Er:YAP, or erbium-doped yttrium aluminum oxide, is a laser crystal that is used in a variety of applications, including laser marking and laser cutting. The crystal is doped with erbium ions, which provide the laser emission when excited by light. The main advantage of Er:YAP is its high gain and good thermal conductivity, which makes it a good choice for high-power laser systems. Er:YAP lasers operate in the 2 micrometer spectral region, and have found widespread use in medical, industrial and scientific applications, including ophthalmology, dentistry and spectroscopy.