Nonlinear Optical Properties of Semiconductor-Doped Sol-Gel Waveguides

Thin silica-titania films doped with CdS and PbS nanocrystals have been prepared by the sol-gel route. Their nonlinear properties have been studied using the tech - niques of degenerated four-wave mixing and m-lines with picosecond (ps) and nanosecond laser pulses. Depending on wavelength, doping level, and laser pulse duration, high negative nonlinearity was found for CdS-doped (n2 = — 2 = 10-8 cm2 / kW) and PbS-doped films (—10-10 to — 2 = 10 7 cm2 / kW). The response time of the nonlinearity was below 35 ps. Saturation of the nonlinearity was observed. Straight, monomode channel waveguides have been fabricated on these films. The influence of MIE-scattering due to the nanoparticles is investigated. © 2000 Taylor & Francis.