Tunneling of obliquely incident waves throughPT-symmetric epsilon-near-zero bilayers

Abstract

We show that obliquely-incident, transversely-magnetic-polarized plane waves can be totally transmitted (with zero reflection) through epsilon-near-zero (ENZ) bi-layers characterized by balanced loss and gain with parity-time (PT ) symmetry. This tunneling phenomenon is mediated by the excitation of a surface-wave localized at the interface separating the loss and gain regions. We determine the parameter configurations for which the phenomenon may occur and, in particular, the relationship between the incidence direction and the electrical thickness. We show that, below a critical threshold of gain and loss, there always exists a tunneling angle which, for moderately thick (wavelength-sized) structures, approaches a critical value dictated by the surface-wave phasematching condition. We also investigate the unidirectional character of the tunneling phenomenon, as well as the possible onset of spontaneous symmetry breaking, typical of PT -symmetric systems. Our results constitute an interesting example of a PT -symmetry-induced tunneling phenomenon, and may open up intriguing venues in the applications of ENZ materials featuring loss and gain.

Optical PT-Symmetric Counterparts of Ordinary Metals

“…Since metals can easily be shaped into thin planar sheets and active QD-enriched sheets can be deposited on them, the configuration of a bi-layer [42], [43], [44] (two successive layers of the same thickness d) fits well within our considerations. Therefore, we consider two layers positioned backto-back parallel to yz plane (normal to thex axis): one made of the considered metal of dielectric constant ε 1 and another made of the corresponding mixture (with dielectric constant ε 2 = ε * 1 ) of quantum dots (permittivity ε QD ) hosted in a suitable background medium (permittivity ε host ).…”

Wide-angle absorption of visible light from simple bilayers

“…Such a structure, despite its minimalistic nature, is extensively utilized to describe various effects, such as tunneling in epsilon-near-zero layers [22] and phase transition in parity-time symmetric slabs [23]. It is the simplest model that can capture the interaction between two adjacent components.…”

Simultaneous realization of a coherent perfect absorber and laser by zero-index media with both gain and loss

“…Since the real parts of both ε and μ are zero [22][23][24][25][26], we call such a unique type of electromagnetic medium as a zero-index medium with both gain and loss (ZIMGL). Interestingly, we find that the CPA laser can be achieved when |ε| = |μ|.…”