“…21 However, according to crystal growth experience, the crystal with a co-doped sensitizer ion is relatively easier to crack during the crystal growth process, and this may be due to the participation of doping ions increasing the lattice distortion inside the crystal, which will weaken the interaction force between particles. 22 With the development of laser diodes (LDs), the Er 3+ -ions can be directly pumped into the laser upper level 4 I 11/2 by the commercial ∼970 nm LD to generate a 2.7-3 μm laser, which is beneficial to improve the energy utilization efficiency. In 2021, Hu et al realized a maximum output power of 1.37 W and slope efficiency of 23.62% on the 30 at% Er:YSGG crystal with an LD end-pumped system.…”