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II-VI binary and ternary chalcogenides (e.g. ZnS, ZnSe; CdZnTe, ) doped with transition metal (TM) ions such as Cr, and Fe are arguably the materials of choice for effective mid-IR lasers potentially covering 1.8-9 µm spectral range. This talk summarizes progress in Cr:ZnS/Se and Fe:ZnSe laser systems, enabling a wide range of tunability (1.8-5.0µm) with output power levels of up to 140 W, as well as Fe doped ternary chalcogenides with tunability potentially extended up to 9 um.
TM:II-VI media feature a unique combination of superb ultra-fast laser capabilities with high nonlinearity enabling exceptional output characteristics of polycrystalline Cr:ZnS/Se oscillators in Kerr-Lens-Mode-Locked (KLM) regime over 2-2.6 um and effective up and down conversion of fs pulses via random phase matching (RFM). Extension of mid-IR spectral coverage to 3-8 um is demonstrated by Cr:ZnS KLM laser pumped subharmonic parametric oscillators (OPOs) based on quasi-phase matching in OP-GaAs, and RFM in polycrystalline ZnSe.
Fe:II-VI semiconductors are complimentary to Cr doped compounds and 3-8 um KLM ultrafast oscillators based on Fe doped chalcogenides are feasible. Another important feature of Fe:II-VI media is excellent energy storage capability at 77-200K (~60 µs luminescence life time) enabling efficient Q-switched regime and high energy amplification of ns and ultrafast pulses.
One of the major problems in the development of CW, gain switched, Q-switched and KLM ultrafast Fe:II-VI lasers was the absence of convenient pump sources overlapping with absorption band (2.7-4.5 um) of Fe: gain media. Potential utilization of Quantum Cascade Lasers (QCL) as pump sources of Fe:II-VI lasers will be discussed in the form QCL-solid state laser hybrid platforms as well as Fe doped active layers integrated in QCL structures.
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