High sensitivity microsensor assisted by Fano resonance in InSb based terahertz plasmonic waveguide

Abstract

We propose a compact terahertz plasmonic structure comprising an InSb-dielectric-InSb waveguide side-coupled with two stub resonators. Due to the coherent interference of the splitting discrete and quasi-continuum modes, the reflection spectrum possesses a sharp asymmetric Fano resonance dip, which stems from the phase difference between the two stub resonators. Owing to the permittivity temperature dependent property of InSb, the Fano resonance dip can be actively controlled by tuning temperature. The physical features contribute to a highly efficient plasmonic sensor for both refractive index and temperature sensing. The microsensor yields a sensitivity of ~2.9 THz/RIU and 1.8 × 10-3 THz/°C. This multiparameter high sensitivity microsensor may find important applications in medical sensing, biosensing and on-chip sensing working in terahertz region.