temporal and spin coherence.