Significant third-order optical nonlinearity enhancement of gold nanoparticle incorporated mesoporous silica thin films by magnetic field thermal treatment

Thermal treatments from 600 to 1100°C with and without 6 T external magnetic fields were applied to the prepared gold nanoparticle (NP) incorporated mesoporous silica thin films (MSTFs). Significantly enhanced third-order optical nonlinear susceptibilities of the thin films thermally treated with the magnetic field were achieved as compared with that of those thermally treated without the magnetic field. The enhancement reached almost one order of magnitude from 700 to 800°C (i.e. at around the melting point of the gold NPs). The homogeneous dispersion of gold NPs can be maintained up to 1000°C under the magnetic field compared to the exaggerated growth of gold NPs thermally treated without the magnetic field. The origin for such optical nonlinearity enhancement is discussed.