Abstract

Owing to the non-zero average cube of the coherent superposition of a light wave with its second harmonic, nonlinear optical interactions permit the polar orientation of initially centrosymmetric material. This possibility is revealed by the observation of second-harmonic generation in optical fibers prepared by an intense light with a simultaneous seeding light at double frequency. Such a <E³>-induced χ⁽²⁾ effect can be viewed as a six-wave mixing process.^[1] In order to demonstrate such a process in an organic dye solution we have performed an experiment of Phase-Conjugation Pumped at Half-Frequency (PCPHF).

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