Optical frequency combs: Coherently uniting the electromagnetic spectrum

Optical frequency combs were introduced around 20 years ago as a laser technology that could synthesize and count the ultrafast rate of the oscillating cycles of light. Functioning in a manner analogous to a clockwork of gears, the frequency comb phase-coherently upconverts a radio frequency signal by a factor of [Formula: see text] to provide a vast array of evenly spaced optical frequencies, which is the comb for which the device is named. It also divides an optical frequency down to a radio frequency, or translates its phase to any other optical frequency across hundreds of terahertz of bandwidth. We review the historical backdrop against which this powerful tool for coherently uniting the electromagnetic…

• NI
  National Institute of Standards and Technology
• DA
  Defense Advanced Research Projects Agency

  Award: HROO1 1-15-C-0055 and FA9453-19-C-0029
• AF
  Air Force Office of Scientific Research

  Award: FA9550-16-1-0016 and FA9550-18-1-0353