Metasurface Terahertz Perfect Absorber with Strong Multi-Frequency Selectivity

Abstract

In this paper, we design a metasurface terahertz perfect absorber with multi-frequency selectivity and good incident angle compatibility using a double-squared open ring structure. Simulations reveal five selective absorption peaks located at 0−1.2 THz with absorption 94.50% at 0.366 THz, 99.99% at 0.507 THz, 95.65% at 0.836 THz, 98.80% at 0.996 THz, and 86.70% at 1.101 THz, caused by two resonant absorptions within the fundamental unit (fundamental mode of resonance absorption, FRA) and its adjacent unit (supermodel of resonance absorption, SRA) in the structure, respectively, when the electric field of the electromagnetic wave is incident perpendicular to the opening. The strong frequency selectivity at 0.836 THz with a Q-factor of 167.20 and 0.996 THz with a Q-factor of 166.00 is due to the common effect of the FRA and SRA. Then, the effect of polarized electromagnetic wave modes (TE and TM modes) at different angles of incidence (θ) and the size of the open rings on the device performance is analyzed. We find that for the TM mode, the absorption of the resonance peak changes only slightly at θ = 0−80°, which explains this phenomenon. The frequency shift of the absorption peaks caused by the size change of the open rings is described reasonably by an equivalent RLC resonant circuit. Next, by adjusting two-dimensional materials and photosensitive semiconductor materials embedded in the unit structure, the designed metasurface absorber has excellent tunable modulation. The absorption modulation depth (MD) reaches ≈100% using the conductivity of photosensitive semiconductor silicon (σ SI-ps ), indicating excellent control of the absorption spectrum. Our results can greatly promote the absorption of terahertz waves, absorption spectrum tunability, and frequency selectivity of devices, which are useful in the applications such as resonators, biodetection, beam-controlled antennas, hyperspectral thermal imaging systems, and sensors.

Terahertz Metasurface Modulators Based on Photosensitive Silicon

“…By calculation, the skin depth of THz waves in metal materials remains essentially below 100 nm. [ 68 ] Therefore, $$T \approx 0$$, i.e., $$A \approx 1 - R$$. In the presence of electromagnetic waves, an electrical response (electric dipole resonance) exists in the upper surface structure of the modulator.…”

“…To the GaN‐HEMT‐based THz metasurface modulator has a high MD, the MR is approximately at GHz level, and it is more difficult to reach MHz, and it also has the problems of complicated process and high cost. [ 68 ] The graphene‐based metasurface THz modulation device designed in this section has both excellent MR and MD, which provides an important research idea for the development of high‐speed tunable THz functional devices.…”

“…By calculation, the skin depth of THz waves in metal materials remains essentially below 100 nm. [68] Therefore, T ≈ 0, i.e., A ≈ 1 − R. In the presence of electromagnetic waves, an electrical response (electric dipole resonance) exists in the upper surface structure of the modulator. The upper surface structure generates a reverse current with the underlying metal due to electromagnetic interaction, which causes a magnetic response (magnetic dipole resonance).…”

An electrical/thermal dual-controlled quad-functional terahertz metasurface absorber

“…Terahertz (THz) waves, with a frequency range of 0.1-10 THz, have attracted significant research interest due to their high permeability 1,2 and imaging resolution, 3,4 which makes them useful in a wide range of applications such as military search, 5,6 wireless communication, [7][8][9] and security inspection. 10,11 Perfect absorption of THz waves is important for THz detectors, 12 sensors, 13,14 and stealth applications, [15][16][17] so how to achieve efficient absorption of THz waves has emerged as a crucial area of research.…”

Tunable Wideband Cylindrical Dielectric Resonator Inspired Metasurface Absorber for Medical Sensing Applications

“…Graphene based structure achieved 98% of absorptivity at 0.53 and 1.53THz and metallic based structure achieved 98% of absorptivity at 7 and 25THz. Paper [27] proposes a THz metasurface absorber with multi-frequency selectivity (absorption 94.50% at 0.366THz, 99.99% at 0.507THz, 95.65% at 0.836THz, 98.80% at 0.996THz, and 86.70% at 1.101THz) and good incident angle compatibility property. It is useful in resonators, bio detection, beam-controlled antennas, hyper-spectral thermal imaging systems, and sensors as shown in Fig.…”