Optically tunable terahertz chiral metasurface based on multi-layered graphene.

Area of Science:

• Optics and Photonics
• Materials Science
• Terahertz Technology

Background:

• Active polarization control at terahertz frequencies is vital for spectroscopy and imaging.
• Natural materials offer limited polarization manipulation, necessitating advanced solutions like chiral metamaterials.
• Developing dynamically tunable terahertz chiral metamaterials remains a significant challenge.

Purpose of the Study:

• To demonstrate a terahertz metasurface capable of dynamic polarization modulation.
• To investigate the use of multi-layered graphene (MLG) integrated with conjugated resonators for tunable chiroptical response.
• To explore optical pumping as a method for active control of terahertz polarization states.

Main Methods:

• Fabrication of a terahertz metasurface composed of four conjugated "petal" resonators integrated with MLG.
• Optical pumping using a 980 nm continuous wave (CW) laser to induce changes in the metasurface's optical properties.
• Analysis using temporal coupled-mode theory to understand the influence of optical pumping on resonance modes and chiroptical response.

Main Results:

• The proposed metasurface exhibits a dynamically tunable chiroptical response under optical pumping.
• An ellipticity angle change of 20° was observed around 0.76 THz.
• Optical pumping significantly influences the loss parameters of resonance modes, enabling active control.

Conclusions:

• The MLG-based terahertz metasurface offers a promising platform for active polarization manipulation.
• This work provides a pathway towards realizing fundamental terahertz components with dynamic polarization control capabilities.
• The findings have implications for advanced terahertz spectroscopy, sensing, and communication applications.