Investigation of the upconversion process in nanocrystalline Gd_3Ga_5O_12:Ho^3+ and Gd_3Ga_5O_12:Ho^3+, Yb^3+
Abstract
The past decade has seen a proliferation in the amount of papers published on lanthanide doped nanocrystalline phosphors due to their different luminescence properties and excited state kinetics when compared to micrometer counterparts. In this paper, we report intense upconversion luminescence for the first time in a Ho^3+ doped nanocrystalline material. Anti-Stokes blue and green luminescence was noted in nanocrystalline Gd_3Ga_5O_12 doped with 1 mol% Ho^3+ after excitation into the ^5F5 level with 647 nm radiation. Excitation at 756 nm into the ^5I4 level resulted in green and red anti-Stokes emission. In both cases, an excited state adsorption (ESA) mechanism is thought responsible for the observed upconversion luminescence. The temporal dependence of the upconverted luminescence for the two excitation wavelengths revealed that the ^5I7 level was the intermediate level in both two-photon processes. The effect of Yb^3+ co-doping on the upconversion luminescence in Gd_3Ga_5O_12:Ho^3+ will also be discussed. Excitation of a Gd_3Ga_5O_12 sample doped with 1 mol% Ho^3+ and 1 mol% Yb^3+ resulted in green and red anti-Stokes emissions from the (^5F_4, ^5S_2) and ^5F5 levels respectively. The temporal evolutions of both emissions revealed that two distinct Energy Transfer Upconversion (ETU) mechanisms from the ^5I6 and ^5I7 Ho^3+ levels were responsible for the green and red upconversion emissions.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARU34009B