Metasurface for multi-channel terahertz beam splitters and polarization rotators

Abstract

Terahertz beam splitters and polarization rotators are two typical devices with wide applications ranging from terahertz communication to system integration. However, they are faced with severe challenges in manipulating THz waves in multiple channels, which is desirable for system integration and device miniaturization. Here, we propose a method to design ultra-thin multi-channel THz beam splitters and polarization rotators simultaneously. The reflected beams are divided into four beams with nearly the same density under illumination of linear-polarized THz waves, while the polarization of reflected beams in each channel is modulated with a rotation angle or invariable with respect to the incident THz waves, leading to the multi-channel polarization rotator (multiple polarization rotation in the reflective channels) and beam splitter, respectively. Reflective metasurfaces, created by patterning metal-rods with different orientations on a polyimide film, were fabricated and measured to demonstrate these characteristics. The proposed approach provides an efficient way of controlling polarization of THz waves in various channels, which significantly simplifies THz functional devices and the experimental system.

Polarization‐Insensitive Metalens with Extended Focal Depth and Longitudinal High‐Tolerance Imaging

“…However, the phase profiles for both RM‐ and AM‐based lenses should continuously vary from 0 to 2π, indicating that the curvature surface of the designed element must smoothly vary to yield the desired phase, resulting in extreme difficulty in fabrication. Optical metasurfaces, the 2D counterparts of metamaterials, have opened up new avenues in manipulating the phase, amplitude, and polarization of light at subwavelength resolution. Benefiting from the unprecedented ability to manipulate the electromagnetic wavefront and ease of fabrication, a plethora of metalenses, such as dual‐polarity plasmonic metalenses, multifoci lenses, multifunctional metalenses, broadband achromatic metalenses, and metalens arrays, with novel functions that are challenging to achieve by using traditional lenses have been proposed and realized.…”

Terahertz Metasurfaces: Toward Multifunctional and Programmable Wave Manipulation

“…Although the significant feature of the passive metasurface is its fixed structure, functional multiplexing can still be achieved. Multifunctional passive metasurfaces can be divided into frequency multiplexing metasurfaces [31,32] and polarization multiplexing metasurfaces [33][34][35][36][37][38].…”

“…Furthermore, there are many circumstances belonging to polarization multiplexing. To our knowledge, two principles are commonly employed to design polarization multiplexed metasurfaces, one is Pancharatnam-Berry (PB) phase [33][34][35][36][37] and the other is anisotropy [38]. PB phase can be realized by rotating metasurface unit cell structures, such as the C-shaped structure and rod-shaped structure aforementioned, and there exist a specific relationship between the orientation angle and the PB phase.…”

Terahertz Beam Splitter Based on I-Shaped Metasurface

“…Working frequency Beam number Exit angle Gao et al [16] 0.8-2.0 THz variable invariable Headland et al [17] 1 THz 2 variable Wei et al [18] 0.6-1.0 THz 2 variable Lee et al [19] 0.58-1.00 THz 2 variable Yi et al [20] 0.22-0.30 THz 2 invariable Zhang et al [21] 0.8 ∼ 1. to [17][18][19][20][21][22][23].…”

“…Using the metasurface, the terahertz wave is reflectively divided into two waves in the band of 0.22-0.30 THz, and their deflection angle can be effectively controlled, and this device can be applied as beam splitters in low-cost and compact terahertz imaging systems. In 2018, Zhang et al [21] designed a reflective terahertz metasurface beam splitter. The metasurface is formed by metal rods in different directions on polyimide film.…”