Triple-band metamaterial perfect absorber for refractive index sensing in THz frequency

Abstract

A triple-band metamaterial perfect absorber (MPA) is founded of monolayer graphene in THz region which is adjustable and polarization-independent is presented. The first layer of the structure from top contains of a graphene ring at the center of structure with four graphene wheel-shaped around it and four graphene triangles in the corner. This proposed structure has caused us to achieve 98.64%, 99.97% and 99.98% perfect absorptions peaks at 8.17 THz, 9.74 THz and 11.95 THz, respectively. We can vary the absorption peak frequencies to our desirable frequencies by changing the Fermi level of graphene. By tunining the incident angle waves up to 60 degrees, the frequency peaks and the value of absorption change slightly. Moreover, very significant matter about suggested absorber structure design is that it is polarization independent so by tuning the polarization angle, the frequency peaks and the value of absorption remain unchanged. These aspects make the suggested absorber proper for applications such as imaging, detecting, filtering and sensing. We have investigated the application of the MPA in the sensing of refractive index. The refractive index of the unknown material can be measured through shifts of frequency peaks. Based on the obtained results, it seems that the metamaterial perfect absorber is a good candidate for biosensors application.