Hertz-Level Clock Spectroscopy of ~(171)Yb Atoms in a One-Dimensional Optical Lattice

An ultra-narrow spectroscopy of clock transition with high signal-to-noise ratio is crucial for a high-performance atomic optical clock.We present a detailed study about how to obtain a Hertz-level clock transition spectrum of~(171)Yb atoms.About 4 × 10~4 atoms are loaded into a one-dimensional optical lattice with a magic wavelength of 759 nm,and a long lifetime of 3 s is realized with the lattice power of 1 W.Through normalized shelving detection and spin polarization,~(171)Yb clock spectroscopy with a Fourier-limited linewidth of 5.9 Hz is obtained.Our work represents a key step toward an ytterbium optical clock with high frequency stability.     

Application of Magnetically Induced Transitions of 87Rb Atoms in Coherent Optical Processes

Optics and Spectroscopy - We experimentally demonstrated that magnetically induced (MI) Fg = 1 → Fe = 3 transitions of the D2-line of 87Rb are promising for the generation of optical...     

Magnetic field measurement on ~(87)Rb atomic fountain clock

<正>An experiment on measuring the magnetic field in Ramsey interaction region of the atomic fountain clock by detecting the Zeeman frequency shift of ~(87)Rb hyperfine transition is presented.By mu-metal shielding and coils compensating,the magnetic fluctuations resulting from asymmetry and instability are less than 10 and 0.025 nT,respectively.The relative frequency uncertainty of atomic fountain clock caused by the magnetic field is less than 5.4×10~(-16).     

Theoretical simulation of ~(87)Rb absorption spectrum in a thermal cell

In this paper,we present a theoretical simulation of ~(87)Rb absorption spectrum in a thermal cm-cell which is adaptive to the experimental observation.In experiment,the coupling and probe beams are configured to copropagate but perpendicular polarized,making up to five velocity selective optical pumping(VSOP) absorption dips able to be identified.A A-type electromagnetically induced transparency(EIT) is also observed for each group of velocity-selected atoms.The spectrum by only sweeping the probe beam can be decomposed into a combination of Doppier-broadened background and three VSOP dips for each group of velocity-selected atoms,accompanied by an EIT peak.This proposed theoretical model can be used to simulate the spectrum adaptive to the experimental observation by the non-linear least-square fit method.The fit for the high quality of experimental observation can determine valuable transition parameters such as decaying rates and coupling beam power accurately.     

Trapping of Neutral^87Rb Atoms on an Atomchip

We report an experiment of trapping of neutral ^87Rb atoms on a self-made atomchip. The H-shaped atomchip is made by magnetron sputtering technology, which is different from the atomchip technology of other teams. We collect 3×10^6 ^87Rb atoms in the mirror magneto-optical trap （MOT） using the external MOT coils, and 1×10^5 ^87 Rb atoms are transferred to U-MOT using U-shaped wire in chip and a pair of bias coils.     

冷~(85)Rb原子中的非共线非简并四波混频的实验研究

文章介绍了在磁光阱制备的Rb85冷原子团中通过特定时序的光场进行四波混频的实验研究,我们观察到了混频光强度的空间分布,简要讨论了三束作用光场的频率和光强对混频光产生的影响.时序调制下的四波混频实验为利用冷原子系综制备非经典关联光子对提供了基础.     

Optimization of temperature characteristics of a transportable ~(87)Rb atomic fountain clock

A high-performance transportable fountain clock is attractive for use in laboratories with high-precision time-frequency measurement requirements. This Letter reports the improvement of the stability of a transportable rubidium-87 fountain clock because of an optimization of temperature characteristics. This clock integrates its physical packaging, optical benches, microwave frequency synthesizers, and electronic controls onto an easily movable wheeled plate. Two optical benches with a high-vibration resistance are realized in this work. No additional adjustment is required after moving them several times. The Allan deviation of the fountain clock frequency was measured by comparing it with that of the hydrogen maser. The fountain clock got a short-term stability of 2.3 × 10~(-13) at 1 s and long-term stability on the order of 10~(-16) at 100,000 s.     

