arXiv subjects

Mathilde Fouché

Publications and source records attributed to Mathilde Fouché.

At least 19 recordsLinked to original sources

arXiv2020

A comparison of g(1)(τ), g(3/2)(τ), and g(2)(τ), for radiation from harmonic oscillators in Brownian motion with coherent background

We compare the field-field g(1)(τ), intensity-field g(3/2)(τ), and intensity-intensity g(2)(τ) correlation functions for models that are of relevance in astrophysics. We obtain expressions for the general case of a chaotic radiation, where the amplitude is Rician based on a model with an ensemble of harmonic oscillators in Brownian motion. We obtain the signal to noise ratios for two methods of measurement. The intensity-field correlation function signal to noise ratio scales with the first power of |g(1)(τ)|. This is in contrast with the well-established result of g(2)(τ) which goes as the square of |g(1)(τ)|.

physics.optics↗

arXiv2020

Connecting field and intensity correlations: the Siegert relation and how to test it

The Siegert relation relates the electric field and intensity correlations of light, under given assumptions. After a brief history of intensity correlations, we give a derivation of the relation. Then we present an experiment, which can be easily adapted for an undergraduate setup, and that allows measuring both field and intensity correlations at the same time, thus providing a direct test of the Siegert relation. As a conclusion, we discuss typical situations where the relation fails.

physics.atom-ph↗

arXiv2019

Mollow triplet in cold atoms

In this paper, we measure the spectrum of light scattered by a cold atomic cloud driven by a strong laser beam. The experimental technique is based on heterodyne spectroscopy coupled to single-photon detectors and intensity correlations. At resonance, we observe the Mollow triplet. This spectrum is quantitatively compared to the theoretical one, emphasizing the influence of the temperature of the cloud and the finite-size of the laser beam. Off resonance measurements are also done showing a very good agreement with theory.

physics.atom-ph↗

arXiv2018

Intensity Interferometry revival on the Côte d'Azur

Recent advances in photonics have revived the interest in intensity interferometry for astronomical applications. The success of amplitude interferometry in the early 1970s, which is now mature and producing spectacular astrophysical results (e.g. GRAVITY, MATISSE, CHARA, etc.), coupled with the limited sensitivity of intensity interferometry stalled any progress on this technique for the past 50 years. However, the precise control of the optical path difference in amplitude interferometry is constraining for very long baselines and at shorter wavelengths. Polarization measurements are also challenging in amplitude interferometry due to instrumental effects. The fortuitous presence of strong groups in astronomical interferometry and quantum optics at Universite Cote d'Azur led to the development of a prototype experiment at Calern Observatory, allowing the measure of the temporal correlation g(2)(τ, r=0) in 2016 and of the spatial correlation g^(2)(r) in 2017 with a gain in sensitivity (normalized in observing time and collecting area) of a factor ~100 compared to Hanbury Brown and Twiss's original Narrabri Interferometer. We present possible ways to further develop this technique and point to possible implementations on existing facilities, such as CTA, the VLTI ATs or the summit of Maunakea, which offer a unique scientific niche.

astro-ph.IM↗

arXiv2018

Optical long baseline intensity interferometry: prospects for stellar physics

More than sixty years after the first intensity correlation experiments by Hanbury Brown and Twiss, there is renewed interest for intensity interferometry techniques for high angular resolution studies of celestial sources. We report on a successful attempt to measure the bunching peak in the intensity correlation function for bright stellar sources with 1 meter telescopes (I2C project). We propose further improvements of our preliminary experiments of spatial interferometry between two 1 m telescopes, and discuss the possibility to export our method to existing large arrays of telescopes.

astro-ph.IM↗

arXiv2018

Diffusing-Wave Spectroscopy of Cold Atoms in Ballistic Motion

Diffusing-wave spectroscopy is a powerful technique which consists in measuring the temporal correlation function of the intensity of light multiply scattered by a medium. In this paper, we apply this technique to cold atoms under purely ballistic motion and we investigate the transition between the single and the multiple scattering regime. The intensity correlation function changes from a simple Gaussian function, whose width reveals the sample temperature, to a more complex decay shortened by the frequency redistribution in the thick cloud. These features are quantitatively compared to simulations with a phase-coherent and an incoherent model. Both show a very good agreement with the experiments.

physics.atom-ph↗

arXiv2016

Noise spectroscopy with large clouds of cold atoms

Noise measurement is a powerful tool to investigate many phenomena from laser characterization to quantum behavior of light. In this paper, we report on intensity noise measurements obtained when a laser beam is transmitted through a large cloud of cold atoms. While this measurement could possibly investigate complex processes such as the influence of atomic motion, one is first limited by the conversion of the intrinsic laser frequency noise to intensity noise via the atomic resonance. This conversion is studied here in details. We show that, while experimental intensity noise spectra collapse onto the same curve at low Fourier frequencies, some differences appear at higher frequencies when the probe beam is detuned from the center of the resonance line. A simple model, based on a mean-field approach, which corresponds to describing the atomic cloud by a dielectric susceptibility, is sufficient to understand the main features. Using this model, the noise spectra allow extracting some quantitative informations on the laser noise as well as on the atomic sample.

