Ultraviolet emissions from Gd3+ ions excited by energy transfer from Ho3+ ions

Ultraviolet (UV) upconversion (UC) emissions of Gd3+ ion were investigated in Y-1 Gd-838-x(x)(Yb0 16Ho0002O3 (x=0 0 16 04 1 1 4) bulk ceramics under 976 nm laser diode (LD) excitation The UC emissions centered at 309 and 315 nm are assigned to the transition of P-6(5/2)-> S-8(7/2) (Gd) and P-6(7/2)-> S-8(7/2) (Gd) The (6)Pj levels of Gd3+ ions are populated by an energy transfer (ET) process from S-8(7/2) (Gd)+F(P-3(1) L-3(8) 3M/(10)) ( Ho)->(6)p(j) (Gd)+I-5(8) (Ho) A four-photon ET UC process was confirmed by the dependence of the P-6(7/2) level emission intensity on the pumping power We found that the intensity of the UC emissions increased with Gd3+ ion concentration and peaked at 8 mol% then starts to decrease until the Gd3+ ion concentration reached 70 mol% The variation in the UV emission intensity is the result of the competition between the ET process and concentration quenching effect Theoretical calculations based on steady-state equations validated the proposed UC mechanisms (C) 2010 Elsevier BV All rights reserved