%0 Journal Article %T Nonlinearity of Microwave Electric Field Coupled Rydberg Electromagnetically Induced Transparency and Autler-Townes Splitting %J Applied Sciences | An Open Access Journal from MDPI %D 2019 %R https://doi.org/10.3390/app9081720 %X An electromagnetically induced transparency (EIT) of a cascade-three-level atom involving Rydberg level in a room-temperature cell, formed with a cesium 6 S 1 / 2 -6 P 3 / 2 -66 S 1 / 2 scheme, is employed to detect the Autler-Townes (AT) splitting resulted with a 15.21-GHz microwave field coupling the 66 S 1 / 2 ¡ú 65 P 1 / 2 transition. Microwave field induced AT splitting, f A T , is characterized by the distance of peak-to-peak of an EIT-AT spectrum. The f A T dependence on the microwave Rabi frequency, ¦¸ M W , demonstrates two regions, the strong-coupling linear region, f A T ¡Ö ¦¸ M W and the weak-coupling nonlinear region, f A T £¿ ¦¸ M W . The f A T dependencies on the probe and coupling Rabi frequency are also investigated. Using small probe- and coupling-laser, the Rabi frequency is found to enlarge the linear regime and decrease the uncertainty of the microwave field measurements. The measurements agree with the calculations based on a four-level atomic model. View Full-Tex %U https://www.mdpi.com/2076-3417/9/8/1720