Phase-coherent link from optical to microwave frequencies by means of the broadband continuum from a 1-GHz Ti:sapphire femtosecond oscillator

An optical clockwork is created with a compact 1-GHz repetition-rate laser and three nonlinear crystals. The broadband continuum output of the laser covers sufficient bandwidth to provide direct access to its carrier-envelope offset frequency without the use of a microstructure fiber. We phase lock the femtosecond comb to a Ca optical standard and monitor the stability of the repetition rate, $f_r$, at 1 GHz. We demonstrate that the short-term stability of the microwave output of the optical clock is at least as good as that of a high-performance hydrogen maser.