High non-resonant third-order optical nonlinearity of Ag–glass nanocomposite fabricated by two-step ion exchange

•Ag nanoparticles were fabricated by two-step ion exchange into glass.•Third-order nonlinearities were studied using Z-scan technique.•A femtosecond laser at 800 nm wavelength was used as excitation source.•The high nonlinear refractive index n2 at the level of 10−10 cm2/W was obtained.•The measured nonlinear absorption coefficient β of −1.9 × 10−5 cm/W was extremely high.

We observe high third-order optical nonlinearity of Ag–glass nanocomposite fabricated by a two-step ion exchange method. The nonlinear refractive index and absorption are studied using the well-known Z-scan technique. In our experiments, we use a femtosecond Ti–Sapphire laser source operating at 800 nm, which is far from the plasmon resonance of the Ag nanoparticles. Our nanoparticles possess a high positive nonlinear refractive index and also a very high saturable absorption. We estimate the nonlinear refractive index to be on the order of 10−10 cm2/W and the saturable absorption to be on the order of 10−5 cm/W.