Atomic Funnel Research Articles

A novel all-optical surface atomic (molecular) funnel

We propose a novel scheme to build an all-optical surface atomic (or molecular) funnel using an optical system consisting of three cylindrical lenses, which can be used to produce a funnel-shaped intensity distribution near the focal plane of the last lens when the optical system is illuminated by a red-detuned Gaussian laser beam. We calculate the corresponding intensity distribution, the optical dipole potential and its dipole force for 23Na atoms. Our study shows that the proposed atom (or molecular) funnel can be used for the efficient loading of cold atoms in the surface optical guid, beam splitter and interferometer and surface microtrap, and so on. So our funnel has important applications in the integrated atom optics and its atom chip.

Atomic nanofabrication by laser manipulation of a neutral cesium beam

In this work, we report on the results of a nanolithography experiment with a cold cesium beam. We have realized a brilliant and collimated cesium beam with a low longitudinal velocity (10 m/s) exploiting laser cooling techniques, in particular a pyramidal atomic funnel. The cesium atomic beam has been utilized to pattern gold substrates, using Self Assembled Monolayers (SAM) of thiols as resist, and a wet etching process. The pattern generated by a light mask, a one-dimensional standing e.m. wave, was characterized by diffraction and Atomic Force Microscopy (AFM) measurements, showing the presence of lines spaced half the wavelength of the standing wave (426 nm) with lateral size well below 100 nm.

Atomic Funnel Composed of an HE11-Mode Output HollowBeam

Using exact solutions of Maxwell equations based on the vector model,we calculate the diffracted near- and far-field distributions of theHE11-mode output beam from a micron-sized hollow optical fibreunder the Fresnel approximation, and compare the differences betweenthe HE11- and LP01-mode output beams. Our study showsthat it is unsuitable to calculate the diffracted near-fielddistribution of the hollow fibre by using weakly waveguidingapproximation, and the near- and far-field intensity distributions ofthe HE11-mode output beam are doughnut-like, which can be usedto form a simple atomic funnel as it is blue-detuned.

Diffracted field distributions from the HE11mode in a hollow optical fibre for an atomic funnel

The diffracted near field distribution from an LP01 mode in a hollow optical fibre was recently calculated using a scalar model based on the weakly waveguiding approximation (Yoo et al 1999 J. Opt. B: Quantum Semiclass. Opt. 1 364). It showed a dominant Gaussian-like distribution with an increased axial intensity in the central region (not a doughnut-like distribution), so the diffracted output beam from the hollow fibre cannot be used to form an atomic funnel. Using exact solutions of the Maxwell equations based on a vector model, however, we calculate the electric field and intensity distributions of the HE11 mode in the same hollow fibre and study the diffracted near-?and far-field distributions of the HE11-mode output beam under the Fresnel approximation. We analyse and compare the differences between the output beams from the HE11 and LP01 modes. Our study shows that both the near-?and far-field intensity distributions of the HE11-mode output beam are doughnut-like and can be used to form a simple atomic funnel. However, it is not suitable to use the weakly waveguiding approximation to calculate the diffracted near-field distribution of the hollow fibre due to the greater refractive-index difference between the hollow region (n0 = 1) and the core (n1 = 1.45 or 1.5). Finally, the 3D intensity distribution of the HE11-mode output beam is modelled and the corresponding optical potentials for cold atoms are calculated. Some potential applications of the HE11-mode output beam in an atomic guide and funnel are briefly discussed.

Magnetic guiding of cold neutral atoms using a V-shaped current-carrying conductor

A new scheme to magnetically guide cold, neutral atoms using a V-shaped current-carrying conductor is proposed. The spatial distributions of the magnetic fields, potentials and forces generated by the V-shaped current-carrying conductor are calculated, and the relationship between the magnetic field and the parameters of the V-shaped current-carrying conductor are analyzed in detail. Our study shows that the V-shaped current-carrying conductor proposed here can be used to guide cold atoms in the weak-field-seeking state, and to construct various atom-optical elements, such as atomic funnel, atomic beam-splitter and atom interferometer and so on, and even to realize a single-mode atomic waveguiding under certain conditions.

