Application of the light-shift effect to laser frequency stabilization with reference to a microwave frequency standard

A new method allowing laser frequency stabilization with reference to a microwave oscillator, independently of the laser intensity, is described. The method makes use of the dependence of the ground-state hfs transition frequency on the optical radiation frequency in alkali atoms irradiated by quasi-resonant light. Preliminary experimental investigations are reported in the case of a cw GaAs diode laser tuned to the D₂ absorption line in a cesium gas cell. The absolute laser frequency exhibited variations of 1.4 MHz r.m.s. around an average value determined to within 2 parts in 10¹⁰ for a period of 5 minutes. The possibility of defining a cesium beam, reference wavelength connected with the time standard is discussed.