Fig. 5: Summary for nonlinear semiconductor core fibre demonstrations in the mid-infrared regime.

a Simulation results of FWM efficiency as a function of signal wavelength and Si core diameters when pumped at 2 μm. b Measured mid-infrared FWM output spectra for a Si core fibre with a core diameter of 1.6 μm over a length of 4 cm. c Measured average on-off Raman gain in a Si core fibre with a waist diameter of 1.59 μm and a length of 6 cm. d Simulation results of cascaded Raman scattering when pumped at 2.2 μm wavelength with a peak power of 20 W. e Si core fibre profile designed for mid-infrared supercontinuum generation. f Measured output supercontinuum generation spectra obtained in an asymmetric tapered Si core fibre for different pump peak powers, as labelled. a, b Reproduced from ref. ⁹⁹ with the permission from AIP Publishing. c, d, f Reproduced from refs. ^72,75 with the permission from Springer Nature.