Optical nonlinearities of silicate oxide glass with gold nanoparticles outside the spectral range of surface plasmon resonance

The Z-scan technique, with the use of femtosecond laser pulses at 813 nm and of 1 kHz repetition rate, was applied for measurement of the nonlinear optical properties of silicate glass with embedded gold nanoparticles, produced by the standard melt-quenching method and then annealed at 550 °C. At irradiance levels of 10¹² W m^-2 it exhibited two-photon absorption with β = 3.8 × 10^-15 m W^-1 and positive Kerr lensing effect with n₂ = 1.85 × 10^-20 m² W^-1 which resulted in the nonlinear susceptibility χ⁽³⁾ = (0.031 + 2.366 i) × 10^-14 esu. These values, although remarkably low, indicate that the nonlinear refraction effects significantly dominate the nonlinear absorption and when appropriately increasing the doping with Au nanoparticles, this nanocomposite glass can be considered for the optical switching applications outside the spectral range of the surface plasmon resonance.