We demonstrate that the stability of the current optical frequency comb generated by a Kerr-lens mode-locked femtosecond laser is limited by the microwave reference used for phase locking the comb spacing. Hence we implement precision frequency/phase control of the entire comb to the fundamental and second-harmonic frequencies of a stable cw laser without any external microwave reference. The stability of a cw iodine-stabilized laser is transferred to millions of comb lines (with an instability of 3 × 10<sup>-13</sup>) covering more than one octave of the optical frequency spectrum. In addition, the mode spacing of the comb can be used as a stable microwave frequency derived directly from a stable optical oscillator.
© 2000 Optical Society of America
(120.3930) Instrumentation, measurement, and metrology : Metrological instrumentation
(190.2620) Nonlinear optics : Harmonic generation and mixing
(220.4840) Optical design and fabrication : Testing
(230.4910) Optical devices : Oscillators
(320.7090) Ultrafast optics : Ultrafast lasers
Jun Ye, John L. Hall, and Scott A. Diddams, "Precision phase control of an ultrawide-bandwidth femtosecond laser: a network of ultrastable frequency marks across the visible spectrum," Opt. Lett. 25, 1675-1677 (2000)