Omnidirectional Circularly Polarized Thermal Radiation Enabled by Chiral Metasurface

Recently, thermal chiral metasurfaces have attracted significant attentions due to their remarkable ability to manipulate thermal radiation, finding broad applications in chiral imaging, and holographic technologies. However, the design of symmetry‐broken structures with both high circular dichroism (CD) and practical manufacturability remains challenging. This work reports a mid‐infrared (MIR) chiral metasurface with spin‐selective absorption, achieving near‐unity left‐handed circular polarization emissivity at 5.77 μm induced by localized resonance enhancement, which is more than eight times higher than that in the opposite polarization, corresponding to a high CD of 0.84. Momentum‐space analysis of angular emissivity spectra demonstrate that the proposed metasurface achieves a high circular polarization response across wide angular range, and the net optical helicity reaches 54% of the fundamental limit. The experimentally measured absorptivity spectrum and thermal images further prove that the proposed metasurface can function directly as a compact wide‐angle MIR thermal emitter, opening avenues for high‐performance on‐chip sensing and imaging applications.