In this article, we report how the growth method used for barium beta-borate beta-BaB2O4 (BBO) impacts its high power second harmonic generation properties in the deep-UV. We compared a BBO crystal grown by flux (Top Seeded Solution Growth or TSSG) and a BBO crystal grown by the Czochralski (CZ) method. We first characterized their transparency properties, then we measured their single-pass second harmonic conversion efficiencies with both a low average power and a high average power nanosecond pulsed lasers. We show that both crystals have comparable linear absorption and conversion efficiencies at low power, whereas in a high power experiment, the CZ-grown BBO yields higher conversion efficiency than the TSSG grown BBO. With a 30W, 150 kHz, 8 ns green laser, the use of a CZ BBO led at best to a 40% increase in available average output power at 257 nm. (C) 2015 Elsevier Masson SAS. All rights reserved.

We report on 33 W picosecond pulse laser pumped Raman comb generation with fifty spectral lines over two frequency octaves from the visible to the near infrared range obtained in hydrogen-filled hypocycloid-core Kagome HC-PCF.

We investigate the influence of repetition rate on the operation and output of a gain-switched fiber laser. We derive an equation relating pump pulse duration to repetition rate, which provides insight into the parameters of the operating laser such as absorbed pump power and internal losses. The change in laser pulse duration with varying repetition rate is measured and found to be negligible. Finally, the derived theory is compared to experimental results obtained using a ytterbium-doped rod type fiber laser.

We report on generation of two strong ps-laser emissions at 1.8 μm and 2 μm through hydrogen-filled Kagome HC-PCF. Each line exhibits tens of kW of peak power and operates in a single mode fashion.

We report on a new technique to produce high power sub-picosecond pulses from a fiber amplifier. We use parabolic pulse shaping of 27 ps transform-limited pulses in order to control nonlinear effects in the fiber amplifier. 63 MW, 780 fs pulses with 25 W average power were obtained, and ways to scale the technique to higher peak powers were identified.

This paper presents accurate modeling and experimental results concerning a self-starting ring cavity laser whose pulse duration can be changed from the fs to the ps regime. This laser delivers more than 10 W of averaged power. The active medium is a large mode area double clad Ytterbium doped rod type fiber. The effect of changing the width of the spectral filter is discussed, and the comparison with an accurate `first principle' numerical model will shed light on the physical mechanisms at hand.

We developed a high power picosecond laser system at 80 MHz for third harmonic generation. We obtained 291 W at 1030 nm under 580 W of pump power at 976 nm from an all fiber master oscillator power amplifier based on rod-type fibers. By frequency tripling, we obtained 63 W at 343 nm with excellent beam quality (M-2 < 1.2).

We developed a high power picosecond laser system at 80 MHz for third harmonic generation. We obtained 291 W at 1030 nm under 580 W of pump power at 976 nm from an all fiber master oscillator power amplifier based on rod-type fibers. By frequency tripling, we obtained 63 W at 343 nm with excellent beam quality (M2<1.2).

Yb-doped double-cladding photonic crystal fibers have become key components for power scaling in fiber laser systems, by providing many advantages, especially an ultra large effective area. The single-mode regime, which is a mandatory requirement for high quality laser beams, can be obtained in such large core active fibers only through a careful design. In this paper the cut-off properties of 19-cell photonic crystal fibers have been thoroughly investigated with the avoided-crossing approach, in order to find guidelines for the design of single-mode fibers. The air-hole diameter and the core refractive index have been changed, as well as the number of air-hole rings in the fiber inner cladding. Simulation results have shown that, regardless of the air-hole ring number, the guided-mode cut-off properties are strongly influenced by the main design parameters, especially by the core refractive index. In particular, a wider single-mode wavelength range can be obtained in 19-cell fibers with small air-holes and low core refractive index. Moreover, double-cladding photonic crystal fibers with larger inner-cladding provide better guided-mode cut-off properties, which can have positive effects on the amplification process in practical applications.

By simultaneously providing ultra large mode effective area (ULMA) and close to diffraction limited laser beams, Yb-doped double-clad photonic crystal fibers have become key components for power scaling in fiber laser systems. Despite their advantages, such fibers suffer from some drawbacks among which tremendous fabrication complexity and arising costs, high bending losses and poor integrability. In this paper, we show how the REPUSIL technique, which is an alternate synthesis method to produce high-quality doped-silica, enables the design of a new generation of ULMA rare-earth-doped fibers. Some examples of innovative fiber designs will be shown and commented together with a first experimental demonstration of all-solid Yb-doped double-cladding fiber fabrication. The thermal effects, which play a major role at high power laser level and drastically compromise the single-mode regime, are also investigated. The very first experimental results for the fiber and laser characterization are given.

We present Q-switched laser products based on very simple MOPA architecture with rod-type fibers delivering 300W at 1030nm, 130W at 515nm and 50W at 343nm with pulse duration down to 10ns and M2<1.2

We report on a picosecond laser system that can run from single shot to 50MHz, with energies up to 100μJ. High power picosecond lasers are being used extensively in the industry but their market is presently limited by the complexity and cost of classical solid state laser solutions based on regenerative amplifiers. We report here on a high power picosecond fiber laser that uses only single or double pass amplifiers.

We report on a 93W, 1.1µJ, 83MHz, 35ps MOPA fibre laser based on an Yb mode-locked fibre oscillator and a rod-type LMA amplifier. This configuration can generate up to 20W at 343nm and we demonstrated over 2W at 257nm.

We report on 83W, 14μJ, 5.9MHz, 30ps MOPA fiber laser based on an Yb modelocked fiber oscillator and a rod-type LMA amplifier. By frequency tripling, this configuration can generate up to 20W of UV.

Une technique prometteuse pour la realisation de dispositifs laser solides emettant dans l'ultraviolet consiste a disposer en cascade plusieurs cristaux non lineaires generant des sommes de frequence a partir d'une emission laser fondamentale situee dans le proche infra-rouge. Cependant, a ce jour, peu de cristaux non lineaires offrent la possibilite de generer de maniere efficace des longueurs d'onde voisines ou inferieures a 250 nm. Dans ce but, les plus gros efforts de recherche actuels s'orientent vers des cristaux contenant des groupements borate. Apres une description des principaux cristaux non lineaires proposes pour ce type d'application, nous presenterons les etudes que nous menons sur des materiaux de type fluoroborate, derives des oxoborates de terre rare et de calcium TrCa4O(BO3)3 (Tr = terre rare), et sur des materiaux de structure huntite TrMe3(BO3)4 (Me = Al, Ga, Sc).

We derive an expression describing pre-compensation of pulse-distortion due to saturation effects in short pulse laser-amplifiers. The analytical solution determines the optimum input pulse required to obtain any arbitrary target pulse at the output of the saturated laser-amplifier. The relation is experimentally verified using an all-fiber amplifier chain that is seeded by a directly modulated laser-diode.

We numerically and experimentally analyze gain limitations due to pump light bleaching in large core short length fiber amplifiers and discuss consequences such as the efficiency and accumulated nonlinear phase.

The optimum seed pulse-profile for a desired output pulse-profile in saturated ns-pulsed fiber-amplifiers is determined with an analytical solution for the amplification process. It can be regarded as an inverse Frantz-Nodvik-equation for the seed photon-density.