Phase Characters of Optical Dark Solitons with the Third-order Dispersion and Delayed Nonlinear Response

TL;DR

This paper analyzes the phase jump properties of dark solitons in optical fibers with third-order dispersion and delayed nonlinear response, revealing new behaviors and collision dynamics of double-valley dark solitons.

Contribution

It uncovers the existence of two distinct phase jumps at the same velocity for single-valley dark solitons and explores their topological and collision properties.

Findings

Single-valley dark soliton admits two phase jumps at the same velocity.

Double-valley dark solitons exhibit U-shaped or double-step phase distributions.

Inelastic collisions can switch phase distribution types, analyzed via topological phase and magnetic monopole fields.

Abstract

Dark soliton is usually seen as one of the simplest topological solitons, due to the phase jump across its density dip. We investigate the phase jump properties of dark solitons in a single mode optical fiber with the third-order dispersion and delayed nonlinear response, based on exact analytical solutions of Hirota equation. Our analysis indicates that a single-valley dark soliton (SVDS) can admit two distinct phase jumps at the same velocity, in sharp contrast to the dark soliton with only the second-order dispersion and self-phase modulation, which admits a one-to-one match between the velocity and phase jump. We further uncover the different topological vector potentials underlying the distinct phase jumps. The relations between phase jump and velocity of the SVDS can explain the generation of the previously reported double-valley dark soliton (DVDS). The detailed analysis on the two phase jumps characters of the DVDS with one identical velocity enables us to obtain U-shaped type or double-step type phase distribution. We further explore collision properties of the DVDSs by analyzing their topological phase, which can be considered as the generalization of topological phase (Phys. Rev. E 103, L040204). Strikingly, the inelastic collision can lead to the conversion between the two types of phase distributions for DVDS. The results reveal that inelastic or elastic collision can be judged by analyzing the magnetic monopole fields.