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Spectral singularities appearing in parity-time (PT)-symmetric non-Hermitian optical systems have aroused a growing interest due to their new exhilarating applications, such as bifurcation effects at exceptional points and the coexistence of coherent perfect absorber and laser (so-called CPAL point). We introduce here how the concept of CPAL action provoked inPT-symmetric metasurfaces can be translated into practical implementation of a low-loss zero/low-index open channel supporting a nearly undamped fast-wave propagation. Such aPT-synthetic metachannel shows the capability to produce a high-directivity leaky radiation, with a tunable beam angle that depends on the gain-loss parameter. The proposed structure may enable new kinds of super-directivity antennas, as well as many applications that demand extreme dielectric properties, such as epsilon-near-zero (ENZ).
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Cascaded PT-symmetric artificial sheets: multimodal manipulation of self-dual emitter-absorber singularities, and unidirectional and bidirectional reflectionless transparencies
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.
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- Award ID(s):
- 1917678
- PAR ID:
- 10304577
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Journal of Physics D: Applied Physics
- Volume:
- 55
- Issue:
- 8
- ISSN:
- 0022-3727
- Page Range / eLocation ID:
- Article No. 085301
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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