Abstract

Parametric processes are widely used in precision measurements of optical frequencies with uncertainties of 10^-11 or less. These experiments use, for instance, like optical second-harmonic generation assuming that the frequency ratio of 1:2 between fundamental and harmonic light is exact at least at the 10^-12 level. To our knowledge only two experiments have been performed to determine whether this is true.^1,2 They confirmed the ratio with a relative uncertainty or order 10^-6. Here we are reporting an experiment, which allowed us to check the validity of the 1:2 ratio with 2·10^-13 uncertainty for multiplicative shifts.

© 1994 IEEE