By means of critical coupling and impedance matching theory, we have numerically simulated the perfect absorption of monolayer graphene. Through the critical coupling effect and impedance matching, we studied a perfect single-band absorption of the monolayer graphene and obtained high quality factor (Q-factor = 664.2) absorption spectrum which has an absorbance close to 100% in the near infrared region. The position of the absorption spectrum can be adjusted by changing the ratio between the radii of the elliptic cylinder air hole and the structural period. The sensitivity of the absorber can be achieved S = 342.7 nm/RIU (RIU is the per refractive index unit) and FOM = 199.2 (FOM is the figure of merit), which has great potential for development on biosensors. We believe that our research will have good application prospects in graphene photonic devices and optoelectronic devices.

https://www.mdpi.com/2079-4991/10/1/95/pdf

High Quality Factor, High Sensitivity Metamaterial Graphene-Perfect Absorber Based on Critical Coupling Theory and Impedance Matching.

In this paper, we present a dual-band metamaterial absorber for graphene surface plasmon resonance at terahertz frequency. We use the finite difference time domain (FDTD) method to study the absorption characteristics of the homocentric graphene ring and disk nanostructure. These simulation results show that the change of the geometrical parameters and the substrate thickness of the nanostructure can change the absorption characteristics and the emergence of dual-band absorption peaks. Moreover, we study the field distribution of nanodisks with different radius in detail. By changing the Fermi level of graphene, the wavelength of their absorption peaks can be adjusted flexibly. In addition, the proposed dual-band absorber also shows a good angle tolerance for both TE and TM polarizations. By calculation the surface-filled water (n = 1.332) and 25% aqueous glucose solution (n = 1.372) for the metamaterial absorber, the sensitivities of mode I and mode II are 5.0 μm/RIU and 15.0 μm/RIU. These research results will have broad application prospects for sensing and spatial light modulators.

A dual-band metamaterial absorber for graphene surface plasmon resonance at terahertz frequency

In this paper, a triple-band perfect metamaterial absorber based on Cu-dielectric-Cu triple-layer nanostructure is reported. The top metal film structure consists of a ring and four pairs of capacitor plates, which has a frequency selection effect, allowing the absorber to resonate in the near infrared range. Theoretical study shows that the absorption of the three absorption peaks (872.54 nm, 1008.69 nm and 1138.62 nm) are 87.1%, 99.9% and 99.6%, respectively. The average absorption is 95.53%, including two perfect absorption peaks. Changing the structural parameters can affect its absorption peaks and resonant wavelengths. At the same time, due to the high symmetry of the absorber, it is not sensitive to the polarization angle and incident angle. Whether in the TE mode or the TM mode, the absorber at a wide incident angle (0-60°) also exhibits good operating angle polarization tolerance. Therefore, the perfect metamaterial absorber we designed can be widely used in sensing.

Triple-band perfect metamaterial absorber with good operating angle polarization tolerance based on split ring arrays

In this paper, we propose a graphene nanoribbon-ring cross structure. A multi-band absorber is obtained by a simple combination of graphene nanoribbons and and graphene ring. We obtain that the theoretical absorption of three resonance wavelengths are 99.8%, 98.4% and 65.7%, respectively. We carefully analyzed each resonance wavelength, and the compact structure makes that small changes in the position of graphene nanoribbons and graphene ring have a great influence on the number of resonance wavelength. Meanwhile, the small changes in the chemical potential of graphene can tune the position of resonance wavelengths in the spectrum. At last, we discuss the sensing properties of this structure. The FoM (figure of merit) values of the three resonance wavelengths are high, and the FoM of the three peaks can reach 4.1, 3.679 and 12.66. The absorbers have great adjustability and great application potential in sensing.

Nanoribbon-ring cross perfect metamaterial graphene multi-band absorber in THz range and the sensing application

We demonstrate a dual-band plasmonic perfect absorber (PA) based on graphene metamaterials. Two absorption peaks (22.5 μm and 74.5 μm) with the maximal absorption of 99.4% and 99.9% have been achieved, respectively. We utilize this perfect absorber as a plasmonic sensor for refractive index (RI) sensing. It has the figure of merit (FOM) of 10.8 and 3.2, and sensitivities of about 5.6 and 17.2 μm/RIU, respectively. Hence, the designed dual-band PA-based RI sensor exhibits good sensing performance in the infrared regime, which offers great potential applications in various biomedical, tunable spectral detecting, environmental monitoring and medical diagnostics.

https://www.mdpi.com/2072-666X/10/7/443/pdf

Dual-Band Plasmonic Perfect Absorber Based on Graphene Metamaterials for Refractive Index Sensing Application.

Dual Fano resonance control and refractive index sensors based on a plasmonic waveguide-coupled resonator system

A plasmonic waveguide coupled system that is composed of a square ring cavity and a metal–insulator–metal (MIM) waveguide with two silver baffles is proposed. The transmission and reflection properties of the proposed plasmonic system are investigated numerically using the finite element method. The normalized Hz field distributions are calculated to analyze the transmission mode in the plasmonic system. The extreme destructive interference between light mode and dark mode causes plasmonically induced reflection (PIR) window in the transmission spectrum. The PIR window is fitted using the coupled mode theory. The analytical result agrees with the simulation result approximately. In addition, the PIR window can be controlled by adjusting structural parameters and filling different dielectric into the MIM waveguide and the square ring cavity. The results provide a new approach to designing plasmonic devices.

https://iopscience.iop.org/article/10.1088/1674-1056/26/12/124212/pdf

Lian-Jun Ma

Papers

Dual Fano resonance control and refractive index sensors based on a plasmonic waveguide-coupled resonator system

Plasmonically induced reflection in metal-insulator-metal waveguides with two silver baffles coupled square ring resonator *