Highly sensitive frequency metrology for optical anisotropy measurements

In this paper we present a novel apparatus aimed at measuring very small birefringences and anisotropies, based on frequency metrology and not on polarimetry as usual. In our experiment, a very high finesse resonant cavity is used to convert the phase difference into a resonance frequency difference, which can then be measured with very high accuracy. We describe the set-up and present the results of experimental tests which exhibited a sensitivity dn ~ 2 x 10?18, allowing for the measurement of long-predicted magneto-electro-optical effects in gases. Since the shotnoise limited sensitivity of our apparatus lies well below the state-of-the-art sensitivity, frequency metrology appears as a promising technique for small birefringence measurements.Comment: Accepted for publication in Review of Scientific Instrument

Status of the BMV experiment

In this contribution we present the status of the BMV experiment whose goal is to measure the vacuum magnetic birefringence

Search for photon oscillations into massive particles

International audienceIn this paper, we present the final results of our experiment on photon-axion oscillations in the presence of a magnetic field, which took place at LULI (Laboratoire pour l'Utilisation des Lasers Intenses, Palaiseau, France). Our null measurement allowed us to exclude the existence of axions with inverse coupling constant $M>9.\times 10^5$ GeV for low axion masses and to improve the preceding BFRT limits by a factor 3 or more for axion masses $1.1\, \mbox{meV

Polarization state of the optical near-field

The polarization state of the optical electromagnetic field lying several nanometers above complex dielectric structures reveals the intricate light-matter interaction that occurs in this near-field zone. This information can only be extracted from an analysis of the polarization state of the detected light in the near-field. These polarization states can be calculated by different numerical methods well-suited to near--field optics. In this paper, we apply two different techniques (Localized Green Function Method and Differential Theory of Gratings) to separate each polarisation component associated with both electric and magnetic optical near-fields produced by nanometer sized objects. The analysis is carried out in two stages: in the first stage, we use a simple dipolar model to achieve insight into the physical origin of the near-field polarization state. In the second stage, we calculate accurate numerical field maps, simulating experimental near-field light detection, to supplement the data produced by analytical models. We conclude this study by demonstrating the role played by the near-field polarization in the formation of the local density of states.Comment: 9 pages, 11 figures, accepted for publication in Phys. Rev.

Atomes froids dans des réseaux optiques - Quelques facettes surprenantes d'un système modèle

This thesis is devoted to the experimental study of atoms trapped and cooled in several types of optical structures. In order to characterise these media, we used different techniques such as time-of-flight techniques, direct imaging of the atomiccloud and pump-probe spectroscopy. We thus obtained information about kinetic temperature, spatial diffusion of atoms and atomic motion in the optical potential wells.We first studied the dynamics of cesium atoms in three-dimensional bright optical lattices when a magnetic field is applied. In particular, we showed that optical lattices operating in the jumping regime do provide good trapping and cooling efficiencies and that a motionnal narrowing effect gives birth to narrowvibrational sidebands on pump-probe transmission spectra. Still with cesium atoms, we created and characterised a three-dimensional bright optical lattice obtained with only two laser beams through the Talbot effect, and also a random mediumgenerated by a speckle field.We endly studied a ``brownian motor'' for $^(87)$Rb atoms in a grey asymmetric potential. The results of the experimental study are in good qualitative agreement with semi-classical Monte-Carlo numerical simulations.Cette thèse est consacrée à l'étude expérimentale d'atomes piégéset refroidis dans plusieurs types de structures lumineuses. Nous avons utilisé pour caractériser ces milieux des techniques de temps de vol, d'imagerie directe du nuage atomique et de spectroscopie pompe-sonde, afin d'obtenir des informations sur la température et la diffusion spatiale des atomes ainsi que sur leur mouvement dans les puits de potentiel.Nous avons d'abord étudié la dynamique d'atomes de césium dans desréseaux optiques tri-dimensionnels brillants en présence d'un champmagnétique, et nous avons en particulier montré que les réseaux optiques fonctionnant en régime sautant donnent lieu à un refroidissement et un piégeage efficaces, et qu'un mécanisme de rétrécissement par le mouvement y conduit à des raies vibrationnelles étroites sur les spectres de transmission pompe-sonde. Avec des atomes de césium, nous avons également créé etcaractérisé un réseau optique tri-dimensionnel brillant obtenu avecseulement deux faisceaux laser grâce à l'effet Talbot, puis un milieu aléatoire engendré à partir d'un champ de tavelures.Enfin, nous avons étudié un ``moteur brownien'' pour des atomes de $^(87)$Rb dans un réseau gris asymétrique. Les résultats de l'étudeexpérimentale sont en bon accord qualitatif avec des simulations numériques Monte-Carlo semi-classiques