Romualda Grzymala

Optical characterization of a homogenous photosensitive layer by thin film resonance method

Polypeptide material layers can be used for different optical applications as diffractive optical elements or diffractive storage memory. The optical parameters of the polypeptide layers must be precisely known before implementing these applications. These optical parameters are the layer thickness, layer refractive index, and layer substrate refractive index. Thin film resonance (TFR) is one of the most adapted methods to evaluate the refractive index and the thickness of a homogenous photosensitive polypeptide layer. We restrict our method to transparent films layered on a transparent substrate. The proposed method is more convenient for layers having thicknesses greater than a few microns. The photosensitive material we consider is a polypeptide layer with thickness greater than 10 µm. The measurement of these optical parameters are provided separately. A low absorption of this layer is considered. We validate the possibility of easily measuring these parameters. The excellent agreement between the calculated and measured data confirms the practical efficiency of this method. This method is applied as an example to two standard holographic emulsions PFG-04 and PFG-03M for validation. After these tests, the method is applied to characterize the coated polypeptide layer elaborated in our laboratory. We analyze the measurements performed with our proposed method on four polypeptide layers prepared with different added quantities of doping agents. The main interest of our method is to allow the measurement of the layer and substrate refractive indexes (even when they are close) jointly with the layer thickness measurement just by using a simple setup based on monochromatic light as a source and an angular scanning.

Polypeptide/polysaccharides holographic micro-structuration for biophysics applications

Protein and polysaccharide nano-patterning is of prime interest for biological applications but also for applications in the field of diffractive optics. In this work, we used a photo-nano-patterning process based on light interferences through a photo-sensitive material for patterning polysaccharides and polypeptides pure and mixed gels of gelatin, hyaluronan, and chitosan. Chromium ions were incorporated in the gels to render them photo-sensitive. Polyelectrolyte multilayer thin films of poly(L-lysine)/hyaluronan were also investigated either by incorporating chromium ions or by adsorbing a photo-sensitive hyaluronan. Depending on the weights ratios of the polymers, respectively gelatin/chitosan and gelatin/hyaluronan, the gel surfaces exhibit different fringe patterns, as can be visualized by atomic force microscopy. The diffracted intensity characterizing the holographic grating was also depending on gel type. Pure gelatin gels was taken as the reference material. The best results in terms of surface patterns and diffracted intensities were obtained for the gelatin/chitosan gels prepared at acidic pH and exposed at energies ranging from 100 to 400 mJ/cm2. Our results show that surface patterns of various depths and structures can be created by the photo-patterning technique on biological polymers. These results open new perspectives for the surface control of biological materials but also for making use of the optical properties of these biocompatible biopolymers.

From protein to photoprotein, validating application to diffractive optics

Photopolymers are widely used to elaborate diffractive components by light wavefront engineering. Photopolymer material is light structured through wavefront engineering causing interferences that will be printed in photopolymer layer to constitute the diffractive structure. We show that good diffractive components results can be obtained with photoprotein produced by metal doping of selected proteins coming form biology or biotechnology. We validate this for one application concerning the diffractive storage.

Protein Nanostructures Light Control for Data Storage

Biophotonics can be considered as the crossing of photonics physics, and biotechnology. A few years ago by a fundamental research collaboration between our laboratory : «the Photonics Systems Laboratory», and the «laboratory of the Strasbourg School of Biotechnology », we have identified a method and process for producing specific proteins molecules adapted to some expected applied photonic uses by local light modulation at a nanometric scale inside a protein molecule distribution organized as a layer.