Ultrafast electron transfer dynamics in Ag/TiO_2 nanocomposite for tailoring of optical nonlinearity

摘要

The nanocomposite of titanium dioxide (TiO2) with noble metallic nanoparticles (NPs) are widely used catalysis systems for various photonic applications owing to the well-known ultrafast dynamics process, electron transfer. In this work, the traditional electron transfer mechanism is further improved based on the nanocomposite chip with embedded Ag NPs in TiO2 semiconductor (AgNP:TiO2). Considering the increased absorption efficiency of Ag NPs, the delay time of electron-electron scattering and electron-phonon scattering are measured to indicate the evidence of electron transfer process. It is proved that the enhancement of optical nonlinearity is closely associated with the hot electron transfer between TiO2 and Ag NPs. Benefiting from the electron transfer mechanism induced nonlinearity tailoring of TiO2, low-threshold mode-locked lasers have been realized with AgNP:TiO2 as saturable absorber (SA) with low saturation intensity (decreased by 76.5%). This work not only fills the blank of optical nonlinearity modification by embedded Ag NPs in TiO2 nanocomposites, but also build a bridge between hot electron transfer process and nonlinearity tailoring, suggesting potential applications in ultrafast dynamics and optoelectronics.