Profiling a Rydberg-Atom Electric Field Sensor for Off-Resonant Detection of Sub-100 MHz RF Signals

Abstract: We present a Rydberg-Atom electric field sensor optimized to detect signals at sub-100 MHz carrier frequencies. The sensing setup employs a sapphire vapor cell that allows for detection of signals below 100~MHz -- typical vapor cells made of glass or quartz demonstrate strong screening of radio frequency (RF) signals in this frequency regime. Applied signals are detected by observing AC Stark shifts in the atomic vapor energy levels. As a test case for the commercial utility of this receiver, we perform our tests at several carrier frequencies in the Industrial, Scientific, and Medical (ISM) band. At each carrier frequency, we report sensitivity, minimum detectable field, and detectable electric-field dynamic range. We also present a routine for optimizing off-resonant signal detection by tuning experimental parameters such as Rydberg coupler laser detuning and RF local oscillator strength. This Python-based optimization routine, which can be used at any off-resonant carrier frequency, is shared on Github for others to use in their own investigations.