Optical-RF frequency stability transformer.

An optical technique based on stability transfer among modes of a monolithic optical microresonator is proposed for long term frequency stabilization of a radio frequency (RF) oscillator. We show that locking the frequency difference of two microresonator modes with dissimilar sensitivity to an applied forcing function to a master RF oscillator improves the long term stability of a slave RF oscillator locked to the frequency difference of another pair of modes with nearly identical sensitivity to the same forcing function. For instance, the stability of a 10 MHz master oscillator with Allan deviation of 10(-7) at 10(3) s can be improved and transferred to a slave oscillator with identical free running stability performance, so that the resultant Allan deviation of the slave oscillator becomes equal to 10(-13) at 10(3) s. The suggested method does not require absolute frequency references.