Free‐Standing Single‐Layer Metasurface for Efficient and Broadband Tailoring of Terahertz Wavefront

Abstract

During the past decade, metasurfaces have provided a versatile platform for controlling the amplitude, phase, and polarization of electromagnetic waves, thus showing great potential for developing compact photonic devices. However, compact and broadband terahertz (THz) components are still scarce for high‐speed communication and spectroscopy analysis. Here, a free‐standing metasurface is designed to realize broadband and efficient wavefront manipulation in the THz regime. The proposed metasurface consists of a single patterned metallic layer on an ultra‐thin flexible substrate. The full‐span phase control of circularly cross‐polarized waves can be achieved based on the Pancharatnam‐Berry phase mechanism only by spatially varying the element orientation. Besides, it can operate in a broadband range of 0.35–1.21 THz (relative bandwidth of 111%), with the efficiency approaching the theoretical limit of the ultra‐thin single‐layer metasurface. It is demonstrated that the free‐standing metasurface can be used for numerous applications, including but not limited to THz beam steering, focusing, and vortex generation. The broadband performances allow the pulsed spectral imaging system to record the evolution process of broadband vortex beam in real‐time. The proposed metasurface may trigger many exciting opportunities in THz wireless communication, medicine, and spectroscopy applications.

Multifunctional beam modulation based on gratings combined with additive metasurfaces

“…Figure 1(a) shows the Metal-Dielectric-Metal element structure consisting of an Ag rectangular antenna and a very thin Ag film, which were separated by a SiO 2 dielectric layer. According to the acquired data from Johnson and Christy [19], the dielectric constant of silver (Ag) can be obtained from equation (1),…”

Ultrathin and Ultra‐Broadband Terahertz Single‐Layer Metasurface Based on Double‐Arrow‐Shaped Resonator Structure for Full‐Space Wavefront Manipulation

“…Figure 1a,b describe the front and perspective view of the MS unit-cell, respectively. In this design, the metal CCP structure is mainly used to effectively weaken the coupling between the MS unit-cells [34,44] . The metal DASR structure has a typical anisotropy, which enables the lack of structural mirror, revealing a remarkable mirror symmetry breaking.…”

Broadband circular polarization conversion metasurface with half-transmission and half-reflection simultaneously for full-space wavefront manipulation application

“…Figures 1(a,b) present the front and perspective views of the unit-cell structure of the proposed single layer MS. Similarly to the previous design of the MSs [34,[38][39][40], the S-shaped structure can behave as a dipole resonator and couples an electric component of the incident EM wave and generate a partial polarization conversion in a broadband range. In addition, as shown in Fig.…”

“…To improve the utilization e ciency of space resources, full-space MSs for both transmission and re ection are highly desirable [30][31][32][33]. As a result, the raised attention and great efforts have been devoted to manipulate the re ected and transmitted EM waves simultaneously or independently [34][35][36][37][38][39][40][41]. For instance, Cai et al, proposed a new type of MS with polarization-dependent re ection and transmission properties, which can manipulate full-space EM waves [32].…”