Dirac-Point Solitons in Nonlinear Optical Lattices

TL;DR

This paper reports the discovery of a new type of solitons at the Dirac point in nonlinear optical lattices, which are supported without photonic bandgaps, expanding the understanding of soliton phenomena in periodic systems.

Contribution

It introduces Dirac-point solitons supported by Dirac points instead of photonic bandgaps, offering new insights into soliton existence in periodic systems.

Findings

Solitons can exist at the Dirac point without photonic bandgaps.

Dirac-point solitons exhibit dramatic stability characteristics.

These solitons are realizable in Kerr and photorefractive nonlinear materials.

Abstract

The discovery of a new type of solitons occuring in periodic systems without photonic bandgaps is reported. Solitons are nonlinear self-trapped wave packets. They have been extensively studied in many branches of physics. Solitons in periodic systems, which have become the mainstream of soliton research in the past decade, are localized states supported by photonic bandgaps. In this Letter, we report the discovery of a new type of solitons located at the Dirac point beyond photonic bandgaps. The Dirac point is a conical singularity of a photonic band structure where wave motion obeys the famous Dirac equation. These new solitons are sustained by the Dirac point rather than photonic bandgaps, thus provides a sort of advance in conceptual understanding over the traditional gap solitons. Apart from their theoretical impact within soliton theory, they have many potential uses because such solitons have dramatic stability characteristics and are possible in both Kerr material and photorefractive crystals that possess self-focusing and self-defocusing nonlinearities. The new results elegantly reveal that traditional photonic bandgaps are not required when Dirac points are accessible. The findings enrich the soliton family and provide valuable information for studies of nonlinear waves in many branches of physics, including hydrodynamics, plasma physics, and Bose Einstein condensates.