Asymmetry analysis of Autler-Townes doublet in the trap-loss fluorescence spectroscopy of cesium MOT with single step Rydberg excitation

Autler-Townes (AT) doublet, a fundamental manifestation of quantum interference effects, serves as a critical tool for studying the dynamic behavior of Rydberg atoms. Here, we investigate the asymmetry of the Autler-Townes (AT) doublet in trap-loss fluorescence spectroscopy (TLFS) of cesium (Cs) atoms confined in a magneto-optical trap (MOT) with single-step Rydberg excitation using a 319-nm ultraviolet (UV) laser. A V-type three-level system involving the ground state $6{\text{S}}_{1\mathrm{/}2}$ ($\text{F}$=4), excited state $6{\text{P}}_{3\mathrm{/}2}$ (${\text{F}}^{{}^{\mathrm{\prime }}}$=5) , and Rydberg state ($n{\text{P}}_{3\mathrm{/}2}$ (${\text{m}}_{\text{J}}$=+3/2)) is theoretically modeled to analyze the nonlinear dependence of the AT doublet’s asymmetry and interval on the cooling laser detuning. Experiments reveal that as the cooling laser detuning ${\mathrm{\Delta }}_1$ decreases from $-$15 MHz to $-$10 MHz, the AT doublet exhibits increasing symmetry, while its interval shows a nonlinear decrease. Theoretical simulations based on the density matrix equation and Lindblad master equation align closely with experimental data, confirming the model’s validity. This study provides insights into quantum interference dynamics in multi-level systems and offers a systematic approach for optimizing precision measurements in cold atom spectroscopy.