High order cascaded Raman random fiber laser with high spectral purity

Abstract

An up to 8th order cascaded Raman random fiber laser with high spectral purity is achieved with the pumping of a narrow linewidth amplified spontaneous emission source. The spectral purity is over 90% for all the 8 Stokes orders. The highest output power is 6.9 W at 1691.6 nm with an optical conversion efficiency of 21% from 1062.0 nm. As a comparison, with conventional FBG-based fiber oscillator as pump source, only 47% spectral purity is achieved at 8th order. The temporal stability of the pump laser is proved to play a key role, because the time fluctuation of pump laser is transferred directly to Raman outputs and results in power distribution among different Stokes orders.

Effective suppression of mode distortion induced by stimulated Raman scattering in high-power fiber amplifiers

“…The explanation for the influence of the forward feedback coefficient on the threshold power is more likely the enhanced SRS configuration because the end surface of the rear port in the seed source together with the fiber in the amplifier constitutes a half-opening cavity, which can also be regarded as a shortcavity random Raman laser with a half-opening cavity [39] . According to the threshold theory of random Raman lasers, when the cavity length is relatively short, even extremely weak forward feedback power can also provide very effective positive feedback for the SRS effect and play a critical role in reducing the threshold of random Raman lasers [40][41][42] , and this is the reason why the SRS-induced mode distortion is extremely sensitive to the forward feedback power value. Thus, it can be seen that both of the above methods indirectly suppress SRS-induced mode distortion in fact by efficiently suppressing the SRS effect.…”

2-kW-level superfluorescent fiber source with flexible wavelength and linewidth tunable characteristics

“…Superfluorescent fiber source (SFS), which originates from the superfluorescent radiation in the gain medium of optical fiber, not only has the advantages of fiber lasers such as high efficiency and high beam quality [1,2], but also inherits the merits of superfluorescent sources such as broadband emission and low coherence [3,4], thus showing great application potential in sensing, spectroscopy, biomedical imaging and so on [5][6][7][8]. Compared with fiber oscillators which have well-defined cavities, SFS shows higher temporal stability while maintaining good power scalability [9,10], so it is pretty suitable for pumping the optical parametric oscillators (OPOs) [11,12] and Raman fiber lasers (RFLs) [13,14]. However, broadband-emitted SFS is not preferred for these applications.…”

Greater than 2 kW all-passive fiber Raman amplifier with good beam quality

“…Compared with Ybdoped fiber lasers (YDFLs), the most attractive feature of the RFL is wavelength flexibility. It can emit across almost the whole spectrum of transparency of a silica window, in particular beyond the emission band of rare-earth-doped fiber lasers [9][10][11][12][13][14][15][16][17][18][19] .…”