Temperature Dependence of Dark Lines in Coherent Population Trapping

我们在协调人口在作为房间温度的一个函数充满混合缓冲区气体 N-2 和 Ar 的 Rb 蒸汽房间套住测量信号振幅和一根黑暗的线的线宽。我们发现黑暗的线由于熄灭 N-2 的效果在更高的温度在 49 度 C 然后落下与温度表明振幅增加直到最大值。黑暗的线的 Thelinewidth 仍然保持基本上不变，在 1080 Hz。我们也作为激光紧张的功能测量黑暗的线的线宽。线宽与激光紧张线性地增加。Rb 房间的内在的线宽(在 3.4 GHz 的 FWHM=896 Hz ) 被获得。

Ultranarrow absorptive spectral line induced by microwave field

This paper investigates the absorptive spectral lines of four-level atomic system driven by a coupling, probe and microwave fields. Due to the perturbation of the microwave field, the original electromagnetically induced transparency is changed to electromagnetically induced absorption and the absorptive spectral line can be very narrow. This ultranarrow spectral line has potential applications to the microwave atomic frequency standard and the measurement of very weak magnetic field.

The dispersive properties of an excited-doublet four-level atomic system

We have investigated the dispersive properties of excited-doublet four-level atoms interacting with a weak probe field and an intense coupling laser field. We have derived an analytical expression of the dispersion relation for a general excited-doublet four-level atomic system subject to a one-photon detuning. The numerical results demonstrate that for a typical rubidium D1 line configuration, due to the unequal dipole moments for the transitions of each ground state to double excited states, generally there exists no exact dark state in the system. Close to the two-photon resonance, the probe light can be absorbed or gained and propagate in the so-called superluminal form. This system may be used as an optical switch.

An effective pumping method for increasing atomic utilization in a compact cold atom clock

We propose a simple pumping method to increase the effective population of cold atoms in the clock state and investigate the factors which affect the pumping efficiency in cold atom systems.We report the theory and demonstrate the corresponding experiment in an ^(87)Rb integrating sphere cold atom clock.The experimental results show that the population of cold atoms in the Zeeman sublevel|F=2,mF=0>is approximately 1.62 times that of the result using optical pumping alone.This method can also be applied to increase the effective population in any one of the target Zeeman sublevels in other cold atom systems.

Transient responses of transparency in a far-off resonant atomic system

Transient coherent oscillations in a closed A system under far-off resonant Raman fields were investigated theoreti- cally. It has been found that the coherent superposition of the ground states can be formed due to the absorption even for initial maximal mixed ground states. The absorption oscillates with a period depending on the two-photon detuning when the system is initially in a transparent state and the two-photon Raman detuning is suddenly changed. The amplitude of the absorption decays with the decay rate of the ground states, which is different from the case when the lasers are applied resonantly. These transient coherent oscillations can be used to measure the relaxation rate of the ground states.

Analytical solution of microwave transition spectral lines for ^(87)Rb atoms in a Hanle configuration

This paper theoretically investigates the microwave transition spectrum of STRb atomic D1 line with specially prepared atomic state in a Hanle configuration. The approximate analytical results have shown that the 0-0 transition spectral line has the highest contrast and can be applied to microwave frequency standards.

Gain and Absorption of a Probe Light in an Open Tripod Atomic System

We theoretically investigate an open four-level atomic system interacting with control,probe and microwave fields.When there is no repumping light and a microwave field is applied,the probe light can be absorbed or amplified,which has different features than those of a system whose populations are pumped into only one ground state.In this system the microwave field and the population distributions of the ground states can be used as switches to control the propagation of the probe light.

应用于积分球冷原子钟的窄线宽激光稳频系统

通过调制转移光谱稳频的方式,将外腔半导体激光器频率锁定于^(87)Rb原子D_(2)线超精细跃迁5^(2)S_(1/2),F=2→5^(2)P_(3/2),F=3,使激光器线宽由自由运转的382.18 kHz压窄至稳频后的37.94 kHz。稳频后的窄线宽激光用于积分球冷原子钟的探测光,可以将激光频率噪声对原子钟短期稳定度的影响降低至5.6×10^(-14)τ^(-1/2)。

脉冲光镊分离和捕获被吸附粒子的数值模拟

通过分析脉冲光镊作用下的聚苯乙烯小球的受力情况得到小球的运动方程,然后解粒子的运动方程得到小球的 运动轨迹。我们进一步假设粒子与载玻片表面吸附作用力Hamaker常数满足正态分布,来模拟不同粒子与表面的吸附状 态的差异,得到了单脉冲分离效率与脉冲能量、轴向位移的关系。理论计算结果与实验定性相符。

一种用于冷原子重力仪的低相噪微波频综研制

研制了一种用于冷原子重力仪的集成化、低相噪、多通道微波频率综合器。利用锁相环技术,将100 MHz晶振锁定到10 MHz晶振上,改善了100 MHz晶振近端的相位噪声,使输出至后级倍频链路的100 MHz信号的相位噪声同时具备10 MHz及100 MHz晶振的优点。通过搭建超低相噪倍频链路,得到^(87)Rb原子基态跃迁所需的6.834 GHz微波信号。通过互相关法测量得到在频偏为1 Hz和10 kHz处的相位噪声分别为-60 dBc/Hz和-120 dBc/Hz,其频率分辨率为1.42×10^(-6)Hz,并评估了其相位噪声对冷原子重力仪测量分辨率的影响。该微波频综方案具有普适性,可广泛应用于原子钟和干涉仪等量子精密测量领域。

