Is phase noise of the coupling laser beam good or bad for Rydberg phase-noise spectroscopy (PNS) measurement: case study of Rydberg PNS with ladder-type three-level Cesium atomic vapor

We describe experiments relevant to Rydberg-EIT and Rydberg phase-noise spectroscopy (Rydberg-PNS) with ladder-type Cesium atomic vapor. We readout Rydberg-EIT and Rydberg-PNS via output of the 852-nm probe beam, which connects 6S_1/2 state and 6P_3/2 state. We focus on phase noise of the 509-nm coupling beam, which couples 6P_3/2 state and 43D_5/2 Rydberg state. The phase-to- amplitude noise conversion via atomic absorption and dispersion plays important role and depends on the two-photon detuning. We show that Rydberg-PNS with the phase-modulated coupling beam can improve Rydberg-PNS’ signal-to-noise ratio. We demonstrate the proof of concept for micro-wave (MW) electric field sensing based on the phase-modulated Rydberg-PNS scheme. It has higher precision and lower error, compared with MW sensing based on Rydberg-EIT scheme.