Ultra-flat and high-efficient mid-infrared supercontinuum generation in indium fluoride fiber

Abstract

We demonstrate ultra-flat and high-efficient mid-infrared supercontinuum (MIR SC) generation in indium fluoride (InF3) fiber with output average power of 9.9 W, power conversion efficiency of 67.8 % and 3 dB-spectrum width of >1570 nm. It is pumped by amplified 2 μm noise-like pulses and generated in a piece of 10 m InF3 fiber with core diameters of 9.5 μm. The 2 μm noise-like pulses is realized by nonlinear amplifying loop mirror mode-locking technique and amplified by two-stage amplifiers with pulse repetition rate of 1.513 MHz and 3-dB pulse envelope width of 2.2 ns. To further increase efficiency, the InF3 fiber is spliced directly to the pigtail of main amplifier with 92.47 % coupling efficiency, which is in good agreement with 92 % theoretical result of fundamental-mode coupling efficiency. To the best of the authors’ knowledge, this work achieves the flattest (3 dB spectral coverage of 2120–3690 nm) and corresponding highest efficiency (67.8 %) in MIR SC seeded by 2 μm pulses.