Search results for "optique"

Nonlinear phase shift measurement by heterodyne detection in waveguides optics

2022

Nonlinear optics has been a productive field of research and investigation for a few decades now, but the rapid progression of photonic integration platforms in recent years has opened up a whole new range of applications. On-chip integration of effective saturable absorbers and secondary sources including Brillouin laser, supercontinua, or frequency combs are few examples of the very wide possibilities offered by nonlinear nanophotonics. In this context, materials with large third-order optical nonlinearities become highly sought after, as they enable the development of nonlinear functionalities at low input powers. Given a large number of potential candidates as material for nonlinear nan…

Le dioxyde de titane : un matériau nouveau pour la photonique à 1.55 µm et à 2 µm

2018

In the next decades, the limits of current optical communication systems will be reached unless new solutions are adopted. On of them is the use of a new spectral range around 2 µm enabled by the emergence of thulium-doped fiber amplifiers. In this thesis, we will focus on it in the context of very short distances transmissions on photonic chips. Various materials, mainly titanium dioxide (TiO2), will be explored.This thesis work has two main objectives. On the one hand, it aims to demonstrate that a material relatively unexplored, titanium dioxide, is promising for telecom applications by comparing it to more mature plateforms. On the other hand, it tends to introduce the spectral band aro…

Coupled experiment/simulation approach for the design of radiation-hardened rare-earth doped optical fibers and amplifiers

2011

We developed an approach to design radiation-hardened rare earth -doped fibers and amplifiers. This methodology combines testing experiments on these devices with particle swarm optimization (PSO) calculations. The composition of Er/Yb-doped phosphosilicate fibers was improved by introducing Cerium inside their cores. Such composition strongly reduces the amplifier radiation sensitivity, limiting its degradation: we observed a gain decreasing from 19 dB to 18 dB after 50 krad whereas previous studies reported higher degradations up to 0°dB at such doses. PSO calculations, taking only into account the radiation effects on the absorption efficiency around the pump and emission wavelengths, co…

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 …

Self-organization of incoherent optical waves : Condensation, thermalization and repolarization

2019

The subject of this thesis concerns the study of phenomena of self-organization of incoherentoptical waves. This work is essentially theoretical and numerical and relies on different formalisms of waveturbulence theory, the Hamiltonian singularities, and different experiments.The first part of the thesis deals with the irreversible processes of thermalization and condensation ofincoherent waves. The phenomenon of condensation is characterized by the formation of a large scale co-herent structure (condensate) that remains immersed in a sea of small scale fluctuations (uncondensedparticules). In spite of the large propagation lengths required to reach the condensed equilibrium state, wehave i…

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

2009

Sur le rôle des singularités hamiltoniennes dans les systèmes contrôlés : applications en mécanique quantique et en optique non-linéaire.

2012

This thesis has two goals: the first one is to improve the control techniques in quantum mechanics, and more specifically in NMR, by using the tools of geometric optimal control. The second one is the study of the influence of Hamiltonian singularities in controlled systems. The chapter about optimal control study three classical problems of NMR : the inversion problem, the influence of the radiation damping term, and the steady state technique. Then, we apply the geometric optimal control to the problem of the population transfert in a three levels quantum system to recover the STIRAP scheme.The two next chapters study Hamiltonian singularities. We show that they allow to control the polar…

Study of supercontinuum sources based on tellurite glass optical fibers for mid-infrared absorption spectroscopy applied to gas sensing

2015

This work focuses on the development of mid-infrared supercontinuum light sources and their application for gas detection through absorption spectroscopy. The study of supercontinuum sources is based on nonlinear ultrashort pulse propagation in tellurite glass (80TeO2-10ZnO-10Na2O) and used in three different forms, namely a thin bulk sample, a microstructured suspended-core fiber, and a tapered suspended-core fiber. These technical means adapt themselves to distinct laser sources commercially available, thus optimizing the implementation of ultrawide-band infrared light sources. Experimental observations are compared to corresponding numerical simulations, thus pointing out the different u…

Frequency comb generation by electro-optic modulation and applications

2020

The work presented in this thesis relates the development of a dual frequency comb spectrometer based on the electro-optic modulation of a continuous wave laser, and its utilisation for spectroscopic applications in the near- and mid-infrared.Since their discovery in the 1960s, frequency combs have revolutionised the physics, especially in metrology but also in spectroscopy, which lead to the Nobel Prize in Physics in 2005. In this domain of applications, dual frequency comb spectrometers are known to be complex to develop and use. A possibility to bypass these constraints is to build the spectrometer with electro-optic modulators. This particular architecture makes the experimental setup e…

Impact du profil de phase initial sur l'évolution asymptotique d'impulsions dans un amplificateur à fibre

2009

National audience; Nous étudions numériquement l'impact d'une dérive de fréquence initiale ou d'un saut de phase initial sur la dynamique asymptotique d'une impulsion se propageant dans un amplificateur à fibre à dispersion normale. Nous montrons notamment que si l'enveloppe de l'impulsion reste correctement décrite par l'expression analytique d'un similariton parabolique, des structures sombres peuvent néanmoins se superposer à cette enveloppe.