Bichromatic laser frequency stabilization with Doppler effect and polarization spectroscopy

The interaction between polychromatic fields and atoms is an important subject in quantum optics.Frequency locking for small frequency interval multi-field is usually required in some experiments.In this letter,we experimentally demonstrate a holistic scheme for bichromatic laser frequency stabilization.Compared with traditional saturation absorption methods and complicated frequency shift schemes,offset locking for bichromatic fields is simply achieved using polarization spectroscopy and Doppler effect.Frequency locking with a wide-range asymmetry of the detuning is also shown.Our scheme makes laser spectroscopy experiments with polychromatic fields more convenient.     

Polarization of atoms by simultaneous electromagnetic pulses of different frequency ranges

A method is proposed for the fast and deep polarization of a system of ground-state hyperfine sublevels of an atom having an optical excited level or a system of excited-state sublevels. The method is based on the simultaneous action of pulsed bichromatic resonance fields of optical and microwave ranges. The scheme of the ground-state sublevel polarization by bichromatic or monochromatic microwave fields is also considered.     

Experimental preparation of pure superposition states of atoms via elliptically polarized bichromatic radiation

We propose a simple and effective way of creating pure dark superposition states. The generation of pure states is carried out by using bichromatic radiation with controllable polarization ellipticity. We experimentally confirm analytic formulas for polarization ellipticity to obtain m-m pure dark states in the system of Zeeman sublevels of alkali atoms. For 87Rb we experimentally accumulated 60% of the atoms in the 0-0 dark state and 50% into the (+/-1) - (+/-1) dark states.     

Simultaneous electromagnetically induced transparency and absorption in thermal atomic medium

A three-level lambda system driven by multicolor control, pump, and probe fields is investigated. The pump and probe fields are derived from the same laser with opposite propagating directions. Due to the Doppler effect, the zero group-velocity atoms face bichromatic fields, while other atoms face trichromatic fields. The atomic medium shows distinct characteristics and exhibits simultaneous electromagnetically induced transparency(EIT) and electromagnetically induced absorption(EIA) at two frequencies. EIT and EIA peaks have a fixed relationship with frequency, which is determined by the Doppler shifts.     

Polarization properties of a one-atom maser under a step-wise two-photon pump

The theory of a one-atom maser, when the atoms enter the microresonator being excited to the upper maser level from its ground state by the bichromatic laser field resonant with the two adjacent optically allowed transitions with arbitrary angular momenta, is built. This theory is applied to the investigation of the polarization properties of a one-atom maser, i.e., the dependence of the maser field characteristics on the mutual orientations of the polarization vectors of the maser field mode and of the pump laser field. New experiments are proposed to study such polarization properties, which may be performed within the framework of the experimental setup used by Professor H. Walther and collaborators [1–3].     

双模激光场中电子-原子散射

在一阶玻恩近似的基础之上,本文首次在激光场的极化方向平行于入射电子的方向这种散射模式下,应用二阶玻恩近似理论对双模激光场中电子-氩原子散射的自由-自由跃迁过程进行了研究,并与一阶玻恩近似结果进行比较.结果表明,二阶玻恩近似理论在多模激光场中的应用也是比较成功的.     

光脉冲序列对三能级原子重力仪测量精度的影响

提出了一种通过改变激光脉冲序列来提高三能级原子重力仪测量精度的方法.利用提出的描 写原子运动的3×3阶矩阵方法，分析了三能级原子与双色光场的正交相互作用，计算了 原子干涉仪中的相位差，得到了原子重力仪的相位差与重力加速度的关系.发现通过选择合 适的光脉冲序列，可以提高三能级原子重力仪的精度. 关键词： 原子光学 原子重力仪 矩阵方法     

Three-dimensional rectification of a gradient force in a strong nonmonochromatic field

