Solitons in a linearly coupled system with separated dispersion and nonlinearity

Area of Science:

• Nonlinear Optics
• Optical Waveguides
• Photonic-Crystal Fibers

Background:

• Cubic nonlinearity and group-velocity dispersion (GVD) are key phenomena in optical systems.
• Traditional models often mix these effects within a single nonlinear Schrödinger (NLS) equation.
• Understanding their interplay in separated cores is crucial for novel soliton dynamics.

Purpose of the Study:

• To introduce and analyze a dual-core waveguide model with spatially separated nonlinearity and GVD.
• To investigate the formation and stability of solitons sustained by indirect coupling.
• To explore unique soliton behaviors in different spectral gaps.

Main Methods:

• Development of a theoretical model for a dual-core waveguide.
• Analysis of the system's spectral properties, including gap structures.
• Numerical investigation of soliton dynamics under anomalous and normal GVD conditions.

Main Results:

• Solitons fill the semi-infinite gap under anomalous GVD, exhibiting stability similar to NLS solitons but with distinct component shapes.
• Stable, two-tier gap solitons emerge in the finite gap under normal GVD, a novel phenomenon absent in standard NLS models.
• Soliton persistence depends on the sign of additional GVD in the nonlinear core.

Conclusions:

• The dual-core model provides a platform for studying soliton dynamics driven by indirect nonlinearity-GVD interplay.
• Distinct soliton families exist in semi-infinite and finite spectral gaps, with unique characteristics under different GVD regimes.
• The findings offer new possibilities for designing optical systems with tailored soliton properties.