Fig. 1. Spectroscopic properties of Nd∶MgO∶LN crystal. (a) Absorption spectra; (b) fluorescence spectrum

Fig. 2. Energy level diagram of Nd∶MgO∶LN crystal

Fig. 3. Experimental setup and output characteristics of self-Q-switched SOPO based on Nd∶MgO∶PPLN crystal^[33]. (a) Schematic of experimental setup; (b) single pulse width versus absorbed pump power; (c) peak power and pulse width versus repetition frequency

Fig. 4. Experimental setup and output characteristics of LD end-pumped c-cut Nd∶MgO∶LN crystal^[35]. (a) Schematic of experimental setup; (b) CW laser output power versus absorbed pump power; (c) pulsed laser output power versus absorbed pump power

Fig. 5. Experimental setup and output characteristics of 1.1 μm Nd∶MgO∶LN laser^[37]. (a) Schematic of experimental setup; (b) laser spectra at different pump powers; (c) output power versus absorbed pump power at 1108 nm; (d) laser spectrum at 1114 nm; (e) output power versus absorbed pump power at 1114 nm

Fig. 6. Experimental setup and output characteristics of an intra-cavity Q-switched SOPO based on two-dimensional Nd∶MgO∶PPLN^[46]. (a) Schematic of experimental setup; (b) variations of single pulse width and single pulse energy with pump power

Fig. 7. Experimental setup and output characteristics of an intra-cavity acousto-optically Q-switched SOPO based on Nd∶MgO∶PPLN crystal^[53]. (a) Schematic of experimental setup; (b) output power and conversion efficiency of 2.1 μm laser under different output mirror transmittances; (c) pulse width of 2.1 μm laser at 40 kHz

Fig. 8. Experimental setup and output characteristics of mid-infrared SOPO based on LD fiber-direct-pumped Nd∶MgO∶PPLN crystal^[58]. (a) Schematic of experimental setup; (b) output power versus absorbed pump power

Fig. 9. Representative research achievements in recent years across a range from fundamental frequency light to mid-infrared idler light, realized using Nd∶MgO∶PPLN crystals

Fig. 10. Variation of output energy with pump energy under different conditions. (a) Under the same pump pulse width and different repetition frequencies; (b) under the same repetition frequency and different pump pulse widths

Fig. 11. Variation of output energy with pump energy. (a) 1084 nm fundamental frequency light; (b) mid-infrared idler light

Fig. 12. Spectrum of mid-infrared idler light

Fig. 13. Single pulse width and pulse train diagram of mid-infrared idler light

Fig. 14. Schematic diagram of experimental setup of an electro-optic Q-switched mid-infrared SOPO based on pulse-pumped Nd∶MgO∶PPLN