Tunable and switchable multifunctional terahertz meta-mirror based on graphene and vanadium dioxide

Area of Science:

• Metamaterials
• Terahertz (THz) Technology
• Optics and Photonics

Background:

• Terahertz (THz) technology requires advanced components for manipulating electromagnetic waves.
• Existing THz devices often lack multifunctionality and tunability.
• Polarization control is crucial for various THz applications like imaging and sensing.

Purpose of the Study:

• To design and demonstrate a multifunctional meta-mirror for THz applications.
• To integrate multiple polarization modulation functions into a single device.
• To achieve switchable polarization control using temperature and voltage stimuli.

Main Methods:

• Fabrication of a meta-mirror using two-layered graphene metasurfaces and a vanadium dioxide (VO2) layer on a gold substrate.
• Utilizing temperature control of the VO2 film and Fermi level adjustments of graphene for switching functions.
• Characterization of polarization conversion ratio (PCR), linear dichroism (LD), and circular dichroism (CD) across THz frequencies.

Main Results:

• Achieved switchable linear-to-linear polarization conversion with PCR > 0.9 (2.89-4.02 THz).
• Demonstrated switchable linear dichroism (LD) with a maximum value of 0.6 at 3.84 THz.
• Realized switchable linear-to-circular polarization conversion and circular dichroism (CD) with ellipticity > 0.9 (2.32-2.69 THz) and CD value of 0.71 at 2.45 THz.

Conclusions:

• The proposed meta-mirror is the first THz metamaterial device to integrate four switchable functions: linear-to-linear polarization conversion, linear-to-circular polarization conversion, linear dichroism, and circular dichroism.
• This multifunctional meta-mirror offers a promising design for compact system integration in THz imaging, sensing, and biological detection.
• The temperature and voltage tunability provides dynamic control over THz wave polarization.