Helicity-selective and spectrally tunable chiral thermal emissions

Area of Science:

• Photonics
• Metasurfaces
• Thermal Engineering

Background:

• Current thermal emitters have static responses, limiting applications in high-precision sensing.
• Nonlocal metasurfaces offer temporal and spatial coherence, and chirality in thermal emissions.

Purpose of the Study:

• To present an anisotropic thermal metasurface for helicity-switchable and wavelength-tunable circularly polarized coherent thermal emissions.
• To harness elevated temperatures for dynamic control of thermal emission properties.

Main Methods:

• Designed an anisotropic thermal metasurface featuring high-Q quasi-guided mode resonances with opposite chirality.
• Utilized temperature changes (250 K) to tune emission wavelength and switch helicity.
• Experimentally demonstrated control over emission circular dichroism and temporal coherence (Q > 150).

Main Results:

• Achieved helicity-switchable circularly polarized thermal emissions in the mid-infrared.
• Demonstrated wavelength tunability over ~100 nm via temperature variation.
• Obtained strong emission circular dichroism (>0.8) and high temporal coherence.

Conclusions:

• The developed thermal metasurface offers dynamic control over thermal emission polarization and wavelength.
• Simple geometric design allows for full polarization tailoring.
• This platform provides a compact, scalable solution for on-chip applications like circular dichroism spectroscopy for enantiomer identification.