Nonstationary behavior of the upconversion processes of $Er^{3+}:Yb^{3+}$ ions pair doping the $Y_2O_3$ ceramic illuminated with 976 nm laser light

TL;DR

This paper reveals that the upconversion emission in Er^{3+}:Yb^{3+} doped Y_2O_3 ceramics fluctuates over time under constant laser illumination, indicating complex energy transfer dynamics.

Contribution

It uncovers nonstationary, fluctuating upconversion behavior in a well-studied system, challenging the assumption of static emission under constant illumination.

Findings

Upconversion emission fluctuates over time at constant illumination.

Emission variations appear as superimposed intensity waves.

Energy transfer processes involve complex absorption, saturation, and relaxation dynamics.

Abstract

The studies of the upconversion response of RE ions in various hosts usually depict a static picture, whereas, at constant illumination, the upconverted emission is also constant. We discovered here that, at least in the case of $Y_2O_3$ doped with $Er^{3+}:Yb^{3+}$, this is not the case. At constant illuminated power, the upconversion emission is not only fluctuating, but it varies in a manner which seems to be a superposition of intensity waves with different frequencies. We present here the results of the measurements we've performed on $Y_2O_3$ with $1\%Er^{3+}-2\%Yb^{3+}$. The origin of this effect remain to be established but it shows that the energy transfers during the upconversion are an interplay of absorption-saturation-emission-relaxation processes.