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1.
We investigate one-dimensional position microscopy of a three-level atom moving through a stationary wave region under the condition of electromagnetically induced transparency.The precise position information of an atom is observed on the resonance absorption and dispersion distribution spectrum of a weak probe field.Single and multiple localization peaks are observed in specific directions of the corresponding wave numbers and phase of the standing wave fields.The strength of space-independent Rabi frequency reduces the position uncertainty in the localized peaks without disturbing the probability of the atom.In a hot atomic medium the localized probability of an atom is reduced which depends upon the temperature of that medium.Our results provide useful applications in the development of laser cooling,atom nanolithography and Bose-Einstein condensation. 相似文献
2.
V.Yu. Argonov 《Physics letters. A》2011,375(7):1116-1119
The motion of an atomic wave packet in a standing light wave can be described in terms of two periodic potentials. Single atom may perform Landau-Zener (LZ) transitions between these two energy states. In this Letter we have found regimes when atom is localized in the momentum space in the vicinity of its initial momentum. We argue that this localization is caused by the asymmetry of LZ transitions (i.e. probability of tunneling depends on its direction) due to the interference. 相似文献
3.
A theoretical study is presented for two-dimensional (2D) and three-dimensional (3D) atom localization in a four-level atomic system involving a Rydberg state. The scheme is based on a mixture of two well-known V- and ladder-type systems illuminated by a weak probe field as well as control and switching laser beams of larger intensity, which could be standing waves. As a result of space-dependent atom? light interaction and due to the effect of Rydberg electromagnetically induced transparency or Rydberg electromagnetically induced absorption, various 2D and 3D localization structures appear. Specifically, the detecting probability and precision of 2D and 3D atom localization can be remarkably enhanced through suitable adjusting the controlling parameters of the system. The proposed scheme may provide a promising approach to achieve high precision and perfect resolution 2D and 3D atom localization. 相似文献
4.
Within the framework of the Floquet theorem, we have
investigated single-electron photon-assisted tunneling in a
double-well system using the transfer matrix technique. The
transmission probability displays satellite peaks on the both sides
of main resonance peaks and these satellite peaks originate from
emission or absorption photons. The single-electron resonance
tunneling can be control through changing applied harmonically
potential positions, such as driven potential in wells, in barriers,
or in whole double-well system. This advantage should be useful in
the optimization of the parameters of a transmission device. 相似文献
5.
提出了一种基于量子相干控制吸收的对准Λ型四能级原子进行二维局域化方案. 利用密度矩阵微扰理论, 得到了确定原子空间位置信息的筛选函数解析表达式. 在缀饰态表象中, 分析了在相干控制场作用下原子初始状态对原子局域的影响. 数值模拟了控制场参量对原子局域化结果的影响. 研究发现原子局域化结果与初始时刻在控制场作用下原子在下能态的布局、下能级间产生的极化密切相关; 不管探测场与耦合场是否满足电磁感应透明配置条件, 通过改变控制场中的行波场的振幅和探测场的失谐量, 均可实现高精度原子局域化, 在亚波长范围内测量到原子的概率达到100%. 相似文献
6.
We have investigated the two-dimensional (2D) atom localization via probe absorption in a coherently driven four-level atomic system by means of a radio-frequency field driving a hyperfine transition. It is found that the detecting probability and precision of 2D atom localization can be significantly improved via adjusting the system parameters. As a result, our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization. 相似文献
7.
Quantum-well states above the Fermi energy in thin Yb(111) metal films deposited on a W(110) single crystal were studied by low-temperature scanning tunneling spectroscopy. These states are laterally highly localized and give rise to sharp peaks in the tunneling spectra. A quantitative analysis of the spectra yields the bulk-band dispersion in the Gamma-L direction as well as quasiparticle lifetimes. The quadratic energy dependence of the lifetimes is in quantitative agreement with Fermi-liquid theory. 相似文献
8.
The optical reflectance by a metallic plate arranged with array consisting of subwavelength periodic square hole is investigated by using the three-dimensional finite-difference time-domain method (3D-FDTD). There are dips in the reflectivity spectra, which indicate the absorption peaks. The absorption peaks behave differently according to the ratio of hole width and the period of the hole array. Combined with the near fields of the absorption peaks, it is found that the surface plasmon (SP) resonance on the surface of plate and localized SP in the hole play a major role for the two absorptions. 相似文献
9.
