Antiresonances in the excitation and absorption spectra ofCr3+-doped fluoride glasses

Absorption and excitation spectra of ${\mathrm{Cr}}^{3+}$-doped fluoride glasses exhibit features that can be interpreted as Fano antiresonance lines due to interactions between the ${}_{}{}^2{}_{}{}^{}$E, ${}_{}{}^2{}_{}{}^{}$ ${\mathit{T}}_1$ sharp levels and the vibrationally broadened ${}_{}{}^4{}_{}{}^{}$ ${\mathit{T}}_2$ quasicontinuum. A study of the influence of glass inhomogeneity on the antiresonance profiles of ${\mathrm{Cr}}^{3+}$ time-resolved laser-excitation spectra at 4.2 K was performed for four fluoride glasses. The Fano theory adapted by Sturge, Guggenheim, and Pryce has also been used to develop a method to analyze the change of the resonance-line-shape parameter q as a function of the peak position and half width of the background absorption spectrum. The analysis includes background spectra consisting of a single- and a double-Gaussian function. A qualitatively good agreement with the experimental data for several fluoride glasses has been obtained.