Efficiency improvement of up–conversion luminescence of Yb^sup 3+^/Tm^sup 3+^ co-doped tellurite glass microsphere

Three potential techniques, i.e. the optical taper fiber–microsphere device(OFMD), employment of the low phonon energy tellurite glass and the optimal concentration of rare-earth ions are investigated and identified for improving the efficiency of up-conversion (UC) luminescence for rare-earth ion doped materials excited by laser. The tellurite glass with composition of 77TeO2–12Na2O–5ZnO–5La2O3 was synthesized with different Yb3+/Tm3+co-doped concentration. The OFMD with high efficiency coupling and high energy density whispering gallery mode (WGM) was constructed. By the excitation of 976 nm laser, the WGM resonance enhancement UC blue (475 nm) and red (648 nm) light were obtained. The WGM resonance enhancement UC luminescence mechanism, the rare-earth ions energy transfer mechanism and the optimal Tm3+ concentration were investigated.