Fig. 1. The principle of OPA, OPCPA and DC-OPA

Fig. 2. Schematic of an optical parametric amplifier

Fig. 3. Collinear and non-collinear phase-matching geometries

Fig. 4. Calculated gain spectrum of a 3 mm BBO under the type-I phase-matching condition, and the calculated gain spectrum at the pump wavelength of 708 nm with different phase-matching angle^[19]

Fig. 5. A typical seed generation scheme

Fig. 6. Spectral range of the supercontinuum generated in various material while driven by light of different wavelengths^[25]

Fig. 7. Reflectance and GDD of the complementary chirped mirror pair in the wavelength of 2~4 μm^[26]

Fig. 8. Measured reflectance, transmittance, absorption and GDD curves of the chirped mirror^[27]. Reprinted with permission from Ref.[27] ©The Optical Society

Fig. 9. Transmittances and GVD of several typical materials for dispersion management

Fig. 10. Transmittance of the liquid-crystal in the SLM and the setup of the SLM based pulse shaper^[30]

Fig. 11. Some typical reports on the performance of mid-infrared femtosecond sources based on optical parametrical amplification technique driven by pumps of different wavelength in recent years

Fig. 12. Schematic of DC-OPA with peak power of 0.3 TW^[40]

Fig. 13. Schematic of the mid-infrared source with average power of 15.1 W^[46]

Fig. 14. 9 μm femtosecond mid-infrared source based on LiGaS₂^[52]. Reprinted with permission from Ref.[52] ©The Optical Society

Fig. 15. 7 μm femtosecond mid-infrared source with pulse energy of millijoule level^[59]. Reprinted with permission from Ref.[59] ©The Optical Society

Fig. 16. Proof-of-principle schematic setup of the 4~12 μm mid-Infrared source^[60]

Fig. 17. Layout of the Ho:YAG thin-disk laser

Fig. 18. Thermal imaging of BBO crystal pumped with optical power of 120 W at 515 nm and the photograph of the BBO-sapphire sandwich structure ^[63-64]

Fig. 19. Schematic of the wavelength tunable optical vortex OPA system^[65]. Reprinted with permission from Ref.[65] ©The Optical Society

Fig. 20. Schematic of the 4 μm optical vortex OPCPA system^[66]

Fig. 21. Spectra of the optical vortex beam measured at four different quadrants^[66]

Fig. 22. Schematic of the experimental setup for second harmonic generation of radially polarized beam with two nonlinear crystals^[67]. Reprinted with permission from Ref.[67] ©The Optical Society