Electrically Controlled Exceptional Points in Intersubband Polaritonic Metasurfaces

The non-Hermitian physics underlying metasurfaces provides new opportunities for enhanced control over light-matter interactions. A metasurface acts as an open system, continuously exchanging or absorbing energy between the incident field and resonant nanostructures. At exceptional points (EPs), these systems undergo parity-time symmetry breaking, leading to complex scattering phenomena linked to optical singularities. EPs have predominantly been realized in passive systems, though they are highly sensitive to fabrication errors. To address these limitations, electrically controlled EPs using materials like graphene [1] or germanium [2] have been demonstrated in the terahertz regime. In this study, we present non-Hermitian degeneracies, specifically EPs, utilizing an electrically reconfigurable intersubband polaritonic metasurface. The metasurface integrates the electromagnetic modes of two orthogonal plasmonic resonators and Stark tuning of intersubband transitions (IST) by applying bias voltages to the MQW layer.