Angle enhanced circular dichroism in bilayer 90°-twisted metamaterial

Area of Science:

• Metamaterials
• Plasmonics
• Optics

Background:

• Chiral responses in metamaterials are crucial for polarization control.
• The interplay between intrinsic and extrinsic chirality is not well understood.
• Asymmetrically split aperture dimers offer a platform to investigate chiral responses.

Purpose of the Study:

• To demonstrate and analyze angle-enhanced chiral dichroism in metamaterials.
• To investigate the separation of intrinsic and extrinsic chiral responses.
• To enable independent utilization of intrinsic and extrinsic chirality for light manipulation.

Main Methods:

• Numerical simulations and experimental fabrication of metamaterials with asymmetrically split aperture dimers.
• Characterization of circular dichroism spectra at normal and oblique incidence.
• Analysis of chiral dichroism spectra at positive and negative incident angles.

Main Results:

• Metamaterial exhibits triple-band resonant circular dichroism at normal incidence.
• Oblique incidence leads to giant enhancement of circular dichroism at low frequencies.
• Resonance splitting of circular dichroism observed at high frequencies.
• Asymmetry in circular dichroism spectra at positive and negative angles confirms intrinsic chirality.
• Method developed to isolate intrinsic chirality by superimposing spectra.

Conclusions:

• The study successfully demonstrates angle-enhanced chiral dichroism and separates intrinsic from extrinsic chirality.
• The developed metamaterial shows potential for enhanced chiral responses and independent control of polarization states.
• This work provides a pathway for individually investigating and utilizing intrinsic and extrinsic chiral properties in metamaterials.