Précipitation induite par laser : cinétique de photodéposition et application à la réalisation de réseaux de diffraction permanents.

Ce travail porte sur l'étude d'un procédé de microfabrication par laser : la déposition photochimique. Celle-ci consiste en une réaction de précipitation à la surface d'un substrat déclenchée par une onde laser. Les expériences réalisées dans une solution photosensible à base de chromate avec un laser Argon ionisé continu montrent qu'il existe un seuil en intensité permettant d'obtenir une transition liquide/solide. La trempe en concentration induite par le faisceau laser est déterminée à partir d'une équation de réaction-diffusion. Grâce à un modèle thermodynamique de croissance de goutte, la cinétique d'un dépôt est déduite et comparée à des résultats expérimentaux. Un comportement universel de la croissance aux temps longs est alors trouvé. L'application de la déposition photochimique à la réalisation de réseaux de diffraction est montrée et l'ajustement du modèle thermodynamique à partir de la figure de diffraction expérimentale permet de décrire l'évolution temporelle de la morphologie induite par le champ laser. D'autres applications (écriture sur surface planes et courbes) sont également présentées.In this study, we analyze a laser microfabrication process : the photochemical deposition. A precipitation reaction is triggered by a laser wave on a substract. Experiments realized in a chromate based photosensitive mixture with a continuous Argon laser show the existence of an intensity threshold above which a liquid/solid transition occurs. The quench in concentration is determined by a reaction-diffusion equation. Using a droplet growth model, we deduced the kinetics of a deposit which is compared with experimental results. An universal single-scaled dynamics is then found at late stage. The application of photochemiacal deposition to the recording of diffraction gratings is shown and a fit of the experimental diffraction pattern with the model allows us to describe the temporal behavior of the laser induced morphology. Others applications (planar and curved surfaces writing) are also illustrated

Universal behavior of photochemical deposition in liquid solutions driven by a one-photon transition

Even if photochemical deposition of nearly all types of materials has been used for decades to pattern almost any kind of substrate for various applications catalysis, chemical sensing, magnetic data storage, optoelectronics, spin-dependent electron transport, and solar cells, a rationalized description is still missing. This paper aims at fulfilling this lack by presenting a unified approach of the photodeposit growth initiated by a onephoton photochemical reaction. We experimentally investigate the robustness of growth scalings predicted for photochemical deposition driven by a continuous laser wave. Three types of one-photon photochemical reactions photoexcitation of chromates, photodissociation of permanganates, and photocondensation of colloidal selenium and three parameters solvent pH variations, concentration in photoactive reagent, and influence of the exciting optical wavelength were cross analyzed. In all the cases, including data taken from the literature, the same dynamic master behavior emerges from the data rescaling of measured deposit growth laws. The nice agreement observed between system-independent predictions and the whole data set strongly supports a universal description of the photodeposit growth whatever the photosensitive medium and the involved onephoton chemical reaction. Such an approach also points out the quantitative sorting of photochemical reactions in terms of deposition efficiency. This rationalization of the kinetics of photodeposition anticipates new methodologies to predict, design, and control substrate micropatterning for chemical, lithographic, and optoelectronic applications

Universal behavior of photochemical deposition in liquid solutions driven by a one-photon transition

Even if photochemical deposition of nearly all types of materials has been used for decades to pattern almost any kind of substrate for various applications catalysis, chemical sensing, magnetic data storage, optoelectronics, spin-dependent electron transport, and solar cells, a rationalized description is still missing. This paper aims at fulfilling this lack by presenting a unified approach of the photodeposit growth initiated by a onephoton photochemical reaction. We experimentally investigate the robustness of growth scalings predicted for photochemical deposition driven by a continuous laser wave. Three types of one-photon photochemical reactions photoexcitation of chromates, photodissociation of permanganates, and photocondensation of colloidal selenium and three parameters solvent pH variations, concentration in photoactive reagent, and influence of the exciting optical wavelength were cross analyzed. In all the cases, including data taken from the literature, the same dynamic master behavior emerges from the data rescaling of measured deposit growth laws. The nice agreement observed between system-independent predictions and the whole data set strongly supports a universal description of the photodeposit growth whatever the photosensitive medium and the involved onephoton chemical reaction. Such an approach also points out the quantitative sorting of photochemical reactions in terms of deposition efficiency. This rationalization of the kinetics of photodeposition anticipates new methodologies to predict, design, and control substrate micropatterning for chemical, lithographic, and optoelectronic applications

Précipitation induite par laser (cinétique de photodéposition et application à la réalisation de réseaux de diffraction permanents)

