All-Silica Fiber Ultra-Flat 2-3 μm Supercontinuum Source Based on Highly Nonlinear Silica Fiber

In this letter, we demonstrated an all-silica fiber 1.5-
$3.2 ~\mu \text{m}$
supercontinuum (SC) source based on germanium-doped highly nonlinear fibers (HNLF). By optimizing the length of HNLF, as the pump injected into the HNLF increased to 6 W, a 4.12 W broadband SC source extending from 1516 to 3182 nm was obtained. The 3 dB spectrum bandwidth was up to 1022 nm ranging from 1855 nm to 2877 nm, and the 1 dB bandwidth was up to 878 nm covering from 1959 nm to 2837 nm. To the best of our knowledge, this is the flattest SC in the 2-
$3 ~\mu \text{m}$
region based on doped silica fiber to date.