Ultra-sensitive singular-phase terahertz refractive index biosensor using graphene aided Tamm plasmonic resonance and variable angle ellipsometry

This study introduces, for the first time, to our knowledge, the development of an ultra-sensitive singular-phase refractive index biosensor based on a graphene Tamm plasmonic structure, operating at terahertz frequencies. A significant phase change occurs at the phase singularity or dark points, where surface reflection is nearly absent. Previous studies exploiting phase singularity points have involved complex techniques such as nanopatterning or integrating devices like gratings. Tamm plasmonic structures using noble metals, operating at visible light, have been studied before. The proposed structure simplifies the design by using a multilayer geometry and enhances the sensitivity using a stack of multilayer graphene, operating at 1 THz, achieving a remarkable sensitivity of 1.36×10 6∘ /RIU in the gaseous phase, surpassing previous studies. In the liquid phase, a sensitivity of 1.05×10 5∘ /RIU is obtained, which is higher than previous results. Such large sensitivity values are achieved by exploiting phase singularity concepts along with variable angle ellipsometry. The results are obtained using a fast and accurate transfer matrix method.