title: Adiabatic self-focusing in media with spatially variable nonlinearity.
abstract: An optical medium whose nonlinearity can be spatially adjusted is considered to study beam reshaping. The concept is applied to perform adiabatic self-focusing of broad beams. Experimental results are obtained in a photorefractive lithium niobate crystal where the self-focusing nonlinearity is controlled over propagation by a temperature gradient. As a demonstration, gradual self-focusing is shown to transform an incoming beam into an output circular spot 10 times smaller over a 2 cm long crystal submitted to a 30 °C temperature gradient. Once formed, the adiabatic self-focused beam has inscribed a funnel waveguide in the crystal.
authors.affiliation: FEMTO-ST, UMR CNRS 6174, Université de Franche-Comté, 16 Route de Gray, 25000 Besançon, France.
authors.forename: Luai Al
authors.initials: LA
authors.lastname: Fares
authors.forename: Fabrice
authors.initials: F
authors.lastname: Devaux
authors.forename: Mathieu
authors.initials: M
authors.lastname: Chauvet