Mid-infrared supercontinuum covering the 1.4-13.3 μm molecular fingerprint region using ultra-high NA chalcogenide step-index fibre

The mid-infrared spectral region is of great technical and scientific interest because most molecules display fundamental vibrational absorptions in this region, leaving distinctive spectral fingerprints(1,2). To date, the limitations of mid-infrared light sources such as thermal emitters, low-power laser diodes, quantum cascade lasers and synchrotron radiation have precluded mid-infrared applications where the spatial coherence, broad bandwidth, high brightness and portability of a supercontinuum laser are all required. Here, we demonstrate experimentally that launching intense ultra-short pulses with a central wavelength of either 4.5 mu m or 6.3 mu m into short pieces of ultra-high numerical-aperture step-index chalcogenide glass optical fibre generates a mid-infrared supercontinuum spanning 1.5 mu m to 11.7 mu m and 1.4 mu m to 13.3 mu m, respectively. This is the first experimental demonstration to truly reveal the potential of fibres to emit across the mid-infrared molecular 'fingerprint region', which is of key importance for applications such as early cancer diagnostics(3), gas sensing(2,4) and food quality control(5).