Cr:ZnSe – Chromium zinc selenide (Cr2+:ZnSe) exhibits high absorption coefficient and can be very efficiently pumped over broad 1450-2100 nm range of various sources or used as passive Q-switch in this range.

Cr:ZnSe is tunable and it lases at wide wavelength range from 1900 nm to 3300 nm. Probably biggest disadvantage of chromium zinc selenide crystal is strong thermal lensing effect which creates power limits.

Unlike usually found in the market poly-crystalline form, 3photon Cr:ZnSe is mono-crystalline.

https://3photon.com/crznse-cr2znse-chromium-doped-zinc-selenide/