Diatomic terahertz metasurfaces for arbitrary-to-circular polarization conversion

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Polarization control is essential for manipulating light-matter interactions.
• Miniaturized terahertz (THz) devices require advanced control over arbitrarily polarized waves.
• Metasurfaces offer unprecedented capabilities for wave manipulation.

Purpose of the Study:

• To demonstrate an all-silicon metasurface for converting arbitrary polarization states to circular polarization in the THz band.
• To show controllable conversion intensities based on polarization evolution on the Poincaré sphere.
• To explore the potential of metasurfaces for chiral wavefront manipulation.

Main Methods:

• Utilized monolayer achiral meta-atoms for mutual interference.
• Investigated polarization conversion using the Poincaré sphere.
• Employed the geometric phase principle for chiral wavefront manipulation.

Main Results:

• Achieved conversion of arbitrary incident polarization to circular polarization in the THz band.
• Demonstrated controllable conversion intensities.
• Observed broadband circular dichroism (BCD) due to spin-selective interference.
• Experimentally verified theoretical derivations.

Conclusions:

• The proposed all-silicon metasurface offers a versatile platform for polarization control in the THz range.
• This ultrathin meta-platform can replace bulky optical components.
• Potential applications include chiral spectroscopy, imaging, and optical communication.