Coherent supercontinuum generation beyond 2.6 μm in all-normal dispersion silica microstructured fibers

Femtosecond pumping in an anomalous chromatic dispersion results in the generation of ultra-broad supercontinuum (SC) spectrum [1, 2]. However, such SC is associated with many pulses in the time domain and it is not flat in the spectral domain. Heidt et al. have shown that SC generated by pumping all-normal dispersion (ANDi) fiber is single pulse, has high coherence and spectral flatness [3-5]. Such all-normal dispersion supercontinuum is well suited for applications in an ultrafast spectroscopy. Mid-infrared SC is of particular interest since strong absorption lines of numerous chemical compounds are located in this spectral range. Unfortunately, long wavelength range of ANDi SC generated in silica microstructured fibers was limited so far to only 1.5 μm [4]. It means that full transparency window of silica glass was not covered. ANDi SC in mid-infrared was generated in more exotic glasses like soft-glass [6], ZBLAN-chalcogenide [7] and chalcogenide [8].