Fig. 1. Basic optical properties of silica, tellurite, fluoride, and chalcogenide glasses^[35-38]. (a) Transmission spectra; (b) normalized Raman gain spectra

Fig. 2. Material dispersion characteristics of silica, tellurite, fluoride, and chalcogenide glasses^[42]. (a) Refractive index curves; (b) dispersion curves

Fig. 3. Raman gain spectrum of TBY glass^[43]

Fig. 4. Measured output power from chalcogenide glass Raman fiber laser versus launched pump power with output spectrum of fiber laser at maximum pump power shown in inset^[44]

Fig. 5. Experimental setup of As₂S₃-based RFL^[46]

Fig. 6. Output Stokes average (left) and peak (right) powers versus 3 μm launched pump average power ^[46]

Fig. 7. Experimental setup of As₂S₃-based 3.77 μm cascaded RFL^[23]

Fig. 8. Transmission spectra (dashed lines) of different fiber gratings in laser cavity and output laser spectra close to threshold power and at maximum peak pump power of 3.9 W ^[23] . (a) Pump grating; (b) Stokes 1 grating; (c) Stokes 2 grating

Fig. 9. Average output power (left) of 3.766 μm Stokes and estimated peak power (right) versus launched pump power for output couplers with peak reflectivity of 98%, 92%, and 80%, and solid lines indicating simulated results^[23]

Fig. 10. Experimental setup of the all-fiber Raman laser operating at 2185 nm^[48]

Fig. 11. Output power of 2185 nm Raman laser versus launched pump power^[48]

Fig. 12. Experimental setup of nested cavity fluoride Raman fiber laser^[24]

Fig. 13. Output power of 2231 nm Raman laser versus launched pump power^[24]

Fig. 14. Spectra of redshifted soliton at different wavelengths in 2 m long InF₃ glass fiber^[33]. (a) Measured results; (b) calculated results

Fig. 15. Principle diagram of Raman frequency shift of fourth-order tellurite Raman fiber laser

Fig. 16. Measured output power of Raman laser versus wavelength at pump power of 20 W at 2.8 μm^[25]. (a) 1^st-order Raman laser; (b) 2^nd-order Raman laser

Fig. 17. Measured output spectra of 50-cm long tellurite micro-structured fiber pumped at 2 μm femtosecond laser, corresponding calculated spectra, and filtered Raman soliton spectra in time domain^[56]

Fig. 18. Characteristic parameters of LP01 modes propagating in fast and slow axes of birefringent fluorotellurite micro-structured fibers^[57]. (a) Group velocity dispersion curves, and cross-sectional scanning electron micrograph of birefringent fluorotellurite microstructured fiber shown in inset; (b) confinement loss curves

Fig. 19. Experimental results of dispersive wave generation in birefringent fluorotellurite microstructured fiber^[57]. Evolutions of output spectra in fiber with average power of excited light as 1560 nm femtosecond laser propagates along (a) fast axis and (b) slow axis

Fig. 20. Calculated output spectra when pump laser is polarized along fast axis of fibers 16^[58]

Fig. 21. Dependence of measured spectra from the fluorotellurite fiber on peak pump power of 1960 nm femtosecond fiber laser^[43]

Fig. 22. Principle diagram of shower of Raman solitons generated at preset wavelength^[59]

Fig. 23. Parameters of nonlinear fiber^[59]. (a) Core diameter of tapered fluorotellurite fiber versus fiber length with cross-sectional scanning electron micrograph of untapered fluorotellurite fiber shown in inset; (b) calculated GVD curves for different core diameters of fluorotellurite fibers

Fig. 24. Experimental results^[59]. (a) Measured output spectra of tapered fiber for different average pump powers of 0.48, 0.65, 0.84, 1.0, 1.14, 1.30, 1.52, 1.74, 2.0, 2.2, 2.48, and 2.7 W (from bottom to top); (b) measured output spectrum in linear scale for pump power of 2.7 W

Table 1. Comparison of laser damage threshold, peak Raman shift, peak Raman gain coefficient, and nonlinear refractive index of five typical fiber materials^[18,38-41]