Excitation of Fe(2+) ions via Cr(2+)->Fe(2+) and Co(2+)->Fe(2+) energy transfer in co-doped chalcogenide laser crystals (Conference Presentation)

Abstract

Recent progress in iron doped II-VI chalcogenide laser materials enabled important advancements in room temperature high energy, high power laser systems operating over 3.5-6.0 um. However, a lack of efficient and convenient pump sources for direct pumping of Fe(2+) ions limits possible applications of these materials. One viable option is using readily available pump sources to excite iron centers via Forster-Dexter energy transfer between transition metal ions. This paper reports on the characterization of iron-chromium and iron-cobalt energy transfer in Fe:Cr:ZnSe and Fe:Co:ZnSe co-doped crystals. The kinetics photoluminescence and spectroscopic measurements at 5T2-5E chromium and iron transitions indicated an efficient resonance energy transfer between ions even at room temperature. It was demonstrated that an energy transfer rate in Fe-Cr centers could be shorter than the upper level lifetime of Fe(2+) ions in ZnSe with total TM ions concentration larger than 10^19 cm^-3. Therefore, this mechanism can serve as an effective pump pathway for Fe lasing. Analysis of the dipole-dipole coupling between Fe(2+) and Cr(2+) ions demonstrated the for the shortest distance between iron and chromium ions in ZnSe host, the energy transfer rate is smaller than 1 ns. The absence of excited state absorption in Fe:Cr:ZnSe host make this materials more attractive in comparison with Fe:Co:ZnSe where Fe lasing due to excited state absorption of Co(2+) ions was limited only to low (<30K) temperature.