4.24  μm mid-infrared laser based on a single Fe²⁺-doped ZnSe microcrystal

In this Letter, we report for the first time, to the best of our knowledge, a micron-sized mid-infrared Fe²⁺:ZnSe laser based on a single microcrystal. Typical laser emissions centering at 4.24 μm are observed from a selected Fe²⁺-doped ZnSe microcrystal under 2.94 μm excitation of Er:YAG laser at room temperature. The laser linewidth is ∼10  nm, the pulse width is ∼50  ns, and the lasing threshold is ∼7.4  mJ/pulse. The lasing wavelength is stable as the pump energy increases and is consistent with the strong absorption position of carbon dioxide in the atmosphere.