Yb-doped Potassium Yttrium Tungstate (Yb:KYW) is a type of crystal that is used in laser technology and spectroscopy. The crystal is made by doping the potassium yttrium tungstate crystal with ytterbium ions (Yb3+) which act as the active laser medium. Yb:KYW has good thermal stability, high optical damage threshold and broad emission spectra, making it a useful material in various applications, including fiber lasers, solid-state lasers and laser cooling. Additionally, it also has good spectroscopic properties, making it suitable for use in spectroscopy, laser pumping and laser frequency conversion.