OPTICAL NONLINEARITY OF Au METAL NANOPARTICLE DISPERSED (Ba,Sr)TiO3 THIN FILMS.

Nearly spherical Au nanoparticles of about 3.83 nm diameter were embedded into the (Ba,Sr)TiO₃ matrix using alternating sputtering method, showing the characteristic surface plasmon resonance absorption band at 571 nm. Dispersion in the third-order optical nonlinearity was investigated at several wavelengths from 450 to 680 nm around the resonance peak by a single beam Z-scan technique with a wavelength tunable picosecond laser system. The real and imaginary parts of third-order nonlinear susceptibility were resolved and the relative contributions are quantitatively compared at each wavelength. The maximum absolute value of third-order susceptibility as large as 4.312 × 10^-8esu was obtained at the surface plasmon frequency. The temporal response was also characterized by the femtosecond time-resolved optical Kerr gate measurement and the nonlinear response time was evaluated to be 192 fs at the laser wavelength of 800 nm. [ABSTRACT FROM AUTHOR]