An Optimization Strategy for High-Energy, Few-Cycle Pulse Generation Directly from Er-Doped Mamyshev Oscillators

This paper examines the dispersion and nonlinearity limitations of 1.5-μm fiber lasers and numerically proposes an optimization strategy for a Mamyshev oscillator (MO) utilizing conventional Er-doped fibers to generate high-energy, few-cycle pulses. The approach focuses on reducing the nonlinear chirp while enhancing linear chirp characteristics in high-energy degraded-parabolic solitons through two key steps: configuring an initial MO for stable self-similar soliton evolution near the 40 nm gain bandwidth, and employing dispersion delay lines (DDLs) and highly nonlinear fibers (HNLFs) for chirp-managed spectral expansion towards few-cycle generation. Spectrogram analysis reveals that precise passive fiber layout reduces optical wave breaking and stimulated Raman scattering, critical for parabolic pulse formation. For spectral broadening, a large negative dispersion DDL suppresses Raman effects while a moderate longer HNLF compensates for nonlinear chirp through positive dispersion. The optimized MO produces 12 fs (2.4 cycles) pulses with 21 nJ energy and >1.2 MW peak power. Importantly, the DDL-HNLF incorporation enables spectral broadening without destabilizing the core self-similar attractor, evidenced by strong correlations (Pearson r >0.95, p <0.01) between two-stage configurations. This avoids the need for comprehensive cavity redesign, thereby reducing complexity compared to monolithic-design broadband pulsed fiber oscillators.