Cascading of second-order processes in a planar Ti-indiffused LiNbO3 waveguide:: application to frequency shifting

We studied the cascading of two second order processes and its use for frequency conversion (generation of a pulse at frequency omega p - Delta omega from a signal at omega(p) + Delta omega under the action of a pump at omega(p)) in a planar Ti-indiffused lithium niobate waveguide. Consistently with the predictions of a numerical model based on the fabrication parameters of the waveguide and the substrate refractive index, we find that the TE1 mode best serves as the intermediate sum-frequency field for the TM0 signals and pump. With a propagation length of 17 mm, pulses of 20 ps time duration and lambda approximate to 1.1 mu m, we observed wavelength conversion with 4% efficiency when the energy of the pump pulse per unit width was about 20 mu J/m. (C) 1999 Elsevier Science B.V. All rights reserved.