A cold cesium atomic beam produced out of a pyramidal funnel

We have built an atomic funnel which produces a slow and cold cesium atomic beam. The atomic funnel is based on a pyramidal Magneto Optical Trap (MOT) with a small hole at its apex. Characterization of the funnel operation has been carried out by fluorescence emission and absorption spectroscopy, and optical time of flight (TOF) methods. The atomic beam has a longitudinal velocity in the range 8–12 m/s and a spread less than 1.5 m/s. The transverse temperature is close to the Doppler limit. Typically, an atom flux ∼4×10 9 atoms/ s is attained. These features, combined with the compactness and simplicity of the experimental arrangement, make this system an ideal source for experiments in atom lithography and atom optics.

Magnetic Guide and Trap for Cold Neutral Atoms with Current‐Carrying Wires and Conductors

AbstractWe propose two novel schemes for guiding cold, neutral atoms using static magnetic fields generated by several cylindrical arrays of current‐carrying wires or a few different‐shaped (V‐, or U‐shaped, etc.) current‐carrying conductors, and calculate the corresponding magnetic‐field contours and their trapping potentials. Our study shows that some guiding schemes can be used to form an atomic funnel, or an atomic beam‐splitter, or even construct an atomic interferometer, and some guiding schemes can be used to realize a single‐mode wave guide of ultracold atoms (or coherent matter waves, BEC) under certain conditions. We also propose a few new schemes to microscopically trap neutral atoms by using various planar arrays of current‐carrying wires and calculate the spatial distribution of the magnetic fields. Our research shows that these microtrap arrays can be used to form 1D, 2D or 3D atomic magnetic lattices, and then to prepare 1D, 2D or 3D photonic crystals, even to realize a 1D, 2D or 3D array of magnetically‐trapped BECs or Bose Clusters.

Cold atomic beam from a rubidium funnel

We report an experimental demonstration of a continuous, slow and cold beam of rubidium atoms from a two-dimensional magneto-optic trap or atomic funnel. Typically 7.3(7)×108 atoms/s are ejected from the funnel with a variable velocity in the range 2–8 m/s and a temperature of 45–55 μK in the moving frame. This represents the first demonstration of sub-Doppler laser cooling in an atomic beam and temperatures as low as ≈25 μK have been observed.

Diffracted near field of hollow optical fibre for a novel atomic funnel

The diffracted field of a hollow-core optical fibre is studied and it is shown how the near field of a guided mode develops into the far field. We then describe our method of producing a diffracted output in the shape of a diverging dark hollow beam with a minimum dark spot of a few µm, which is comparable to the hollow-core diameter, by superposing two LP11 modes which have node lines and polarizations orthogonal to each other. Its possible application to an efficient, novel atomic funnel which guides cold atoms into the hollow fibre is also discussed.

Erratum: Evanescent light-wave atomic funnel: A tandem hollow-fiber, hollow-beam approach [Phys. Rev. A57, 1957 (1998)

Erratum: Evanescent light-wave atomic funnel: A tandem hollow-fiber, hollow-beam approach [Phys. Rev. A<b>57</b>, 1957 (1998)

Erratum: Evanescent light-wave atomic funnel: A tandem hollow-fiber, hollow-beam approach [Phys. Rev. A57, 1957 (1998)

Erratum: Evanescent light-wave atomic funnel: A tandem hollow-fiber, hollow-beam approach [Phys. Rev. A<b>57</b>, 1957 (1998)

Evanescent light-wave atomic funnel: A tandem hollow-fiber, hollow-beam approach

We propose an atomic funnel consisting of a dark hollow, divergent laser beam and an evanescent light in a short micron-sized hollow optical fiber. The cold atoms extracted from a magneto-optical trap experience effective Sisyphus cooling in the dark hollow beam. We calculate the potential barriers for atomic guiding in the evanescent light and the dark hollow beam, and analyze the atomic losses during the guiding and funneling process. Our results show that the equilibrium three-dimensional root-mean-square momentum of about $4.5\ensuremath{\Elzxh}k$ (temperature $\ensuremath{\sim}2.5\ensuremath{\mu}\mathrm{K}$) and the funneling efficiency of about 95% could be obtained. A low-velocity, intense coherent atomic beam can be generated in this funnel scheme and its potential applications in atom optics are briefly discussed.

