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The mid-IR supercontinuum (SC) light source is in demand for many chemical, biological, medical, and astronomical
applications. It is of great significance to develop a mid-IR SC light source whose spectrum is wide and flat.
We obtained ultra-broadband mid-IR SC by using a piece of fluoride glass through filamentation. Though the SC
generation by filamentation needs a powerful laser chain to be the pump source, it has some advantages in comparison
with that based on fiber. First, the optical path length in the glass can be very short due to the adopted high pump power.
The negative influence of accumulated loss can be reduced greatly, so the transparent range of glass is much larger than
fiber. Secondly, it is convenient in light-coupling, and the coupling efficiency can be high. In comparison with it, the
coupling of the small core (usually the core is small to ensure a high nonlinearity) mid-IR glass fiber is troublesome.
Thirdly, the glass piece is cost-effective, and can be fabricated easily.
We obtained a SC spectrum covering 0.2-8.0 μm by using a 32mm-thick fluoride glass sample. The 3 dB bandwidth
covers 1.15-4.76 μm. The 20 dB bandwidth spans from 0.39 to 7.4 μm. The glass thickness, optical path, and pump
conditions are optimized to enable the SC to be as wide as possible. This work shows that the SC generation through
filamentation in bulk glass can be an effective way to obtain an ultra-broadband mid-IR light source, which will find
various applications in mid-IR regions.
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