Cognitive ability experiment with photosensitive organic molecular thin films

We present an optical experiment which permits to evaluate the information exchange necessary to self-induce cooperatively a well-organized pattern in a randomly activated molecular assembly. A low-power coherent beam carrying polarization and wavelength information is used to organize a surface relief grating on a photochromic polymer thin film which is photo-activated by a powerful incoherent beam. We demonstrate experimentally that less than 1% of the molecules possessing information cooperatively transmit it to the entire photo-activated polymer film.Comment: 16 pages, 4 figure

Relationship between structure, surface topography and tribo-mechanical behavior of Ti-N thin films elaborated at different N2 flow rates

Titanium nitride films were deposited by reactive magnetron sputtering on Si (100) wafers, glass and Ti6Al4V substrates. The film deposition was carried out in a gas mixture of Ar and N2. The nitrogen content was varied between 0 and 30 % of the total gas mixture. This variation led to the formation of different films with different microstructures. The microstructure of the Ti-N coatings presented nanocomposites with a low tendency to surface oxidation. From a pure Ti to tetragonal Ti2N and cubic Ti-N microstructures, the films showed a (111) TiN plane growth that led to an increase in the lattice strain and a decrease in the grain size when increasing the nitrogen flow rate. The water-film contact angle measurements showed that the surface hydrophobicity increased with the increase of nitrogen content in the film. Mechanical properties were measured and a strong dependence between microstructure and hardness was found. The Ti-N deposited under 20 % of N2 exhibited the highest hardness, the best adhesion and wear resistance, and the lowest friction coefficient with the presence of (111) fiber texture

Photomolecular motions on azopolymer nano-objects: Toward new applications for photonics and biology

review of applications with self-organizing azopolymerInternational audienc

Preparation and characteristics of new chiral photochromic copolymers

International audienceThe copolymers consisting of chiral (S)-(−)-1-(4-nitrophenyl)pyrrolidin-2-yl]methyl 2-methacrylate ((S)-PYM) and azobenzene methacrylic co-monomers: 2-(methyl{4-[(E)-(5-methylisoxazol-3-yl)diazenyl]phenyl}amino)ethyl 2-methacrylate (ISM) or 2-{[4-[4-{(2,6-dimethylpirymidin-4-yl)amino]sulfonyl}phenyl) diazenyl]phenyl}-(methyl)amino]ethyl 2-methacrylate (SUM) were synthesized by radical polymerization. The quantum chemical calculations were carried out to predict spectral and nonlinear optical properties of the materials in question. The copolymers showed reversible photochromic properties under illumination with light by change of UV–vis spectra and ellipsometric parameters. The ellipsometric measurements made it possible to determine the change of refractive index under illumination that was in the range between 0.017 and 0.041 depending on copolymer type. Photochromic gratings were inscribed on the surface of polymer films in two kinds of experiments, leading to interesting conclusion that the surface relief grating could be recorded by two interfering laser beams as well as by a single linearly polarized laser beam. The chirooptical properties of the materials were investigated by circular dichroism spectroscopy.</p

Light-Induced Electroluminescence Patterning: Interface Energetics Modification at Semiconducting Polymer and Metal-Oxide Heterojunction in a Photodiode

International audienc

Instantaneous photoinduced patterning of an azopolymer colloidal nanosphere assembly

International audienceColloidal azopolymer nanospheres assembled on a glass substrate were exposed to a single collimated laser beam. The combination of photo-fluidic elongation of the spherical colloids and light induced self-organization of the azopolymer film allows the quasi-instantaneous growth of a large amplitude surface relief grating. Pre-structuration of the sample with the nanosphere assembly supports faster creation of the spontaneous pattern. Confinement into the nanospheres provides exceptionally large modulation amplitude of the spontaneous relief. The method is amenable to any kind of photoactive azo-materials

Photoinduced deformation of azopolymer nanometric spheres

International audienceNanometric spheres of an azopolymer are obtained by micellization from a solution. We observe photoinduced deformation of the individual nanospheres under white light illumination. The diameter expands up to 35% parallel to the substrate surface. The magnitude of the force that is necessary to produce the same effect is estimated.</p

Thin laser beam wandering and intensity fluctuations method for evapotranspiration measurement

International audienceWe compare in this study two simple optical setups to measure the atmospheric turbulence characterized by the refractive index structure parameter [View the MathML source] Cn2. The corresponding heat flux values sensed by the laser beam propagation are calculated leading to the plant evapotranspiration. The results are discussed and compared to measurements obtained with a well-known and calibrated eddy-covariant instrument. A fine analysis gives a good insight of the accuracy of the optical devices proposed here to measure the crop evapotranspiration. Additional evapotranspiration values calculated with meteorological sensor data and the use of different models are also compared in parallel

Multi-scale pattern with surface quasi crystal for wettability tuning

International audienceNew all-optical poling (AOP) experiments conducted in multi-core dye-doped poly(methyl methacrylate) optical fibers show that self-sustained and faster rise time second harmonic generation is possible in polymers. OCIS codes: (060.4005) Microstructured fibers; (060.4370) Nonlinear optics fibers. The possibility to convert by light the nature of a transparent material and to reveal its nonlinear optical properties is always challenging [1]. Second-order nonlinear effects are forbidden in centrosymmetric materials. However a pump beam with a simultaneous seeding light at double frequency has revealed the possibility of inducing a second-order nonlinear optical susceptibility (2) by light [2]. The origin of the effect was found in an orientational hole burning. All-optical poling (AOP) has been developed as a self-induced second harmonic generation process. Despite a huge activity dedicated to the study of AOP in polymer materials, the stable induction of a second harmonic (SH) signal was never conclusively demonstrated [3]. T h e reason e x p l a i n i n g t h i s r e s u l t i s that the light inducing the second harmonic response can destroy it. A long-term stability of the second harmonic generation (SHG) photoinduced in different types of fibers (single core or multi-core) can be induced. After destroying the photoinduced SHG by rotating the polarization of the fundamental laser beam, the photoinduced SHG c a n grow again till its initial value or above. This gives the evidence that self-sustained SHG is achieved in polymers optical fibers. The AOP process consists in two alternated periods: the writing phase where the fundamental laser beam is sent together with the SH seeding beam; and the readout phase where only the fundamental laser beam is sent to probe the SHG. When the seeding beam is stopped measurements shows the self-sustain of the SHG. In order to e n s u r e the self-reconstructing SHG, the simplest idea was to destroy the all-optical polling organization and let it be reconstructed without the assistance from the SH-seed beam. To do so, the polarization of the reading IR was turned. The SHG almost vanished in longer fibers, before reconstruction. This experiment has revealed the efficiency of SHG self-reconstruction in plastic optical fibers. Dye-doped single and multi-core PMMA optical fibers demonstrate efficient optical fiber component for SHG. Single-core or multi-core fibers show self-sustained SHG. Most importantly, SHG grows back to its initial value or above after destruction of the polar order [4]