BORDEAUX1-BU Sciences-Talence (335222101) / SudocSudocFranceF

Amplification fibrée de forte énergie pour les lasers de puissance

Ces travaux concernent le développement d un amplificateur à fibre optique souple, microstructurée, double-gaine, dopée ytterbium (Yb), et monomode à large coeur, dans la gamme d impulsion nanoseconde, multi-kiloHertz et milliJoule, pour l injection de chaînes lasers de puissance. L architecture amplificatrice est mise en oeuvre dans une configuration MOPA (Master Oscillator Power Amplifier) à plusieurs étages. Un modèle numérique de l amplification sur fibre double-gaine dopée Yb, incluant l émission spontanée amplifiée, a été développé pour étudier le comportement de ce type d amplificateur fibré et procéder au dimensionnement du dispositif expérimental. Afin de s affranchir du processus de saturation par le gain, un algorithme de contre-réaction permettant de déterminer numériquement la forme temporelle optimale a été associé au modèle. Nous avons obtenu des résultats expérimentaux en bon accord avec les simulations numériques, et avec les performances suivantes : une énergie de 0.5 mJ par impulsion à une fréquence de répétition dans la gamme de 1 kHz à 10 kHz, sur des impulsions à spectre étroit centré à la longueur d onde 1053 nm, à profil temporel super-gaussien d ordre 20 de durée 10 ns, avec un rapport signal-sur-bruit optique supérieur à 50 dB et un taux de maintien de la polarisation à 20 dB. Le profil spatial en sortie de système est monomode (M =1.1). Ce dispositif peut également délivrer des énergies jusqu à 1.5 mJ. Nous avons ensuite mis à profit ces performances pour l amplification d impulsions à dérive de fréquence, et avons obtenu une énergie par impulsion de 0.7 mJ sur une durée de 570 fs, à une fréquence de répétition de 10 kHz.This work concerns the development of a double-clad ytterbium-doped single-mode microstructured flexible fiber-based amplifier, in the nanosecond, multi-kiloHertz and milliJoule regime, for large-scale laser facilities seeding. We have used a multi-stage master oscillator power amplifier fibered architecture. A numerical model of ytterbium-doped double-clad fiber-based amplification, including amplified spontaneous emission, was developed in order to study the behaviour of such amplifier and to correctly design the experimental set-up. This model was completed by a feed-back algorithm to numerically predict the optimal temporal shape to compensate the gain saturation process. We demonstrated experimental results in good agreement with numerical simulations, with the following performances: 0.5 mJ pulse energy, at a frequency repetition from 1 kHz to 10 kHz, with a narrow bandwidth spectrum centred at 1053 nm wavelength, with 10 ns pulse duration on a perfect super-Gaussian temporal profile, an optical signal-to-noise ratio better than 50 dB and a polarization extinction ratio of 20 dB. We checked that the beam quality was diffraction limited, with an M measurement of 1.1. Moreover, the system can deliver energies up to 1.5 mJ. Then, we took the advantage of such results to amplify chirped pulses. We demonstrated 0.7 mJ pulse energy, with 570 fs duration at 10 kHz repetition frequency.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF

Numerical analysis of broad band fiber optical parametric amplifiers pumped by two chirped pulses

International audienceOptical parametric amplifier pumped by two chirped pump pulses has been analytically and numerically investigated to predict the spectral gain bandwidth and its temporal distribution. We highlight that the properties of the amplifier depend strongly on the relative chirp values and a uniform spectro-temporal gain can be obtained when the two chirps have opposite signs. A chirped signal pulse owing a very broad bandwidth has also been injected and we demonstrate the amplification of ultra-short pulse with this type of amplifiers

Influence of the substrate/photo-active solution interaction in patterning and adhesion of photo-deposited films

Using the photo-chemical deposition of chromium hydroxide layers driven by a continuous Ar+ laser wave in a potassium chromate solution, we explored the adhesion and patterning properties of the induced deposit on glass substrates versus the composition and the pH of the photo-active solution. The experiments were performed with two interfering beams imprinting an optical pattern on the substrate and analyzing the resulting morphology of the deposit. The solubility, patterning and adhesion are investigated using both organic (acetic acid) and inorganic (HCl) acids. The observed adhesion as a function of the pH in the photo-deposition process (surface versus bulk) was compared for several substrates

Universal behavior of photochemical deposition in liquid solutions driven by a one-photon transition

Even if photochemical deposition of nearly all types of materials has been used for decades to pattern almost any kind of substrate for various applications catalysis, chemical sensing, magnetic data storage, optoelectronics, spin-dependent electron transport, and solar cells, a rationalized description is still missing. This paper aims at fulfilling this lack by presenting a unified approach of the photodeposit growth initiated by a onephoton photochemical reaction. We experimentally investigate the robustness of growth scalings predicted for photochemical deposition driven by a continuous laser wave. Three types of one-photon photochemical reactions photoexcitation of chromates, photodissociation of permanganates, and photocondensation of colloidal selenium and three parameters solvent pH variations, concentration in photoactive reagent, and influence of the exciting optical wavelength were cross analyzed. In all the cases, including data taken from the literature, the same dynamic master behavior emerges from the data rescaling of measured deposit growth laws. The nice agreement observed between system-independent predictions and the whole data set strongly supports a universal description of the photodeposit growth whatever the photosensitive medium and the involved onephoton chemical reaction. Such an approach also points out the quantitative sorting of photochemical reactions in terms of deposition efficiency. This rationalization of the kinetics of photodeposition anticipates new methodologies to predict, design, and control substrate micropatterning for chemical, lithographic, and optoelectronic applications