Vanadium dioxide-assisted broadband absorption and linear-to-circular polarization conversion based on a single metasurface design for the terahertz wave

Abstract

Integrating tunable characteristics and multiple functions into a single metasurface has become a new scientific and technological undertaking that needs to deal with huge challenges, especially in the terahertz frequency region. The multifunctional design combining the broadband absorption and broadband polarization conversion using a single switchable metasurface is proposed in this paper. The switchable performance can be realized by treating the insulation to metal phase transition properties of vanadium dioxide (VO2). At high temperature (74 °C), the proposed metasurface can be used as a broadband absorber which consists of a VO2 square ring, polyimide (PI) spacer, and VO2 film. Simulated results show that the terahertz wave absorption can reach above 90% with the bandwidth ratio of 75% in the frequency range of 0.74 THz-1.62 THz. This absorber is insensitive to polarization resulted from the symmetry structure and also shows a good performance at large incident angles. Once the temperature is lower than the cooling phase transition temperature (about 62 °C) and VO2 is in insulation state, the metasurface can be transformed into a broadband linear-to-circular polarization converter. Numerical simulation depicts that the ellipticity reaches to -1 and the axis ratio is lower than 3 dB from 1.47 THz to 2.27 THz. The designed switchable metasurface provides the potential to be used in the fields of advanced research and intelligent applications in the terahertz frequency region.

A VO2 film-based multifunctional metasurface in the terahertz band

“…We can get the Stokes parameters as follows [25,41] : (n is an integer) are satisfied simultaneously, the perfect linear-to-circular polarization conversion can be achieved. The normalized ellipticity is defined as χ = V I to characterize the polarization conversion performance of the designed structure, where χ = 1 and χ = −1 indicate the perfect LCP and RCP waves [42][43][44] .…”

Tunable and switchable multi-functional terahertz metamaterials based on a hybrid vanadium dioxide–graphene integrated configuration

“…29,30 Over the last few decades, a variety of elaborate structures based on graphene or VO 2 have been presented to obtain tunable functions. [31][32][33][34][35][36] For example, Y. Huang et al proposed a graphene-based metamaterial with dual functionality of both the circular polarization conversion and AT effect in the terahertz region. 37 Zhang et al proposed a broadband terahertz polarization converter, in which the quarter-wave plate and half-wave plate can be electrically modulated by altering the Fermi energy of graphene.…”

A Thermally Switchable Bifunctional Metasurface for Broadband Polarization Conversion and Absorption Based on Phase‐Change Material

“…Li et al also adopted this design idea to realize the conversion between a broadband absorber and broadband polarization converter. [ 30 ] And, He et al realized the transformation of these two functions without using such a complex structural design. [ 31 ] However, its performance is slightly inferior to those of the previous two articles.…”

“…Li et al also adopted this design idea to realize the conversion between a broadband absorber and broadband polarization converter. [30]…”