Transition-metal-doped II-VI semiconductor materials enable high power
lasers in the mid-infrared range and combine superb ultra-fast laser
capabilities with high nonlinearity and polycrystalline microstructures that provide random
quasi-phase matching. A femtosecond polycrystalline Cr:ZnS and Cr:ZnSe laser with a flexible design was developed by the authors; this figure shows the microstructure of polycrystalline Cr:ZnS, which is optimized for high SFH output. See Vasilyev et al. Opt. Mater. Express 7, 2636-2650 (2017).