Energy transfer up-conversion in Tm3+-doped silica fiber

TL;DR

This paper investigates the mechanisms of infra-red to near infra-red up-conversion in Tm3+-doped silica fibers, identifying energy transfer up-conversion as a key process at certain dopant concentrations.

Contribution

It provides experimental evidence and analysis distinguishing between excited state absorption and energy transfer up-conversion mechanisms in Tm3+-doped silica fibers.

Findings

Upconversion luminescence at 800 nm depends quadratically on 1800 nm luminescence.

Energy transfer up-conversion occurs at Tm2O3 concentrations above 200 ppm.

Decay characteristics support the energy transfer up-conversion mechanism.

Abstract

A study of the mechanisms responsible for the infra-red to near infra-red up-conversion in Tm3+-doped silica fibers is presented. Upconversion luminescence was observed from the 3H4 level of Tm3+ under 1586 nm pumping into the 3F4 level. The quadratic dependence of the up-conversion luminescence at 800 nm on the 1800 nm luminescence from the 3F4 level confirms that the 3H4 level is populated by a two photon process. Two possible processes are proposed as mechanisms responsible for the up-conversion: excited state absorption and energy transfer up-conversion. The decay characteristics of the luminescence from the 3H4 level were studied under direct and indirect pumping at 786 and 1586 nm, respectively. By comparing the decay waveforms to the solution of a simple set of rate equations, the energy transfer up-conversion process (3F4, 3F4 ! 3H4, 3H6) was established at Tm2O3 concentrations greater than 200 ppm.