Femtosecond harmonic optical-Injection mode-locked semiconductor optical amplifier based fiber lasers

Abstract

A 30nm wavelength-tunable backward dark-optical-comb injection-mode-locked semiconductor optical amplifier fiber laser (SOAFL) with pedestal-free is reported after high-order soliton compression with maximum pulse compression ratio of up to 80. Shortest mode-locked SOAFL pulsewidth of 15 ps at 1 GHz is generated, which can further be compressed to 180 fs after linear chirp compensation, nonlinear soliton compression, and bireftingent filtering. The pedestal-free eighth-order soliton can be obtained by injecting the amplified pulse with peak power of 51 W into a 107.5m-long single-mode fiber (SMF), providing a linewidth and timebandwidth product of 13.8 mn and 0.31, respectively. The tolerance in SMF length is relatively large (100-300 m) for obtaining < 200fs SOAFL pulsewidth at wavelength tuning range of 1530-1560 mn. By extending the repetition frequency of dark-optical-comb up to 10 GHz, the mode-locked SOAFL pulsewidth can be slightly shortened from 5.4 ps to 3.9 ps after dispersion compensating, and further to 400 fs after second-order soliton compression. The lasing linewidth, time-bandwidth product and pulsewidth suppressing ratio of the SOAFL soliton become 4.5 nm, 0.33, and 10, respectively.