Patent ID: 7583711

Claim:
A method for stabilizing the absolute frequency f of a single laser in relation to a stable reference frequency f REF comprising the steps of: (a) locking the frequency f of the single laser to a resonant frequency of an etalon; (b1) generating sidebands at frequencies f−f FSR * and f+f FSR * wherein f FSR * approximates the FSR of the etalon; (b2A) temporally dithering the sideband frequencies f−f FSR * and f+f FSR * by a small magnitude f D at frequency f M ; (b2B) detecting the intensity response (transmission or reflection) of the etalon at the sideband frequencies f−f FSR * and f+f FSR * at dither frequency f M ; (b2C) comparing the phase of the intensity response at frequency f M with the phase of the dither signal at frequency f M to generate a first error signal; (b2D) adjusting f FSR * to minimize the magnitude of the first error signal; and (b3) adjusting the etalon FSR to cause the f FSR * to match f REF .