Magnetic field diagnostics of plasmas based on coherent population trapping: theory and experiment.

We propose a local, all-optical method of magnetic field diagnostics for plasmas. This method is based on the phenomenon of coherent population trapping in a multilevel medium. The proposed technique allows one to detect both the strength and the orientation of the field. The feasibility of the method was tested in a proof-of-principle experiment in a low-pressure neon discharge.