Mid-Infrared Ultraflat Broadband Supercontinuum Generation with 10 dB Bandwidth of 2340 nm in a Tapered Fluorotellurite Fiber

We demonstrate mid-infrared ultraflat broadband supercontinuum (SC) generation in a 40 cm long tapered fluorotellurite fiber pumped by a Raman soliton source. By tapering the end of the large-core-diameter fluorotellurite fiber, the dispersion is regulated and the nonlinear effect is enhanced, which effectively extends the mid-infrared SC spectral range and increases the spectral flatness. Finally, we obtained an SC light source with a spectral range from 1.8 to 4.7 μm; the 10 dB bandwidth of the source completely covers 1.88–4.22 μm, which has the farthest flat spectral edge in fluorotellurite fibers. The output power of the SC laser is about 1.04 W, and the power ratio of those above 3 μm in the spectrum to the total SC is ~24%. The optical-to-optical conversion efficiency is about 75%. Our results show that tapering of fluorotellurite fiber is an effective method to further extend and flatten the mid-infrared SC.