Self-induced laser line sweeping and self-pulsing in double-clad fiber lasers in Fabry-Perot and unidirectional ring cavities

Abstract

8 pagesInternational audienceRare-earth doped fiber lasers are subject to instabilities and various self-pulsed regimes that can lead to catastrophic damage of their components. An interesting self-pulsing regime accompanied with laser wavelength drift with time is the so called self-induced laser line sweeping (SLLS). Despite the early observations of the SLLS in solid-state ruby lasers, in fiber lasers it was first time mentioned in literature only in 2009 where such a laser wavelength drift with time was observed in a relatively broad range of about 1076 -1084 nm in ring ytterbium-doped fiber laser (YDFL). The main characteristic of the SLLS is the scanning of the laser wavelength from shorter to longer wavelength, spanning over large interval of several nanometers, and instantaneous bounce backward. The period of this sweeping is usually quite long, of the order of seconds. This spectacular effect was attributed to spatial-hole burning caused by standing-wave in the laser cavity. In this paper we present experimental investigation of the SLLS in YDFLs in Fabry-Perot cavity and ring cavities. The SLLS was observed also in erbium-doped fiber laser around 1560 nm. We present for the first time observation of the laser wavelength sweep in reverse direction, i.e., from longer towards shorter wavelengths. It was observed in YDFL around 1080 nm

Reverse spontaneous laser line sweeping in ytterbium fiber laser

“…Indeed, the SLLS may trigger the self-Q-switched regime of fiber lasers. In the case of a self-swept ring fiber laser, the self-Q-switched regime was observed from a certain pump power level, while for the same setup with carefully suppressed parasitic reflections and no SLLS the self-Q-switched regime was not observed [7,13,15,16]. Lobach et al also confirmed that, in the time domain, the SLLS regime has the character of single or few simultaneously oscillating modes and discovered that frequency increment during the sweeping procedure equates to frequency intermodal spacing [14,17].…”

“…An interesting type of instability is the selfinduced or spontaneous laser line sweeping (SLLS) regime. Despite early observation of the SLLS in ruby lasers [3], this type of instability was observed in fiber lasers only recently, both in Fabry-Perot [4,5] and ring cavity arrangements [6,7] based on ytterbium active medium emitting near 1.08 μm. Peculiar to this regime is spontaneous but steady sweeping of the laser line within a certain spectral range, with a line jump between the final and starting positions of the sweep range.…”

“…The sweeping regimes in reverse direction, i.e. from longer to shorter wavelengths, were mentioned shortly thereafter in both ytterbium fiber lasers near 1.07 μm and erbium fiber lasers near 1.56 μm [7,8]. However, the reasons for the reverse direction of sweeping were not explained in those brief conference reports as pointed out for example in [18].…”

Optimization and control of the sweeping range in an Yb-doped self-sweeping fiber laser

“…It was also demonstrated that in some conditions one can obtain sweeping in the so-called reverse direction. The reverse self-sweeping was reported for the first time in [6]. The instantaneous spectrum can contain many longitudinal modes or have only one mode (single-frequency self-sweeping operation) depending on the cavity parameters [5].…”

Self-Sweeping Yb-Doped Fiber Laser Based on Large-Mode Area Fiber

“…Эффект самосканирования обусловлен тем, что во время генерации в активной среде возникают динамические решетки коэффициента усиления и показателя преломления, которые влияют на генерацию последующих мод, что приводит к постоянному изменению спектра выходного сигнала [4]. В волоконных лазерах наблюдается ска-нирование длины волны генерации как в сторону увеличения [4], так и в сторону уменьшения [5]. Наиболее популярным направлением явля-ется изучение сканирования в иттербиевых волоконных лазерах вблизи 1 мкм [2][3][4], однако не прекращаются попытки расширения диапазона сканирования за счет использования других активных сред.…”