Search results for "FEMTOSECOND"
showing 10 items of 238 documents
Higher-order Kerr terms allow ionization-free filamentation in gases
2010
International audience; We show that higher-order nonlinear indices (n4 , n6 , n8 , n10) provide the main defocusing contribution to self-channeling of ultrashort laser pulses in air and Argon at 800 nm, in contrast with the previously accepted mechanism of filamentation where plasma was considered as the dominant defocusing process. Their consideration allows to reproduce experimentally observed intensities and plasma densities in self-guided filaments.
Laser induced field-free molecular alignment
2008
Talk given by O. Faucher; International audience
Field-free molecular alignment of ethylene
2007
Talk given by O. Faucher; International audience
High-order Kerr nonlinearity of air calibrated with transient molecular alignment
2009
Talk given by O. Faucher; International audience; Nonlinear electronic Kerr index of the major air constituents has been measured up to high order terms using transient molecular alignment as a reference. Sign reversal associated to negative nonlinearity is observed above a pulse intensity of 26 TW/cm^2.
La molécule d'éthylène soumise à des impulsions laser femtosecondes : spectroscopie rotationnelle et alignement
2006
Talk given by B. Lavorel
Control and optimization of postpulse molecular alignment by shaped laser pulse
2008
Talk given by O. Faucher; International audience
Laser induced molecular alignment of ethylene
2007
Talk given by O. Faucher
Suppression of plasma contribution in femtosecond degenerate four-wave mixing (fs-DFWM) at high intensity
2007
Femtosecond degenerate four-wave mixing (fs-DFWM) experiments in CO2 exhibit a strong background due to plasma produced at high intensity (≥20 TW/cm2), when significant molecular alignment is likely to arise. This perturbing phenomenon renders the measurements of alignment very difficult. It is shown that the plasma contribution can be avoided by employing perpendicular polarizations for the two pump pulses. The effect is explained on the basis of the different diffraction angles between signals produced by molecular alignment and plasma. Copyright © 2007 John Wiley & Sons, Ltd.
Generation of a 160-GHz transform-limited pedestal-free pulse train through multiwave mixing compression of a dual-frequency beat signal.
2002
International audience; We report the experimental generation of a 160-GHz picosecond pulse train at 1550 nm, using multiple four-wave mixing temporal compression of an initial dual-frequency beat signal in the anomalous-dispersion regime of a nonzero dispersion-shifted fiber. Complete intensity and phase characterizations of the pulse train were carried out by means of a frequency-resolved optical gating technique, showing that 1.27-ps transform-limited pedestal-free Gaussian pulses were generated.
All-fibered high-quality low duty-cycle 160-GHz femtosecond pulse source
2008
International audience; In this paper, we report the experimental demonstration of an all-optical fiber-based 160-GHz femtosecond pulse source exhibiting a duty cycle as low as 1/17. The 380-fs wellseparated Gaussian pulses are generated thanks to the strong temporal compression of an initial beat-signal propagating into three distinct segments of optical fiber. Experimental results are supported by numerical simulations based on the generalized nonlinear Schrödinger equation. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)