Controlled soliton formation in a femtosecond optical parametric oscillator with positive group delay dispersion

Soliton formation in a femtosecond optical parametric pumped by the second harmonic of a Yb: KGW solid-state oscillator was investigated. The intracavity group delay dispersion was positive, and the soliton condition was satisfied by introducing negative nonlinearity from cascaded quadratic nonlinearity (CQN). Controllable CQN was induced by an additional second-harmonic-generating nonlinear crystal inside the same resonator. Close to zero-phase mismatch, high CQN allows higher-order soliton formation, which leads to output power increase, self-phase modulation phase-matched dispersive wave formation, pulse splitting under perturbations of higher orders of nonlinear phase, and stable time/spectral domain oscillations with soliton period. Numerical simulations were employed to aid interpretations of the experimental data. (C) 2020 Optical Society of America