Enhancement of Upconversion Luminescence from Er Doped Al_2O_3 Films by a Thin Metal Layer

摘要

The effect of a metal layer on upconversion luminescence of Er doped Al_2O_3 thin films is studied. Three visible luminescence peaks, which are assigned to 2~H_(11/2)→4~I_(15/2), 4~S_(3/2)→4~I_(15/2), and 4~F_(9/2)→4~I_(15/2) transitions of Er~(3+), are observed by excitation with 978.5nm light. When a Au or Ag layer is deposited on top of the samples, the upconversion luminescence intensity is strongly enhanced. Roughness at an Al_2O_3-metal interface is considered to play a significant role for the enhancement. From the comparison of the enhancement factors between the upconversion PL and downconversion PL excited by 488.0nm light, the mechanism of the PL enhancement is discussed.