Sensitive imaging of electromagnetic fields with paramagnetic polar molecules

We propose a method for sensitive parallel detection of low-frequency electromagnetic fields based on the fine structure interactions in paramagnetic polar molecules. Compared to the recently implemented scheme employing ultracold ${}^{87}$Rb atoms [B{"o}hi $\mathit{\text{et}}\mathit{\text{al.}}$, Appl. Phys. Lett. $\mathbf{\text{97}}$, 051101 (2010)], the technique based on molecules offers a 100-fold higher sensitivity, the possibility to measure both the electric and magnetic field components, and a probe of a wide range of frequencies from the dc limit to the THz regime.