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 at 2.6 GHz from the \(^{133}\)Cs 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.