A study of the nonlinear refractive index in amorphous Ge–As–S layers and nanocomposites with gold nanoparticles

Nonlinear refractive indices of simple and composite chalcogenide glasses with gold nanoparticles are measured by the Z-scan method using a femtosecond Ti:sapphire laser with a central wavelength of 800 nm and a pulse duration of 40 fs. It is shown that introduction of nanoparticles into thin layers of amorphous GeS2, As30Ge20S50, and As3Ge35S62 leads to a decrease in the total nonlinear refractive index due to additional absorption of femtosecond laser radiation without efficient excitation of localized plasmons outside the resonance region. For example, the nonlinear refractive index decreases with addition of gold nanoparticles from 16.1 × 10–12 to 13.0 × 10–12 cm2/W for GeS2, from 3.9 × 10–12 to 3.2 × 10–12 cm2/W for As30Ge20S50, and from 5.8 × 10–12 to 4.7 × 10–12 cm2/W for As3Ge35S62.