Impact of polarization and gain control in the optimization of output pulse properties in ultralong ultrafast ring fibre lasers

Abstract

The application of limited polarization and gain control to the recently demonstrated mode-locked ultralong ultrafast, EDFA-based and Raman-assisted pulsed ring fibre lasers is shown to reduce output pulse duration and noise, as well as to increase pulse peak power in cavities of 10 km with repetition rates as low as 38 kHz and pulse durations below 200 fs FWHM, which remain effectively depolarized at the output in the optimized case, accompanied by improved mode-locking stability. The impact of polarization state optimization prior to the doped-fibre amplification section on these devices is studied for different lengths of fibre, harmonic modes, and Raman amplification values. Peak power is nearly doubled thanks to temporal compression and spectral broadening, with a wide choice of regimes of operation dynamically available for a given cavity length, allowing the modification of laser output towards targeted pulse characteristics.

Keywords

• Polarization
• Polarization Hole Burning
• Ultrashort high-energy pulse generation
• Mode-locked fibre oscillator
• Ultralong-ultrafast ring fibre lasers (UURFL)
• Soliton