Multi-band, tunable, high figure of merit, high sensitivity single-layer patterned graphene—Perfect absorber based on surface plasmon resonance

This paper propose a perfect absorber with multi-band, adjustable, high figure of merit (FOM) and high sensitivity is based on single-layer patterned graphene surface plasmon resonance (SPR). The wave absorber is composed of a patterned graphene structure etched in a circular shape in the middle and a bottom metal film separated by a SiO2 dielectric layer. It has simple structural features and can greatly simplify the manufacturing process. In the mid-infrared band of 3 μm ~ 5 μm, the numerical results of FDTD method show that the absorbers have three perfect absorption peaks, which are λ1 = 3275.31 nm, λ2 = 3706.12 nm and λ3 = 4481.76 nm, respectively. The absorption rates are 99.44%, 98.22% and 99.10%, respectively. The resonant wavelength of the absorber can be tuned by controlling the Fermi energy level and relaxation time of the graphene layer. In addition, the wave absorber is insensitive to polarization and can keep high absorption in a wide range of incident angles from 0° to 50°. At last, we explore the sensitivity and FOM of the absorber by changing the environmental refractive index. The results show that the sensitivity of its three resonance absorption peaks is 666.75 nm/RIU, 760.50 nm/RIU and 907.88 nm/RIU (RIU is the per refractive index unit), and the FOM is 86.82, 53.03 and 56.14, respectively. Therefore, we believe that the absorber can be used in the fields of narrow-band thermal radiation, narrow-band light detection and narrow-band sensor.