Concentration dependence of nonresonant nonlinearity in CdS/sub x/Se/sub 1-x/ doped glasses

Semiconductor doped glasses containing quantum dots of cadmium sulphoselenide are known to have an optical Stark effect nonlinearity at photon energies between half the band gap and the band gap. We report measurements of this nonresonant nonlinearity using the z-scan technique on a series of glasses doped with semiconductor concentrations between 0.05 and 3.5 wt.%. The nonlinear refractive index is found to increase approximately linearly over this range. The highest concentration glass measured gave a nonlinear refractive index of 2.5/spl times/10/sup -17/ m/sup 2/ W/sup -1/, approximately three orders of magnitude higher than that of fused silica, and the highest nonresonant nonlinearity of any glass system reported to date. Predicted figures of merit, based on nonlinearity and on scattering loss calculations, indicate that these glasses should be suitable materials for practicable all-optical switching devices.<>