Features of dark spatial optical solitons in planar waveguides on lithium niobate

Summary form only given. Photorefractive spatial solitons can exist in crystals like SBN, BTO and LiNbO/sub 3/ at light powers of a microwatt range. It makes such solitons a promising candidate for all-optical information technology. The photovoltaic effect in LiNbO/sub 3/ results in the self-defocusing nonlinearity and dark photovoltaic spatial solitons have already been observed in bulk LiNbO/sub 3/. Optical waveguides in LiNbO/sub 3/ with their surface doping by impurities like Fe and Cu can show much higher photorefractive nonlinearity with respect to bulk material and this nonlinearity may be strongly inhomogeneous over a waveguide depth. Besides, waveguides allow simultaneous propagation of several guided modes in the same direction. All that may result in the considerable features of spatial solitons in similar planar waveguides. The main aim of the work is the experimental study of dark spatial solitons in planar waveguides formed in LiNbO/sub 3/ by indiffusion of different combinations of Ti, Fe, and Cu.