Light gap bullets in defocusing media with optical lattices

TL;DR

This paper investigates the formation and stability of three-dimensional light gap bullets—localized spatiotemporal solitons within finite spectral gaps—in periodic media with defocusing nonlinearity, expanding understanding of stable optical localized modes.

Contribution

It introduces and analyzes the existence and stability of 3D light gap bullets, including gap solitons and vortices, in finite band gap media, a previously unexplored regime.

Findings

Light gap bullets are stable within certain existence domains.

Both 3D gap solitons and vortices with topological charge m=1 are reported.

The study extends the concept of localized modes to finite band gap media.

Abstract

Searching for three-dimensional spatiotemporal solitons (also known as light/optical bullets) has recently attracted keen theoretical and experimental interests in nonlinear physics. Currently, optical lattices of diverse kinds have been introduced to the stabilization of light bullets, while the investigation for the light bullets of gap type -- nonlinear localized modes within the finite gap of the underlying linear Bloch spectrum -- is lacking. Herein, we address the formation and stabilization properties of such light gap bullets in periodic media with defocusing nonlinearity, theoretically and in numerical ways. The periodic media are based on two-dimensional periodic standing waves created in a coherent three-level atomic system which is driven to the regime of electromagnetically induced transparency, which in principle can also be replaced by photonic crystals in optics or optical lattices in ground-state ultracold atoms system. The temporal dispersion term is tuned to normal (positive) group velocity dispersion so that to launch the light gap bullets under self-repulsive nonlinearity; two types of such light gap bullets constructed as 3D gap solitons and vortices with topological charge m=1 within the first finite gap are reported and found to be robustly stable in the existence domains. On account of the light bullets were previously limited to the semi-infinite gap of periodic media and continuous nonlinear physical systems, the light gap bullets reported here thus supplement the missing type of three-dimensional spatiotemporal localized modes in periodic media which exhibit finite band gaps.