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This study introduces a single-layer patterned graphene metamaterial, composed of a graphene ring (GR), two parallel graphene strips (TPGSs), two vertical graphene strips (TVGSs), and a graphene block (GB), which achieves triple plasmon-induced transparency (TPIT) in the terahertz (THz) frequency range using coupled mode theory (CMT) and the finite-difference time-domain (FDTD) technique. Moreover, a synchronized electro-optical switch with four modulation modes is implemented by dynamically adjusting graphene's Fermi level, exhibiting modulation degrees of amplitude (MDA) of 88.3%, 94.7%, 86.9%, and 89.0% at 1.69 THz, 3.14 THz, 3.95 THz, and 4.67 THz, respectively. In addition, the modes excited by TPGSs and TVGSs interconvert due to the proposed structure's symmetry, accounting for the polarization insensitivity of TPIT. The enhanced MDA and polarization insensitivity of the electro-optical switch presented in this study significantly surpass those of comparable electro-optical switches. As a result, the polarization insensitivity of multiple optical switches to incident light fields offers a promising approach for designing optoelectronic devices. [ABSTRACT FROM AUTHOR]

A monolayer metamaterial consisting of a rectangle graphene strip and four L-shaped graphene blocks was proposed to achieve a quintuple plasmon-induced transparency (quintuple-PIT). The numerical simulation results based on the finite difference time domain method agree well with the calculated results of the coupled mode theory. By modulating the Fermi energy level of graphene, an octuple-frequency asynchronous switch and a sextuple-frequency synchronous switch are designed and studied, which have excellent amplitude modulation degree (up to 97.7%), extinction ratio (up to 16.41 dB), insertion loss (low to 5.4%), and dephasing time(low to 3.86 ps). Furthermore, the results show that the proposed metamaterials has polarization-sensitive characteristics due to their non-central symmetry. Further research shows that the group index is as high as 604 which has a good slow light effect and can be used for optical storage. Hence, the quintuple-PIT proposed structure in this paper has good application value in the expansion of multi-function optical switches and the research of high-quality optical memory. [ABSTRACT FROM AUTHOR]

Double narrowband induced perfect absorption in the terahertz region is achieved in a graphene–dielectric–gold hybrid metamaterial, whose physical mechanism is analyzed using the coupled-mode theory (CMT), which agreed well with the finite-difference time-domain (FDTD) simulation. This study found that the Fermi level of graphene can be adjusted to improve the absorptivity when the refractive index (RI) nd of the chosen dielectric cannot achieve a good absorption effect. In addition, the blue shift of absorption spectrum can be used in the design of dual-frequency electro-optical switches, of which the modulation degree of amplitude (MDA) can reach as high as 94.05% and 93.41%, indicating that this is a very promising electro-optical switch. Most significantly, the RI sensing performance is investigated, which shows an ultra-high absorption sensitivity SA = 4.4°/RIU, wavelength sensitivity Sλ = 9.8°/RIU, and phase shift sensitivity Sφ = 2691°/RIU. At last, an interesting finding is that the two peaks (R1 and R2) of plasmon-induced absorption (PIA) show different polarization characteristics (insensitive or sensitive) to the incident light angle; this polarization-sensitive is particularly important for the PIT/PIA-based optical polarizers. Undoubtedly, this paper is of great significance to the research and design of terahertz photonic devices and sensors. [ABSTRACT FROM AUTHOR]

This article proposes a multifrequency narrow-band perfect absorber based on a single-layer graphene-patterned metamaterial, its absorption spectrum in the near-infrared (NIR) band is calculated by the finite-difference time-domain (FDTD) method. The absorption at 2120.5 nm, 2143 nm, 2216.5 nm, and 2325.5 nm, exhibit a high absorption rate of 99.993 %, 99.771 %, 93.004 %, and 99.179 %, respectively. The absorber's absorption spectra are studied with respect to various factors such as polarized light, graphene pattern, graphene Fermi energy and relaxation time, the refractive index of the dielectric layer, ambient refractive index, and angle of incidence. The study reveals that using graphene designs with constantly changing slopes (such as circular or elliptical) at the pattern boundaries generates more absorption peaks than other designs. Furthermore, a refractive index sensor can be developed based on the effect of the ambient refractive index on the absorber's range of absorption. The absorption peaks display quality figure of merit (FOM) values of 99.53, 85.16, 111.23, and 72.13, with sensitivities of 405, 425, 450, and 455 nm/RIU, respectively. The absorber has a high absorption sequence over a wide range of 0° to 65°, and it is insensitive to the angle of incidence of light from 0° to 65°. Due to its numerous wavelengths, high absorbance, polarization insensitivity, tuneability, and high FOM, the suggested absorber may find widespread application in NIR thermal radiation, optical detectors, and NIR sensors. [Display omitted] • Multi-frequency narrowband near-infrared (NIR) absorbers enable efficient absorption. High absorption peaks are located at 2120.5 nm, 2143 nm, 2216.5 nm, and 2325.5 nm. • The theoretical and physical mechanisms of high absorption by surface plasmon resonance (SPR) structures are discussed. • The highest quality figure of merit (FOM) value of the absorption peak reaches 111.23. • The designed absorber possesses the characteristics of an adjustable absorption peak wavelength and adjustable efficiency. • The absorber is insensitive to the polarization angle of the incident light source and is insensitive to a wide range of incidence angles (0°-65°). [ABSTRACT FROM AUTHOR]