Terahertz polarization sensing with a four-level cesium Rydberg-atom system

A Rydberg atom detector provides a promising approach for characterizing terahertz (THz) electric fields. Electric field polarization detection is crucial for accurately characterizing THz wave propagation, identifying signal sources and interference, and so on. This paper demonstrates a method for accurate measurement of THz polarization using a four-level cesium Rydberg-atom system. By analyzing the evolution of electromagnetically induced transparency and Autler-Townes spectra under different polarization configurations, the THz polarization angle is quantitatively determined from the relative intensities and asymmetry of the spectral peaks. The results show that the spectral response exhibits a clear dependence on the polarization angle with symmetry about 90°, enabling unambiguous angle determination, and a polarization resolution of 1.28° is achieved. Furthermore, compared with a Schottky diode detector, the proposed method exhibits comparable sensitivity while providing improved fitting consistency and robustness. This approach simplifies both theoretical analysis and experimental implementation for THz polarization measurement, and is promising for applications in THz sensing and spectroscopy.