Measurement of the nonlinear phase shift induced by cascaded interactions in a periodically poled lithium niobate waveguide

We report on the measurement of nonlinear phase shift phi(NL) induced by a strong pump at wavelength lambda(p) on a weak signal at lambda(s) through a cascade of two second-order interactions in a periodically poled lithium-niobate waveguide. The experiment is performed by use of an interferometric scheme especially designed to be insensitive to slow mechanical and thermal drift effects. The observed behavior of phi(NL) as a function of pump power and of wavelength difference lambda(p) - lambda(s) is in good agreement with the theoretical predictions. (c) 2005 Optical Society of America.