Measurement of Asymmetric Sideband Formation in Rydberg Electrometry through the Optical Heterodyne Method

We explored the response bandwidth of a Rydberg receiver in a room-temperature vapor cell and found that higher coupling power leads to a higher response bandwidth. Previous work attributed the increased bandwidth at high coupling power to six-wave mixing. The two sidebands generated from six-wave mixing are expected to exhibit different behavior. When measuring only the probe absorption, we can extract an amplitude oscillating signal that represents the sum of positive and negative amplitude modulation sidebands from the oscillating probe field. Differentiating between these sidebands relies on heterodyning the transmitted probe field with a local oscillator field using an acousto-optic modulator to define the frequency difference. Through this method, we experimentally confirm the prediction that the negative sideband has a significantly higher response at higher modulation frequencies compared to the positive sideband. We study the bandwidth roll-off by varying the coupling power and probe power. This study contributes to a better understanding of bandwidth-limiting atomic features for the advancement of future atomic Rydberg receiving technology. Furthermore, the technique sheds light on the behavior of six-wave mixing.