500 MHz spaced Yb:fiber laser frequency comb without amplifiers.
An optical frequency comb based on Yb:ring fiber laser was demonstrated. This is the first time, to our knowledge, f(ceo) has been generated directly from the oscillator without further amplifications above 500 MHz repetition rate. The signal-to-noise ratio of the offset frequency was above 40 dB at 300 kHz resolution bandwidth, which supports easy stabilization. The offset frequency was stabilized for more than 6 h in an open air environment without temperature control. The stabilized repetition rate has an in-loop tracking stability of 4.46×10(-13)/τ(1/2).