Laser frequency stabilization by Doppler-free magnetic dichroism

We report a method of laser stabilization to an atomic transition frequency, which is based on a magnetically induced nonlinear circular dichroism in the counter-propagating pump-probe configuration. The proposed method does not require any modulation of the laser frequency. In comparison to the linear, Doppler-broadened dichroic lock, the proposed version provides a precise locking to a well-defined atomic resonance at a cost of a smaller capture range. A simple model description of the locking signal is presented and two experimental realizations are shown: for a dye laser at λ=589.6 nm (Na D1 line) and for a diode laser at 795 nm (Rb D1).