Enhancement of ultraviolet upconversion in Yb3+ and Tm3+ codoped amorphous fluoride film prepared by pulsed laser deposition

Abstract

${\mathrm{Zn}}_{\text{0.3}}{\mathrm{Al}}_{\text{0.25}}{\mathrm{Pb}}_{\text{0.3}}{\mathrm{Li}}_{\text{0.098}}{\mathrm{Yb}}_{\text{0.1}}{\mathrm{Tm}}_{\text{0.002}}{\mathrm{F}}_{\text{2.354}}$ amorphous fluoride film was prepared by pulsed laser deposition. Ultraviolet and blue up-conversion emissions were observed under infrared excitation at 978 nm. In comparison with the upconversion of the target, the ultraviolet emissions are enhanced greatly. The enhancement is attributed to a decrease of the Judd–Ofelt parameter ${\Omega }_2$ induced by pulsed laser deposition, which precludes the transition rate from ${}^3{F}_2$ to ${}^3{F}_4$ and enhances the energy transfer process and populates the ${}^1{D}_2$ level: ${}^3{F}_2{\to }^3{H}_6\mathrm{ (}{\mathrm{Tm}}^{\text{3+}}{\mathrm{):}}^3{H}_4{\to }^1{D}_2\mathrm{ (}{\mathrm{Tm}}^{\text{3+}}\mathrm{).}$