We report a simple method for fabricating transition metal (TM) doped II-VI powders with average size of about 10-
20μm as well as room temperature mid-infrared (2-3 μm) random lasing based on Cr2+-doped ZnSe and ZnS powders
prepared without crystal growth stage under optical intra-shell excitation of chromium. Fabrication of Cr2+-doped ZnSe
and ZnS powders involved two simple stages. At the first stage, pure ZnSe, (ZnS) and CrSe, (CrS) (with a concentration
of Cr2+ ion 2×10-19 cm-3 and 5 × 10-19 cm-3 for ZnSe and ZnS respectively) chemicals with an average grain size of 10μm were uniformly mixed by means of a mechanical shaker. At the second stage the obtained ZnSe/CrSe mixture was sealed into evacuated (~10-4 Torr) quartz ampoule and annealed either at 1200°C for 15 minute, or 1000°C for 3 days. In
the case of ZnS/CrS mixtures the annealing was performed in evacuated quartz ampoule at 1000 °C for 14 days. After
annealing, under 1560 nm excitation, the powders demonstrated room temperature middle-infrared luminescence of Cr2+
similar to Cr2+ emission in bulk ZnSe and ZnS. Moreover, the output-input characteristic clearly demonstrated the
threshold-like behavior of the output signal with the threshold pump energy density of ~44.5 mJ/cm2 ~7.46 mJ/cm2, and 63.6 mJ/cm2 for Cr:ZnSe annealed for 15 min, 3 days, and Cr:ZnS respectively.
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