Fig. 1. (a)–(c) Wavelength-dependent curves of dispersion D of the fundamental guided mode of single-index fibers with distinct rod diameters in the cases of GST, TZL, and SiO2 fibers. (d)–(f) Calculated wavelength-dependent curves of rod nonlinear coefficient for the same diameters. Insets: normalized spatial power distributions of the electric field for the fundamental guided mode calculated at pump wavelength for two values of rod diameters (initial and waist diameters).

Fig. 2. (a) Schematic view of optimized tapered rod for each glass (left side), and corresponding refractive index profiles and input cross-section images (right side). (b) Experimental setup used for SC generation. The laser pump used can either come from (i) the signal and idler or (ii) the DFG module. The fiber under study is placed on a V-groove mounted on a five-axis stage. Output SC is characterized with detection (1) for GST fibers and detection (2) for TZL and SiO2 fibers. A power sensor is also used to characterize the output power of the spectrum and a visible/near-IR camera for near-field imaging.

Fig. 3. SC spectra obtained in 5-cm-long segments of single-index Ge-Se-Te glass rods with (a), (b) uniform and (c), (d) tapered sections and different input peak powers. Left panels: experimental measurements. Right panels: corresponding numerical results of SC generation obtained over 200 simulations. The calculated modulus of complex degree of first-order coherence (right axis), and the RIN (left axis) are also depicted in (d) for the tapered rods.

Fig. 4. SC spectra obtained in 5-cm-long segments of single-index TeO2-ZnO-La2O3 glass rods with (a), (b) uniform and (c), (d) tapered sections and different input peak powers. Left panels: experimental measurements. Right panels: corresponding numerical results of SC generation obtained over 200 simulations. The calculated modulus of complex degree of first-order coherence is also depicted in (d) for the tapered rods.

Fig. 5. SC spectra obtained in 5-cm-long segments of multimode step-index SiO2 fibers with (a), (b) uniform and (c), (d) tapered sections and different input peak powers. Left panels: experimental measurements. Right panels: corresponding numerical results of SC generation obtained over 200 simulations. The calculated modulus of complex degree of first-order coherence is also depicted in (d) for the tapered fibers.

Fig. 6. SC spectra obtained in tapered (a) GST fiber, (c) TZL fiber, and (d) SiO2 multimode fiber with maximum output average powers. (b) Current state-of-the-art of mid-IR SC average power as a function of the long mid-IR spectral edge with direct pumping in the femtosecond regime and for cascaded systems with long pulses (ps or ns). The works cited are Refs. [12–15" target="_self" style="display: inline;">–15,2022" target="_self" style="display: inline;">–22,41,42].