Fig. 1. Schematic of 1550 nm laser operation mechanism based on Er³⁺-doped crystal^[2]

Fig. 2. Experimental setup for measuring the internal temperature distribution of Er∶Yb∶LuAB crystal under the operation of 1550 nm laser^[15]

Fig. 3. Temperatures at different positions Z inside the Er∶Yb∶LuAB crystal at different incident pump powers under the operation of 1550 nm laser^[15]

Fig. 4. Spectroscopic properties of the Er∶Yb∶YAB crystal in 300--800 K^[20]. (a) Absorption cross-section spectra in σ-polarized direction from 900 nm to 1040 nm; (b) emission cross-section spectra in σ-polarized direction from 1450 nm to 1650 nm; (c) gain cross-section spectra in σ-polarized direction from 1500 nm to 1620 nm (inversion parameter β=0.5); (d) fluorescence lifetime of ⁴I_13/2 of Er³⁺

Fig. 5. Diffusion-bonded Er∶Yb∶YAB/YAB composite crystal^[24]. (a) Picture of the composite crystal, and transmission spectra of Er∶Yb∶YAB/YAB and Er∶Yb∶YAB crystals in 250--850 nm; (b) 1550 nm CW laser performances of Er∶Yb∶YAB/YAB and Er∶Yb∶YAB crystals under the same experimental condition

Fig. 6. Diffusion-bonded sapphire/Er∶Yb∶YAB/sapphire composite crystal^[26]. (a) Bonding preparation process and picture of the composite crystal; (b) 1550 nm CW laser performances of sapphire/Er∶Yb∶YAB/sapphire and Er∶Yb∶YAB crystals under the same experimental condition

Fig. 7. Performance of micro-laser with Er∶Yb∶YAB of sandwich-structure^[27]. (a) CW laser; (b) passively Q-switched pulse laser

Fig. 8. Laser performances of Er∶Yb∶LPS crystal^[46]. (a) 1564 nm multi-longitudinal-mode CW laser; (b) 1537 nm single-longitudinal-mode CW laser