Middle-IR Random lasing of Cr:ZnS nanocrystalline powder - from diffusion to photon localization regimes

First room temperature mid-IR lasing due to intra-shell transitions in the doped semiconductor nanocrystals (NC) is reported. The 27 nm Cr:ZnS NCs oscillate at 2200 nm with 325 mJ/cm
²
laser threshold. Temperature dependence of photoluminescence decay, lasing threshold and lasing wavelength maxima of Cr:ZnS NCs are studied.