Dark resonances in potassium vapor for absolute measurement of magnetic fields

In this communication, we present a new approach for development of optical magnetometer based on the D2 line of potassium (K), where the hyperfine transitions are strongly overlapped. Magnetically unshielded, 8-mm-long cell (containing K + 30Torr Ne) is introduced, in order to reduce the gradients influence of laboratory magnetic field Blab to spectral width of Dark Resonances (DRs), which are used for magnetic field (MF) measurement. K vapor is irradiated by the light of frequency-modulated distributed feedback DFB diode laser that results in formation of narrow resonances with reduced absorption, i.e. DRs. Dark Resonance (DR) spectrum is shown as a function of frequency . Depending on the value of measured MF, different modulation frequencies fm can be used. The spectral transition overlapping results in very good signal, non-critical to laser frequency shifts that is not the case with other alkali. The proposed approach can be used for MF measurement produced by different sources, for example of archaeological origin. Moreover, the principle of MF measurement allows development of self-calibrated optical magnetometer with potential for calibrating various commercially available magnetometers that need frequent calibrations.