Using amplitude modulation of the microwave field to improve the sensitivity of Rydberg-atom based microwave electrometry

The microwave (MW) field can be measured by the Autler-Townes (AT) splitting of the electromagnetically induced transparency (EIT) spectrum in the Rydberg atomic system; however, the EIT-AT splitting method fails in weak MW fields. We used the amplitude modulation of the MW field to resolve the EIT-AT splitting in weak MW fields. The EIT-AT splitting interval can be directly obtained, and the minimum detectable MW strength is improved by six times compared with the traditional EIT-AT splitting method. The proposed method is more intuitive and convenient for measuring the strength of weak MW fields in practical applications.