Sensing electromagnetic fields with the AC-Stark effect in two-photon spectroscopy of cold trapped HD+
Résumé
This contribution evaluates the potential for SI-traceable measurements of electromagnetic fields from precision measurements of two-photon rovibrational transitions of cold trapped HD+ ions interpreted with accurate theoretical models. Zeeman spectroscopy of a hyperfine component of the (v,L)=(0,0)→(2,2) two-photon transition is exploited for the measurement of a static magnetic field. The absolute sensitivity and accuracy is estimated at the 10^(-10) T level in the case of frequency measurements at the quantum projection noise limit. Measurements of the AC-Stark shifts of different Zeeman components of the (v,L)=(0,0)→(2,0) two-photon transition at different orientations of the magnetic field are exploited to measure the polarisation and the intensity of a THz-wave off-resonantly coupled to HD+ rotational levels. The sensitivity is estimated at the 10^(-7) W/m^2 level. A reference THz-wave with an intensity of 1 W/m^2 can be calibrated in intensity with a fractional accuracy limited at the 10^(-2) level by the accuracy of the theoretical calculations and at the 10^(-4) level by the experimental errors. In addition, an approach for retrieval of the full polarisation ellipse is demonstrated with a selected THz-wave. The fractional accuracy of the calibration is better than 5% for the amplitudes and better than 10% for the phases of the electric field components of the THz-wave.
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