No abstract

No abstract

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 = 800 nm and the pulse duration = 180 fs. The energy gap width evaluated from the extinction spectra is found to equal ≈ 2.4 eV and 2.2 eV for Fe2O3 films synthesized on the substrates at temperatures of 293 K and 800 K, respectively, and ≈ 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 (3) ∼ 10 −6 esu for Fe2O3 films and Re (3) ∼ 10 −7 esu for Cr2O3 ones. The determined values of Im (3) amounted to about 10 −6 ÷10 −7 esu for Fe2O3 films and about 10 −8 esu for Cr2O3 ones. Probable mechanisms of refractive nonlinearity have been proposed. K e y w o r d s: cubic optical nonlinearity, thin Fe2O3 and Cr2O3 films, laser sputtering method, femtosecond laser radiation.

The article presents results of the parameters of optical cubic nonlinearity (OCN) of thin amorphous Cu2O films under 532 and 1064 nm pulsed laser excitation. The films were synthesized on SiO2 (silica) substrates by reactive pulsed laser deposition technique at 293 or 800 K under a different oxygen pressure of 1, 3, or 5 Pa. The bandgap of the films was determined from the absorption spectra. The films synthesized under 1 and 3 Pa oxygen pressure at 293 K demonstrated at 1064 nm positive OCN, whereas the films obtained at 293 K, 5 Pa, and 800 K, 1 Pa demonstrated negative OCN. The largest nonlinear refractive index of n2 = + 1.35 × 10−6 cm2/W was obtained for the film synthesized at 293 K, 1 Pa. Under 532 nm excitation, the films also revealed positive or negative OCN, depending on the synthesis parameters, with the absolute value of | n2| on the order of 10−7 cm2/W. The largest | n2| = 5.16 × 10−7 cm2/W was obtained for the 293 K, 3 Pa film. Depending on the manufacturing conditions, the films exhibited saturated absorption or reversed saturated absorption.