We have developed a method to image a beam of neutral atoms (chiefly usable for alkalis) that is essentially an extension to two dimensions of the usual hot wire method of detection. The beam of neutral atoms first passes through a a highly transparent, positively charged grid and then impinges on a heated grid of electroformed nickel with lower transparency and at ground potential. Atoms with ionization potential less than the work function of Ni that strike the heated grid are ionized at its surface and are then pushed through it by the 250-V/cm field produced by the voltage on the first grid. The ions are then accelerated through ~700 V to a pair of multichannel plates (MCPs) ~3 mm away where the single charged ion signal is amplified. The output electrons from the MCPs are accelerated by 1.7 kV to a phosphor screen ~3 mm away that glows when the electrons strike it. The phosphor screen is viewed by a TV camera whose output goes to a frame processor in a PC. The system has been used for studying transverse laser cooling (optical collimation) of a Rb beam done with diode lasers.
We have developed a method to image a beam of neutral atoms (chiefly usable for alkalis) that is essentially an extension to two dimensions of the usual hot wire method of detection. The beam of neutral atoms first passes through a a highly transparent, positively charged grid and then impinges on a heated grid of electroformed nickel with lower transparency and at ground potential. Atoms with ionization potential less than the work function of Ni that strike the heated grid are ionized at its surface and are then pushed through it by the 250-V/cm field produced by the voltage on the first grid. The ions are then accelerated through ~700 V to a pair of multichannel plates (MCPs) ~3 mm away where the single charged ion signal is amplified. The output electrons from the MCPs are accelerated by 1.7 kV to a phosphor screen ~3 mm away that glows when the electrons strike it. The phosphor screen is viewed by a TV camera whose output goes to a frame processor in a PC. The system has been used for studying transverse laser cooling (optical collimation) of a Rb beam done with diode lasers.
We have discovered a new cooling process that uses an applied magnetic field to mix differentially light shifted atomic ground state sublevels. In related experiments cooling is achieved by mixing caused by polarization gradients. Because the energy loss mechanism stems from the light shift and not the momentum transfer of a scattering event, the accessible temperature is much lower than the limit of Doppler cooling. We used this method for optical collimation of an 85Rb atomic beam to a transverse rms speed of 3 cm/s, well below the v = ( 7 ℏ γ / 20 M ) ≅ 10 cm / s of the Doppler limit for two-level atoms in this 1-D optical molasses. This low velocity, limited only by experimental geometry, is achieved only when a magnetic field of ~20 µT is applied perpendicular to the axis of the circularly polarized diode laser beam. We use a thermal beam of natural Rb produced by an oven at T ~ 150°C with an ~0.33-mm diam aperture and a defining aperture of ~0.33-mm diam about 24 cm away. The atoms are optically collimated by laser beams transverse to their motion that excite the transition at λ = 780 nm. The atomic beam profile is measured with a vertically oriented scanning hot tungsten wire, 25 µm in diameter, 1.3 m away.
In the field of atom optics, there has been much interests in developing components such as lenses, mirrors, beam splitters and waveguides to manipulate neutral atoms. Especially many clever methods to focus neutral atoms have been developed. The lenses have been constructed using the static electrical and magnetic fields, Fresnel zone plates, and radiation pressure forces. Before the laser cooling and trapping techniques were invented, the electrostatic fields could not be used for manipulating neutral atoms because of its weak interaction energy with atoms. After the cold atoms were available, it has been possible to manipulate atoms with weak electrostatic interaction energy. We developed an atom lens system using electrostatic fields.
