Generating multiple resonances in ultrathin silicon for highly selective THz biosensing

Abstract A technique is implemented for achieving the multiband terahertz (THz) absorption with high-quality factor in an absorber containing an ultrathin silicon resonator. The symmetrical perturbation is done in the silicon layer for obtaining the multiple multi-order electric and magnetic resonances. The proposed absorber structure provides the polarization insensitive absorption spectrum with ten absorption peaks out of which seven remain with the level of more than 90%. The ultranarrow absorption spectrum can be utilized in THz biosensing applications specially for the detection of breast cancer, malaria in blood and glucose in water. It offers highest sensitivity as 0.416 THz/thickness unit (TU) and 1.02 THz/refractive index unit (RIU) during analyte thickness and refractive index sensing, respectively. The proposed absorber can provide the high value of quality factor along with all other improved parameters like sensitivity and figure of merit. Moreover, graphene nano-rings can also be utilized for obtaining the controllability in the frequency response of the absorber.