Fig. 1. Refractive indices of glass hosts and fiber transmission loss. (a) Refractive indices of fiber core, inner cladding glass, and outer cladding glass; (b) loss of single-clad and double clad fibers

Fig. 2. Structure and refractive index profile of double-clad chalcogenide fiber taper. (a) Schematic of double-clad chalcogenide fiber taper; (b) cross-section and refractive index profile of double-clad chalcogenide fiber

Fig. 3. Fundamental mode dispersion characteristic curves of double-clad (solid) and single-clad (dashed) fiber tapers

Fig. 4. SC spectra generated from double-clad (dashed) and single-clad (solid) fiber tapers pumped by ultrashort laser pulses with different wavelengths. (a) 4 μm; (b) 5 μm; (c) 6 μm

Fig. 5. SC spectra generated from double-clad fiber tapers with different transition region lengths

Fig. 6. Simulated SC spectrum and its coherence property curve in double-clad fiber taper