A method for building an optical-to-microwave frequency chain and for
measuring optical frequencies relative to the cesium primary frequency
standard is described. Based on optical frequency division via parame
tric oscillators, the concept is to generate two known ratios (1/2 and
4/9) of an optical calibration frequency f(1) whose frequency differe
nce is measured relative to the cesium clock. The (1/2) ratio is obtai
ned by either a 2:1 frequency division of f(1) or second-harmonic gene
ration of (1/2) f(1). The (4/9) ratio of f(1) can be generated with a
3:1 frequency divider driven by a second laser at f(2) that is chosen
to be near (2/3)f(1), which in turn is obtained with a f(1)-pumped 3:1
frequency divider. A set of auxiliary Optical Parametric Oscillators
(OPOs) with outputs centered at (1/2) f(1) is used to facilitate the d
ifference-frequency measurement between the two ratios. A practical co
nfiguration utilizing a YAG and a Ti:Al2O3 laser and its application t
o a number of precision measurements of interest are presented.