Femtosecond fiber laser with hybrid organic small molecule material as saturable absorber

This study presents the development of an ultrafast mode-locked fiber laser utilizing a hybrid organic small molecule (HOSM) based on Tris-(8-hydroxyquinoline) aluminum (Alq₃) and N,N′-Di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB), as a passive saturable absorber (SA). The SA thin-film was integrated into the laser cavity to serve as a mode-locker. Through a series of experiments varying the cavity length, the efficacy and stability of the developed SA were examined. In these experiments, with cavity lengths of 112 m, 61.5 m, and 22.5 m, accompanied by group velocity dispersions (GVDs) of −2.365, −1.249 ps², and −0.4 ps² respectively, we observed a consistent and singular soliton mode-locking state. Notably, we achieved a remarkable pulse width tunability ranging from 1.98 ps to 712 fs by adjusting the cavity length. Operating in the 1560 nm region, this femtosecond soliton fiber laser holds significant promise for various applications, including high-precision optical metrology, frequency-comb generation, and broadband absorption spectroscopy.