Experimental Realization of Degenerate Fermi Gases of ~(87)Sr Atoms with 10 or Two Spin Components

We report the experimental realization of quantum degenerate Fermi gases of~(87)Sr atoms under controlled 10-and dual-nuclear-spin configurations.Based on laser cooling and evaporative cooling,we achieve an ultracold Fermi gas of 105 atoms equally distributed over 10 spin states,with a temperature of T/T_F = 0.21.We further prepare a dual-spin gas by optically pumping atoms to the mF = 9/2 and mF = 7/2 states and observe a slightly lower T/T_F than that for a 10-spin gas under the same trapping condition,showing efficient evaporative cooling under a decreasing number N of spin states(N≥2)despite the increasing importance of Pauli exclusion.Given that rethermalization becomes less efficient with N approaching unity,we evaporatively cool an almost polarized gas to 130 nK.The simple and efficient preparation of ultracold Fermi gases of ~(87)Sr with tunable spin configurations provides a first step towards engineering topological quantum systems.     

Loading of cold ~(87)Rb atom with diffuse light in an integrating sphere

<正>Cold ~(87)Rb atom's loading in an integrating sphere with diffuse light is analyzed theoretically and experimentally. The experimental results show that diffuse light cooling has the greatest efficiency to cool the most atoms when the red detuning between the frequencies of cooling light and atom transition is about 3.3r(Γis the natural linewidth,6.065 MHz).Theoretical analysis using rate equation and numerical calculations on the cold atom number and loading time agree with the experimental results.This integrating sphere cooling would be a novel method for cooling atoms and lead to a new and robust cold atom source for atomic clock.     

基于铯原子光泵磁共振的磁场传感实验系统设计

给出了铯原子光泵磁共振测量磁场的原理.利用MEMS封装与制造技术,设计了一种芯片级的激光铯磁场传感系统,可实现对微弱磁场的检测.     

Simple and robust method for rapid cooling of ~(87)Rb to quantum degeneracy

We demonstrate a simple and fast way to produce ~(87)Rb Bose–Einstein condensates. A digital optical phase lock loop(OPLL) board is introduced to lock and adjust the frequency of the trap laser, which simplifies the optical design and improves the experimental efficiency. We collect atoms in a magneto-optical trap, then compress the cloud and cut off hot atoms by rf knife in a magnetic quadrupole trap. The atom clouds are then transferred into a spatially mode-matched optical dipole trap by lowering the quadrupole field gradient. Our system reliably produces a condensate with 2 × 10~6 atoms every7.5 s. The compact optical design and rapid preparation speed of our system will open the gate for mobile quantum sensing.     

用光学-光学双共振光谱技术研究Cs蒸气中的共振交换碰撞

利用窄带半导体激光器泵浦所有具有相同z分量速度的基态Cs原子至激发态,研究了Cs(6P_3/2, v) +Cs(6S_1/2, v′)→Cs(6S_1/2, v) +Cs(6P_3/2, v′)的共振交换碰撞过程。与泵浦光反向平行的另一单模激光器激发6P_3/2至8S_1/2态,以检测6P_3/2态原子的速度分布,确定激发态原子的热能化效应。通过测量8S_1/2→6P_1/2荧光的尖峰强度与相应的多普勒背景的强度比,得到共振交换碰撞速率系数为k=9.62×10-7 cm3·s-1。证明了在纯碱金属蒸气中,由共振交换机制产生的热能化效应的大小比由速度改变碰撞引起的大3个数量级。     

High quality electromagnetically induced transparency spectroscopy of ~(87)Rb in a buffer gas cell with a magnetic field

We have studied the phenomenon of electromagnetically induced transparency(EIT) of ~(87)Rb vapor with a buffer gas in a magnetic field at room temperature. It is found that the spectral lines caused by the velocity selective optical pump effects get much weaker and wider when the sample cell is mixed with a 5-Torr N_2 gas while the EIT signal is kept almost unchanged. A weighted least-square fit is also developed to remove the Doppler broadening completely. This spectral method provides a way to measure the Zeeman splitting with high resolution, for example, the Λ-type EIT resonance splits into four peaks on the D_2 line of ~(87)Rb in the thermal 2-cm vapor cell with a magnetic field along the electric field of the linearly polarized coupling laser. The high-resolution spectrum can be used to lock the laser to a given frequency by tuning the magnetic field.     

