中文摘要：

本文主要研究了调制探测激光场中铯Rydberg原子阶梯型三能级系统的电磁感应透明（EIT）效应.铯原子基态6S-1/2）,第一激发态6P-3/2）和Rydberg态形成阶梯型三能级系统,探测光作用于6S-1/2）（F=4）→6P′-3/2）（F=5）的跃迁,耦合光在Rydberg跃迁线6P-3/2）→49S-1/2）附近扫描,形成Rydberg原子EIT.当对探测光频率施加一个几kHz的调制时,调制解调后的EIT信号分裂为两个峰,双峰间距与调制频率无关,而与调制幅度导致的失谐量大小（频率调制幅度）成正比,双峰间隔的一半等于探测光频率调制幅度的λp/λc=1.67倍.实验结果与理论计算相一致.本文的研究结果可应用于激光线型和频率抖动的实时监测.

英文摘要：

Rydberg atoms,with large principal quantum number n,have been widely investigated in recent years due to their peculiar properties,such as big sizes,long lifetimes and strong interactions with fields and other Rydberg atoms.Rydberg atoms are very sensitive to external fields due to their large polarizabilities scaling as n7.These make Rydberg atoms an ideal candidate for the quantum information,the many-body interaction,etc.In this work,we investigate the Rydberg atoms using electromagneticlly induced transparency（EIT）in a ladder three-level system.The EIT is a quantum interference effect between two excitation path-ways driven by two laser fields.The main idea is performed in a room temperature cesium vapor cell,where the probe laser frequency is modulated.The ground state（6S-1/2））,excited state（6P-3/2））,and Rydberg state（n S-1/2））constitute a Rydberg three-level system,in which the probe laser is fixed to the 6S-1/2）（F = 4）→6P-3/2）（F′= 5）transition by saturated absorption spectrum technique,whereas the coupling laser is scanned across the 6P-3/2）→ 49S-1/2）transition.We detect the demodulated EIT signal with the lock-in amplifier（SR830）.The demodulated EIT signal shows a two-peak structure.The measured spacing between two peaks increases with the frequency detuning,caused by the modulation amplitude,and half the spacing between the peak-to-peak is nearly 1.67 times the modulation amplitude of the probe laser;the measured results show that the splitting is independent of the modulation frequency.The experimental results are in agreement with the theoretical calculations.The results in our work can be used for real-time monitoring of the laser-line profiles and the fluctuation of laser frequency.