Bifunctional sensing based on an exceptional point with bilayer metasurfaces

Exceptional points (EPs), the critical phase transition points of non-Hermitian parity-time (PT) systems, exhibit many novel physical properties and associated applications, such as ultra-sensitive detection of perturbations. Here, a bilayer metasurface with two orthogonally oriented split-ring resonators (SRRs) is proposed and a phase transition of the eigenpolarization states is introduced via changing the conductivity of vanadium dioxide (VO2) patch integrated into the gap of one SRR. The metasurface possesses a passive PT symmetry and an EP in polarization space is observed at a certain conductivity of the VO2. Two sensing schemes with the metasurface are proposed to achieve high-sensitivity sensing of temperature and refractive index in the terahertz (THz) range. The metasurface is promising for applications in THz biosensing and polarization manipulation. (c) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

Automated summary

This study proposes a bilayer metasurface with orthogonally oriented split-ring resonators (SRRs), in which a phase transition of eigenpolarization states is introduced by changing the conductivity of vanadium dioxide (VO2) patch. The metasurface exhibits a passive parity-time (PT) symmetry, and an exceptional point (EP) in polarization space is observed at a certain conductivity of the VO2. Two sensing schemes using the metasurface are proposed for high-sensitivity sensing of temperature and refractive index in the terahertz (THz) range. The metasurface shows great potential for THz biosensing and polarization manipulation applications.