Search results for "Spectral"
showing 10 items of 3116 documents
Quasi-soliton spatial autoguidé en milieu non lineaire quadratique
2021
International audience; Nous démontrons ici des phénomènes d'autoguidage optique existant dans les milieux à non-linéarités quadratiques. En plus de la formation puis disparition d'un phénomène auto confiné, nous observons des effets de commutation ultrarapide et de démultiplication spatiale, ainsi qu'une restructuration temporelle suivie d'élargissements spectraux.
Line coupling in Anisotropic Raman Branches
1994
Direct connection between collisional Raman cross sections and state‐to‐state rotational ones permits, within the sudden approximation, to evidence drastic decouplings from isotropic to anisotropic lines. These decouplings are consistent with the results obtained by using the strong collision model. Convenient energy corrections to the sudden approximation are used for N2 to calculate the resulting effects on the isotropic and anisotropic Q‐branch profiles in a large density range (several hundred bars). The comparison of the calculations with experimental coherent anti‐Stokes Raman scattering (CARS) and stimulated Raman (SRS) spectra of nitrogen exhibits a good agreement. Such effects coul…
Étude expérimentale d'un système hybride WDM/DS-OCDMA pour un réseau d'accès optique haut-débit
2008
National audience; Nous présentons une solution hybride WDM/DS-OCDMA pour l'application réseau d'accès optique haut-débit.
Temporal coherence in mirrorless optical parametric oscillators
2012
International audience; One of the unique features of mirrorless optical parametric oscillators based on counterpropagating three-wave interactions is the narrow spectral width of the wave generated in the backward direction. In this work, we in- vestigate experimentally and numerically the influence that a strong phase modulation in the pump has on the spectral bandwidths of the parametric waves and on the efficiency of the nonlinear interaction. The effects of group-velocity mismatch and group-velocity dispersion are elucidated. In particular, it is shown that the substan- tial increase in temporal coherence of the backward-generated wave can be obtained even for pumping with a temporally…
H-2 vibrational spectral signatures in binary and ternary mixtures: theoretical model, simulation and application to CARS thermometry in high pressur…
2001
International audience; A summary of the main results obtained by the two groups in the field of H-2 vibrational spectral line signatures for various mixtures. in connection with CARS diagnostics of H-2-O-2 combustion systems, is presented. H-2-X Systems may have specific large inhomogeneous spectral features, due to the dependence of the line broadening and line shifting on the (H-2) radiator speed, particularly at high temperature. Thus, careful attention has to be paid to rigorously analyze such features, both from the experimental point of view (Dijon) and from the theoretical one (Besancon). Applications of the present results to high-pressure H-2/air flame thermometry are also briefly…
Tensorial development of the rovibronic Hamiltonian and transition moment operators for octahedral molecules
2001
Abstract We present a development of the Hamiltonian, dipole moment and polarizability operators of octahedral XY 6 molecules in a degenerate electronic state. These rovibronic operators are written with the aid of a tensorial formalism derived from the one already used in Dijon in the case of molecules in a non-degenerate electronic state. Electronic operators are defined from the group theory properties. Transition moment operators are introduced in order to consider rovibronic transitions. Spectrum simulations are made thanks to a new version of the HTDS sofware [J. Quant. Spectrosc. Radiat. Transfer 66 (2000) 16] used for the calculation of rovibrational spectra.
Reduction of the internal electric field in GaN/AlN quantum dots grown on the a ‐plane of SiC substrates
2005
We present a study of the emission of a multi-layer stack of self-assembled GaN/AlN quantum dots grown on the a -plane of 6H-SiC. We look for signatures of the internal electric field in the power dependence of the time-integrated and time-resolved photoluminescence spectra. The lack of a dynamical red-shift reveals that internal electric fields are significantly reduced in these dots. A band on the low energy side of the emission is observed whose intensity quenches fast when increasing the temperature. The polarization selection rules of the emission are examined in order to determine the physical nature of this band. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Estimation of the constant measurement error of stable random field
1999
International audience
Spectral density estimate for alpha-stable p-adic processes
2012
International audience
Estimation de la densité de la mesure spectrale mixte pour un processus symétrique stable strictement stationnaire
1994
International audience