Ytterbium-doped silica slab waveguide with large nonlinearity

We report an experimental investigation of the nonlinear refractive index change of a highly ytterbium-doped silica slab waveguide. It is found that a negative index change of 2/spl times/10/sup -4/ can be obtained at pump power of 350 mW and it is predicted that this could be reduced to about 30 mW by optimizing the experimental conditions.