Tunable and enhanced optical activity in twisted graphene metasurface bilayers

Area of Science:

• Optics and Photonics
• Materials Science
• Condensed Matter Physics

Background:

• Optical activity is crucial for polarization optics, biosensing, and analytical chemistry.
• Graphene metasurfaces offer tunable optical properties for advanced applications.

Purpose of the Study:

• To theoretically investigate optical activity in twisted graphene metasurface bilayers (TGMBs).
• To explore the tunability of circular dichroism (CD) and other optical responses by adjusting physical parameters.
• To identify potential regimes for strong optical activity in stacked TGMBs.

Main Methods:

• Theoretical modeling of optical activity in TGMBs.
• Analysis of circular dichroism (CD), circular birefringence, and ellipticity spectra.
• Investigation of parameter influence: separation distance, applied voltage, and twist angle.

Main Results:

• Large circular dichroism (CD) values are tunable via physical parameters.
• Twist angle manipulation allows broadband control over CD, birefringence, and ellipticity spectra.
• Strong optical activity responses are predicted near specific near-zero regimes in stacked TGMBs.

Conclusions:

• Graphene metasurfaces exhibit tunable optical activity, controllable by physical parameters.
• The findings pave the way for developing tunable, compact, on-chip terahertz devices.
• Exploiting optical activity in TGMBs offers new possibilities for terahertz technology.