Fig. 1. (a) Typical emission spectrum^[42] and (b) wavelength coverages^[19] of Er³⁺-, Ho³⁺-, and Dy³⁺-doped lasers.

Fig. 2. (a) Simplified energy-level diagram of Er³⁺-doped gain medium and sensitizer and deactivated effect of Yb³⁺ and Pr³⁺ ions; (b) the summary of the room temperature CW output power and slope efficiency of Er-doped crystalline lasers at 2.7–3 µm; (c) the schematic of a diode-side-pumped Er:YSGG slab laser at 2.79 µm^[83]; (d) the experimental setup of the LD end-pumped high-power Er:YAP laser^[15].

Fig. 3. (a) Experimental setup of high-energy LN EO Q-switched Er:YAG laser^[94]; (b) the schematic diagram of the LD arrays side-pumped Er,Pr:GYSGG laser (inset: side-pumped symmetry)^[60]; (c) the experimental setup and (d) output characterizations of the Fe:ZnSe passively Q-switched Er:YSGG laser^[99].

Fig. 4. (a) Simplified energy-level diagram of Ho³⁺-doped gain medium and sensitizer and deactivated effect of Yb³⁺ and Pr³⁺ ions; (b) the fluorescence life time “reversion” of Ho:⁵I₆ and Ho:⁵I₇ in Ho,Pr:YLF crystals with doping concentrations of 0.498 at.% and 0.115 at.% for Ho³⁺ and Pr³⁺ ions^[131]; (c) the output laser power of a Raman laser end-pumped Ho,Pr:YLF (Ho³⁺: 0.498 at.% and Pr³⁺: 0.115 at.%) laser^[131]; (d) the experimental setup and laser output power of dual-end-pumped EO Q-switched Ho,Pr:YLF laser^[132].

Fig. 5. (a) Simplified energy-level diagram of Dy³⁺-doped gain medium and sensitizer effect of Yb³⁺ ions; (b) and (c) are the schematic of the actively Q-switched Dy:ZBLAN fiber laser and corresponding laser output characterizations^[145].

Table 1. Laser Performance of CW Er-Doped Solid-State Crystal Lasers

Table 2. Laser Performance of Diode-End-Pumped Passively Q-Switched Er3+-Doped Crystalline Lasers

Table 3. Flashlamp-Pumped and CW Laser Performance of Ho-Doped 2.7–3 µm MIR Lasers

Table 4. Actively and Passively Q-Switched Laser Performance of 2.7–3 µm Ho-Doped Crystalline Lasers