Frequency Calibration Method Based on Cesium Atom nDJ Rydberg State Laser Spectroscopy

This paper presents a measurement technique for low-frequency electric fields based on the Rydberg atoms. It utilizes the principle of the Stark effect, where non-resonant external electric fields cause the splitting of atomic energy levels, leading to spectral peak frequency shifts. In the measurement system, the photoelectrically converted signal is typically directly connected to an oscilloscope to display the corresponding spectrogram. Therefore, calibration of the laser spectral frequency variations is necessary to convert the time axis of the oscilloscope into a frequency axis. This paper proposes a calibration method that utilizes the existence of two optical peaks, corresponding to the nD3/2 and nD5/2 states of cesium (Cs) atoms, in the absence of an electric field. The theoretical calculation of the frequency difference between these two peaks provides an internal frequency scale without the need for external devices. By applying this calibration method, the time shift of the two peaks measured on the oscilloscope is converted into a frequency shift, allowing the determination of the applied field strength based on the mathematical relationship between the frequency shift and the applied electric field. The principles of the technique are described, and experimental validation is performed.