Guided Quasicontinuous Atom Laser

We report the first realization of a guided quasicontinuous atom laser by rf outcoupling a Bose-Einstein condensate from a hybrid optomagnetic trap into a horizontal atomic waveguide. This configuration allows us to cancel the acceleration due to gravity and keep the de Broglie wavelength constant at 0.5 $\mu$m during 0.1 s of propagation. We also show that our configuration, equivalent to pigtailing an optical fiber to a (photon) semiconductor laser, ensures an intrinsically good transverse mode matching.Comment: version published in Phys. Rev. Lett. 97, 200402 (2006

Investigation of Damp Heat aging on soda-lime glass for photovoltaic applications

International audienceDamp heat test was performed on commercial soda-lime glass to characterize functional properties of glass in photovoltaic applications and to define aging mechanisms. In addition to the measurements of optical properties, FTIR, SEM-EDX and XPS analyses were carried out. The damp heat exposed samples presented an increased transmittance in UV, visible and near-IR ranges. The results were explained by hydration of glass network with heat. Molecular water adsorption involves a leaching process of network modifier cations and especially sodium ions. Hydrolysis also occurs in silica network with free molecular water reaction. This phenomenon enhances concentration of hydroxyl groups in glass highlighted by FTIR measurements and promotes formation of silanol groups. The tin side dependence on sodium leaching which acts as a passivating barrier for ionic transport is emphasized which would be worth taking into consideration for photovoltaic module design

Self-trapping in an array of coupled 1D Bose gases

We study the transverse expansion of arrays of ultracold $^{87}$Rb atoms weakly confined in tubes created by a 2D optical lattice, and observe that transverse expansion is delayed because of mutual atom interactions. A mean-field model of a coupled array shows that atoms become localized within a roughly square fort-like self-trapping barrier with time-evolving edges. But the observed dynamics is poorly described by the mean-field model. Theoretical introduction of random phase fluctuations among tubes improves the agreement with experiment, but does not correctly predict the density at which the atoms start to expand with larger lattice depths. Our results suggest a new type of self-trapping, where quantum correlations suppress tunneling even when there are no density gradients

Thermal study of an aluminium nitride ceramic heater for spray CVD on glass substrates by quantitative thermography

A thermographic approach is used to determine the temperature of an aluminium nitride hot plate as a glass substrate heater for depositing thin films by spray CVD (Chemical Vapour Deposition). In this context, the temperature of the hot plate is conditioned by the evaluation of both effective emissivity and environment temperature with calibration curve of the commercial camera. We first examined the consistency of the thermosignal/temperature correspondence by employing the software calibration. The environment temperature is evaluated by means of a ruffled aluminium foil according to ASTM. The effective emissivity is measured in situ by using a commercial IR camera on the temperature range of [40°C, 540°C] with a better than 3% accuracy. Absolute value of effective emissivity is in agreement with spectrometric values up to 120°C. Above this temperature, a strong dependence with temperature is highlighted. The radiometric temperature values are thereby corrected with an exactitude of temperature better than 2.5% in Celsius degree for the highest temperatures considered

A Circuit-Based Approach to Simulate the Characteristics of a Silicon Photovoltaic Module With Aging

The aging of photovoltaic modules results inevitably in a decrease of their efficiency all through their lifetime utilization. An approach to simulate the evolution of electrical characteristics of a photovoltaic module with aging is presented. The photovoltaic module is modeled by an equivalent electrical circuit whose components have time-dependent characteristics determined under accelerated tests. By entering sun irradiance and temperature, I–V and P–V curves as well as efficiency evolution can be simulated over years assuming equivalent time. The methodology is applied for the case of a monocrystalline photovoltaic module modeled by a one-diode circuit and aging laws are determined with experimental results of damp heat (DH) tests 85 °C/85% RH performed by Hulkoff (2009, “Usage of Highly Accelerated Stress Test (HAST) in Solar Module Aging Procedures,” M.S. thesis, Chalmers University of Technology, Göteborg, Sweden). A power degradation rate of 0.53%/yr is found. A parametric study shows that the rundown of optical transmittance of the upper layers with aging has the most important impact by reducing the initial efficiency by 11.5% over a 25-year exposure contrary to electrical degradations which cause a decrease of 1.85% of the initial efficiency

