Generation of a 650 nm - 2000 nm Laser Frequency Comb based on an   Erbium-Doped Fiber Laser
  We present a laser frequency comb based upon a 250 MHz mode-locked erbium-doped fiber laser that spans more than 300 terahertz of bandwidth, from 660 nm to 2000 nm. The system generates 1.2 nJ, 70 fs pulses at 1050 nm by amplifying the 1580 nm laser light in Er:fiber, followed by nonlinear broadening to 1050 nm and amplification in Yb:fiber. Extension of the frequency comb into the visible is achieved by supercontinuum generation from the 1050 nm light. Comb coherence is verified with cascaded f-2f interferometry and comparison to a frequency stabilized laser. 
Gabriel Ycas and Steve Osterman and Scott A. Diddams
physics.optics astro-ph.IM physics.atom-ph