CUBIC OPTICAL NONLINEARITY OF THIN Fe2O3 AND Cr2O3 FILMS SYNTHESIZED BY PULSED LASER DEPOSITION

The extinction spectra and the parameters of cubic optical nonlinearity in thin Fe2O3 and Cr2O3 films deposited on glass substrates with the use of the laser sputtering method have been measured. The cubic optical nonlinearity is studied, by using femtosecond laser radiation with the wavelength lambda = 800 nm and the pulse duration tau = 180 fs. The energy gap width evaluated from the extinction spectra is found to equal E-g approximate to 2.4 eV and 2.2 eV for Fe2O3 films synthesized on the substrates at temperatures of 293 K and 800 K, respectively, and E-g approximate to (3) eV for Cr2O3 films deposited on the substrate heated up to 800 K. Rather high values are obtained for the coefficients of refractive nonlinearity: Re chi((3)) similar to 10(-6) esu for Fe2O3 films and Re chi((3)) similar to 10(-7) esu for Cr2O3 ones. The determined values of Im chi((3)) amounted to about 10(-6) divided by 10(-7) esu for Fe2O3 films and about 10(-8) esu for Cr2O3 ones. Probable mechanisms of refractive nonlinearity have been proposed.