Search results for "Impulsions ultrabrèves"
showing 2 items of 2 documents
Ultrafast optics in coherently spinning molecules
2020
This thesis reports on the study of unidirectional rotation of molecules and focuses on the rotational Doppler effect occuring in the course of third-harmonic generation in coherently spinning molecules.The rotational Doppler effect appears when a circularly polarized wave interacts with an anisotropic rotating object. During the interaction, an exchange of angular momentum and energy between the field and the object occurs, leading to a frequency shift of the wave. In this work, the frequency shift of the third-harmonic generated in unidirectionaly rotating molecules has been observed. An anlytical model developped in the mansucript forsees four kinds of frequency shifts depending on the m…
Alignement moléculaire par impulsions laser ultrabrèves : Mesures & Applications
2009
The interaction of an intense ultrashort laser pulse with a molecular sample leads, after the end of the pulse, to molecular alignment at specific time under field-free conditions. This thesis is dedicated to the measurements and applications of this effect. The degree of alignment is determined through the variation of the refractive index induced by the rearrangement of the molecular dipoles. A two-dimensional technique allowing to measure molecular alignment on a single-shot basis is reported in this document. The alignment is then exploited in order to determine physical quantities which are usually difficult to estimate through others methods. The "cross-defocusing technique" has been …