Liquid Crystal-Based Programmable Meta surface for Terahertz Beam Manipulation

This manuscript presented the programmable metasurface based on LC (liquid crystal) material to manipulate the THz (terahertz) wave. To manipulate the EM (electromagnetic wave), the programmable and digital coding metasurfaces have been widely used in the microwave range using the semiconductor controlling elements (PIN diode and varactor diode). However, in the THz range, these semiconductor components have limited applications. Herein, a 1-bit digital programmable metasurface based on LC is proposed to achieve the THz wave manipulation with electrical control. The 1-bit digital coding metasurface is composed of two kinds of meta-atoms including "0" and "1" digital codes corresponding to the opposite reflection phase response "0" and "." respectively. The reflection phase of the metasurface element is nearly 1800 manipulating between biased (1) and unbiased (0) states of the coding sequence. When the different coding sequence is applied to the metasurface array, the phase profile between metasurface elements is changed dynamically and manipulate the incident THz beam. The proposed LC-based THz metasurface unit cell is applied with the different biasing voltages and in result the relative permittivity of the LC material is changed from 2.63 to 3.67 based on the orientation of the LC molecules. However, the resonant frequency is switching from 0.121 THz to 0.108 THz and achieved the 180 degree phase differences. Furthermore, 36x36 metasurface array is enabled to perform multi-functionalities including dual beam and multi-beam steering, beam splitting that could be implemented in the application of sensing, imaging, defence RCS (radar cross section) reduction and wireless communication such as RIS (Reconfigurable Intelligent Surfaces).