RESEARCH ACTIVITIES   Surface Plamson Enhanced Luminescence in Rare-earth doped materials 79. Nobuto, Managaki, Minoru Fujii, Toshihiro Nakamura, Yoshiko Usui, and Shinji Hayashi, "Enhancement of Photoluminescence from Yb and Er Co-doped Al2O3 Films by an Asymmetric Metal Cavity,” Applied Physics Letters, Vol. 88, No. 4, pp. 042101-1-3, January (2006). The effects of Au thin layers on luminescence properties of Er and Yb co-doped Al2O3 films were studied. The 1.54 μm emission of Er3+ excited by the energy transfer from Yb3+ is found to be strongly enhanced by placing a Au layer on top of the films. Photoluminescence excitation spectra of the 1.54 μm PL of Er3+ and time transients of the 980 nm emission of Yb3+ revealed that PL enhancement arises from two different mechanisms. The first one is the enhancement of local electric fields accompanied by the excitation of surface plasmons of rough Au surfaces. The other one is the enhancement of energy transfer rate from Yb3+ to Er3+ caused by the modification of the local photonic mode density at the position of the Yb–Er coupled system. 72. Masanori Fukushima, Nobuto Managaki, Minoru Fujii, Hisao Yanagi, and Shinji Hayashi, "Enhancement of 1.54 Micrometer Emission from Er Doped Sol-gel SiO2 Films by Au Nanoparticles Doping,” Journal of Applied Physics, Vol. 98, pp. 024316-1-4, July (2005). A 1.54-μm emission from erbium-doped sol-gel SiO2 was strongly enhanced by doping Au nanoparticles. The enhancement factor depended on Au concentration and was the largest at the concentration of 1.0 mol %. The photoluminescence enhancement was accompanied by the lengthening of the lifetime, suggesting that the enhancement is caused by the decrease of hydroxyl groups. In addition, enhancement due to strong fields induced by localized surface plasmon of Au nanoparticles was observed.