ÉTUDE DES PROPRIÉTÉS DE PROPAGATION<br />D'UN LASER À ATOMES

This manuscript presents various experimental and theoretical aspects concerning a specificsystem of atom optics : the atom laser. In our experiment, this one results from aBose-Einstein condensate of rubidium 87 and we thus initially detail the various coolingtechniques used to obtain this coherent atomic source in a hybrid ferromagnetic trap.The atom lasers we produce are extracted from the condensed cloud by radiofrequency,and propagate vertically under the effect of gravity. One specificity of our setup lies in thestrong magnetic confinement used, which results in non negligible collisional interactions betweenthe laser and the condensed source. We show that this has an influence, not only on theatom laser coupling dynamics, but also on its propagation. We indeed observe a transversestructure containing caustics on the laser beam. By using methods initially developed forphotonic optics (eikonal approximation, Fresnel-Kirchhoff integral, ABCD matrices), we calculatethe atom laser wavefunction. Moreover, we characterize the matter wave propagationin the paraxial regime by using the beam quality factor M2.We finally report the realization of an atom laser, guided by a horizontal optical potential,which enables us to cancel the acceleration due to gravity in such way, that the De Brogliewavelength remains constant throughout propagation.Ce manuscrit présente différents aspects expérimentaux et théoriques concernant un systèmepropre à l'optique atomique : le laser à atomes. Dans notre expérience, celui-ci est issud'un condensat de Bose-Einstein de Rubidium 87. Aussi, dans un premier temps, nous détaillonsles différentes techniques de refroidissement que nous mettons en oeuvre pour obtenircette source atomique cohérente dans un piège ferromagnétique hybride.Les lasers à atomes que nous réalisons sont extraits du nuage condensé par radiofréquence,et se propagent verticalement sous l'effet de la gravité. Une spécificité de notre expérienceréside dans le fort confinement magnétique utilisé, ce qui a pour conséquence de rendre importantesles interactions collisionnelles entre le laser et le condensat-source. Nous montronsque ceci a une influence, non seulement sur la dynamique de couplage du laser, mais aussi sursa propagation. Nous observons en effet une structure transverse du faisceau laser contenantdes caustiques. En utilisant des méthodes initialement développées pour l'optique photonique(approximation iconale, intégrale de Fresnel-Kirchhoff, matrices ABCD), nous calculons lafonction d'onde du laser à atomes. De plus, nous caractérisons la propagation de l'onde dematière dans le régime paraxial à l'aide du facteur de qualité M2.Enfin, nous rapportons la réalisation d'un laser à atomes guidé par un potentiel optiquehorizontal, ce qui nous permet d'annuler l'accélération due à la gravité de telle façon à ceque la longueur d'onde de De Broglie reste constante tout au long de la propagation

Etude des propriétés de propagation d'un laser à atomes

Cette thèse présente différents aspects expérimentaux et théoriques concernant un système propre à l'optique atomique: le laser à atomes. Dans notre expérience, celui-ci est issu d'un condensat de Bose-Einstein de Rubidium 87. Aussi, dans un premier temps, nous détaillons les différentes techniques de refroidissement que nous mettons en oeuvre pour obtenir cette source atomique cohérente dans un piège ferromagnétique hybride. Les lasers à atomes que nous réalisons sont extraits du nuage condensé par radiofréquence, et se propagent verticalement sous l'effet de la gravité. Une spécificité de notre expérience réside dans le fort confinement magnétique utilisé, ce qui a pour conséquence de rendre importantes les interactions collisionnelles entre le laser et le condensat-source. Nous montrons que ceci a une influence, non seulement sur la dynamique de couplage du laser, mais aussi sur sa propagation. Nous observons en effet une structure transverse du faisceau laser contenant des caustiques. En utilisant des méthodes initialement développées pour l'optique photonique (approximation eikonale, intégrale de Fresnel-Kirchhoff, matrices ABCD), nous calculons la fonction d'onde du laser à atomes. De plus, nous caractérisons la propagation de l'onde de matière dans le régime paraxial à l'aide du facteur de qualité M2. Enfin, nous rapportons la réalisation d'un laser à atomes guidé par un potentiel optique horizontal, ce qui nous permet d'annuler l'accélération due à la gravité de telle façon à ce que la longueur d'onde de De Broglie reste constante tout au long de la propagation.This thesis presents various experimental and theoretical aspects concerning a specific system of atom optics: the atom laser. In our experiment, this one results from a Bose-Einstein condensate of rubidium 87 and we thus initially detail the various cooling techniques used to obtain this coherent atomic source in a hybrid ferromagnetic trap. The atom lasers we produce are extracted from the condensed cloud by radiofrequency, and propagate vertically under the effect of gravity. One specificity of our setup lies in the strong magnetic confinement used, which results in non negligible collisional interactions between the laser and the condensed source. We show that this has an influence, not only on the atom laser coupling dynamics, but also on its propagation. We indeed observe a transverse structure containing caustics on the laser beam. By using methods initially developed for photonic optics (eikonal approximation, Fresnel-Kirchhoff integral, ABCD matrices), we calculate the atom laser wavefunction. Moreover, we characterize the matter wave propagation in the paraxial regime by using the beam quality factor M2. We finally report the realization of an atom laser, guided by a horizontal optical potential, which enables us to cancel the acceleration due to gravity in such way, that the De Broglie wavelength remains constant throughout propagation.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Influence of the window thermal diffusivity on the silicon wafer temperature in a rapid thermal system

The heating of a silicon wafer in a rapid thermal process is studied by numerical simulation. In the model, the equations of conservation of mass and energy are solved with the finite volume method and the determination of the solutions of the radiative transfer equation is based on the Monte-Carlo method. The results of numerical simulations, without optimization and in steady-state, show a close relationship between the thermal profiles of the silicon wafer and the ones of the quartz window. By introducing a high thermal diffusivity value for the window, the homogeneity of the wafer temperature is improved by 54%. The effect of heat storage by the quartz window on the temperature profile of the silicon substrate is hence well appreciated. Finally, a selection of materials is proposed for the implementation of the high diffusivity infrared window