A multifrequency narrow-band perfect absorber based on graphene metamaterial

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.