All-fiber format source of 50 nJ 9 cycle pulses at 2.95 μm

The development of all-fiber format sources delivering high-energy few-cycle pulses at high repetition rate in the near-infrared takes advantage of the availability of telecom-grade optical fibers and components [1] . Similar development in the middle-wave infrared (mid-IR) spectral domain has remained, however, an elusive goal, although such sources are of high significance for applications such as high-precision frequency metrology and molecular spectroscopy [2] . Here, we demonstrate that picosecond pulses at 2 μm from a MHz repetition rate fiber laser can trigger the formation of frequency-shifted solitons up to 2.95 μm with 50 nJ energy and 86 fs duration in a cascade of Large Mode Area (LMA) silica and fluoride fibers. The instantaneous power of the 9-cycle pulse is 580 kW, which represents tenfold improvement compared to previously reported sub-100 fs pulses generated at this wavelength via soliton self-frequency shift from near-infrared lasers [3] , [4] .