Observation of asymmetric sideband generation in strongly driven Rydberg atoms

Improving the bandwidth of Rydberg-atom-based receivers is an ongoing challenge owing to the long-lived Rydberg state lifetimes that limit the refresh rate of ground-state atoms. In particular, the local-oscillator-based Rydberg mixer approach allows for bandwidths into the few-megahertz range. Here we use heterodyne detection of the Rydberg-atom receiver probe laser to separate the negative and positive sidebands that originate from distinct six-wave-mixing processes, in order to investigate their individual bandwidths. We experimentally confirm the prediction that the negative sideband exhibits a higher bandwidth than the positive sideband. We further explore the effect of coupling and probe laser Rabi frequency on the bandwidth, which we find to be in close agreement with our model. We achieve maximum experimental (and theoretical) bandwidths of $10.5\ifmmode\pm\else\textpm\fi{}0.4$ (11.6) and $3.4\ifmmode\pm\else\textpm\fi{}0.2$ (5.4) MHz for the negative and positive sidebands, respectively, from the $\ensuremath{-}3$ dB roll-off point for optimized field parameters. This work provides insight into the bandwidth-limiting features of Rydberg-atom receivers and points the way towards further optimization of their response.