Femtosecond-laser-based optical clockwork with instability ≤ 6.3 x 10-16 in 1 s

Two octave-spanning optical-frequency combs (750-MHz comb spacing) are phase locked to a common continuous-wave laser diode. The measured instability of the heterodyne beat between the two combs demonstrates that the intrinsic fractional frequency noise of a comb is less than or equal to6.3 x 10(-16) in 1 s of averaging across the similar to 300-THz bandwidth. Furthermore, the average frequencies of the elements of the two combs are found to agree within an uncertainty of 4 x 10(-17) across the entire octave. We demonstrate the possibility of transfering the stability and accuracy of the best current optical standards to similar to 500,000 individual oscillators across the visible and near-infrared spectrum.