Search results for "HIF"
showing 10 items of 1515 documents
Parabolic pulse generation in dispersion decreasing fiber amplifier
2007
We obtain an exact dispersion profile that permits for the analytical description of self-similar pulse amplification and supercontinuum generation in tapered nonlinear fiber amplifiers.
Cascaded intermodal four-wave mixing in a few-mode fiber
2019
During the last few years, intensive works on multimode fibers allowed for the observation of a series of complex and novel nonlinear spatiotemporal phenomena such as: multimode solitons, geometric parametric instability, supercontinuum generation, and self-induced beam cleaning [1-4]. Among these phenomena, intermodal four-wave mixing (IMFWM) demonstrated larger frequency shifts in comparison with single-mode fibers. In this work, we studied IMFWM in a few-mode graded-index fiber (GRIN-FMF) pumped in the normal dispersion regime at 1064 nm. We report parametric sidebands detuned by hundreds of THz from the pump.
Collisional effects on spectral line shape from the Doppler to the collisional regime: A rigorous test of a unified model
2000
International audience; The paper presents high resolution Raman investigations of the Q(1) line of H-2 in Ar mixture from low density (Doppler regime) to high density (collisional regime) analyzed with a unique line shape profile. Measurements are performed by stimulated Raman gain spectroscopy between 300 and 1000 K in a wide density range (from 0.2 to 11 amagat). All the observed spectral features are accurately described by a unified model recently proposed by two of the authors. This model accounts for a velocity-memory process, not restricted to the usual hard and soft limits. It also includes correlation between velocity- and phase-changing collisions. An exhaustive analysis of vario…
Experimental and theoretical study of line mixing in methane spectra. III. The Q branch of the Raman nu(1) band
2000
International audience; The shape of the nu(1) Raman Q branch of CH4 perturbed by Ar and He at room temperature has been studied. Stimulated Raman spectroscopy (SRS) experiments have been made in the 2915-2918 cm(-1) spectral region for total pressures from 0.4 to 70 atm and mixtures of approximate to 5% CH4 with He and Ar. Analysis of the spectra demonstrates that the shape of the Q branch is significantly influenced by line mixing and much narrower than what is predicted by the addition of individual line profiles. For the first time, a model is proposed for the calculation and analysis of the effects of collisions on the considered spectra. In this approach, the rotational part of the re…
New fiber laser architecture with transform-limited nonlinear spectral compression
2012
International audience; We numerically demonstrate a new fiber laser architecture supporting spectral compression of negatively chirped pulses in passive normally dispersive fiber. Such a process is beneficial for improving the energy efficiency of the cavity as it prevents narrow spectral filtering from being highly dissipative. The proposed laser design provides an elegant way of generating transform-limited picosecond pulses.
All-optical measurement of residual chromatic dispersion and OSNR using self-phase modulation in optical fiber
2011
International audience; We describe a new all-fibered device providing high accuracy all-optical measurements of both optical signal to noise ratio and residual chromatic dispersion. Taking advantage of the self-phase modulation driven spectral evolution of pulses propagating in a highly non-linear medium, we have numerically and experimentally validated the benefits of using an anomalous dispersive fiber combined with a central spectral filtering.
Second zero dispersion wavelength measurement through soliton self-frequency shift compensation in suspended core fibre
2008
International audience; A simple experimental technique to evaluate the second zero dispersion wavelength of very small core microstrutured fibres is described. Based on the effect of soliton self-frequency shift and its subsequent compensation in the vicinity of the second zero dispersion. the proposed method is applied to both standard and suspended core microstructured fibres by simply measuring the frequency stabilised soliton spectrum, avoiding any calculation and knowledge of any experimental parameters.
Variations spatiales et temporelles de communautés adventices des cultures annuelles en France
2010
Résumé de thèse; National audience
Evolution rétrospective du risque gélif hivernal en climat tempéré suite au réchauffement climatique
2018
Prod 2019-139 BAP POLE EA GEAPSI INRA AGROSUP; National audience; Les modalités du réchauffement climatique sur l’Europe de l’ouest montrent pour les températures une rupture nette en 1987/1988. Deux régimes distincts de température ont eu cours de part et d’autre de cette rupture. Cela offre une opportunité pour évaluer un impact du réchauffement en Bourgogne Franche-Comté. Peu de travaux documentent néanmoins les conséquences du réchauffement hivernal sur la végétation en général et les cultures en particulier. Pourtant, ces dernières années, des travaux suggèrent une augmentation du risque gélif présentée comme un effet paradoxal du réchauffement climatique. En combinant, sur la période …
Le réchauffement climatique diminue-t-il le risque de dégâts par le gel pour les cultures de climat tempéré ?
2014
Does global warming reduce the freezing injury risk to temperate climate crops? Winter crop response to a temperature increase is complex. Recent works point out, for cold climate vegetation, a paradoxical increase in freezing injury in a warming climate. Complementary works are needed to support these results for winter crops in temperate areas. To achieve this goal, five climatic records spanning a fifty years-long period for both daily minimum and maximum temperatures were analyzed with a model predicting frost hardiness and freezing damage for the winter pea crop. The methodological approach was based on three main steps: 1) the climate warming analysis of the 1987/1988 temperature shif…