Effect of the concentration of the Er 3+ ion on the spectral intensity parameters of Er:YAG crystals

Abstract

The absorption spectra of Er:YAG (YAG, yttrium-aluminium-garnet) crystals containing different concentrations of the trivalent erbium ion were measured and the spectral intensity parameters were calculated from these experimental spectra using the Judd-Ofelt model. The results indicate that the phenomenological intensity parameters, Ω λ ( λ = 2, 4 and 6), vary as a function of the concentration of the Er 3+ ion in the Er:YAG crystal, but no variation in the fluorescence-branching ratios as a function of the concentration of the Er 3+ ion is found. An empirical formula is proposed to describe the relationship between the spectral intensity parameters and the Er 3+ ion concentration in the Er:YAG crystal. The spectral intensity parameters exhibit a maximum in Er:YAG crystals containing about 1–1.5 at.% Er 3+ ion. The effect of the Er 3+ ion concentration on the spectral intensity parameters may be attributed to the inhomogeneous lattice distortion in the cell of the Er:YAG crystal caused by the dopant erbium ions.