Direct RF to optical frequency measurements with a femtosecond laser comb

By spanning an optical octave (> 300 THz) with a broadened femtosecond lase r frequency comb, we directly measure the frequencies of optical standards at 1064/532 nm, 633 nm and 778 nm in terms of the microwave frequency that controls the tomb spacing. This microwave frequency can be linked directly to the cesium standard.