Exceptional points of degeneracy and -symmetry in photonic coupled chains of scatterers
arXiv:1610.00414 · doi:10.1103/PhysRevB.95.104305
Abstract
We demonstrate the existence of exceptional points of degeneracy (EPD) of periodic eigenstates in non-Hermitian coupled chains of dipolar scatterers. Guided modes supported by these structures can exhibit an EPD in their dispersion diagram at which two or more Bloch eigenstates coalesce, in both their eigenvectors and eigenvalues. We show a second-order modal EPD associated with the parity-time () symmetry condition, at which each particle pair in the double chain exhibits balanced gain and loss. Furthermore, we also demonstrate a fourth-order EPD occurring at the band edge. Such degeneracy condition was previously referred to as a degenerate band edge in lossless anisotropic photonic crystals. Here, we rigorously show it under the occurrence of gain and loss balance for a discrete guiding system. We identify a more general regime of gain and loss balance showing that -symmetry is not necessary to realize EPDs. Furthermore, we investigate the degree of detuning of the EPD when the geometrical symmetry or balanced condition is broken. These findings open unprecedented avenues toward superior light localization and transport with application to high-Q resonators utilized in sensors, filters, low-threshold switching and lasing.
12 pages, 13 figures
References in corpus (7)
- Unidirectional Nonlinear PT-symmetric Optical Structures
- Physical realization of -symmetric potential scattering in a planar slab waveguide
- Gain-Driven Discrete Breathers in PT-Symmetric Nonlinear Metamaterials
- Exceptional points and lasing self-termination in photonic molecules
- Coulomb analogy for nonhermitian degeneracies near quantum phase transitions
- Light transport in PT-invariant photonic structures with hidden symmetries
- Slow light with flat or offset band edges in multi-mode fiber with two gratings