摘要
研究了里德伯原子系统采用直接解调法对微波调幅信号进行解调时的工作点与基带信号非线性失真之间的关系。首先,利用里德伯原子的电极化率理论表达式,得到在耦合光、探测光和微波的频率均为零失谐条件下,里德伯原子系统对微波调幅信号的解调模型;然后,计算探测光透射率对微波拉比频率的一阶导数和二阶导数,并利用二阶导数为0这一条件,得到里德伯原子汽室的非线性失真最小的点,即最佳线性工作点;最后,采用总谐波失真(THD)来分别研究里德伯原子汽室的静态工作点、基带信号的幅度与解调所引起的非线性失真之间的关系。仿真结果表明,对于里德伯原子133Cs(采用能级6S_(1/2)、6P_(3/2)、47D_(5/2)、48P_(3/2)),当耦合光拉比频率为2π×2.7 MHz,并且调幅微波基带信号的电场强度幅值为1 mV/m时,工作在最佳线性工作点附近的原子汽室所引入的THD可低至-95.4984 dB。
Objective Rydberg atom system can strongly respond to weak microwave signals on the electromagnetically induced transparency(EIT)effect and Aulter-Townes(AT)effect.Therefore,people want to utilize this system to detect and demodulate microwaves instead of the traditional mode.At present,there are two methods to demodulate amplitude modulation(AM)microwave signals using the Rydberg atom system,including indirect demodulation and direct demodulation.In the indirect method,the first step is to scan the probe or coupling laser frequency near the zero-detune point,and the second step is to measure the splitting peak-to-peak frequency separation in the probe transmission spectrum.The third step is to calculate the microwave electric field(E-field)strength because the above frequency separation is proportion to the microwave E-field strength.Without complicated processes,in direct demodulation,it is simply to detect the variance of probe laser transmission intensity using photodetector while the Rydberg atom system is at the zero-detune.The photo-generated current is approximately the baseband signal.However,due to the nonlinear relationship between the transmissivity of the Rydberg atom cell and microwave E-field strength,the direct demodulation method will result in nonlinear distortion.The optimum linear operation point of the Rydberg atom system should be studied to decrease the distortion.As far as we know,until now,there is no theoretical analysis about the optimal linear operation point of the Rydberg atom system,and the relationship between the baseband signal amplitude and nonlinear distortion in the AM microwave demodulation.We focus on the optimal linear operation point and nonlinear distortion in the Rydberg atom system.Methods We build a simplified Rydberg atom system model(Fig.1)and numerically simulate the probe laser transmissivity in the Rydberg atom system when 133Cs(energy levels of 6S_(1/2),6P_(3/2),47D_(5/2),and 48P_(3/2))is chosen as Rydberg atom.Our simulation assumes the coupling laser Rabi frequ
作者
金袁凯
饶睿坚
吴金云
张引发
Jin Yuankai;Rao Ruijian;Wu Jinyun;Zhang Yinfa(College of Information and Communication,National University of Defense Technology,Wuhan 430035,Hubei,China)
出处
《光学学报》
EI
CAS
CSCD
北大核心
2023年第22期34-40,共7页
Acta Optica Sinica
基金
国防科技大学基金(YJKT-RC-2112)。
关键词
原子与分子物理学
里德伯态
极化率
拉比频率
透射率
总谐波失真
atomic and molecular physics
Rydberg states
polarizability
Rabi frequency
transmissivity
total harmonic distortion
