Photo-Excited Switchable Terahertz Metamaterial Polarization Converter/Absorber

Abstract

In this paper, a photo-excited switchable terahertz metamaterial (MM) polarization converter/absorber has been presented. The switchable structure comprises an orthogonal double split-ring resonator (ODSRR) and a metallic ground, separated by a dielectric spacer. The gaps of ODSRR are filled with semiconductor photoconductive silicon (Si), whose conductivity can be dynamically tuned by the incident pump beam with different power. From the simulated results, it can be observed that the proposed structure implements a wide polarization-conversion band in 2.01–2.56 THz with the conversion ratio of more than 90% and no pump beam power incident illuminating the structure, whereas two absorption peaks operate at 1.98 THz and 3.24 THz with the absorption rates of 70.5% and 94.2%, respectively, in the case of the maximum pump power. Equivalent circuit models are constructed for absorption states to provide physical insight into their operation. Meanwhile, the surface current distributions are also illustrated to explain the working principle. The simulated results show that this design has the advantage of the switchable performance afforded by semiconductor photoconductive Si, creating a path towards THz imaging, active switcher, etc.

Switchable metamaterials for broadband absorption and generation of vector beams

“…Although the ABS bandwidth of Song and Zhang [15] is better than the proposed MMs, its structure is relatively complex and only LPC is realized. Yu et al [16] realizes ABS and LPC with a relatively simple structure, but it only realizes dual-band ABS with an ABS peak under 90%, and its polarization conversion bandwidth…”

“…Although there are several methods that can generate THz vector beams, such as segmented half-wave plate [8] and photoconductive antennas with concentric electrodes [9], the exploration of new method, especially using MMs, to generate vector beams in THz region is still crucial to promoting the application of THz technology. In recent years, some devices based on MMs with ABS function and polarization conversion function have attracted researchers' interest [10][11][12][13][14][15][16]. However, these MMs only realize the functional switching between linear polarization conversion (LPC) and narrowband/broadband ABS, few people realize the combination of broadband ABS and vector beams generation.…”

Triple-Mode Switchable Terahertz Metamaterial Absorber with Tunable Absorption Characteristics

“…Metamaterial is an artificially synthesized electromagnetic material with periodic structure. Metamaterial devices attract significant global interest due to their strong responses to terahertz (THz) waves [1][2][3][4][5]. Since the first metamaterial perfect absorber was proposed by Landy in 2008 [6], many devices have been explored, including absorbers, switches, filters, and converters [7][8][9][10].…”