Optimization of Mode Locking in a Tm-Doped Fiber Oscillator with Frequency Shifted Feedback

Mode-locked fiber lasers using frequency shifted feedback (FSF) for pulse formation relies on the interplay between the frequency shift of an acousto-optic modulator (AOM), Kerr nonlinearity in optical fibers and optical filtering effect to prevent CW operation leading to a pulsed output [1]. To ensure minimal cavity losses, the AOM is typically operated with maximum possible transmission. However, many FSF lasers reported to date suffer from relatively high pulse intensity fluctuations of several percent. In this work, we propose taking advantage of the variability of AOM transmission in controlling cavity dynamics. Following the procedure hereafter, it was possible to investigate and minimize the pulse intensity fluctuations in a Tm-doped FSF fiber laser.