This dissertation presents progress on an atomic beam brightening and focusing experiment that has been shown to create a beam with higher brightness and greater resolution than that of any previous atomic focusing experiment. Our method of beam brightening relies upon using a permanent magnetic hexapole as a lens in conjunction with transverse laser cooling to focus and collimate a supersonic beam of metastable neon atoms. We then use an adjustable electromagnetic hexapole as a lens to focus the brightened atomic beam. Neutral atom beams have long been used as a tool to spectroscopically probe two dimensional surfaces, however the lack of a means to create bright, high-resolution neutral atom beams has limited their utility as a nanoscale resolution probing mechanism. While optical and electron microscopy have been the workhorses of microscopy for decades, we believe that our scheme for beam brightening and focusing will unleash the promise of neutral atom microscopy. Our scheme of beam brightening and focusing can be repeated in series and reveals a pathway to true high density nanoscale neutral atom focusing. Simulations suggest that when combined with aberration correction, our scheme will be able to produce an atomic beam with sufficient brightness and resolution to be useful as a surface sensitive nanoscale probe.
We study a photoionization method to detect and image a narrow beam of cold atoms traveling along a high-gradient two-wire magnetic guide that is continuously on. Ions are accelerated in a compact acceleration region, directed through a drift region several centimeters in length, and detected using a position-sensitive ion detector. The potentials of several electrodes can be varied to adjust the imaging properties. Using ion trajectory simulations as well as experiments, we study the passage of the ions through the detection system, the magnification of the detection system, and the time-of-flight characteristics.
Neutral atoms trapped in optical lattices are promising candidates for quantum information processing and quantum simulation. Over the last decades, elegant tools for the manipulation of the internal and external states of optically trapped atoms have been developed. The crucial capability of scalable internal state readout in these systems, however, still relies on destructive methods. In spite of the important role of near-resonant illumination for the manipulation and detection of atoms in the lattice, there also exists a significant lack of studies on the heating and cooling dynamics of optically trapped atoms interacting with near-resonant light. An in-depth understanding of the heating and cooling processes is essential to finding the conditions of illumination that enable the non-destructive internal state readout of multiple atoms. This work presents an experimental system to cool, trap, manipulate, and detect the internal and external states of a small ensemble of 87Rb neutral atoms trapped in a one-dimensional optical lattice. A high photon detection efficiency in our experimental system allows for fast fluorescence imaging with acquisition times of 20 ms and fast position determination of atoms in the optical lattice with an accuracy of ∼ 40 nm. Using this experimental system, we investigate the heating dynamics of a neutral atom trapped in a standing wave dipole trap illuminated by a single near-resonant laser beam. A theoretical description to describe our measurements is provided in two experimentally relevant regimes. First, we consider the case of a weak near-resonant beam and later the case of off-resonant illumination. From this analysis, we find settings for the illumination light which allows an atom to scatter many photons before it is expelled from the trap. Building on these results we demonstrate simultaneous, non-destructive determination of the internal state of spatially resolved atoms trapped in a one-dimensional optical lattice with a fidelity of 98.6 ± 0.2% and a survival probability of 99.0 ± 0.2%. During the readout process, less than 2% of the atoms change their initial ground state. In order to determine the state of atoms that are not spatially resolved, a novel image analysis technique is presented. The technique uses Bayesian methods, which include the statistics of the detected photons as well as the response from the EMCCD camera. The Bayesian method is implemented on experimental data for atoms trapped in a one-dimensional optical lattice and its accuracy is tested by numerical simulations. In addition, an extension of this algorithm for atoms trapped in two-dimensional lattices is provided. Finally, the non-destructive state detection method is utilized as a tool for the state determination following the coherent control of the internal and external states of atoms in the optical trap. Here Raman sideband cooling is implemented and utilized in an atomic compression sequence for the creation of a small and dense atomic ensemble. These techniques will play an important role in experiments studying the collective light interaction of the atomic ensemble in a recently added optical fiber cavity.
A laser-cooled neutral-atom beam from a low-velocity intense source is split into two beams while it is guided by a magnetic-field potential. We generate our multimode beam-splitter potential with two current-carrying wires upon a glass substrate combined with an external transverse bias field. The atoms are guided around curves and a beam-splitter region within a 10-cm guide length. We achieve a maximum integrated flux of 1.5x10(5)atoms/s with a current density of 5x10(4)amp/cm (2) in the 100-microm -diameter wires. The initial beam can be split into two beams with a 50/50 splitting ratio.