Diffraction control in PT-symmetric photonic lattices: from beam rectification to dynamic localization

TL;DR

This paper explores how light beams propagate in PT-symmetric photonic lattices with longitudinal modulation, demonstrating control over diffraction phenomena like rectification and localization by tuning system parameters and gain-loss balance.

Contribution

It introduces a method to control diffraction in PT-symmetric lattices through longitudinal modulation and gain-loss tuning, enabling transitions between beam rectification and dynamic localization.

Findings

Beam rectification achieved without diffractive broadening.

Dynamic localization restores initial intensity distribution periodically.

Transition between regimes controlled by gain-loss tuning in PT-symmetric systems.

Abstract

We address the propagation of light beams in longitudinally modulated PT-symmetric lattices, built as arrays of couplers with periodically varying separation between their channels, and show a number of possibilities for efficient diffraction control available in such non-conservative structures. The dynamics of light in such lattices crucially depends on the ratio of the switching length for the straight segments of each coupler and the longitudinal lattice period. Depending on the longitudinal period, one can achieve either beam rectification, when the input light propagates at a fixed angle across the structure without diffractive broadening, or dynamic localization, when the initial intensity distribution is periodically restored after each longitudinal period. Importantly, the transition between these two different propagation regimes can be achieved by tuning only gain and losses acting in the system, provided that the PT-symmetry remains unbroken. The impact of Kerr nonlinearity is also discussed.