Broadband and top-flat mid-infrared supercontinuum generation with 3.52 W time-averaged power in a ZBLAN fiber directly pumped by a 2-µm mode-locked fiber laser and amplifier

Supercontinuum generation from 1.87 to 4.03 µm in a ZBLAN fiber is reported. A home-made passively mode-locked thulium-doped fiber laser and amplifier, providing 21.4-ps pulses at 81 MHz is used as a pump. The continuum output power is 3.52 W, of which 1.45 and 0.88 W corresponds to wavelengths longer than 3 and 3.5 µm, respectively. A spectrum flatness of 2 dB over a bandwidth of 1710 nm, from 2.02 to 3.73 µm, is also reported. This represents, to our knowledge, the best power conversion in the mid-infrared region and the best spectral flatness for high power supercontinuum generation in ZBLAN fibers directly pumped by 2-µm CW mode-locked fiber lasers and amplifiers.