“…However, the Er3+ only has several narrow band absorption peaks, which greatly limits the absorption efficiency of the Er3+-doped crystal for the xenon lamp pump light and the output efficiency of the mid-infrared laser. For this situation, the chromium has been co-doped as one sensitizer to increase the pumping efficiency, and ultimately improve the laser efficiency, such as in the Cr,Er:YSGG, Cr,Er:YAG, Cr,Er:GGG, and Cr,Er,Pr:GYSGG crystals 13 , 17 – 19 Now, the xenon lamp-pumped Er:YAP laser has been proved to possess excellent laser performance, whereas the work about the Cr3+, Er3+ co-doped YAP crystal and laser needs to be promoted further.…”