Harnessing Spectral Singularities in Non-Hermitian Cylindrical Structures

Abstract

Non-Hermitian systems characterized by suitable spatial distributions of gain and loss can exhibit "spectral singularities" in the form of zero-width resonances associated to real-frequency poles in the scattering operator. Here, we study this intriguing phenomenon in connection with cylindrical geometries, and explore possible applications to controlling and tailoring in unconventional ways the scattering response of sub-wavelength and wavelength-sized objects. Among the possible implications and applications, we illustrate the additional degrees of freedom available in the scattering-absorption-extinction tradeoff, and address the engineering of zero-forward-scattering, transverse scattering, and gain-controlled reconfigurability of the scattering pattern, also paying attention to stability issues. Our results may open up new vistas in active and reconfigurable nanophotonics platforms.

arXiv comment12 pages, 10 figures; some typos corrected

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• Spaser and Optical Amplification Conditions in Graphene-Coated Active Wires
• Lasing condition for trapped modes in subwavelength--wired PT--symmetric resonators
• Scattering by a collection of $\delta$-function point and parallel line defects in two dimensions
• Synthesizing quasi-bound states in the continuum in epsilon-near-zero layered materials