Fig. 1. Structure diagram of combustion-driven continuous wave HF/DF chemical laser^[6]

Fig. 2. System composition of an electrically excited chemical laser^[6]

Fig. 3. HBr laser output spectrum and laser output power curve^[10]

Fig. 4. Diagram of fiber gas laser based on population inversion^[16]

Fig. 5. Single-pass configuration experiment of fiber acetylene gas CW laser output^[20]. (a) Diagram of experimental setup; (b) output laser power as a function of absorbed pump powers at different pressures

Fig. 6. Experiment of OPO pumping CO₂-filled silver plating capillary^[21]. (a) Diagram of experimental setup; (b) output spectrum and energy level transition principle

Fig. 7. Output characteristics of fiber acetylene gas laser^[24]. (a) Laser output spectra under different signal powers at 300 Pa pressure; (b) signal power versus pump power at 300 Pa pressure with output light field shown in inset

Fig. 8. Schematic diagrams of energy level transitions of Tm³⁺, Ho³⁺ and Er³⁺(from left to right)^[29]

Fig. 9. Overall experimental scheme^[36]. (a) Energy level diagram of GSA and ESA dual-wavelength pumped scheme; (b) experimental arrangement for GSA and ESA dual-wavelength pumped Tm³⁺∶YAP laser

Fig. 10. Configuration of tunable multi-wavelength Ho³⁺ doped fiber laser^[49]

Fig. 11. Diagrams of side-pumped Er³⁺∶YSGG slab laser; (a) Top view; (b) side view^[52]

Fig. 12. Schematic diagram of 140 W Cr²⁺∶ZnSe laser system^[67]

Fig. 13. Joule level Fe²⁺∶ZnSe mid-IR laser pumped by Er³⁺∶YAG lasers^[69]

Fig. 14. 30.6 mJ, Fe²⁺∶ZnSe mid-IR laser pumped by HF laser operating at room temperature^[70]

Fig. 15. Schematic diagram of band structure of quantum cascade laser

Fig. 16. Schematic diagram of experimental apparatus for polarization beam combination^[86]

Fig. 17. Schematic diagram of conversion process under several nonlinear frequencies^[87]

Fig. 18. Schematic diagram of violet jade laser pumped AgGaS₂ and GaSe MIR-DFG^[89]

Fig. 19. Schematic diagram of MIR source based on ps-laser pumped BaGa₄Se₇ crystal^[94]

Fig. 20. Schematic diagram of CW MIR source based on BaGa₄Se₇-DFG^[96]

Fig. 21. PPLN-OPO structure diagram^[100]

Fig. 22. MgO∶PPLN-OPO experimental apparatus^[104]

Fig. 23. Experiment of mid-infrared laser source based on ZnGeP₂-OPO; (a) Tm3+-doped fiber+Ho³⁺∶YAG rod pumped ZGP-OPO mid-infrared laser^[109]; (b) based on Rb∶PPKTP pumped mid-infrared ZnGeP₂-OPO^[111]