Abstract
We introduce cascaded parity-time (PT)-symmetric artificial sheets (e.g. metasurfaces or frequency selective surfaces) that may exhibit multiple higher-order laser-absorber modes and bidirectional reflectionless transmission resonances within the PT-broken phase, as well as a unidirectional reflectionless transmission resonance associated with the exceptional point (EP). We derive the explicit expressions of the gain–loss parameter required for obtaining these modes and their intriguing physical properties. By exploiting the cascaded PT structures, the gain–loss threshold for the self-dual laser-absorber operation can be remarkably lowered, while the EP remains unaltered. We further study interferometric sensing based on such a multimodal laser-absorber and demonstrate that its sensitivity may be exceptionally high and proportional to the number of metasurfaces along the light propagation direction.
Highlights
Introduction cri ptPT-symmetry takes its roots from open quantum physics systems [1], where non-Hermitian Hamiltonians commute with parity and time reversal operators, and may exhibit real eigenvalues and eigenstates
For the sake of simplicity, we assume that metasurfaces have purely real surface conductances and zero surface susceptances associated with reactive or stored energy
We have introduced multimodal coherent perfect absorber-laser (CPAL) and Fabry-Perot transmission resonance (FPTR) devices based on ce cascaded PT-symmetric metasurfaces with scalar surface conductances
Summary
Introduction cri ptPT-symmetry (space-time reflection symmetry) takes its roots from open quantum physics systems [1], where non-Hermitian Hamiltonians commute with parity and time reversal operators, and may exhibit real eigenvalues and eigenstates. [10], a CPAL sensor made of a PT-symmetric pair of artificial electromagnetic sheets (e.g., active and passive metasurfaces) was studied, and limits of detection and sensitivity were derived.
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