Progress in Mid-IR Lasers Based on Cr and Fe-Doped II-VI Chalcogenides

Transition metal (TM) doped II-VI chalcogenide laser materials offer a unique blend of physical, spectroscopic, and technological parameters that make them the gain media of choice for cost effective broadly tunable lasing in the Mid-IR. The II-VI semiconductor hosts provide a low phonon cut-off, broad IR transparency, and high thermal conductivity. When doped with transition metal ions, these materials feature ultrabroadband gain, low saturation intensities, and large pump absorption coefficients. This combined with the low-cost mass production technology of crystal fabrication by postgrowth thermal diffusion, as well as broad availability of convenient pump sources, make these materials ideal candidates for broadly tunable mid-IR lasing in CW, gain-switched, free running, and mode-locked regimes of operation. This review summarizes experimental results on optically pumped lasers based on Cr and Fe doped II-VI wide band semiconductors providing access to the 1.9-6 mu m spectral range with a high (exceeding 60%) efficiency, multi-Watt-level (18 W in gain switch and 30 W in pure CW) output powers, tunability in excess of 1000 nm, short-pulse (<50 fs) multi-watt oscillation, multi-Joule long-pulse output energy, and narrow spectral linewidth (<100 kHz).