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Femtosecond laser-induced structural changes in LiNbO3 are studied. Depending on the laser processing parameters two different types of modification are identified and their origin is discussed. Both types of modification can be described within the framework of induced lattice defects. For strong material damage a refractive index increase can be obtained due to the induced stress field. By appropriate tailoring of this stress field thermally stable and highly symmetric waveguides can be obtained well suited for nonlinear integrated-optical applications

The observation of discrete spatial solitons in fs laser written waveguide arrays in fused silica is reported for the .rst time. The fs writing process permits the speci.c setting of the linear and nonlinear guiding properties of the waveguides. The results in this paper reveal a new avenue for the fabrication of various nonlinear optical devices.

The observation of a two-dimensional discrete soliton in a cubic 5 x 5 fs laser written waveguide array in fused silica is reported for the first time. In addition to the localization the sharp edges of the array allow to study the influence of the array's boundaries. The results are in excellent agreement with theoretical predictions and provide the basis for a variety of future applications for nonlinear two-dimensional integrated optical devices.

Optical waveguides in lithium niobate have been fabricated with a femtosecond laser. Different types of modifications depending on the laser parameters were observed and discussed. In these waveguides, frequency doubling of 1064nm radiation was demonstrated utilizing birefringent phase matching. A conversion efficiency of 49% was obtained in a 9.3mm long sample.