Xue Xiaojie, Thitsa Makhin, Cheng Tonglei, Gao Weiqing, Deng Dinghuan, Suzuki Takenobu, Ohishi Yasutake
Opt Express. 2016 Nov 14;24(23):26307-26321. doi: 10.1364/OE.24.026307.
Energy transfer between Tm and Tb dependent on the power density of pump laser was investigated in NaYF: Tb,Tm,Yb microcrystals. Under the excitation of a 976-nm near-infrared laser at various power densities, Tb-Tm-Yb doped samples exhibited intense visible emissions with tunable color between green and blue. The ratio of blue and green emission were determined by energy transfer between Tm and Tb. When the power density of pump laser was low, the energy transfer process from Tm (F) to Tb (F) occurred efficiently. Upconversion processes in Tm were inhibited, only visible emissions from Tb with green color were observed. When the power density increased, energy transfer from the F (Tm) to F level (Tb) was restrained and population on high energy levels of Tm was increased. Contribution of upconversion emissions from Tm gradually became dominant. The emission color was tuned from green to blue with increasing the power density. Energy transfer processes between low-lying levels of activators, such as Tm will greatly reduce the population on certain levels for further high-order upconversion processes. The Tb-Tm-Yb doped phosphors are promising materials for detecting the condition of power density of the invisible near-infrared laser.
在NaYF:Tb、Tm、Yb微晶中研究了Tm和Tb之间的能量转移对泵浦激光功率密度的依赖性。在不同功率密度的976nm近红外激光激发下，Tb-Tm-Yb掺杂样品呈现出强烈的可见光发射，颜色可在绿色和蓝色之间调节。蓝色和绿色发射的比例由Tm和Tb之间的能量转移决定。当泵浦激光功率密度较低时，从Tm(F)到Tb(F)的能量转移过程有效发生。Tm中的上转换过程受到抑制，仅观察到Tb发出的绿色可见光发射。当功率密度增加时，从F(Tm)到F能级(Tb)的能量转移受到抑制，Tm高能级上的粒子数增加。Tm的上转换发射贡献逐渐占主导地位。随着功率密度的增加，发射颜色从绿色调至蓝色。激活剂低能级之间的能量转移过程，如Tm，将极大地减少某些能级上的粒子数，以进行进一步的高阶上转换过程。Tb-Tm-Yb掺杂磷光体是用于检测不可见近红外激光功率密度状况的有前途的材料。