脉冲光抽运原子钟原子相位反馈研究

在基于Ramsey作用的原子钟里,受限于原子的相干时间及晶振的相位噪声,自由演化时间不能太长。提出了大失谐光无破坏测量方法,利用该方法获取了原子相位数据,并将其反馈到微波相位上,从而实现了原子相位反馈,有效地延长了自由演化时间。分别从理论和实验上验证了这种周期性反馈作用的可行性。

正交偏振探测技术型脉冲光抽运原子钟研究进展

介绍了本课题组新概念小型化星载原子钟的研究进展。利用已有的脉冲光抽运技术和独立提出的正交偏振探测技术,将原子钟的钟跃迁信号的对比度从一般吸收法的30%提高到将近100%。该方法主要探测的是光的振幅和相位的总变化,因而能有效提高探测灵敏度和信噪比,从而提高频率稳定度。实验结果表明,正交偏振探测技术原子钟的原子频率稳定度比相同条件下吸收法原子钟的原子频率稳定度提高一个量级;而且在实验的基础上,物理系统的温度稳定度、磁场电流稳定度和激光光强稳定度都能够提高一个量级,正交偏振探测技术原子钟的秒稳能达到1×10-13,天稳能优于1×10-15,将来可能进一步发展并取代氢钟。

双层矩形位相光栅的分束特性

对由两矩形位相光栅构成的双层体积全息光栅的分束特性进行了优化设计，获得了扇出光来数分别为2，3和5，总衍射效率高于89％，光强分布不均匀性小于5％的分束器。

VIPA-based two-component detection for a coherent population trapping experiment

We demonstrate a two-component detection of a coherent population trapping(CPT)resonance based on virtually imaged phased array(VIPA).After passing through a VIPA,the two coupling lights with different frequencies in the CPT experiment are separated in space and detected individually.The asymmetric lineshape is observed experimentally in the CPT signal for each component,and the comparison with the conventional detection is presented.The shift of the CPT resonant frequency is studied with both the two-component and one-component detections.Our scheme provides a convenient way to further study the CPT phenomenon for each frequency component.

Recent improvements on the pulsed optically pumped rubidium clock at SIOM

We report the recent progress of our pulsed optically pumped（POP） vapor cell rubidium clock with dispersive detection.A new compact physics package is made.A rubidium cell with a high precision buffer gases mixing ratio is obtained,and the temperature controlling system is renovated to reduce fractional frequency sensitivity to temperature variation.The resolution of the servo control voltage is also optimized.With these improvements,a clock frequency stability of 3.53×10-13 at 1s is obtained,and a fractional frequency stability of 4.91×10-15 is achieved at an average time of τ=2000 s.

Microwave excited optical transparency enhancement resonances in Hanle-EIT configuration

We report an experimental observation of the optical transparency enhancement resonances in Hanle- electromagnetically induced transparency （EIT） configuration with a microwave field excitation. In this experimental system, a strong control field and a weak probe field form three-level A-type configurations of EIT. The fourth level is coupled by an additional microwave field. With the microwave field excitation, the probe field undergoes a process of absorption to transparency when the probe field decreases. Compared with the EIT effect, this result indicates optical transparency enhancement. A simple theoretical model and a numerical simulation are presented to explain the observed experimental results. The applications of these optical features are also discussed.

High contrast transparent ramsey fringes using microwave pulses interaction with atomic coherent state in warm rubidium vapor

High contrast transparent Ramsey fringes are observed using double microwave pulses interaction with the prepared atomic coherent state in a warm STRb vapor with mixture buffer gases in a closed cell. The Ramsey fringes are generated by the pulsed technique, a strong coupling light pulse and a weak signal light pulse are applied to prepare the atomic coherent state, followed by the application of double microwave pulses to interact with the atomic coherent state. Afterwards, the light pulses are applied again with weaker intensity and detecting the signal transmission is delected. The central line of the transparent Ramsey fringes has narrow linewidth of 125 Hz and high contrast of 21%. The light shift is dramatically reduced since the interrogating process is not involved the light field, and the cavity pulling effect is negligible due to the low Q requirement, which is promising for building small, compact, and stable atomic clocks.

利用磁光效应获得超高对比度的原子钟跃迁谱线

由中科院量子光学重点实验室王育竹院士领导的新型星载原子钟课题组，在2012年12月15日出版的国际学术期刊（《光学快报》上，首次报道了利用基于磁光旋转效应的正交偏振探测技术探测气泡式铷原子钟的钟跃迁信号，获得了对比度高达90％的超高对比度钟跃迁信号，抑制了散弹噪声，压制了激光振幅和相位起伏的噪声，极大地提高了钟跃迁信号的信噪比和原子钟中短期频率稳定度。