# Tunable Chiral Terahertz Wave Absorption and Beam Manipulation Based on Vanadium Dioxide Metasurfaces

## TL;DR

This paper presents a tunable chiral metasurface using vanadium dioxide to control terahertz wave absorption and beam direction, enabling dynamic manipulation of circular polarization.

## Contribution

A novel chiral phase encoding strategy using VO2 metasurfaces for simultaneous absorption and beam shaping of terahertz waves.

## Key findings

- VO2-based metasurfaces enable CD tuning from 0.06 to 0.95 by adjusting conductivity.
- LCP waves are deflected while RCP waves are absorbed, enabling controllable beam manipulation.
- The design offers a compact solution for reconfigurable terahertz applications.

## Abstract

Chiral metasurfaces exhibit enormous potential in optical applications, and their integration with phase-change material vanadium dioxide (VO2) provides a novel pathway for dynamic regulation. In this study, a chiral absorptive metasurface based on VO2 is designed. By tuning the VO2 conductivity around the operating frequency of 2.81 THz, the circular dichroism (CD) can be continuously adjusted from 0.06 to 0.95, realizing a high-contrast chiral switch. On this basis, the Pancharatnam–Berry (PB) phase is introduced to construct a chirality-dependent phase gradient: when the VO2 conductivity is 200,000 S/m, only the left-handed circularly polarized (LCP) wave is subjected to periodic phase modulation, enabling controllable deflection of the reflected beam, while the right-handed circularly polarized (RCP) wave is selectively absorbed. This “chiral phase encoding” strategy simultaneously achieves absorptive CD tuning and reflective beam shaping on a single metasurface, significantly enhancing the flexible manipulation capability of circular polarization states in the terahertz band. It provides a compact and efficient solution for reconfigurable imaging, unidirectional communication, and integrated photonics systems.