Stabilization of a laser on a large-detuned atomic-reference frequency by resonant interferometry

We report a simple technique for stabilization of a laser frequency at the wings of an atomic resonance. The reference signal used for stabilization issues from interference effects obtained in a low-quality cavity filled with a resonant atomic vapour. For a frequency detuned 2.6 GHz from the Cs-133 D-2 6S(1/2) F = 4 to 6P(3/2) F' = 5 transition, the fractional frequency Allan deviation is 10(-8) for averaging times of 300 s, corresponding to a frequency deviation of 4 MHz. Adequate choice of the atomic density and of the cell thickness allows locking the laser at detunings larger than 10 GHz. Such a simple technique does not require magnetic fields or signal modulation.