Third-order optical nonlinearity in silicon oxycarbide films

We study the third-order nonlinear optical properties of amorphous silicon oxycarbide (SiOxCy) films prepared by magnetron sputtering at room temperature and annealed in oxygen atmosphere at the temperature ranging from 200 degrees C to 600 degrees C. The third-order optical nonlinearity of the films was measured by Z-scan method at a wavelength of 1064 nm and a pulse duration 25 ps? The closed-aperture measurements show that the as-deposited films exhibit self-defocusing effect, while the annealed films present self-focusing behavior. The nonlinear refractive index is determined about vertical bar n(2)vertical bar similar to 10(-15) m(2)/W, which is four orders of magnitude larger than that of SiC crystals. The open-aperture results show that the as-deposited SiOxCy films and films annealed at 200 degrees C exhibit strong three-photon absorption behavior, while the SiOxCy films annealed at 400 degrees C and 600 degrees C exhibits nonlinear saturable absorption. The nonlinear absorption coefficients of films dependent on laser intensity are determined, and show saturable tendency. The results indicate that the third-order optical nonlinearity in SiOxCy films can be sensitively affected and tuned by the atom composition and microstructure, thus be of great significance for integrated nonlinear photonic devices.