, Volume 86, Issue 4, pp 653-660
Date: 18 Nov 2006

Upconversion blue emission dependence on the pump mechanism for Tm3+-heavy-doped NaY(WO4)2 crystal

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Abstract

Upconversion blue emissions of Tm3+-ion-heavy-doped NaY(WO4)2 crystals are investigated with three different near-infrared pump mechanisms. The dependence of upconversion efficiency on the pump mechanism is analyzed from the scope of the concentration quenching effect. Three cross-relaxation processes, \({}^3H_5+{}^1G_4\to{}^3H_6+{}^1D_2\) , \({}^1G_4+{}^3H_6\to{}^3F_4+{}^3F_3\) , and \({}^1G_4+{}^3H_6\to{}^3F_3+{}^3F_4\) , which influence the upconversion dominantly in the Tm3+-heavy-doped system, are demonstrated theoretically and experimentally. The results indicate that Yb3+ ions can weaken the concentration quenching effect of Tm3+ ions significantly so that the blue emission efficiency can be enhanced by one order of magnitude. At the same time, the wavelength of the pump source also has considerable influence on both the population of some crucial energy levels and the upconversion mechanism. Experiments show that the upconversion blue emission in Tm3+/Yb3+ co-doped NaY(WO4)2 crystal under 980-nm laser diode excitation is the most intensive of these three different near-infrared pump mechanisms. The conclusions are confirmed by spectra measurements and calculations of Judd–Ofelt theory and Miyakawa–Dexter theory.

PACS

42.70.Hj; 78.55.-m