Ultrafast nonlinear optical response of silver/bismuth oxide nanocomposite films with different silver concentrations

The ultrafast nonlinear optical properties of co-sputtered silver/bismuth oxide (Ag:Bi2O3) nanocomposite films with different Ag concentration (13.2–59.3 at%) were investigated by femtosecond (fs) pump–probe and fs optical Kerr effect (OKE) techniques. The pump–probe measurements revealed the Ag concentration-related energy relaxation dynamics: for films with high concentration of Ag (>50%), the relaxation dynamics consist of a fast excitation power-dependent component (1–2 ps) and a long-lived component (>100 ps). While for films with relative low Ag concentration (<40%), the energy relaxation behaves as a single exponential process, nearly completed within 1 ps. This Ag concentration related dynamical behavior was suggested to be originated from the differences in the structural and thermal properties of both Ag nanoparticles and Bi2O3 matrices. The result of the femtosecond OKE measurements showed that the third-order susceptibilities (image) of Ag:Bi2O3 films have a maximum of 4.1×10−10 esu at Ag concentration of 35.7%.