Manipulation of Plasmonic Oxide Inside Transparent Matrices for Boosting Infrared Optical Nonlinearity and Ultrafast Optical Switching

The integration and manipulation of plasmonic nanostructures inside a stable monolithic medium could be of high interest for solid-state photonic devices. Here, the development of inorganic oxide glasses is demonstrated wherein the growth of plasmonic nanoparticles (NPs) based on indium tin oxide (ITO) through solid-state reaction can be manipulated in a controllable manner. The plasmonic response of the precipitated ITO NPs contributes to boosted and tunable infrared nonlinear optical (NLO) response associated with localized surface plasmon resonance (LSPR) of the ITO NPs. It is further elucidated that the plasmon coupling between ITO NPs in the glass matrix plays an essential role in the 100-fs scale NLO response by accelerating the relaxation of hot electrons, such that the NLO response speed can be enhanced to exceed that in typical noble metal-based plasmonic nanostructures. The ultrafast absorptive optical nonlinearity with a high modulation depth could enable diverse applications, as exemplified here by the robust optical switching for mode-locked pulse generation in fiber lasers. These results could have strong implications for the development of integrated solid-state plasmonic devices for photonics applications.