R. Barille

Photo-responsive polymer with erasable and reconfigurable micro- and nano-patterns: An in vitro study for neuron guidance

The interaction of cells with nanoscale topography has proven to be an important modality in controlling cell responses. Topographic parameters on material surfaces play a role in cell growth. We have synthesized a new bio compatible polymer containing photoswitching molecules. Stripepatterned (groove/ridge pattern) were patterned and erased with ease on this bio azopolymer with two different set-ups: one with the projection of an optical interference pattern and the other one by molecular self-organization with one single laser beam. These two set-ups allow the re-writing of pattern after erasing and its inscription in vitro. PC12 cells were cultured on the bio-photoswitching patterned polymer and compared with PC12 cells growing on a well know substrate: poly-L-lysine. This result is of interest for facilitating contact guidance and designing reconfigurable scaffold for neural network formation in vitro.

Multistate polarization addressing using a single beam in an azo polymer film

Peculiar light–matter interactions can break the rule that a single beam polarization can address only two states in an optical memory device. Multistate storage of a single beam polarization is achieved using self-induced surface diffraction gratings in a photoactive polymer material. The grating orientation follows the incident light beam’s polarization direction. The permanent self-induced surface relief grating can be read out in real time using the same laser beam.

Spontaneous formation of optically induced surface relief gratings

A model based on Ficks law of diffusion as a phenomenological description of the molecular motion, and on the coupled mode theory, is developped to describe single-beam surface relief grating formation in azopolymers thin films. It allows to explain the mechanism of spontaneous patterning, and self-organization. It allows also to compute the surface relief profile and its evolution in time with good agreement with experiments.

Backward stimulated Raman scattering in water

The backward Stimulated Raman scattering (BSRS) is studied in liquid water. We show that BSRS can be produced by small volumes of active materials. Our experimental results and calculations with different geometries and intensities of excitation allow us to choose the best experimental set-up for BSRS efficiencies. The competition with librational scattering is also observed.

Photoinduced deformation of azopolymer nanometric spheres

Nanometric 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.

Cognitive ability experiment with photosensitive organic molecular thin films.

We present an optical experiment which permits us 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 photoactivated by a powerful incoherent beam. We demonstrate experimentally that less than 1% of the molecules possessing information cooperatively transmit it to the entire photoactivated polymer film.

Incoherent light-induced self-organization of molecules

Although coherent light is usually required for the self-organization of regular spatial patterns from optical beams, we show that peculiar light-matter interaction can break this evidence. In the traditional method of recording laser-induced periodic surface structures, a light intensity distribution is produced at the surface of a polymer film by an interference between two coherent optical beams. We report on the self-organization followed by propagation of a surface relief pattern. It is induced in a polymer film by using a low-power and small-size coherent beam assisted by a high-power and large-size incoherent and unpolarized beam. We demonstrate that we can obtain large size and well-organized patterns starting from a dissipative interaction. Our experiments open new directions to improving optical processing systems.

Influence of soliton propagation on the beam-polarization dynamics in a planar waveguide

Strong polarization changes are observed near the soliton power in a planar waveguide filled with an isotropic material (CS2). Only pure TM and TE modes retain their polarization. The presence of even a small input TE component tends to transform the output polarization into TE polarization. The experimental results are in agreement with coupled-mode theory and facilitate optical switching applications.

Multistate polarization addressing using one single beam in an azo polymer film: erratum

Peculiar light-matter interactions can break the rule that a single beam polarization can address only two states in an optical memory device. Multistate storage of a single beam polarization is achieved using self-induced surface diffraction gratings in a photo-active polymer material. The grating orientation follows the incident light beam polarization direction. The permanent self-induced surface relief grating can be readout in real time using the same laser beam.

Self-Induced Diffraction Grating Storage in Polymer Films

ABSTRACT Peculiar light-matter interactions can break the rule that a single beam polarization can address only two states in an optical memory device. Multistate storage of a single beam polarization is achieved using self-induced surface diffraction gratings in a photo-active polymer material. The grating orientation follows the incident light beam polarization direction. The permanent self-induced surface relief grating can be readout in real time using the same laser beam.