Interaction laser-matière aux forts flux

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Nonlinear optics and Nanoinscription

Super-resolution nano inscription can be achieved by tightly focusing laser pulses inside nonlinear optical materials. A thin film can be used to decrease the size of the laser beam (SR layer) by using nonlinear optical phenomena as nonlinear refraction and absorption. A second layer is employed to inscribe photonic components in three dimensions. The inscription can be carried out by local modification of the linear refractive index allowing the fabrication of waveguides or gratings. The local modification of the Second and/or Third Harmonic Generation (SHG/THG) efficiency of a material is also necessary for the fabrication of frequency conversion devices in the bulk of the materials.

Novel materials with high nonlinearities are necessary for these applications. The nonlinear optical studies are performed by means of the Z-scan technique, which can be applied in multiple types of transparent materials (as for example thin film layers, crystals and liquids). It can provide the real and the imaginary part of the third order nonlinear susceptibility as well as their sign. By means of this technique we can determine the self-focusing or self-defocusing, saturable absorptive or reverse saturable absorptive characters of the materials investigated. Several nonlinear optical parameters can be determined such as the nonlinear absorption coefficient (β), the nonlinear refractive index (n2) and the second order hyperpolarizability(γ).