三维光学晶格中铯原子的装载与冷却

建立了四光束的三维光学晶格势场,在铯原子磁光阱和光学粘团的基础上实现了红失谐三维光学晶格中冷原子的装载.借助于短程飞行时间吸收谱测量冷原子温度,通过改变光学晶格的总光强和频率失谐等条件,对光学晶格中铯原子的亚多普勒冷却以及光学晶格中冷原子的寿命进行了研究. 关键词： 光学晶格 磁光阱 光学粘团 冷原子     

对相干态与级联三能级原子相互作用过程中原子与场的动力学特性

研究对相干态与级联三能原子相互作用的动力学特性。结果表明，无论场模与原子的中间能级是否失谐，拉比振荡和互关联函数的时间演化都呈现崩溃与回复现象，但崩溃的持续时间随失谐量的增加而迅速延长，且两模之间随时间的演化即出现关联也出现反关联。     

在克尔媒质中原子和光场的量子信息保真度

讨论了在克尔媒质中原子与光场相互作用及拉曼相互作用时原子、光场和整个系统的量子信息保真度的时间演化过程。研究光场的光强、失谐量及克尔参量对保真度的影响。研究表明，当拉比振荡频率与光子数成正比时保真度表现出周期性的等幅振荡。光强的增加将使保真度下降，失谐量的增加会提高保真度，克尔媒质也对保真度的演化产生影响。失谐量为0，克尔参量为0．5g时以及在能级简并的拉曼过程中保真度表现出很规则的等幅周期振荡。     

原子漏斗及其应用

文章简单介绍了磁、光原子漏斗的基本原理,详细综述了各种原子漏斗方案及其实验结果.这些漏斗方案主要包括采用红失谐高斯光束、蓝失谐消逝波光场和空心光束串联而成的光学原子漏斗,采用载流导线的静磁原子漏斗以及采用磁光凝胶构成的磁光原子漏斗.文章最后还简单介绍了原子漏斗在原子光学领域中的潜在应用.     

Ladder型原子辅助光力学系统的光学多稳响应(英文)

通过解析和数值模拟系统的海森堡朗之万方程的稳态解,研究了Ladder型三能级原子辅助光力学系统的光学响应.结果表明振动镜子和原子系综的稳态行为与弹簧的劲度系数和经典泵浦场的拉比频率有关.随着劲度系数的减小和拉比频率的增大,腔内原子系综和整个光力学系统将呈现多稳现象,并且不同频域对应稳态解的个数有所不同.因此,可以通过改变泵浦场拉比频率和弹簧劲度系数来控制系统的稳态响应.研究结果在量子信息处理和精密测量等领域具有潜在的应用价值.     

三能级三模量子系统中探测场的增益研究

研究了三能级原子与多模光场相互作用的量子系统,从系统的密度矩阵运动方程出发讨论了无粒子数反转探测场的增益条件,发现当驱动场拉比频率取5,探测场拉比频率取1,非相干抽运取3,驱动场失谐量取3时,系统可以在偏离共振的两端获得粒子数无反转而相应的探测场获得了增益,即实现了无粒子数反转激光,其在光通信方面具有重要的应用价值。     

多模1064nm光纤激光器实现一维远失谐光晶格

采用1064 nm多模30 W连续光纤激光器, 搭建了一个周期为25 μm的一维远失谐光学晶格势场. 对铷原子进行磁光阱装载和偏振梯度冷却, 实现了铷冷原子团在光晶格中的装载. 借助于短程飞行时间法, 测量晶格中冷原子温度为20 μK, 为下一步实现量子信息存储实验奠定了基础.     

采用消逝波干涉的二维表面微光阱阵列

提出了一种采用两套超大红失谐消逝波干涉和一束蓝失谐消逝波光场来实现原子二维表面微光阱阵列和原子有效强度梯度冷却的新方案,得到了二维表面微光阱阵列的光强分布和光学势分布.研究发现,二维表面微光阱阵列中微光阱的光学势能够有效地囚禁从标准磁光阱中释放的冷原子,并且被囚禁的冷原子能在蓝失谐消逝波光场的作用下产生有效的强度梯度Sisyphus冷却,对⁸⁷Rb原子而言,原子温度能被冷却到2.56μK.该方案在冷原子物理、原子光学和量子光学领域中有着广阔的应用前景. 关键词： 消逝波干涉 微光阱阵列 原子囚禁 强度梯度冷却     

我国锶原子光钟关键技术研究获进展

由中国计量科学研究院等单位共同承担的"高准确度原子光学频率标准仪的研制与开发"课题,顺利通过了国家质检总局组织的专家验收.该课题建立了锶原子塞曼减速器和激光冷却囚禁装置,研制了宽带钛宝石飞秒光梳和铒光纤光梳,完善了多个次级光学频率标准,掌握了锶原子光钟和光纤光梳研究     

若干参数对瞬态电磁感应透明的影响

研究了原子梯形三能级系统的瞬态电磁感应透明特性,分析了系统各种参数,诸如瞬态作用时间、泵浦场和探测场的拉比频率、激光线宽及消相碰撞等因素对瞬态电磁感应透明的影响。结果表明：在不考虑激光线宽及消相碰撞时,探测场的吸收随时间在零吸收附近作类似于阻尼减幅振荡,系统可实现无反转放大;随着泵浦场的拉比频率的减小及上能级驰豫速率的增大,感应透明将减弱。在考虑到激光线宽及消相碰撞等非相干因素时,对于一定的瞬态作用时间,感应透明将随着探测场拉比频率的增大而减弱。     

Rabi frequency and optical Bloch equations for a short femtosecond optical pulse

We investigate the interaction of a multilevel atom with a short femtosecond optical pulse beyond the scope of the rotating-wave approximation. We consider the behavior of a three-level atom under the action of two optical pulses resonant with two allowed transitions and a two-level atom under the action of a resonant optical pulse. It is shown that the imaginary part of the off-diagonal elements of the density matrix oscillates with high frequency due to the counter-rotating terms. It is shown also that an effective time-dependent addition to the Rabi frequency exists, which is of importance for ultrashort optical pulses.     

