High-power broadband laser source tunable from 3.0 um to 4.4 um based on   a femtosecond Yb:fiber oscillator
  We describe a tunable broadband mid-infrared laser source based on difference-frequency mixing of a 100 MHz femtosecond Yb:fiber laser oscillator and a Raman-shifted soliton generated with the same laser. The resulting light is tunable over 3.0 um to 4.4 um, with a FWHM bandwidth of 170 nm and maximum average output power up to 125 mW. The noise and coherence properties of this source are also investigated and described. 
Tyler W. Neely, Todd A. Johnson, Scott A. Diddams
physics.optics