Rapid prototyping of diffractive optical elements in microstructured sol-gel hybrid material

International audienceTELECOM Bretagne and HOLOTETRIX Company fabricate diffractive optical elements in photoresist by direct-write through a reconfigurable mask. The project is to transfer microstructured patterns of photoresist element to sol-gel hybrid material. This material offers better properties than photoresist to make diffractive optics

Tailoring 3-component photoinitiating systems for use as efficient photopolymerizable holographic material

8 pagesInternational audienceTo enhance the efficiency of photopolymerizable systems as holographic recording materials, the use of 3-component photoinitiating systems was explored. In order to get more insight into the hologram formation, gratings' recording curves were compared to those of monomer conversion obtained by RTFTIR spectroscopy. This work outlines the differences between the photoinitiating systems. A holographic 3-component recording material giving rise to thick phase holograms with both high diffraction yield and high rate of formation is highlighted

Photocyclic initiating system for free radical photopolymerization studied through holographic recording

International audienceThis paper discusses the efficiency of photocyclic initiating system (PCIS) based on a pyrromethene dye (EMP), an amine as electron donor (NPG) and an iodonium salt as electron acceptor (I250) under homogenous irradiation and holographic recording. It is shown that the PCIS is more efficient than the corresponding two component systems. This high efficiency is due to a photocyclic reaction that takes places during the irradiation, inducing the recovery of the dye in the ground state and the formation of two initiating radicals. The beneficial effect on the rate of grating formation and on the diffraction efficiency is clearly noticed. At high irradiation time, the fast polymerization observed with EMP-NPG-I250 even induces the polymerization in the dark fringes leading to a decrease of the holographic diffraction efficiency. This confirms the high performance of the photoinitiating system which can be used in holographic recording provided that the irradiation dose could be controlled

Conformational analysis of some pyridinium phenolates and synthetic precursors based on X-Ray and IR characterisations

7 pagesInternational audienceThis manuscript reports X-Ray and IR characterizations of representative pyridinium phenolates, model compounds for nonlinear optics. These analyses reveal the close dependence existing between molecular structure and the contribution of quinone and zwitterionic limiting forms. The bond length alternation (BLA) values, the well-known parameter correlated to hyperpolarisability β, are also discussed and compared with literature data

Stress birefringence patterning in photopolymer induced by structured illumination

4 pagesInternational audienceWe report on the stress birefringence distribution induced by the photopatterning of a multifunctional crosslinkable acrylate monomer sensitized in the visible range. The patterning of this material, prepared in a glass cell of a few tens of microns thickness, is obtained through illumination in a two steps process. The first step is performed using an illumination pattern with a high contrast and a low spatial frequency. The second one is a uniform illumination. The discrepancies in the shrinkage experimented by the material leads to the apparition of patterned stress birefringence revealed through polarimetry and diffraction measurements

Optimisation de nouveaux systèmes photoamorceurs de polymérisation pour le stockage d'informations par holographie

2 pagesNational audienceDifférents systèmes photoamorceurs mettant en jeu trois composants et destinés à la polymérisation d'un mélange d'acrylates sont ici optimisés en tant que support pour le stockage d'informations par holographie. Ces matériaux donnent naissance à des réseaux de phase épais, fonctionnant en transmission. L'étude basée sur l'enregistrement de réseaux sinusoïdaux sous forme d'une modulation d'indice de réfraction a permis de comparer les systèmes 3-composants aux 2-composants correspondants, les premiers étant plus performants d'un point de vue photochimique (vitesse et taux de polymérisation élevés). L'optimisation des matériaux a conduit à des rendements de diffraction corrigés dans l'ordre 1 supérieurs à 90%

Optimization of a photopolymerizable material based on a photocyclic initiating system using holographic recording

9 pagesInternational audienceA set of photoinitiating systems (PIS) for free radical photopolymerization was studied using time-resolved spectroscopic experiments, real-time FTIR and holographic recording. It is shown that the efficiency of the photoinitiating system can be drastically increased when a redox additive is added to the conventional dye/coinitiator system by virtue of photocyclic behaviour. The homogeneous photopolymerization process was found to reach a fast vitrification, limiting the conversion at about 55%. By contrast, holographic recording underlines the differences in photoinitiating system reactivity, allowing diffraction efficiencies close to unity for the most reactive PIS

Holography, reconstructing by light thanks to a photostructurable medium

During holographic recording, interference patterns produced by a reference beam and the light waves scattered by the object are stored by building-up of refractive index variations or relief profiles in the photosensitive medium. Early holograms used silver halide photographic emulsions as the recording medium. Being able to memorize an incident complex fringe pattern with small features at the submicrometer scale, different polymeric media are also successfully usable. All this optimizing work generated different applications

Technologie d'optique intégrée polymère au laboratoire FOTON

National audienceCet article résume le panorama de l'état de l'art des technologies d'optique intégrée polymère maitrisées au laboratoire Foton (Systèmes Photoniques) et qui sont axées sur des circuits optiques actifs et passifs. Les objectifs sont orientés vers un fort confinement du mode de propagation, la génération d'effets non linéaires, l'hybridation avec d'autres matériaux et la réduction des pertes (couplage et propagation)

Modelling the growth of a polymer micro-tip on an optical fiber end

Manufacturing end-of-fiber optical components able to realize optical functions ranging from a simple lens to more complex functions such as mode selective components is a decisive but \emph{a priori} complex task owing to the fiber core dimensions. Effective low cost methods allowing to grow polymer components by free-radical photopolymerization using the light coming out of the fiber have recently been reported. A novel phenomenological model of the photopolymerization process underlying is here given and used to simulate the polymer component growth in a three dimensional time-resolved manner. The simulations results are thus used to understand and optimize the component growth conditions, focusing particularly on the role of oxygen either present in the atmosphere or dissolved in the solution