Abstract
AbstractIn the past few years, concepts from non-Hermitian (NH) physics, originally developed within the context of quantum field theories, have been successfully deployed over a wide range of physical settings where wave dynamics are known to play a key role. In optics, a special class of NH Hamiltonians – which respects parity-time symmetry – has been intensely pursued along several fronts. What makes this family of systems so intriguing is the prospect of phase transitions and NH singularities that can in turn lead to a plethora of counterintuitive phenomena. Quite recently, these ideas have permeated several other fields of science and technology in a quest to achieve new behaviors and functionalities in nonconservative environments that would have otherwise been impossible in standard Hermitian arrangements. Here, we provide an overview of recent advancements in these emerging fields, with emphasis on photonic NH platforms, exceptional point dynamics, and the very promising interplay between non-Hermiticity and topological physics.
Highlights
Quantum mechanics dictates that every observable should be described by means of a self-adjoint or Hermitian operator
Optical PT symmetry can be readily established by judiciously distributing the gain and loss in such a way that the refractive index profile is an even function of position while the optical gain/loss emerges as an odd function in the spatial coordinates. These early studies incited a flurry of research activities in many and diverse fields such as microwaves [11], electronics [12], mechanics [13], optomechanics [14, 15], acoustics [16, 17], atomic lattices [18,19,20], etc., all aiming to harness the very characteristics of PT symmetry and exceptional points (EPs)
We discussed how various optical platforms exhibiting gain and loss can be utilized to investigate different aspects associated with PT symmetry and NH phenomena
Summary
Quantum mechanics dictates that every observable should be described by means of a self-adjoint or Hermitian operator. Optical PT symmetry can be readily established by judiciously distributing the gain and loss in such a way that the refractive index profile is an even function of position while the optical gain/loss emerges as an odd function in the spatial coordinates These early studies incited a flurry of research activities in many and diverse fields such as microwaves [11], electronics [12], mechanics [13], optomechanics [14, 15], acoustics [16, 17], atomic lattices [18,19,20], etc., all aiming to harness the very characteristics of PT symmetry and EPs. A distinctive feature of optical arrangements is the possibility of controlling both the real and imaginary parts of the electromagnetic permittivity in an independent manner, without being over-restricted by the Kramers– Kronig relations.
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