Steady photo-darkening of thulium alumino-silicate fibers pumped at $1.07~\mu m$: Quantitative effect of lanthanum, cerium and thulium

TL;DR

This study investigates how the composition of thulium alumino-silicate fibers affects photo-darkening when pumped at 1.07 μm, revealing that lanthanum and cerium ions mitigate photo-induced attenuation caused by UV emission.

Contribution

It provides a quantitative analysis of how fiber core composition influences photo-darkening, highlighting the protective roles of lanthanum and cerium ions.

Findings

UV emission from Tm-Tm energy transfer causes photo-darkening.

Lanthanum and cerium ions reduce photo-induced attenuation.

Fiber composition significantly affects PIA severity.

Abstract

By pumping thulium-doped silica-based fibers at 1.07~\mu m, rapid generation of absorbing centers leads to photo-induced attenuation (PIA). This detrimental effect prevents exploiting laser emissions in the visible and near infrared. We report on the characterization of the PIA versus the fiber core composition, particularly the concentration of thulium (Tm), lanthanum (La) and cerium (Ce) ions. We show that UV emision induced by Tm-Tm energy transfers is the source of photo-darkening, and that lanthanum and cerium are efficient hardeners against PIA.