Magnetically tunable room-temperature 2 pi liquid crystal terahertz phase shifter

Area of Science:

• Terahertz (THz) technology
• Materials science
• Optics and photonics

Background:

• Liquid crystals (LCs) offer tunable optical properties.
• Achieving large phase shifts in the THz range is challenging.
• Existing THz phase shifters often lack continuous tunability or broad operational bandwidth.

Purpose of the Study:

• To demonstrate a liquid crystal device capable of a 360-degree tunable phase shift at 1 THz.
• To investigate the use of nematic LCs and magnetic field alignment for THz phase modulation.
• To develop a robust and broadly operational THz phase shifter.

Main Methods:

• Utilized a nematic liquid crystal (E7) with a birefringence of ~0.17 across 0.2-1.2 THz.
• Designed a 3-mm thick LC cell with a sandwiched structure to maximize interaction length and minimize Fresnel losses.
• Employed a magnetic field for aligning the thick LC cell and enabling continuous phase tuning.

Main Results:

• Achieved a continuous phase shift from 0 to 360 degrees at 1 THz.
• The LC device demonstrated effective performance over a broad frequency range near room temperature.
• The magnetic field alignment method proved successful in controlling the LC orientation for phase modulation.

Conclusions:

• A liquid crystal device can effectively achieve a full 360-degree tunable phase shift at 1 THz.
• The combination of a thick LC cell, specific nematic LC material, and magnetic field alignment is key to this performance.
• This THz phase shifter offers a promising solution for various applications requiring precise phase control in the terahertz spectrum.