A compact highly sensitive refractive index sensor using a butterfly-shaped absorber for terahertz biomedical applications

In this work, the design and analysis of a butterfly-shaped perfect absorber is presented for Terahertz applications. The proposed absorber has compact dimensions of 16x16 mu m(2). It comprises three layers, a butterfly-shaped metallic patch on the uppermost layer, a middle layer of Teflon and a metallic ground plane at the bottom. The perfect narrow absorption peak is observed at 4.7 THz with an absorption value of 99%. The design exhibits a fourfold symmetry with a tolerance of 600 for an angle of incidence and is polarisation insensitive. Further, the designed butterfly-shaped absorber is used to sense the analyte with a refractive index ranging from 1 to 3.16 exhibiting an average sensitivity value of 786 GHz/RIU for fixed analyte thickness. The compact and unique design of the sensor enhances its sensing performance, indicating its potential for various applications such as biomedical sensing, hazardous substance detection, and disease diagnosis.