Carrier shock and frequency conversion of a few—cycle pulse laser propagating in a non—resonant two—level atom medium

We have studied the spectral behaviour of few-cycle soliton pulses in a non-resonant two-level atom medium by solving the full Maxwell－Bloch equations. It is demonstrated further that the carrier effects play an important role in the propagation of the few-cycle pulse laser. When the frequency detuning is not very large, both the population distribution and the refractive index of the medium follow the oscillatory carrier field instantaneously; in this case, carrier-wave compression or carrier shock occurs, and a supercontinuum broader than that in the resonant medium may be generated. When the frequency detuning is large, the carrier shock is weak and the spectrum is not continuous, only showing an odd harmonic radiation.     

Radiation forces on a three-level atom in the high-order Bessel beams

The general expressions of the average dissipative and dipole forces acting on a A-configuration three-level atom in an arbitrary light field are derived by means of the optical Bloch equations based on the atomic density matrix elements, and the general properties of the average dissipative and dipole forces on a three-level atom in the linearly-polarized high-order Bessel beams （HBBs） are analysed. We find a resonant property （with two resonant peaks） of the dissipative force and a non-resonant property （with two pairs of non-resonant peaks） of the dipole force on the three-level atom, which are completely different from those on the two-level atom. Meanwhile we find a saturation effect of the average dissipative force in the HBB, which comes from the saturation of the upper-level population. Our study shows that the general expressions of the average dissipative and dipole forces on the three-level atom will be simplified to those of the two-level atom under the approximation of large detuning. Finally, we study the axial and azimuthal Doppler cooling of atoms in ID optical molasses composed of two counter-propagating HBBs and discuss the azimuthal influence of the HBB on the Doppler cooling limit. We also find that the Doppler limit of atoms in the molasses HBB is slightly below the conventional Doppler limit of hГ/（2kB） due to the orbital angular momentum lh of the HBB.     

The generation of terahertz radiation via optical rectification in the self-induced transparency regime

The possibility of efficient terahertz generation via optical rectification in electro-optic crystal doped with the two-level resonant impurities is demonstrated. Under conditions of the self-induced transparency regime the laser pulses slows down to achieve the phase matching condition. The terahertz generation is accompanied by periodic modulation and spectral deformation of the laser pulse. The most efficient generation occurs under condition of small negative detuning from the resonant frequency of the two-level system.     

Generating controllable atom-light entanglement with a Raman atom laser system

We introduce a scheme for creating continuous variable entanglement between an atomic beam and an optical field, by using squeezed light to outcouple atoms from a Bose-Einstein condensate via a Raman transition. We model the full multimode dynamics of the atom laser beam and the squeezed optical field and show that, with appropriate two-photon detuning and two-photon Rabi frequency, the transmitted light is entangled in amplitude and phase with the outcoupled atom laser beam. The degree of entanglement is controllable via changes in the two-photon Rabi frequency of the outcoupling process.     

飞秒激光光镊横向光学力的理论分析

旨在将飞秒激光脉冲序列视为对连续光的周期抽样结果,分析飞秒激光脉冲序列作为光镊光源捕获电介质微粒时产生的横向光学力,并给出受光微粒所受横向光学势阱力的理论模型及计算公式.数值计算结果表明,飞秒激光脉冲所产生的横向光学力能抵消由于布朗运动引起的微粒中心偏移的影响,实现对微粒的稳定束缚.     

Coherent population transfer in four-level ladder systems by single frequency-chirped laser pulse

Adiabatic passage induced by a frequency-chirped laser pulse in four-level ladder systems is investigated. Two different strategies for efficient population transfer (intuitive and counterintuitive laser pulse) are analyzed. For the larger detuning, the four-level ladder system can be reduced to a two-level system with which we are familiar. For the smaller detuning, the main conditions for realization of population transfer are the following: the width of the transform-limited laser pulse envelope frequency spectrum (without chirp) must be smaller and the peak Rabi frequency of the pulse must be larger than the detuning ε₂₁ and ε₂₁∼ε₃₂ in the case of the three-photon resonance. With this laser pulse, it is possible to achieve complete population via the intermediate levels by three successive adiabatic passages. Complete inversion is also obtained by a counterintuitive direction of the frequency sweep.     

Control and coherence of the optical transition of single nitrogen vacancy centers in diamond

We demonstrate coherent control of the optical transition of single nitrogen-vacancy defect centers in diamond. On applying short resonant laser pulses, we observe optical Rabi oscillations with a half period as short as 1 ns, an order of magnitude shorter than the spontaneous emission time. By studying the decay of Rabi oscillations, we find that the decoherence is dominated by laser-induced spectral jumps. By using a low-power probe pulse as a detuning sensor and applying postselection, we demonstrate that spectral diffusion can be overcome in this system to generate coherent photons.     

Analytic solutions of the optical Bloch equations

We present analytic solutions of optical Bloch equations. We found that the solutions exhibit two different types of the behavior: one is oscillatory, and the other is a simple decay. The boundary dividing the two different types of solutions is exactly calculated in a two-dimensional space of the laser detuning and Rabi frequency. We also obtained simple analytic solutions for special conditions.