International audienceExperimental observation of the self-induced laser line sweeping (SLLS) in fiber ring lasers is presented. The SLLS with the same gain fiber is studied in Fabry-Perot cavity for comparison. The SLLS effect manifests itself as a laser wavelength drift with speed of the order of nanometer per second from shorter to longer wavelengths across several nanometers and fast backward jump. Recently, the dynamics of the SLLS in a Fabry-Perot cavity fiber laser was qualitatively described by a dynamic grating induced by spatial-hole-burning in the ytterbium doped fiber where the lifetime of the grating was related to the self-sustained relaxation oscillations. In this paper we address possible discrepancies between the published theoretical model and earlier observations of SLLS, particularly in fiber-ring lasers.We show that the qualitative theoretical model developed for explaining SLLS in the Fabry-Perot cavity can be used also to explain the SLLS effect we observed earlier in fiber-ring lasers

An overview of the latest developments of kilowatt-level diode pumped solid state lasers for advanced applications at the HiLASE Centre is presented. An overview of subcontracted and in-house-developed laser beamlines is presented. The aim of development is to build kW-class beamlines delivering picosecond pulses between 1-and 100-kHz repetition rates and high-energy nanosecond pulses at 10 Hz. The picosecond beamlines are based on Yb:YAG thin-disk amplifiers and chirped pulse amplification. The current status of the beamlines' performance is reported. The advantages of zero-phonon line and pulsed OPEN ACCESS Appl. Sci. 2015, 5638 pumping are demonstrated with respect to efficiency, thin disk temperature and beam quality. New diagnostics methods supporting the high average power lasers' development, such as the high-resolution spectroscopy of Yb-doped materials, in situ thin disk deformation measurements, single-shot M 2 measurement, realization of wavefront correction by a deformable mirror and the laser performance of a new mixed garnet ceramics, are described. The energetic, thermal and fluid-mechanical numerical modeling for the optimization of the multi-slab amplifiers is also described.

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