Scattering properties ofPT- symmetric layered periodic structures

Abstract

The optical properties of PT-symmetric periodic stack of the layers with balanced loss and gain are examined. We demonstrate that tunnelling phenomenon in periodic structures is connected with excitation of surface waves at the boundaries separating gain and loss regions within each unit cell and tunnelling conditions for periodic stack can be reduced to the conditions for one period. Alternatively, it is shown that coherent perfect absorber laser states are mediated by excitation of surface modes localised at all internal boundaries of the structure. The effects of the structure parameters and angle and direction of incidence on the resonant phenomena and spontaneous symmetry breaking transition are determined. It is shown that structure periodicity significantly increases the number of resonant phenomena, especially in stacks with high real and imaginary parts of dielectric permittivity of the layers. Gaussian beam dynamics in this type of structure is examined. The beam splitting in PT-symmetric periodic structure is observed.

The Scattering Problem in PT‐Symmetric Periodic Structures of 1D Two‐Material Waveguide Networks

“…Since the parity‐time ( PT ) symmetry concept was introduced into optics from quantum mechanics, PT ‐symmetric optical systems have attracted great attention from many researchers because of their unique properties . PT ‐symmetric optical systems require that the real part of the refractive index is an even function and the imaginary part is an odd function .…”

“…Interestingly, even multiple pairs of PT ‐symmetric structures can be designed in a unit cell of an optical waveguide network. In addition, periodic optical structures with PT ‐symmetry have received significant attention . It was found that scattering is significantly influenced by the number of unit cells in a periodic photonic crystal system.…”

“…In addition, periodic optical structures with PT ‐symmetry have received significant attention . It was found that scattering is significantly influenced by the number of unit cells in a periodic photonic crystal system. For example, it was recently shown that asymmetric transmission resonances and CPA laser points are highly dependent on the number of unit cells in a PT ‐symmetric photonic crystal system .…”

Chiral Metamaterials with PT Symmetry and Beyond

“…Most recently, some works combined PT-symmetry with metamaterials [22][23][24][25][26][27], which could extend these ideas to new limits, as metamaterials can be designed to have the desired permittivity ε and permeability μ, at almost any frequency [28]. However, an important class of metamaterials, namely chiral metamaterials, remains highly unexplored in the context of PT-symmetry.…”

Accessible phases via wave impedance engineering with PT -symmetric metamaterials

“…While the ability to control the PT-phase can grant access to important properties, such as (a) mixed phases (coexistence of PT-symmetric and PT-broken phase) and (b) phase re-entries (multiple passes among all possible phases), these aspects have not been investigated thoroughly. For example, in [29] the occurrence of mixed phases was shown to require polarization converting elements, while phase reentries were shown in [27] for TE waves in the special case of epsilon near zero (ENZ) metamaterials only.…”