Elizabeth Radue

Surface plasmon polaritons in VO 2 thin films for tunable low-loss plasmonic applications

We report on the first observation of optically excited surface plasmon polaritons (SPPs) in the conducting phase of vanadium dioxide (VO(2)) thin films. VO(2) is low-loss optical material that undergoes an insulator-metal transition (IMT) under suitable thermal, optical, or electrical stimulation, thus enabling tunable SPP excitation of the conducting phase. Here we applied IR light (1520 nm) to excite SPPs while thermally inducing the IMT by changing the VO(2) temperature, and observed a clear trend from nonabsorption in the insulator phase to high absorption in the conducting phase due to SPP excitation in the latter phase. Tunable SPPs in VO(2) enable a range of opportunities for low-loss optoplasmonic applications since the rate of the IMT excitation can also be tailored.

Bulk and surface plasmon polariton excitation in RuO 2 for low-loss plasmonic applications in NIR

Transition-metal oxides, such as RuO₂, offer an exciting alternative to conventional metals for metamaterials and plasmonic applications due to their low optical losses in the visible and near-infrared ranges. In this manuscript we report observation of optically excited surface plasmon polaritons (SPPs) and bulk plasmons in RuO₂ thin films grown using DC reactive magnetron sputtering on glass and TiO₂ (001) substrates. We show that both plasmon modes can exist simultaneously for the infrared region of the optical spectrum, while only the bulk plasmons are supported at higher optical frequencies. Finally, we demonstrate that the film properties can be tailored to favor excitation of either SPP or bulk plasmons.

Substrate-induced microstructure effects on the dynamics of the photo-induced metal–insulator transition in VO2 thin films

We investigate the differences in the dynamics of the ultrafast photo-induced metal–insulator transition (MIT) of two VO2 thin films deposited on different substrates, TiO2 and Al2O3, and in particular the temperature dependence of the threshold laser fluence values required to induce various MIT stages in a wide range of sample temperatures 150–320 K. We identified that, although the general pattern of MIT evolution was similar for the two samples, there were several differences. Most notably, the threshold values of laser fluence required to reach the transition to a fully metallic phase in the VO2 film on the TiO2 substrate were nearly constant in the range of temperatures considered, whereas the VO2/Al2O3 sample showed clear temperature dependence. Our analysis qualitatively connects such behavior to the structural differences in the two VO2 films.