Refractive index change and thermo-optic effect in polydimethylsiloxane nanocomposites with oxide nanoparticles induced by proton beam writing

We studied polydimethylsiloxane nanocomposites with oxides such as TiO2, SiO2, and Al2O3 aiming at proton beam writing (PBW) of buried optical waveguides. Relatively high transmission was achieved for 1.0 wt% TiO2/PDMS composite without aggregation. The refractive index can be tunable by varied TiO2 concentration in nanocomposites. We evaluated refractive index changes by 1.0 MeV proton irradiation. Refractive index of TiO2/PDMS nanocomposite increased at low fluence of less than 100 nC/mm2 and then decreased at higher fluence. On the other hand, we observed monotonic increase of the refractive index as a function of fluence for PDMS and PDMS nanocomposites with SiO2 and Al2O3. We also compared thermo optic effect of PDMS nanocomposites. We evaluated buried optical waveguides in TiO2/PDMS nanocomposite written by PBW for near field patterns with single mode waveguide