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

Phonon‐assisted anti‐Stokes fluorescence is observed in an Yb 3+ 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 −1 . The phonon is identified as the combined vibrational mode of rocking of the nonbridging oxygen atoms of both TeO 3 − and its dimer Te 2 O 5 2− units and the bending of the Te–O–Te linkage of the Te 2 O 5 2− 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 3+ 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.