Optically-biased Rydberg microwave receiver enabled by hybrid nonlinear interferometry

The rapid development in Rydberg-atomic detection of microwave fields has paved the way to a new type of intrinsically calibrated RF measurements. The coupling of Rydberg vapors medium both to microwave and optical fields allows harnessing the merits of all-optical detection, e.g.~weak disruption of the measured field and invulnerability to extremely strong fields, owing to the lack of conventional RF antenna in the detector. The trouble with this approach arises, as the greatest sensitivity is exhibited with the use of additional microwave field acting as a local oscillator, and the measurement can no longer be all-optical. Here we propose a different solution, optical-bias detection, that allows truly all-optical operation, while retaining most of the sensitivity. We tackle the issue of uncorrelated laser phase, emerging in this type of detection, by facilitating separate measurement of the phase spectrum in a nonlinear process and using the results in post-processing. We report the sensitivity of $176\ \mathrm{nV/cm/\sqrt{Hz}}$ and reliable operation up to $3.5\ \mathrm{mV/cm}$ of $13.9\ \mathrm{GHz}$ electric field, while comparing with the state of the art (although not all-optical) method realized in the same setup.