Observation of Non-Vanishing Optical Helicity in Thermal Radiation from Symmetry-Broken Metasurfaces

TL;DR

This paper demonstrates that symmetry-broken metasurfaces can produce spinning thermal radiation with non-zero optical helicity without magnetic fields, enabling new control over thermal emission properties.

Contribution

The study introduces a novel metasurface design that achieves non-vanishing optical helicity in thermal radiation, expanding control over thermal emission beyond magnetic field effects.

Findings

Achieved 39% of the fundamental limit for optical helicity.

Demonstrated omnidirectional spinning thermal radiation.

Provided a general symmetry-based design strategy for thermal radiation control.

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 existence of strong magnetic fields. Here, by designing symmetry-broken metasurfaces, we demonstrate that spinning thermal radiation with a non-vanishing optical helicity can be realized even without applying a magnetic field. We design non-vanishing optical helicity by engineering a dispersionless band which emits omnidirectional spinning thermal radiation, where our design reaches 39% of the fundamental limit. Our results firmly suggest metasurfaces can impart spin coherence in the incoherent radiation excited by thermal fluctuations. The symmetry-based design strategy also provides a general pathway for comprehensively controlling thermal radiation in its temporal and spin coherence.