All-optical isotropic scalar 4He magnetometer based on atomic alignment.

We propose a helium scalar magnetometer based on a triple resonance setup, showing no dead angles, and which can be implemented in an all-optical way. This triple-resonance scheme involves optical pumping with amplitude-modulated light, complemented by a modulated light-shift. Both light beams propagate parallel so that a single optical access to the atomic cell is needed. Experimental results are in good agreement with our theoretical model. The main error sources affecting the magnetometer accuracy are discussed.