Phonon‐Assisted Anti‐Stokes Fluorescence of an Yb³⁺‐Doped Oxide Glass: Phononics and Spectroscopic Analysis of Its Prospects as Solid‐State Laser Cooler

Abstract

Phonon-assisted anti-Stokes fluorescence is observed in an Yb 3þ doped, 30 mol% BaO containing tellurite glass for the first time. Absorption, excitation, and the anti-Stokes fluorescence spectra of the glass show a phonon progression of 150 cm À1. The phonon is identified as the combined vibrational mode of rocking of the nonbridging oxygen atoms of both TeO 3 À and its dimer Te 2 O 5 2À units and the bending of the Te-O-Te linkage of the Te 2 O 5 2À units of the glass structure. These units are known to exist in plenty in such BaO-TeO 2 glasses with high BaO content. Association of the phonon modes with the absorption and anti-Stokes fluorescence spectra of Yb 3þ of the glass, strongly suggests that the phonon is coupled both with the 2 F 7/2 (1) ground and the 2 F 5/2 (5) excited states of the ion; and the observed anti-Stokes fluorescence originates through annihilation of the excited state manifolds of this coupled phonon. Phononics and spectroscopic analysis of the anti-Stokes fluorescence process suggest that the material should be prospective for use as solid-state laser cooler.