Energy transfer upconversion in Er-doped LiTaO3

The fluorescence spectrum of Er-indiffused LiTaO3 was measured and revealed strong anti-Stokes fluorescence (ASF) with upconverted green and red emiss ions when the F-4(9/2) manifold of an Er3+ ion was pumped by either a 632.8 or a 647 nm laser. Investigation into the dependence of fluorescence inten sity on pump intensity and depth profiling of the Stokes and anti-Stokes fl uorescences revealed that the ASF is attributed mainly to energy transfer u pconversion within Er3+ cluster sites. Postindiffusion processing in molten LiNO3 was found to be effective in suppressing the upconversion via decrea se of the cluster site concentration. (C) 2000 American Institute of Physic s. [S0003-6951(00)01916-1].