[en] We review recent progress in coherent combining of femtosecond pulses amplified in optical fibers as a way to scale the peak and average power of ultrafast sources. Different methods of achieving coherent pulse addition in space (beam combining) and time (divided pulse amplification) domains are described. These architectures can be widely classified into active methods, where the relative phases between pulses are subject to a servomechanism, and passive methods, where phase matching is inherent to the geometry. Other experiments that combine pulses with different spectral contents, pulses that have been nonlinearly broadened or successive pulses from a mode-locked laser oscillator, are then presented. All these techniques allow access to unprecedented parameter range for fiber ultrafast sources. (topical review)
Journal
Journal of Physics. B, Atomic, Molecular and Optical Physics; ISSN 0953-4075; 
; CODEN JPAPEH; v. 49(6); [15 p.]
; CODEN JPAPEH; v. 49(6); [15 p.]
[en] After an introduction, the contributions proposed by this book address the following topics: production of femtosecond pulses and new materials for diode pumping, shaping and characterisation of ultra-fast pulses, introduction to the synthesis and the measurement of atto-second pulses, generation, characterisation and applications of femtosecond infrared pulses, Fabry-Perot cavities in pulsed mode and their recent applications, photo-induced electron transfer reactions studied by ultrafast spectroscopy, ultrafast spectroscopy of a single metal nanoparticle, time-resolved optical measurements of the spin coherence in semiconductor nanostructures
Source
1 Jun 2012; 230 p; Editions MRCT CNRS; Paris (France); ISBN 2-86272-339-8;
[en] Cubic crystals are often favored due to their interesting isotropic properties -such as the refractive index, the dilatation, etc-that simplify their use in laser systems. Among all Yb-doped high-symmetry materials, Yb:CaF2 is a very attractive one for high-energy high-power lasers. However, in such systems, thermal loads become important and thermal anisotropic effects can occur even for simple cubic crystals impacting severely the laser system design. In this context, we report here, a study of thermally induced polarization anisotropy in Yb-doped CaF2 laser crystals. Both thermal lens and thermally induced depolarization are precisely studied for different crystal orientations, namely the [110] and the [111] orientation. The study is performed with a pump/probe setup adapted to improve the signal-to-noise ratio under high power pumping. We observed both, classical-thermally induced depolarization and thermal lensing in accordance with previous work, but also, for certain configurations, atypical depolarization figures and astigmatic lenses. These results were also confronted with numerical simulations. The comparison between the [110] and the [111] oriented crystals represents a crucial study to determine the origins of these unusual effects and to allow a better understanding of thermal anisotropy in cubic laser-crystals.
Journal
[en] We report on a compact energy-scalable device for generating high-fidelity femtosecond laser pulses based on spatial filtering through a hollow-core fiber followed by a nonlinear crystal for cross polarized wave (XPW) generation. This versatile device is suited for temporal pulse cleaning over a wide range of input energies (from 0.1 to ≥10 mJ) and is successfully qualified on different ultrafast laser systems. Full characterization of the XPW output is presented. In particular, we demonstrate the generation of 1.6 mJ energy pulses starting from 11 mJ input pulse energy. The temporal contrast of the pulses is enhanced by more than 4 orders of magnitude. In addition, pulse shortening from 40 fs down to 15 fs Fourier-transform limit yields an overall peak-power transmission of up to 50%. This device not only serves as an integrated pulse contrast filter inside an ultrafast laser amplifier but also as a simple back-end solution for temporal post-compression of amplified pulses. (authors)
Journal
Review of Scientific Instruments; ISSN 0034-6748; ; v. 84; p. 043106.1-043106.8
; v. 84; p. 043106.1-043106.8