Fig. 1. Population inversion threshold of parasitic oscillation versus pump spot diameter

Fig. 2. Experimental setup of Fe2+∶ZnSe laser. (a) Schematic; (b) physical map

Fig. 3. Pulse waveform of pump laser

Fig. 4. Transmission and absorption spectra of Fe2+∶ZnSe crystal (The illustration shows Fe2+∶ZnSe crystal)

Fig. 5. Laser spots. (a) Original spot; (b) ?5.2 mm spot after beam shaping; (c) ?9.2 mm spot after beam shaping

Fig. 6. Output energy of Fe2+∶ZnSe laser versus pump energy under different pump spot diameters. (a) ?5.2 mm, ?6.8 mm, ?7.1 mm; (b) ?8.2 mm, ?9.2 mm, ?10.5 mm

Fig. 7. Slope efficiency of Fe2+∶ZnSe laser versus pump spot diameter

Fig. 8. Pulse waveforms of pump laser and Fe2+∶ZnSe laser

Fig. 9. Pulse waveforms of Fe2+∶ZnSe lasers with different output energies