Down-Conversion From Blue to Near Infrared in Tm$^{3+}$–Yb$^{3+}$ Codoped Y$_{2}$O $_{3}$ Transparent Ceramics

Down-conversion from blue to near infrared (NIR) has been demonstrated in $\hbox{Tm}^{3+}\hbox{–}{\hbox {Yb}}^{3+}$ codoped $\hbox{Y}_{2}\hbox{O}_{3}$ transparent ceramics. Upon the 464-nm excitation, the energy transfer (ET) mechanisms consisted of the $\hbox{Tm}^{3+}:{^{1}\hbox{G}}_{4}\rightarrow 2{\hbox {Yb}}^{3+}:{^{2}\hbox{F}}_{5/2}$ cooperative down-conversion and the phonon assisted $\hbox{Tm}^{3+}:{^{1}\hbox{G}}_{4}+{\hbox {Yb}}^{3+}:{^{2}\hbox{F}}_{7/2}\rightarrow\hbox{Tm}^{3+}:{^{3}\hbox{H}}_{5}+{\hbox {Yb}}^{3+}:{^{2}\hbox{F}}_{5/2}$ cross relaxation. The low quantum yield of the latter process, together with the low absorption cross section of $\hbox{Tm}^{3+}$ at 464 nm and the low quenching concentration of ${\hbox {Yb}}^{3+}$ in the $\hbox{Y}_{2}\hbox{O}_{3}$ host, made the ${\hbox {Yb}}^{3+}$ 1030-nm NIR emission too weak for practical application.