A new three-dimensional scheme for rectifying a gradient force is proposed and analyzed. The scheme is based on the use of a strong, partially coherent optical field involving a component with a fluctuating phase. It is shown that the rectification of a gradient force acting on atoms with a nondegenerate ground state is a second-order effect with respect to field strength in this scheme, whereas an analogous effect is third-order in coherent bichromatic fields. Conditions for three-dimensional confinement of atoms are obtained by using the velocity dependence of the rectified radiative force. For a large class of atoms, such as even-even isotopes of ytterbium and alkaline-earth elements, these conditions can be implemented at a relatively high effective temperature (of the particle ensemble) of about 10 K. This finding can be used to widen substantially the range of energies of atoms amenable to effective three-dimensional optical manipulation.     

Sub-half-wavelength atom localization via bichromatic phase control of spontaneous emission

We show that the bichromatic phase control of the spontaneous emission spectrum leads to the sub-half-wavelength atom localization. We consider a three-level Λ-type atom interacting with a bichromatic coupling field and a bichromatic probe field with equal frequency difference. One component of the bichromatic coupling field is a standing-wave field with position dependent Rabi frequency. When the spontaneous emitted photons are detected, the atom is localized in either of the two half-wavelength regions with 50% probability by the variation of the difference between the relative phases of the two bichromatic fields.     

Kinetics of atoms in a bichromatic field

The kinetics of atoms in a bichromatic field is considered. Analytic solutions are obtained for the force, friction coefficient, and diffusion coefficient in the model of a two-level atom without limitations imposed on the intensity of light fields. This effect is observed in the domain of global minima and maxima of the optical potential (i.e., at points where the relative phase of two standing waves is ? = 0, π/2.     

双色反向旋转圆偏振激光场下氩原子高次谐波的产生

通过二阶分裂算符法数值求解了二维含时薛定谔方程,研究了双色反向旋转圆偏振激光场作用下氩原子的高次谐波的产生.研究表明,双色反向旋转圆偏振激光场的幅值比对高次谐波发射的效率有较大影响,当幅值比为1.4时高次谐波的发射效率最高,并应用时频分析方法、经典三步模型以及利萨茹图形等解释了高次谐波发射的物理机制.研究了不同幅值比情况下谐波场的旋转偏振特性,发现对不同频段的谐波谱的电场进行叠加,谐波场的偏振特性随幅值比的不同而发生变化,但谐波场的旋向性与入射激光脉冲的旋向性相同,不受幅值比变化的影响.     

Phase control of spontaneous emission by cascade bichromatic excitation

We study spontaneous emission of a three-level cascade atom driven by a pair of bichromatic fields of equal frequency differences. The fluorescence spectra from the cascade transitions depend strongly on the difference between the relative phases of two bichromatic fields. Selective and almost complete elimination of fluorescence spectra is achieved simply by varying the difference phase.     

Phase Control of Luminescence Excited by Bichromatic Radiation

A new method of phase control of photoprocesses based on the dependence of the power of luminescence excited by a bichromatic field on the phase shift between the monochromatic radiation components is suggested and analyzed. Calculations are carried out by the example of excitation of alkali metal atoms from the ground state to the first excited _s-state with their subsequent luminescence as a consequence of spontaneous transitions to the intermediate p-level. The optimal parameters of the bichromatic field at which the effect is most pronounced are determined. A strong dependence of the luminescence phase modulation on the laser field intensity near the region of saturation of the excited transition is established. It is demonstrated that the wavelengths of bichromatic radiation and luminescence lie in the range easily accessible for an experiment.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 7–14, April, 2005.     

Control for atom response in multicomponent laser fields

A theory of the nonlinear optical response of an atom interacting with a superposition of arbitrarily polarized fields is developed. The theory is based on the analytical solution of the boundary-value problem for an electron moving in a spherically symmetric intraatomic field and in the field of an external electromagnetic field. By means of the example of an argon atom interacting with a bichromatic field formed by the first and second harmonics of a Ti:sapphire laser, it is shown that, when an atom interacts with the field of two polarized pulses the polarization directions of which are not collinear, the response spectrum significantly depends on the laser radiation parameters—the duration and intensity of pulses, the time of delay between them, and the angle between the directions of polarization vectors. Generation of THz radiation is shown to be possible in the ionization-free regime due to intraatomic nonlinearity.     

