Search results for "Ultrafast"

Autour de l’équation de Schrödinger non-linéaire dans les fibres optiques : similaritons, régénération, sources fibrées et évènements extrêmes

2009

Parabolic pulse formation and applications

2009

Parabolic pulses in optical fibers have stimulated an increasing number of applications. We review here the physics underlying the generation of such pulses as well as the results obtained in a wide-range of experimental configurations.

Optical bullets and "rockets" in nonlinear dissipative systems and their transformations and interactions

2006

We demonstrate the existence of stable optical light bullets in nonlinear dissipative media for both cases of normal and anomalous chromatic dispersion. The prediction is based on direct numerical simulations of the (3+1)-dimensional complex cubic-quintic GinzburgLandau equation. We do not impose conditions of spherical or cylindrical symmetry. Regions of existence of stable bullets are determined in the parameter space. Beyond the domain of parameters where stable bullets are found, unstable bullets can be transformed into >rockets> i.e. bullets elongated in the temporal domain. A few examples of the interaction between two optical bullets are considered using spatial and temporal interact…

Complex rogue wave in the fiber optics

2016

This manuscript presents the generation of complex rogue waves related to nonlinear instabilities occurring through the propagation of light in standard optical fibers. Linear and nonlinear physical phenomena involved are first listed, in particular some of them by analogy with the field of hydrodynamics. The different forms of rogue waves induced by the modulation instability process are then presented. They are also known as "breathers", and they are obtained by solving the nonlinear Schrödinger equation. From these exact solutions, various experimental systems were designed by means of numerical simulations based on two rogue-wave excitation methods. The first one is an exact generation …

Universal soliton pattern formations in passively mode-locked fiber lasers

2011

International audience; We investigate multiple-soliton pattern formations in a figure-of-eight passively mode-locked fiber laser. Operation in the anomalous dispersion regime with a double-clad fiber amplifier allows generation of up to several hundreds of solitons per round trip. We report the observation of remarkable soliton distributions: soliton gas, soliton liquid, soliton polycrystal, and soliton crystal, thus indicating the universality of such complexes.

Charge-transfer driven by ultrafast spin-transition in a CoFe Prussian blue analogue

2020

Photoinduced charge-transfer is an important process in nature and technology and is responsible for the emergence of exotic functionalities, such as magnetic order for cyanide-bridged bimetallic coordination networks. Despite its broad interest and intensive developments in chemistry and material sciences, the atomic-scale description of the initial photoinduced process, which couples intermetallic charge-transfer and spin transition, has been debated for decades; it has been beyond reach due to its extreme speed. Here we study this process in a prototype cyanide-bridged CoFe system by femtosecond X-ray and optical absorption spectroscopies, enabling the disentanglement of ultrafast electr…

Excitation energy transfer in isolated chlorosomes from Chloroflexus aurantiacus

2009

Abstract Chlorosomes from green photosynthetic bacteria Chloroflexus aurantiacus have been studied by time-resolved femtosecond transient absorption spectroscopy. The fastest kinetics of 200–300 fs resolved, was interpreted to stem for intra-chlorosomal excitation energy transfer. Energy transfer from the antenna to the baseplate appeared as a major 9.2 ps rise component detected at the baseplate probe wavelength. Excitation energy transfer rates were evaluated for a model chlorosome. Calculated rod to rod, and rods to baseplate rate constants of 200–400 fs and 10–20 ps, respectively, are in accord with the experimental results.

Excitation Energy Transfer in Isolated Chlorosomes from Chlorobaculum tepidum and Prosthecochloris aestuarii

2012

Excitation energy transfer in chlorosomes from photosynthetic green sulfur bacteria, Chlorobaculum (Cba.) tepidum and Prosthecochloris (Pst.) aestuarii, have been studied at room temperature by time-resolved femtosecond transient absorption spectroscopy. Bleach rise times from 117 to 270 fs resolved for both chlorosomes reflect extremely efficient intrachlorosomal energy transfer. Bleach relaxation times, from 1 to 3 ps and 25 to 35 ps, probed at 758 nm were tentatively assigned to intrachlorosomal energy transfer based on amplitude changes of the global fits and model calculations. The anisotropy decay constant of about 1 ps resolved at 807 nm probe wavelength for the chlorosomes from Chlo…

Effects of ligand substitution on the excited state dynamics of the Ru(dcbpy)(CO)2I2 complex

2003

Abstract Spectroscopic evidence suggest [PCCP 3 (2001) 1992] that illumination with visible light of the [trans-I-Ru(dcbpy)(CO)2I2] (dcbpy= 4,4′-dicarboxy-2,2′-bipyridine) complex in solution induces dissociation of a CO group followed by reorganization of the ligands and attachment of a solvent molecule. In the present study, we report results on excited state dynamics of this ruthenium complex and its photoproduct. Femtosecond transient absorption measurements reveal dominance of excited state absorption of the reactant and the photoproduct [cis-I-Ru(dcbpy)(CO)(Sol)I2] (Sol=ethanol or acetonitrile) in the visible spectral region. The time-resolved measurements for the reactant at 77 K ind…

Mechanism of excited state deactivation of indan-1-ylidene and fluoren-9-ylidene malononitriles.

2016

Herein, we report complementary computational and experimental evidence supporting the existence, for indan-1-ylidene malononitrile and fluoren-9-ylidene malononitrile, of a non-radiative decay channel involving double bond isomerisation motion. The results of UV-Vis transient absorption spectroscopy highlight that the decay takes place within hundreds of picoseconds. In order to understand the related molecular mechanism, photochemical reaction paths were computed by employing multiconfigurational quantum chemistry. The results indicate that the excited state deactivation occurs via concerted double bond twisting of the dicyanovinyl (DCV) unit coupled with a pyramidalisation of its substit…