Optical Nonlinearity of Sputtered Co3O4-SiO2-TiO2 Thin Films

Optical non-linearity of cobalt oxide with SiO2-TiO2 additives was investigated, and the change mechanism of the refractive index (n) and extinction coefficient (k), based on the relation between band structure and optical non-linearity of the thin films, was discussed. Refractive index and extinction coefficient of Co3O4 thin films in the ground state were 3.17 and 0.42, respectively. Both n and k decreased by irradiation from a pulse laser with 650 nm of wavelength (1.91 eV). These values in the excited state were 2.91 and 0.41, respectively. n estimated from the change of n and k was -2.8 x 10(exp 11) sq m/W. The film had a band gap corresponding to 2.06 eV, indicating that it was widened by the band filling effect during the laser irradiation at 1.91 eV, and this led to the decrease in absorption coefficient and refractive index.
Pub in: Materials Research Society Symposium Proceedings, Volume 703. Prepared in collaboration with Hitachi Research Laboratory, Japan and Tsukuba Research Laboratory, Japan. This article is from ADA401575 Nanophase and Nanocomposite Materials IV held in Boston, Massachusetts on November 26-29, 2001