Influence of the Ga addition on optical properties of Pr in Ge–Sb–Se glasses

Absorption and emission spectra for the ³H₄↔(³F₂, ³H₆) transition of Pr³⁺ ions embedded in Ge–Sb–Se glasses turned out to change systematically upon the introduction of a small amout of Ga. Clear blueshift of the absorption peak wavelengths together with the decrease of absorption cross-section was evident in these glasses containing Ga. We believe that the Ga addition into the conventional covalent selenide glasses makes chemical bonds between rare earth atoms and Se atoms more ionic due to preferential location of the GaSe₄ tetrahedra at the second coordination shell of a rare earth atom. Taking into consideration the hypersensitive nature of the Pr³⁺: ³H₄↔³F₂ transition, the observed blueshift may manifest the enhanced ionicity of the chemical bonds between Pr and Se in the current Ga-containing glasses.