Towards an optimum saturable absorber for the multi-gigahertz harmonic mode locking of fiber lasers

• DOI: 10.1364/prj.7.001094
• Publication Date: 2019-08-28T17:03:46Z
• Authors: Jakub Bogusławski; Grzegorz Soboń; Rafał Zybała; Jarosław Sotor
• Keywords: Saturable absorption; Mode-Locking; Q-switching

Ultra-high-pulse-repetition-rate lasers are essential for a number of applications, including, e.g., optical communication and ablation-cooled material processing. Despite several techniques to generate pulses with gigahertz-range repetition rate, incorporating mainly short-length resonators, more widespread applications still limited by the lack robust, simple, cost-effective solution. Here, we report first time, best our knowledge, fully passive harmonic mode locking in an all-polarization-maintaining (PM) fiber laser. The design guarantees fixed polarization state stable operation, where cavity is controlled pump power only. Self-starting operation provided antimony telluride (Sb2Te3) thin-film saturable absorber (SA), which facilitates multiple pulse operation. SA acts means low modulation depth, saturation fluence, inverse slope absorption curve. optimum features limiting factors high-repetition-rate generation this regime discussed. As result, 2.2 ps 3 GHz rate generated at 1560 nm wavelength. study reports new approach towards optimal multi-gigahertz practical, all-PM lasers.