Universal polarization terahertz phase controllers using randomly aligned liquid crystal cells with graphene...

Area of Science:

• Optics and Photonics
• Materials Science
• Condensed Matter Physics

Background:

• Terahertz (THz) technology requires efficient polarization control components.
• Liquid crystal (LC) devices offer tunable optical properties but often require complex alignment.
• Graphene's unique electronic and optical properties present opportunities for novel device fabrication.

Purpose of the Study:

• To develop a universal polarization terahertz phase controller.
• To investigate the THz wave interaction with randomly aligned liquid crystals and graphene electrodes.
• To demonstrate voltage-tunable phase control in the THz regime.

Main Methods:

• Fabrication of a liquid crystal cell with graphene electrodes on quartz substrates.
• Utilizing a randomly aligned nematic liquid crystal without specific surface treatments.
• Employing terahertz time-domain spectroscopy (THz-TDS) to measure complex transmittance.
• Applying alternating voltage to the liquid crystal cell via graphene layers.

Main Results:

• The randomly aligned LC cell exhibited high transparency in the THz frequency range.
• Applied voltage eliminated random domain textures and significantly reduced scattering loss.
• Demonstrated voltage-controlled terahertz phase shift, consistent with LC refractive indices.
• Observed minimal change in transmittance with applied voltage, indicating low scattering.

Conclusions:

• Randomly aligned LC cells with graphene electrodes are effective for THz phase control.
• The proposed device offers a universal solution for polarization control in the THz spectrum.
• Graphene electrodes facilitate efficient voltage modulation and minimize scattering losses in THz applications.