Porous films for nonlinear silica-on-silicon integrated optics

The use of porous sol-gel films as hosts for semiconductor microcrystals, with applications in integrated optics, has been examined. Techniques are described for characterizing porosity using ellisometric measurements, and the use of this technique to investigate the effects of process parameters is reported. In particular, the effect on pore microstructure of water concentration, catalyst type and concentration and film annealing temperature are presented. A technique for doping the porous host film with CdS crystallites is then described. Absorption spectra for the doped films are presented which given an indication of the size and concentration of these crystallites, and the way in which these are affected by process parameters is also reported. The cadmium counter-ion is shown to strongly influence the doping concentration, and the film annealing temperature is shown to affect the crystallite size.