Direct 15-GHz mode-spacing optical frequency comb with a Kerr-lens mode-locked Yb:Y(2)O(3) ceramic laser

A 15-GHz mode spacing optical frequency comb based on a Kerr-lens mode-locked Yb:Y₂O₃ ceramic laser has been developed. Individual modes were clearly resolved by a commercial spectrometer. To demonstrate the long-term operation of the optical frequency comb, a single longitudinal mode was phase-locked to a frequency-stabilized continuous wave laser and the repetition rate to a radio frequency standard. To the best of our knowledge, 15 GHz is the largest reported mode spacing (repetition rate) for both a Kerr-lens mode-locked laser and a direct femtosecond laser based-optical frequency comb.