Deep-Subwavelength Detection Using Exceptional Point in an Asymmetric Plasmonic Dipole Resonator

The singularity phenomena in non-Hermitian resonance systems, known as exceptional points (EPs), are widely used to enhance the frequency splitting signal for deep-subwavelength target detection. The reported EP states are usually implemented in electrically large resonators, and external scatterers employed inevitably introduces losses. Here, we propose an EP state based on dipole eigenmode in an asymmetric spoof localized surface plasmon (SLSP) resonator. The proposed EP state exhibits excellent sensing performance that is verified by detection of subwavelength metal scatterers with different diameters. The minimum detectable metal scatterer features a diameter of
$\lambda_{0}/135 (\lambda_{0}$
is the operating wavelength). This work provides a new route for implementing microwave EP states and further improves the sensing performance for deep-subwavelength target detection.