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 long crystal submitted to a temperature gradient. Once formed, the adiabatic self-focused beam has inscribed a funnel waveguide in the crystal.
© 2011 Optical Society of America
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