<i>n</i>S<sub>1/2</sub>→(<i>n</i>+1)S<sub>1/2</sub> two-photon excitation EIT-AT spectrum of Rydberg atom

Abstract

In this work, we present an <i>n</i>S<sub>1/2</sub>→(<i>n</i> + 1)S<sub>1/2</sub> two-photon excitation EIT-AT spectrum of Rydberg atom in the vapor cell. A ground state (6S<sub>1/2</sub>), a first excited state (6P<sub>3/2</sub>) and Rydberg state (69S<sub>1/2</sub>) of cesium atoms constitute a three-level system. A weak probe laser locking to the transition of 6S<sub>1/2</sub> (<i>F</i> = 4)→6P<sub>3/2</sub> (<i>F</i>′ = 5) couples the ground-state transition, and the strong coupling laser drives the Rydberg transition of 6P<sub>3/2</sub>→69S<sub>1/2</sub> to yield electromagnetically induced transparency (EIT) effect, which realizes the optical detection of Rydberg atoms. Two Rydberg 69S<sub>1/2</sub> and 70S<sub>1/2</sub> levels are coupled with the microwave field at a frequency of <i>f</i><sub>MW</sub> = 11.735 GHz, forming a microwave two-photon spectrum. To observe the influence of microwave electric field power on two-photon spectrum, we investigate the microwave coupled Rydberg EIT-AT spectra at different microwave fields. The measurements show that the EIT-AT splitting interval is proportional to the square of the microwave electric field at strong microwave field, and indicvates a nonlinear dependence at weak microwave electric field. The theoretical calculation accords with the experimental measurement. The work here is of significance in precisely measuring the microwave electric field.