Controlled nanostructrures formation by ultra fast laser pulses for color marking

International audiencePrecise nanostructuration of surface and the subsequent upgrades in material properties is a strong outcome of ultra fast laser irradiations. Material characteristics can be designed on mesoscopic scales, carrying new optical properties. We demonstrate in this work, the possibility of achieving material modifications using ultra short pulses, via polarization dependent structures generation, that can generate specific color patterns. These oriented nanostructures created on the metal surface, called ripples, are typically smaller than the laser wavelength and in the range of visible spectrum. In this way, a complex colorization process of the material, involving imprinting, calibration and reading, has been performed to associate a priori defined colors. This new method based on the control of the laser-driven nanostructure orientation allows cumulating high quantity of information in a minimal surface, proposing new applications for laser marking and new types of identifying code

Single- and multi-pulse formation of surface structures under static femtosecond irradiation

International audienceFemtosecond surface structure modifications are investigated under irradiation with laser pulses of 150 fs at 800 nm, on copper and silicon.We report sub-wavelength periodic structures formation (ripples) with a periodicity of 500 nm for both materials. These ripples are perpendicular to the laser polarization and can be obtained with only one pulse. The formation of these ripples corresponds to a fluence threshold of 1 J/cm2 for copper and 0.15 J/cm2 for silicon.We find several morphologies when more pulses are applied: larger ripples parallel to the polarization are formed with a periodicity of 1 mm and degenerate into a worm-like morphology with a higher number of pulses. In addition, walls of deep holes also show subwavelength and large ripple

Delivery of molecules into corneal endothelium using nanoparticles activated by femtosecond laser pulses: proof of concept

International audiencePurpose NanoFemtoTransfection (NFT) is an innovative and promising non-viral technique to transfer molecules into cells (Chakravarty. Nature Nanotechnology 2010;5:607). It consists in temporarily permeabilizing cell membrane by a photoacoustic effect obtained by nanoparticles of black carbon activated by Ti-Saphir femtosecond laser (fsL) pulses. Calcein (622 Da), tagged bovine serum albumine (70 kDa) and one eGFP plasmid (5 MDa) were transfected into two non-adherent cell lines (DU145 prostate-cancer and GS-9L rat gliosarcoma). Our aim was to adapt the NFT to adherent human corneal endothelial cells (HCEC

Study of stromal femtosecond laser ablation for deep corneal cut optimization

International audiencePurpose Anterior and posterior stroma of human cornea present different biophysical characteristics, the later being more hydrated and collagen fibers less tightly packed. Our aim was to investigate interactions between femtosecond laser (FL) and stroma according to the depth of cut in order to optimize FL endothelial graft preparatio

Microcellules électrochimiques en diamant dopé au bore (BDD) obtenues par usinage laser pour la détection de différents métaux lourds : Cd(II), Ni(II), Pb(II), Hg(II), U(VI)

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