All-fiberized, multi-watt 2–5-μm supercontinuum laser source based on fluoroindate fiber with record conversion efficiency

A strictly all-fiberized, multi-watt 2–5-μm supercontinuum (SC) laser source with high conversion efficiency is presented. A broadband thulium-doped fiber amplifier with spectral coverage of 2–2.7 μm is used to pump a piece of single-mode fluoroindate (InF3) fiber. A fusion-spliced joint with loss down to 0.07 dB is achieved between a piece of silica fiber and the InF3 fiber, which retains all-fiber structure and efficient pump power coupling. A 1.35-W SC with spectral coverage of 1.5–5.2 μm and a 4.06-W SC with spectral coverage of 1.9–5.1 μm are obtained with record conversion efficiencies of 59.5% and 63.3%, respectively. Furthermore, measured output power has a normalized root mean square superior to 0.4%, which indicates the excellent power stability of the system. This research, to the best of the authors’ knowledge, demonstrates both record output power and record conversion efficiency of InF3-fiber-based mid-infrared-SC laser sources to date. It is also the first report on strictly all-fiberized SC generation in InF3 fibers.