Laser frequency locking based on the normal and abnormal saturated absorption spectroscopy of ~(87)Rb

We present a practical method to avoid the mis-locking phenomenon in the saturated-absorption-spectrum laserfrequency-locking system and set up a simple theoretical model to explain the abnormal saturated absorption spectrum. The method uses the normal and abnormal saturated absorption spectra of the same transition 5~2S_(1/2), F = 2–5~2P_(3/2), F'= 3 saturated absorption of the ~(87)Rb D_2resonance line. After subtracting these two signals with the help of electronics, we can obtain a spectrum with a single peak to lock the laser. In our experiment, we use the normal and inverse signals of the transitions 5~2S_(1/2), F = 2–5~2P_(3/2), F'= 3 saturated absorption of the ~(87)Rb D_2 resonance line to lock a 780-nm distributed feedback(DFB) diode laser. This method improves the long-term locking performance and is suitable for other kinds of diode lasers.     

87Rb冷原子EIT介质中光学信号存储与释放的实验研究

在87Rb冷原子介质中,利用电磁感应透明(EIT)动力学过程,实现了光学信号的存储与释放.实验研究了Larmor进动导致的释放信号崩塌和复原现象,结果表明,当提供量子化轴的磁场超过100 mG时,实验测量得到的拉莫尔周期与理论计算结果较好的相符,这为下一步开展量子存储研究提供了实验基础.     

Spectroscopy of Rubidium Atoms in a Femtosecond Pulsed Optical Dipole Trap

JETP Letters - The spectral properties of atoms localized in an optical dipole trap formed by femtosecond pulsed radiation are studied experimentally. It is shown that the shift of the absorption...     

Magnetic Resonance Frequency Shifts of Spin-Polarized Cesium Atoms in a Cs–Rb Mixture

The interaction of spin-polarized cesium atoms with cesium and rubidium atoms under conditions of optical orientation of atoms is considered. On the basis of data on spin-exchange complex cross sections in the Cs–Cs and Cs–Rb systems, a calculation of a magnetic resonance frequency shift of cesium atoms in a Cs–Rb mixture, as well as comparison of the calculated values of the frequency shift with experimental data, is performed.     

Study of magnetic-rotation in ~(82)Rb by g-factor measurements

Magnetic rotation in ⁸²Rb has been investigated for the first time by g-factor measurement of intra-band states of the magnetic-rotational band built on the 11- state. The g-factors were measured by a TMF-IMPAD method and calculated by a semi-classical model of independent particle angular momentum coupling assumption. The g-factors and deduced shears angles decrease with the increasing of spin along the band, illustrating a step-by-step alignment of the valence protons and neutrons. The rapid alignment of the valence neutrons leads to a decrease of g-factors. The present results vividly reveal the shears mechanism of magnetic rotation.     

Magic Wavelength Measurement of the ~(87)Sr Optical Lattice Clock at NIM

We report on the magic wavelength measurement of our optical lattice clock based on fermion strontium atoms at the National Institute of Metrology(NIM).A Ti:sapphire solid state laser locked to a reference cavity inside a temperature-stabilized vacuum chamber is employed to generate the optical lattice.The laser frequency is measured by an erbium fiber frequency comb.The trap depth is modulated by varying the lattice laser power via an acousto-optic modulator.We obtain the frequency shift coefficient at this lattice wavelength by measuring the differential frequency shift of the clock transition of the strontium atoms at different trap depths,and the frequency shift coefficient at this lattice wavelength is obtained.We measure the frequency shift coefficients at different lattice frequencies around the magic wavelength and linearly fit the measurement data,and the magic wavelength is calculated to be 368554672(44) MHz.     

Influence on the Lifetime of ~(87)Rb Bose-Einstein Condensation for Far-Detuning Single-Frequency Lasers with Different Phase Noises

We study the influence of the phase noises of far detuning single frequency lasers on the lifetime of Bose-Einstein condensation(BEC)of~(87)Rb in an optical dipole trap.As a comparison,we shine a continuous-wave singlefrequency Ti:sapphire laser,an external-cavity diode laser and a phase-locked diode laser on BEC.We measure the heating and lifetime of BEC in two different hyperfine states:|F=2,m_F=2〉and|F=1,m_F=1〉.Due to the narrow linewidth and small phase noise,the continuous-wave single-frequency Ti:sapphire laser has less influence on the lifetime of~(87)Rb BEC than the external-cavity diode laser.To reduce the phase noise of the external-cavity diode laser,we use an optical phase-locked loop for the external-cavity diode laser to be locked on a Ti:sapphire laser.The lifetime of BEC is increased when applfying the phase-Jocked diode laser in contrast with the external-cavity diode laser.