Optical spectroscopy, 15μm emission, and upconversion properties of Er^3+-doped metaphosphate laser glasses

Abstract

Metaphosphate glasses doped with five concentrations of Er3+ ions have been investigated through absorption and emission spectra, decay curves, and upconversion measurements. Judd-Ofelt parameters have been evaluated from absorption spectrum of the 1.0mol.%Er3+-doped glass, which are in turn used to predict radiative properties of some important luminescence levels of Er3+ ions in these glasses. Gain bandwidths of an optical amplifier have been evaluated and are compared with those of reported Er3+:glass systems. Temperature dependence of the 1.5μm emission has been studied for the 2.0mol.%Er3+-doped glass from 13K to room temperature. Lifetimes of the I13/24 level were measured and are found to decrease with concentration of Er3+ ions after 0.1mol.%. Concentration quenching of lifetimes has been analyzed using the theory developed by Auzel [J. Lumin.94-95, 293 (2001); Opt. Mater.24, 103 (2003)]. Infrared to visible upconversion was also measured for three concentrations of Er3+-doped metaphosphate glasses with 794nm excitation. A mechanism, involving excited state absorption and energy transfer upconversion, has been proposed to explain the upconversion process.