Tm:YLF is a laser active crystal that is doped with Thulium ions in a Lithium Yttrium Fluoride crystal lattice. It is known for its ability to emit laser light in the ultraviolet (UV) range and has been used as a gain medium in laser systems for applications in areas such as medicine, spectroscopy, and scientific research. This crystal has a broad gain bandwidth, high thermal conductivity, and a high absorption cross-section, which makes it a useful material for high-power laser systems. Additionally, Tm:YLF has a high damage threshold and excellent optical quality, making it an attractive option for many laser applications.