Functionalized dye-doped hybrid sol-gel materials: From solid state dye laser to nonlinear applications and organic photorefractivity

We optically functionalized transparent hybrid matrices prepared by the sol-gel process by doping them with organic chromophores. Highly dense and chemically stable bulk and film materials of good optical quality have been synthesized in this way. Such materials can exhibit very different optical properties, depending on the choice of the chromophores and the type of environment provided by the sol-gel matrices. On one hand, the optical properties conferred to the solid state material can be those for which the dyes have been known and optimized in solution; this is, for example, the case of solid state dye lasers which performances have dramatically improved over the past few years, from the possibility of emitting 1,000s of microjoules pulses to 1,000,000s of millijoule pulses, illustrating the huge optimization potential of this material synthesis route! That is also the case of using dyes exhibiting strong reverse saturable absorption for optical limiting applications... On another hand, new properties can be demonstrated in the solid form, in particular, due to the restricted motion of the dopants in rotation and translation; that is the case of all optical memory, of second order nonlinear activity (x(2)), and, most recently, photorefractivity. We will especially detail the photorefractive properties of new media based on hybrid organic-inorganic materials containing charge transporting molecules and second order nonlinear optical chromophores introduced as side-chain units. These materials, prepared by the sol-gel process in the form of few micrometers thick films, were studied by two beam coupling (2BC), electronic absorption, electro-optic and photoconductivity experiments. The presence of a strong static electric field (30 V/μm) inside poled films was evidenced, and can explain the photorefractive properties obtained without applying any external electric field. Finally, one common issue all organic-based materials have to solve to take advantage of their high efficiencies and have potential applications outside the laboratories, is the chromophore photodegradation which limits the operational lifetimes of devices made from such materials. This point is under investigation and initial results show that the quantum efficiencies of these photoinduced chemical reaction can vary by several orders of magnitude, within this class of hybrid materials.