Low-velocity elastic scattering of Rb-Rb

With reference to recent progress in preparing slow and intense Rb beams ({ital rubidium atomic funnel} and {ital low-velocity intense source of atoms from a magneto-optical trap}) we have calculated total and differential elastic scattering cross sections and scattering lengths for ground-state collisions of {sup 85}Rb as well as {sup 87}Rb. Our results are based on the state of the art X{sup 1}{Sigma}{sub g}{sup +} and athinsp{sup 3}{Sigma}{sub u}{sup +} potentials. Pronounced resonances in the total scattering cross sections occur for collision velocities below 15 m/s. We propose scattering experiments with slow Rb beams in order to check the currently known singlet and triplet potential-energy curves. {copyright} {ital 1997} {ital The American Physical Society}

Atomic funnel with evanescent light

We propose an atomic funnel composed of an evanescent-light mirror produced in a conical hollow prism. The funneling of cold Rb atoms released from a magneto-optical trap is simulated in the scheme of the evanescent-light-induced Sisyphus cooling for compensating the heating by gravity. A geometric method of the conversion of a Gaussian light beam into a doughnut-shaped light beam suitable for the atomic funnel is also experimentally demonstrated by means of a double-cone prism. Under the assumption of a proper optical intensity distribution over the inner surface of a specific conical hollow prism, the Monte Carlo simulation including the van der Waals interaction shows that a half of the released Rb atoms can be collected and the mean temperature of the collected atoms is low enough for the application to be guided with a bent hollow optical fiber.

Temperatures near the recoil limit in an atomic funnel

We report on an improved atomic funnel with transverse velocities near the recoil limit. Its central element is an atomic funnel, strongly tilted against the initial atomic beam axis, deflecting, compressing and cooling a laser decelerated metastable neon beam. In spite of a strong magnetic field gradient at 350 G/cm polarisation gradient cooling in the final section of the funnel leads to transverse temperatures far below the Doppler limit. These results were achieved for unusual small laser detunings, which cannot be explained by standard sub-Doppler theory.

Rubidium atomic funnel

A low-velocity beam of rubidium atoms is produced from a two-dimensional magneto-optic trap or atomic funnel. Atoms from a thermal beam are slowed by chirped laser cooling and then loaded into the funnel. The cold atoms are ejected by moving molasses formed with frequency-shifted laser beams. The resultant atomic beam has a controllable velocity in the range of 3 to 10 m/s, a temperature of 500 µK, and a flux of 1010 atoms/s.

Funnel with orientated Cs atoms

The compression of caesium in an atomic funnel is dominated by the transient regime in which the trapping force is strongly dependent on the initial atomic state. We increased the efficiency by Zeeman pumping or initially orientating the atoms with the local magnetic field. The compressed atomic beam was 200 μm in diameter with a density of 3×10 9 atoms cm -3.

Magneto-optical preparation of a slow, cold and bright Ne ∗ atomic beam

An efficient experimental scheme for the generation of a monochromatic, slow and bright atomic beam is reported. It combines the good efficiency of a Zeeman-slower for medium slow final velocities with an optimized atomic funnel design. The two severe problems of a Zeeman-slower, as there is the high final divergence and the vanishing efficiency for very low final velocities, are overcome. The total efficiency in flux of the complete device has been measured to more than 10% of the thermal atomic beam. Using a beam of metastable neon atoms (Ne ∗) a beam with a transverse velocity spread of σ x < 0.34 m/s and a mean longitudinal velocity of 19 m/s with a spread of σ v < 1.5 m/s is prepared. By this preparation technique a purely metastable atomic beam is obtained, all Ne atoms in the 3s[3/2] 2-state.