Observation of Optical Spectrum Dynamics and Longitudinal-Mode Feature in a Single- Frequency Self-Sweeping Fiber Laser

The diversity of operational regimes in an ytterbium-doped fiber laser with a low-Q-factor cavity

“…[3][4][5]), as in cases of 'moderate' feedback: namely, when the YDF is perpendicularly cleaved from both sides (∼3.5% Fresnel reflection), or when it is placed in a cavity with weakly reflecting couplers (usually fiber Bragg gratings (FBGs)), both resulting in coherent or quasi-coherent light generation at ∼1…1.1 µm in peculiar, somewhat uncommon, operational regimes . In particular, in CW-pumped YDFLs with a low-Q-factor cavity, self-induced laser line sweeping (SLLS) at low (up to ∼1.2 thresholds) pump powers was first observed in 2011 [6,7] and subsequently explored in many other FLs [8][9][10][11][12][13][14][15][16]. Meanwhile, at higher pump powers, irregular generation of powerful ('self-Q-switched', SQS) spikes or their bunches [3,5,[17][18][19][20][21][22] was observed, frequently characterized by unusual statistics, and referred to as 'extreme events' or 'rogue-waves' (RWs) [23][24][25][26][27][28][29][30].…”