Crossover from single to two-peak fundamental solitons in nonlocal nonlinear media

Abstract

Bright solitons with two in-phase peaks can form in a nonlinear homogeneous medium due to competing nonlocal interactions. This study explores the emergence and transformation of these solitons, considering both additive and multiplicative models for the competing nonlinear self-focusing and self-defocusing effects. We show that high input power can trigger the formation of the stable, double-peaked solitons. Furthermore, we introduce a semi-analytical approach (SAA) to accurately predict the critical conditions where single-peak solitons transition to double-peak ones. The SAA combines the variational approach with a linear eigenmode solver, achieving good agreement with exact simulations while being significantly faster. Our work emphasizes the importance of nonlocality in soliton formation and introduces SAA as a valuable tool for future investigations.