Optics was certainly one of the first applications of hybrid materials. Thus, organic: inorganic/ organic: organic hybrid materials with high transparency are expected to be new optical materials such as optical fiber, wave-guide and optical lens. Materials with high refractive index, low density and good transparency in visible region are in demand as optical lenses especially for glasses. In order to implement optoelectronic or photonic properties into devices, the materials have to fulfill high optical quality demands and have to be stable over a long period. Furthermore, the control of the materials index as well as the thickness and therefore, the processibility of the materials are important. Due to its low optical losses (high optical quality), silica glass and composites made from it seem to be very useful for those devices. For example, photoconducting composites were prepared by the incorporation of cadmium sulfide particles in a polyvinylcarbazole matrix. The resulting materials allowed the tuning of the band gap of the particular wavelength of operation.