Herein, we propose a scheme for the realization of two-dimensional atomic localization in aλ-type three-level atomic medium such that the atom interacts with the two orthogonal standing-wave fields and a probe field. Because of the spatially dependent atom-field interaction, the information about the position of the atom can be obtained by monitoring the probe transmission spectra of the weak probe field for the first time. A single and double sharp localized peaks are observed in the one-wavelength domain. We have theoretically archived high-resolution and high-precision atomic localization within a region smaller thanλ/25×λ/25. The results may have potential applications in the field of nano-lithography and advance laser cooling technology. 相似文献
10.
11.
We show that it is possible to localize a three-level cascade atom under the resonance condition when it passes through a standing-wave field. The localization peaks appear at the nodes of the standing-wave field, the detecting probability is 50% in the subwavelength domain, and the peaks are narrower on the resonance than the off- resonance. The absorption is the same as that in the usual two-level medium at the nodes and is greatly suppressed outside the nodes due to the Autler-Townes splitting. This is in sharp contrast to the lambda scheme, in which the localization is impossible under the same resonance condition due to the depletion of population of the initial state by the probe field at the nodes and the electromagnetically induced transparency outside the nodes. 相似文献
12.
《中国物理 B》2021,30(5):53202-053202
Rydberg atoms have been widely investigated due to their large size, long radiative lifetime, huge polarizability and strong dipole-dipole interactions. The position information of Rydberg atoms provides more possibilities for quantum optics research, which can be obtained under the localization method. We study the behavior of three-dimensional(3 D)Rydberg atom localization in a four-level configuration with the measurement of the spatial optical absorption. The atomic localization precision depends strongly on the detuning and Rabi frequency of the involved laser fields. A 100% probability of finding the Rydberg atom at a specific 3 D position is achieved with precision of ~0.031λ. This work demonstrates the possibility for achieving the 3 D atom localization of the Rydberg atom in the experiment. 相似文献
13.
We present a simple scheme of atom localization in a subwavelength domain via manipulation of probe absorption spectrum in a four-level atomic system. By applying two orthogonal standing-wave fields, the localization peak position and number as well as the conditional position probability can be controlled by the intensities and detunings of optical fields, and the sub-half-wavelength atom localization is also observed. More importantly, there is 100% detecting probability of the atom in the subwavelength domain when the corresponding conditions are satisfied. 相似文献
14.
We investigate, in one spatial dimension, the quantum mechanical tunneling of an exciton incident upon a heterostructure barrier. We model the relative motion eigenstates of the exciton using a form of the one-dimensional hydrogen atom which avoids difficulties previously associated with 1D hydrogenic states. We obtain probabilities of reflection and transmission using the method of variable transmission and reflection amplitudes. Our calculations may be broadly divided into two sets. In the first set, we consider general qualitative aspects of exciton tunneling, such as the effect of different effective masses for electrons and holes and a relative difference in electron and hole barrier strengths. The second set models the tunneling of an exciton in a GaAs/Al(x)Ga(1-x)As heterostructure. In these calculations we find that, for energies such that the two lowest exciton states are coupled, the probability spectrum for transition from the ground state to the first excited state is identical to that for transition from the first excited state to the ground state. In addition, narrow peaks in the probability spectrum for transition are observed across this energy range for low dopant concentration x. Other interesting phenomena correlated with these peaks in the transition probability are reported. 相似文献
15.
We study the interaction of an asymmetric double semiconductor quantum dot molecule with a weak probe field and a strong pump field. We show that the optical properties of the system are controlled by a gate voltage and the pump field. For example, we find that the application of the pump field leads to controlled probe absorption, optical transparency, and gain for weak tunneling rates, while for stronger tunneling rates optical gain disappears and absorption spectra with double peaks are formed. 相似文献
16.
Resonant transmission and Goos–Hänchen (GH) shift for Dirac fermion beams tunneling through graphene double velocity barrier structures (DVBs) are investigated theoretically. Analytical and numerical results demonstrate that strong resonant tunneling effect occurs in this structure and is highly dependent on the incident angle and the structure of velocity barriers. The resonant tunneling in graphene DVBs belongs to the Fabry–Pérot resonance and leads to oscillated conduction at wide energy range. It is also found that GH shifts in this structure can be enhanced by the resonant tunneling and multi-GH shift peaks with giant magnitudes can occur at these resonant energy positions. These special properties of GH shifts in graphene DVBs may have good application in lateral manipulation of electron beams and valley or spin beam splitter. 相似文献
17.
