Self-induced laser line sweeping in an ytterbium fiber laser with non-resonant Fabry-Perot cavity

A new effect for a CW-pumped ytterbium fiber laser (YFL), self-induced laser line sweeping (SLLS), is reported. The effect's main characteristic is "adiabatic" movement (seconds) of the laser line from shorter to longer wavelengths, spanning over a spectral interval as large as 7 nm, followed by its instantaneous bounce backward. The SLLS regime is observed nearly above the YFL threshold, in excess of pump power up to 70% of its threshold value, whereas at higher pumps it is replaced by the common regime of chaotic spectral bursts in the time domain. SLLS seems to appear owing to the use at the YFL implementation of multi-port GTWave ytterbium-doped fiber as an active medium and non-resonant Fabry-Perot cavity formed by the fiber's cleaved ends, both the features providing highly uniform spectral and spatial conditions at which the laser operates. An analysis of the SLLS effect allows us to reveal that the mechanisms responsible for its presence are nonlinear wave-mixing and spectral hole-burning, i.e. the effects closely related to the intra-cavity modes interference. (C) 2011 by Astro Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA