ZnSe:(Cr,Fe) laser crystal matrices: Challenges related to doping

• Published in: Optical materials. X 2024-05, Vol.22, p.100321, Article 100321
• Main Authors: Lamonova, K.V., Orel, S., Prokhorov, A., Kovalenko, N., Schmidbauer, M., Kwasniewski, A., Kazarinov, Yu, Tomm, J.W.
• Format: Article
• Language: English
• Subjects: Co-doped ZnSe single crystals; EPR’ optical spectra; HR-XRD; Jahn–Teller effect; Modified crystal field theory; SEM
• ISSN: 2590-1478; 2590-1478
• DOI: 10.1016/j.omx.2024.100321

We investigate co-doped ZnSe: (Cr, Fe) laser crystals with an approach that includes both optical spectroscopy and theoretical modelling. We found that concentrations of chromium and iron up to 1018 cm−3 are optimal for obtaining a homogeneous solid solution in designing laser crystals. Higher dopant concentrations lead to the formation of clusters with spinel structure in the ZnSe matrix. The optimal effectiveness of ZnSe laser media with active Cr2+ and Fe2+ elements is achieved at temperatures of around 100 K. Heating induces charge transfers like Fe2+→Fe3+ and Cr2+→Cr3+, while cooling results in phonon freezing. A theoretical model has been developed to explain the observed temperature evolution of the absorption spectrum. The types and values of distortions of the Cr- and Fe-based coordination complexes are determined. We have found that the Jahn-Teller distortions are crucial for modelling the temperature-dependent changes of the absorption spectra. [Display omitted] •Co-doped ZnSe: (Cr, Fe) sample show temperature evolution of the absorption spectrum.•Temperature-induced charge transfers Fe2+.→Fe3+ and Cr2+→Cr3+ are found;•Concentrations of Cr and Fe up to 1018 cm−3 exclude clusterization.•Theoretical model developed explain absorption spectrum temperature evolution.