Non-invasive measurements of plasma electric fields using Rydberg electromagnetically induced transparency

Measurements of plasma electric fields are essential to the advancement of plasma science and applications. Performing non-invasive in situ measurements of plasma fields on sub-millimeter length scales with high sensitivity over a large range of field magnitude remains an outstanding challenge. We introduce and demonstrate a method for plasma electric field measurement that employs electromagnetically induced transparency as a high-resolution quantum-optical probe for the Stark energy level shifts of Rydberg atoms embedded in a plasma and serving as highly sensitive field sensors. The method is applied in diagnostics of plasmas generated by photo-excitation of a cesium vapor. The plasma electric fields are extracted from spatially resolved measurements of field-induced lineshape changes and shifts of Rydberg resonances in rubidium tracer atoms. Measurement capabilities over a range of plasma densities and temperatures are exploited to characterize plasmas in applied magnetic fields and to image electric-field distributions in cyclotron-heated plasmas. Our results pave the way toward further applications of Rydberg-atom-based field sensors to diagnostics and monitoring of electric fields due to plasmas.