Diffraction-induced instability of coupled dark solitary waves

Area of Science:

• Nonlinear Optics
• Soliton Dynamics
• Wave Propagation

Background:

• Coupled dark solitary beams are described by coupled defocusing nonlinear Schrödinger equations.
• Vector dark solitons can exist on backgrounds with different wavelengths and diffraction coefficients.

Purpose of the Study:

• To investigate a novel instability in the propagation of coupled dark solitary beams.
• To understand the behavior of vector dark solitons with differing diffraction properties.

Main Methods:

• Theoretical analysis using perturbation theory.
• Numerical integration of the governing coupled defocusing nonlinear Schrödinger equations.

Main Results:

• The vector dark soliton solution is found to be unstable to radiation modes.
• The component with stronger diffraction radiates energy away.
• A single dark soliton remains in the less diffracting mode/wavelength.

Conclusions:

• A novel instability mechanism for coupled dark solitons is identified.
• Differential diffraction significantly impacts the stability and evolution of vector dark solitons.
• This instability leads to the decay of vector solitons into stable single solitons.