# A Review of Mid-Infrared Supercontinuum Generation in Chalcogenide Glass Fibers
## 3 MIR SC Generation in ChG Fibers
### SC Generation in ChG MOF Fibers  
The ability to tailor the fiber dispersion profile to the particular needs of its intended application is an underlying theme across all glass and fiber designs. The use of MOF technology provides primary flexibility in dispersion control to match the conditions of the pump source. By changing the structural parameters, the waveguide dispersion of MOFs can be controlled, so that the total dispersion can be engineered precisely. A key geometrical parameter of MOFs is the ratio of fiber core diameter (d) and the pitch (\(\Lambda\)), which can control the waveguide dispersion over a wide wavelength range, as shown in Figure 6. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Fiber** & **Fiber Length** &
\begin{tabular}{c} **Pump Wavelength/Pulse** \\ **Width/Repetition** \\ \end{tabular} & **SC Bandwidth** & **Output Power** & **Year** \\ \hline \(\text{As}_{2}\text{S}_{3}\) & 2 m & 2.45 μm/40 ps/10 MHz & 1.9–4.8 μm & 565 mW & 2012 [99] \\ \(\text{As}_{2}\text{Se}_{3}\) & 8.5 cm & 6.3 μm/100 fs/1 kHz & 1.4–13.3 μm & 150 mW & 2014 [105] \\ \(\text{Ge}_{12}\text{As}_{24}\text{Se}_{64}\) & 11 cm & 4.0 μm/330 fs/21 MHz & 1.8–10 μm & 1.26 mW & 2015 [110] \\ \(\text{Ge}_{11.5}\text{As}_{24}\text{Se}_{64}\) & 13.5 cm & 4.1 μm/320 fs/105 MHz & 1.8–9.8 μm & 3 mW & 2015 [55] \\ \(\text{As}_{2}\text{S}_{3}\) & 23 cm & 3.83 μm/450 fs/42 MHz & 30.4–8 μm & 550 mW & 2015 [127] \\ \(\text{As}_{2}\text{Se}_{3}\) & 3 cm & 9.8 μm/170 fs/1 kHz & 2.0–15.1 μm & - & 2016 [113] \\ \(\text{Ge}_{15}\text{Sb}_{15}\text{Se}_{70}\) & 11 cm & 4.485 μm/330 fs/21 MHz & 2.2–12 μm & 17 mW & 2016 [117] \\ \(\text{As}_{2}\text{S}_{3}\) & 3 m & 2.19 μm/18/100 kHz & 2.0–4.0 μm & 143 mW & 2016 [128] \\ \(\text{As}_{2}\text{Se}_{3}\) & 12 cm & 6.5 μm/150 fs/1 kHz & 2.0–12.7 μm & 300 mW & 2017 [129] \\ \((\text{Ge}_{10}\text{Fe}_{43}\text{3}\text{0}\text{-}\text{Ag})_{10}\) & 14 cm & 7.0 μm/150 fs/1 kHz & 2.0–16 μm & - & 2017 [126] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Partial results of supercontinuum (SC) generation in ChG step-index fibers. Figure 5: MIR SC spanning from 2.0 to 16.0 μm, generated in a Ge–Te–Agl fiber when pumped at 7 μm (reproduced with permission from [126], copyright John Wiley and Sons, 2017). The first ChG MOF, made in 2000 by Monro et al., was obtained by extrusion and made of only one ring of holes with an irregular structure, but no light propagation was demonstrated [132]. In 2005, Shaw et al. [97] fabricated an As-Se photonic crystal fiber (PCF) with a core diameter of 10 \(\upmu\)m, and the ZDW of this fiber was estimated to be \(\sim\)6 \(\upmu\)m. SC generation extending from 2.1 to 3.2 \(\upmu\)m was achieved in a 1-m-long fiber pumped with 100 fs pulses from an OPA at 2.5 \(\upmu\)m. Notably, the dispersion of the fiber and pump wavelength did not match well in this demonstration. Subsequently, the ChG MOFs used for MIR SC generation were mainly based on suspended-core fibers (SCFs). An As\({}_{2}\)S\({}_{3}\) SCF with a core diameter of 2.6 \(\upmu\)m, fabricated by El-Amraoui et al. [33], had a ZDW of 2.2 \(\upmu\)m, appearing strongly shifted toward shorter wavelengths in comparison to the ZDW of bulk glass and showing the influence of the geometry, and particular the core diameter, on optical properties. When a 400 fs beam was injected at 1557 nm with a repetition rate of 16.75 MHz and a peak power of 5.6 kW into a 68-cm-long As\({}_{2}\)S\({}_{3}\) MOF, a broadening spectrum spanning from 1 to 2.6 \(\upmu\)m was obtained. To ensure efficient SC generation, researchers have chosen suitable pump wavelengths to excite MOFs in the anomalous dispersion regime. Moller et al. [133] presented SC generation in an 18-cm-long As\({}_{38}\)Se\({}_{62}\) SCF with a core diameter of 4.5 \(\upmu\)m and ZDW of 3.5 \(\upmu\)m pumped at different wavelengths with 320 fs pulses from an OPA.