physics.atom-ph↗

arXiv2015

Circular and linear magnetic birefringences in xenon at $λ= 1064$ nm

The circular and linear magnetic birefringences corresponding to the Faraday and the Cotton-Mouton effects, respectively, have been measured in xenon at $λ= 1064$ nm. The experimental setup is based on time dependent magnetic fields and a high finesse Fabry-Perot cavity. Our value of the Faraday effect is the first measurement at this wavelength. It is compared to theoretical predictions. Our uncertainty of a few percent yields an agreement at better than 1$σ$ with the computational estimate when relativistic effects are taken into account. Concerning the Cotton-Mouton effect, our measurement, the second ever published at $λ= 1064$ nm, agrees at better than $1σ$ with theoretical predictions. We also compare our error budget with those established for other experimental published values.

physics.optics↗

arXiv2013

Faraday and Cotton-Mouton Effects of Helium at $λ= 1064$ nm

We present measurements of the Faraday and the Cotton-Mouton effects of helium gas at $λ=~1064$\,nm. Our apparatus is based on an up-to-date resonant optical cavity coupled to longitudinal and transverse magnetic fields. This cavity increases the signal to be measured by more than a factor of 270\,000 compared to the one acquired after a single path of light in the magnetic field region. We have reached a precision of a few percent both for Faraday effect and Cotton-Mouton effect. Our measurements give for the first time the experimental value of the Faraday effect at $λ$=\,1064\,nm. This value is compatible with the theoretical prediction. Concerning Cotton-Mouton effect, our measurement is the second reported experimental value at this wavelength, and the first to agree at better than 1$σ$ with theoretical predictions.

physics.optics↗

arXiv2011

Magnetic Linear Birefringence Measurements Using Pulsed Fields

In this paper we present the realization of further steps towards the measurement of the magnetic birefringence of the vacuum using pulsed fields. After describing our experiment, we report the calibration of our apparatus using nitrogen gas and we discuss the precision of our measurement giving a detailed error budget. Our best present vacuum upper limit is Dn < 5.0x10^(-20) T^-2 per 4 ms acquisition time. We finally discuss the improvements necessary to reach our final goal.

physics.optics↗

arXiv2011

Observation of the Inverse Cotton-Mouton Effect

We report the observation of the Inverse Cotton-Mouton Effect (ICME) i.e. a magnetization induced in a medium by non resonant linearly polarized light propagating in the presence of a transverse magnetic field. We present a detailed study of the ICME in a TGG crystal showing the dependence of the measured effect on the light intensity, the optical polarization, and on the external magnetic field. We derive a relation between the Cotton-Mouton and Inverse Cotton-Mouton effects that is roughly in agreement with existing experimental data. Our results open the way to applications of the ICME in optical devices.

physics.optics↗

arXiv2010

A Photon Regeneration Experiment for Axionlike Particle Search using X-rays

In this letter we describe our novel photon regeneration experiment for the axionlike particle search using a x-ray beam with a photon energy of 50.2 keV and 90.7 keV, two superconducting magnets of 3 T, and a Ge detector with a high quantum efficiency. A counting rate of regenerated photons compatible with zero has been measured. The corresponding limits on the pseudoscalar axionlike particle-two photon coupling constant is obtained as a function of the particle mass. Our setup widens the energy window of purely terrestrial experiments devoted to the axionlike particle search by coupling to two photons. It also opens a new domain of experimental investigation of photon propagation in magnetic fields.

hep-ex↗

arXiv2010

Dynamical behaviour of birefringent Fabry-Perot cavities

In this paper we present a theoretical and experimental study of the dynamical behaviour of birefringent cavities. Our experimental data show that usual hypothesis which provides that a Fabry-Perot cavity is a first-order low pass filter cannot explain the behaviour of a birefringent cavity. We explain this phenomenon, and give the theoretical expression of the equivalent cavity filter which corresponds to a second-order low pass filter.

physics.optics↗

arXiv2010

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.

physics.optics↗

arXiv2009

Birefringence of interferential mirrors at normal incidence Experimental and computational study

In this paper we present a review of the existing data on interferential mirror birefringence. We also report new measurements of two sets of mirrors that confirm that mirror phase retardation per reflection decreases when mirror reflectivity increases. We finally developed a computational code to calculate the expected phase retardation per reflection as a function of the total number of layers constituting the mirror. Different cases have been studied and we have compared computational results with the trend of the experimental data. Our study indicates that the origin of the mirror intrinsic birefringence can be ascribed to the reflecting layers close to the substrate.

physics.optics↗

arXiv2008

Search for photon oscillations into massive particles

In 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 $1.1 {meV} <m_a<2.6 {meV}$. We also show that our experimental results improve the existing limits on the parameters of a low mass hidden-sector boson usually dubbed "paraphoton" because of its similarity with the usual photon.

hep-ex↗

arXiv2007

An Optical Lattice Clock with Spin-polarized 87Sr Atoms

We present a new evaluation of an 87Sr optical lattice clock using spin polarized atoms. The frequency of the 1S0-3P0 clock transition is found to be 429 228 004 229 873.6 Hz with a fractional accuracy of 2.6 10^{-15}, a value that is comparable to the frequency difference between the various primary standards throughout the world. This measurement is in excellent agreement with a previous one of similar accuracy.

physics.atom-ph↗

arXiv2007

Accuracy Evaluation of an Optical Lattice Clock with Bosonic Atoms

We report the first accuracy evaluation of an optical lattice clock based on the 1S0 - 3P0 transition of an alkaline earth boson, namely 88Sr atoms. This transition has been enabled using a static coupling magnetic field. The clock frequency is determined to be 429 228 066 418 009(32) Hz. The isotopic shift between 87Sr and 88Sr is 62 188 135 Hz with fractional uncertainty 5.10^{-7}. We discuss the conditions necessary to reach a clock accuracy of 10^{-17} or less using this scheme.

physics.atom-ph↗