线偏振双色激光场中氪原子的阈上电离现象

采用基于Guo,Aberg和Crasemann发展的强激光场中的非微扰量子散射理论(GAC理论),研究了线偏振双色激光场中氪(Kr)原子阈上电离的光电子角分布,双色激光场由一系列相同的单周期激光脉冲组成.研究发现光电子角分布有强烈的位相依赖关系,且呈现出反演不对称性、喷射结构和展宽结构等现象,这为实验上通过改变双色激光场的相对相位来观察和控制光电子角分布提供了一种有效的方法.     

Specific Features of the Kinetics of Atoms in a Three-Dimensional Bichromatic Standing Wave

The three-dimensional kinetics of resonance atoms with the J = 0 J = 1 quantum transition in the weak field of mutually orthogonal bichromatic standing waves under conditions of manifestation of the effect of straightening of radiation forces is considered. It is demonstrated that the character of particle motion (induced by the straightened radiation forces) significantly depends on the relative phase difference of standing waves. In general, it is vortex in character and can suppress the process of localization of atoms in the small vicinity of straightened radiation force nodes even in the presence of a strong friction force. The target-oriented choice of phase relationships between the field components with mutually orthogonal polarization directions guarantees a solution of the problem of purely optical localization of atoms in the mode of vortex-free motion.     

Possibilities of the method of phase-polarization selection of laser frequencies in strong fields

The spectra of Faraday rotation of the plane of polarization of laser radiation in strong radiation fields and a magnetic field were investigated for alkali atoms. The spectra were obtained using the known method of computer simulation of polarization effects in real multilevel atoms. The possibility of using these effects in the phase-polarization method of selection of laser frequencies was considered. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 1, pp. 61–64, January–February, 2000.     

Coherent repopulation of hyperfine structure levels in the field of a bichromatic resonant radio-frequency wave

We consider the resonant interaction between atoms with hyperfine energy levels and a bichromatic radio-frequency field. Nuclear Zeeman levels of an impurity center in a magnetic host form a structure of this kind. Using the spin-density-matrix formalism, we solve the problem of coherent repopulation of a system of three of these levels under the action of a bichromatic resonant radio-frequency wave, taking into account transverse relaxation, and note the connection between this effect and the well-known phenomenon of coherent population capture when a laser bichromatic field interacts resonantly with a three-level system. We discuss various possibilities for observation of this effect experimentally. Zh. éksp. Teor. Fiz. 111, 1236–1244 (April 1997)     

Spin-dependent forces on trapped ions for phase-stable quantum gates and entangled states of spin and motion

Favored schemes for trapped-ion quantum logic gates use bichromatic laser fields to couple internal qubit states with external motion through a "spin-dependent force." We introduce a new degree of freedom in this coupling that reduces its sensitivity to phase decoherence. We demonstrate bichromatic spin-dependent forces on a single trapped 111Cd+ ion, and show that phase coherence of the resulting entangled states of spin and motion depends critically upon the spectral arrangement of the optical fields. This applies directly to the operation of entangling gates on multiple ions.     

采用双脉冲提高谐波谱的谱线密度

通过计算线偏振双脉冲激光场与一维氢原子模型相互作用产生的高次谐波辐射谱的含时Schrdinger方程. 研究发现,选用适宜的双脉冲激光组合可以增加谐波谱的密度,这样的谐波谱特别适合作为产生孤立阿秒脉冲的光源. 详细地分析了谐波谱线密度增加的物理机理,给出不同脉宽与谐波谱线密度增加的关系,从而可以有针对性地控制谐波谱线的疏密程度. 关键词： 高次谐波 阿秒脉冲 双脉冲