Heterodyne detection of radio-frequency electric fields using point defects in silicon carbide

Abstract: Sensing electric fields with high sensitivity, high spatial resolution and at radio frequencies can be challenging to realize. Recently, point defects in silicon carbide have shown their ability to measure local electric fields by optical charge conversion of their charge state. Here we report the combination of heterodyne detection with charge-based electric field sensing, solving many of the previous limitations of this technique. Owing to the non-linear response of the charge conversion to electric fields, the application of a separate "pump" electric field results in a detection sensitivity as low as 1.1 (V/cm)/$\sqrt{Hz}$, with near-diffraction limited spatial resolution and tunable control of the sensor dynamic range. In addition, we show both incoherent and coherent heterodyne detection, allowing measurements of either unknown random fields or synchronized fields with higher sensitivities. Finally, we demonstrate in-plane vector measurements of the electric field by combining orthogonal pump electric fields. Overall, this work establishes charge-based measurements as highly relevant for solid-state defect sensing.