Mid-infrared supercontinuum generation in tapered chalcogenide fiber for   producing octave-spanning frequency comb around 3 {\mu}m
  We demonstrate mid-infrared (mid-IR) supercontinuum generation (SCG) with instantaneous bandwidth from 2.2 to 5 {\mu}m at 40 dB below the peak, covering the wavelength range desirable for molecular spectroscopy and numerous other applications. The SCG occurs in a tapered As2S3 fiber prepared by in-situ tapering and is pumped by femtosecond pulses from the subharmonic of a mode-locked Er-doped fiber laser. Interference with a narrow linewidth c.w. laser verifies that the coherence properties of the near-IR frequency comb have been preserved through these cascaded nonlinear processes. With this approach stable broad mid-IR frequency combs can be derived from commercially available near-IR frequency combs without an extra stabilization mechanism. 
Alireza Marandi, Charles W. Rudy, Victor G. Plotnichenko, Evgeny M.   Dianov, Konstantin L. Vodopyanov, Robert L. Byer
physics.optics