Wavelength shifting by cascaded second-order processes

We describe the utilization of a cascade of two second-order processes for the efficient generation of a wavelength-shifted field. The overall process is equivalent to a nearly degenerate, four-wave mixing process. The intere sting aspect is that the corresponding effective third-order nonlinearity i s fast and nonabsorbative, and is much larger than that available in third- order materials. Experiments have been performed with a periodically poled lithium niobate (LN) crystal and a single-mode LN waveguide, by using 20 ps pulses in the near infrared. The obtained results represent a first step t owards the realization of a nonlinear device for application to optical com munications systems.