We report the results of theoretical investigations of tunneling current noise spectra in a wide range of applied bias voltage.
Localized states of individual impurity atoms play an important role in tunneling current noise formation. It was found that
switching “on” and “off” of Coulomb interaction of conduction electrons with two charged localized states results in power
law singularity of low-frequency tunneling current noise spectrum (1/f
α) and also results on high frequency component of tunneling current spectra (singular peaks appear).
The article is published in the original. 相似文献
18.
A scheme of two-dimensional (2D) atom localization based on the phase-sensitive probe absorption is proposed in a four-level Λ-type atomic system with an assisting radio-frequency (rf)-driven field. The obtained 2D atom localization patterns reveal that the maximal probability of finding an atom within the sub-wavelength domain of the standing waves can arrive at unity by appropriate choice of the system parameters. 相似文献
19.
A. M. Bonch-Bruevich E. N. Kaliteevskaya T. K. Razumova A. D. Roshal’ A. N. Tarnovskii 《Optics and Spectroscopy》2000,89(2):216-224
The localization of molecular orbitals in 2,4,6-substituted derivatives of pyrylium is studied. The conformation of three asymmetrical molecules with oxyethyl substituents in positions 2 and 4 and different substituents in position 6 of the pyrylium ring is calculated by the AM1 method. The localization of the four upper occupied and two lower unoccupied MOs is determined, the fragment localization numbers are found, and the energies of five optical transitions, localization numbers, and the numbers of charge transfer between fragments are calculated. The conformation analysis of molecules in the S 0 and S 1 states is performed. Solid and liquid pyrylium solutions of different viscosity and polarity are experimentally investigated. The absorption spectra are recorded and absorption cross sections are measured, as well as fluorescence spectra and fluorescence anisotropy spectra. The following conclusions are made. In nonplanar molecules of pyrylium salts, four absorption transitions are localized at different parts of the molecule containing the pyrylium ring and one of the substituents. Upon excitation of molecules with complex substituents in position 6, the molecular fragment in position 2 turns around. This results in a flattening of the molecular fragment containing the pyrylium ring and substituents 2 and 6 on which the fluorescence transition is localized. The rearrangement involves the lowamplitude motion; it occurs almost without a loss of the excitation energy and only slightly affects the localization of molecular orbitals. As a result, two excited conformers are formed that possess close absorption and fluorescence properties. The radiative transitions in these conformers completely determine fluorescence of liquid solutions of any viscosity, including glycerol solutions. Strong solvatochromism is related to the nonplanar structure of stable pyrylium molecules, whereas the weak solvatochromism of liquid solutions is caused by localization of radiative transitions on a planar fragment of unstable fluorescing conformers. 相似文献
20.
A. Settimi S. Severini C. Sibilia M. Bertolotti A. Napoli A. Messina 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(3):379-391
The present paper discusses the stimulated emission, in strong coupling
regime, of an atom embedded inside a one dimensional (1D) Photonic Band Gap
(PBG) cavity which is pumped by two counter-propagating laser beams. Quantum
electrodynamics is applied to model the atom-field interaction, by
considering the atom as a two level system, the e.m. field as a
superposition of normal modes, the coupling in dipole approximation, and the
equations of motion in Wigner-Weisskopf and rotating wave approximations. In
addition, the Quasi Normal Mode (QNM) approach for an open cavity is adopted, interpreting the local density of states (LDOS)
as the local density of
probability to excite one QNM of the cavity; and therefore rendering this
LDOS dependent on the phase difference of the two laser beams. In this paper
we demonstrate that the strong coupling regime occurs at high values of the
LDOS. In accordance with the results of the literature, the emission
probability of the atom decays with an oscillatory behaviour, so that the
atomic emission spectrum exhibits two peaks (Rabi splitting). The novelty of
this work is that the phase difference of the two laser beams can produce a
coherent control of both the oscillations for the atomic emission
probability and, as a consequence, of the Rabi splitting in the emission
spectrum. Possible criteria to design active delay lines are finally
discussed. 相似文献