Collision-induced Hopf-type bifurcation reversible transitions in a dual-wavelength femtosecond fiber laser

Collision refers to a striking nonlinear interaction in dissipative systems, revealing the particle-like properties of solitons. In dual-wavelength mode-locked fiber lasers, collisions are inherent and periodic. However, how collisions influence the dynamical transitions in the dual-wavelength mode-locked state has still not been explored. In our research, dispersion management triggers the complex interactions between solitons in the cavity. We reveal the smooth or reversible Hopf-type bifurcation transitions of dual-color soliton molecules (SMs) during collision by real-time spectral measurement technique of TS-DFT. The reversible transitions from stationary SM to vibrating SM, revealing that cavity parameters pass through a bifurcation point in the collision process without active external intervention. The numerical results confirm the universality of collision-induced bifurcation behavior. These findings provide new insights into collision dynamics in dual-wavelength ultrafast fiber lasers. Furthermore, the study of intermolecular collisions is of great significance for other branches of nonlinear science.Comment: 11 pages, 4 figure

1,4-Bis(4-pyridylmeth­oxy)benzene

The mol­ecule of the title compound, C18H16N2O2, lies about a center of inversion. The central phenyl­ene ring is aligned at 62.7 (1)° with respect to the pyridyl ring. In the crystal, weak inter­molecular C—H⋯N hydrogen bonds link mol­ecules into sheets parallel to (104). C—H⋯O inter­actions are also present

4,4′-(o-Phenyl­enedioxy­dimethyl­ene)dipyridinium dinitrate

The cation of the salt, C18H18N2O2 2+·2NO3 −, lies about a twofold rotation axis. The pyridinium ring is almost coplanar with the phenyl­ene ring [dihedral angle between rings = 5.69 (9)°]. The crystal structure shows π–π stacking inter­actions [centroid–centroid distance = 3.70 (1) Å] between the pyridinium rings and the phenyl­ene rings, generating a linear chain structure. The cation also forms two N—H⋯O hydrogen bonds to two nitrate groups