The spectroscopic properties of Fe:ZnSe were investigated and 4 micron lasing action was demonstrated for the first time at sub-ambient temperatures. Using an Er:YAG laser as a pump source, the Fe:ZnSe laser produced output energies of 8 µJ/pulse with pulse lengths of 48 µs at a repetition rate of 100 Hz. The output wavelength varied with temperature from 3.98 µm at 14 K to 4.54 µm at 180 K. A slope efficiency of 6.7% at 130 K was obtained.

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