Continuous Atom Laser Research Articles

Space continuous atom laser in one dimension

Cold atom physics in space station arouses a lot of interest of scientists. We investigate the dynamical output process of the space continuous atom laser by solving nonlinear Gross–Pitaevksii equations numerically. Slow-moving continuous atom beams in two directions are observed simultaneously. The slow-moving coherent atom beams can be used as a source of atom interferometer to realize long-time measurements. We also control the output of space atom laser by adjusting the output coupling strength.

Steady-State Magneto-Optical Trap with 100-Fold Improved Phase-Space Density.

We demonstrate a continuously loaded ^{88}Sr magneto-optical trap (MOT) with a steady-state phase-space density of 1.3(2)×10^{-3}. This is 2 orders of magnitude higher than reported in previous steady-state MOTs. Our approach is to flow atoms through a series of spatially separated laser cooling stages before capturing them in a MOT operated on the 7.4-kHz linewidth Sr intercombination line using a hybrid slower+MOT configuration. We also demonstrate producing a Bose-Einstein condensate at the MOT location, despite the presence of laser cooling light on resonance with the 30-MHz linewidth transition used to initially slow atoms in a separate chamber. Our steady-state high phase-space density MOT is an excellent starting point for a continuous atom laser and dead-time free atom interferometers or clocks.

Laser Cooling to Quantum Degeneracy

We report on Bose-Einstein condensation in a gas of strontium atoms, using laser cooling as the only cooling mechanism. The condensate is formed within a sample that is continuously Doppler cooled to below 1 μK on a narrow-linewidth transition. The critical phase-space density for condensation is reached in a central region of the sample, in which atoms are rendered transparent for laser cooling photons. The density in this region is enhanced by an additional dipole trap potential. Thermal equilibrium between the gas in this central region and the surrounding laser cooled part of the cloud is established by elastic collisions. Condensates of up to 10(5) atoms can be repeatedly formed on a time scale of 100 ms, with prospects for the generation of a continuous atom laser.

Quantum kinetic theory model of a continuous atom laser

We investigate the feasible limits for realising a continuously evaporated atom laser with high-temperature sources. A plausible scheme for realising a truly continuous atom laser is to outcouple atoms from a partially condensed Bose gas, whilst continuously reloading the system with non-condensed thermal atoms and performing evaporative cooling. Here we use quantum kinetic theory to model this system and estimate feasible limits for the operation of such a scheme. For sufficiently high temperatures, the figure of merit for the source is shown to be the phase-space flux. The dominant process limiting the usage of sources with low phase-space flux is the three-body loss of the condensed gas. We conclude that certain double-magneto-optical trap (MOT) sources may produce substantial mean condensate numbers through continuous evaporation, and provide an atom laser source with a narrow linewidth and reasonable flux.

Continuous atom laser with Bose–Einstein condensates involving three-body interactions

We demonstrate, through numerical simulations, the emission of a coherent continuous matter wave of constant amplitude from a Bose–Einstein condensate in a shallow optical dipole trap. The process is achieved by spatial control of the variations of the scattering length along the trapping axis, including elastic three-body interactions due to dipole interactions. In our approach, the outcoupling mechanism is atomic interactions, and thus, the trap remains unaltered. We calculate analytically the parameters for the experimental implementation of this continuous wave atom laser.

A pumped atom laser

The experimental demonstration of a continuous and irreversible transfer of cold atoms from a ‘source mode’ to a ‘laser mode’ represents a step closer to a fully continuous atom laser.

High Field Seeking State Atom Laser and Properties of Flux

We present an experimental study on the continuous atom laser. The experiments show that a high field seeking state atom laser with stable flux can be formed by increasing the strength of outcoupling before large density fluctuations appear. It is easy to obtain a long length or high speed output with this kind of atom laser.

Multibeam atom laser: Coherent atom beam splitting from a single far-detuned laser

We report the experimental realization of a multibeam atom laser. A single continuous atom laser is outcoupled from a Bose-Einstein condensate via an optical Raman transition. The atom laser is subsequently split into up to five atomic beams with slightly different momenta, resulting in multiple, nearly copropagating, coherent beams which could be of use in interferometric experiments. The splitting process itself is a realization of Bragg diffraction, driven by each of the optical Raman laser beams independently. This presents a significantly simpler implementation of an atomic beam splitter, one of the main elements of coherent atom optics.

Non-Markovian dynamics in atom-laser outcoupling from a double-well Bose–Einstein condensate

We investigate the dynamics of a continuous atom laser based on the merging of independently formed atomic condensates. In a first attempt to understand the dynamics of the system, we consider two independent elongated Bose–Einstein condensates which approach each other and focus on intermediate inter-trap distances so that a two-mode model is well justified. In the framework of a mean-field theory, we discuss the quasi-steady-state population of the traps as well as the energy distribution of the outcoupled atoms.

Transport of atom packets in a train of Ioffe-Pritchard traps

We demonstrate transport and evaporative cooling of several atomic clouds in a chain of magnetic Ioffe-Pritchard traps moving at a low speed $(<1\phantom{\rule{0.3em}{0ex}}\mathrm{m}∕\mathrm{s})$. The trapping scheme relies on the use of a magnetic guide for transverse confinement and of magnets fixed on a conveyor belt for longitudinal trapping. This experiment introduces a different approach for parallelizing the production of Bose-Einstein condensates as well as for the realization of a continuous atom laser.

Achieving Peak Brightness in an Atom Laser

In this Letter we present experimental results and a simple analytic theory on the first continuous (long pulse) Raman atom laser. We analyze the flux and brightness of a generic two state atom laser with an analytic model that shows excellent agreement with our experiments. We show that, for the same source size, the brightness achievable with a Raman atom laser is at least 3 orders of magnitude greater than achievable in any other demonstrated continuously outcoupled atom laser.

Limits to the flux of a continuous atom laser

We present experimental results demonstrating that the flux of a continuous atom laser beam cannot be arbitrarily increased by increasing the strength of output coupling. We find that the continuous atom laser has large density fluctuations when the Rabi frequency becomes greater than the radial trapping frequency, due to the output coupling populating all accessible Zeeman states. In addition, we find that a state-changing output coupler for a continuous atom laser switches off as the output-coupling strength, parametrized in general by the Rabi frequency, is increased above a critical value. The numerical solution of a one-dimensional five-state Gross-Pitaevskii model for the atom laser is in good qualitative agreement with the experiment.

Adiabatic and nonadiabatic merging of independent Bose-Einstein condensates

Motivated by a recent experiment [Chikkatur et al., Science, 296, 2193 (2002)] on the merging of atomic condensates, we investigate how two independent condensates with random initial phases can develop a unique relative phase when we move them together. In the adiabatic limit, the uniting of independent condensates can be understood from the eigenstate evolution of the governing Hamiltonian, which maps degenerate states (corresponding to fragmented condensates) to a single state (corresponding to a united condensate). In the nonadiabatic limit corresponding to the practical experimental configurations, we give an explanation on why we can still obtain a large condensate fraction with a unique relative phase. Detailed numerical simulations are then performed for the nonadiabatic merging of the condensates, which confirm our explanation and qualitative estimation. The results may have interesting implications for realizing a continuous atom laser based on the merging of condensates.

Technique of quantum-state transfer for a double-Λatomic beam

We theoretically examine the quantum-state transfer process from light to a continuous atom laser by extending the original Fleischhauer-Gong scheme [M. Fleischhauer and S. Gong, 88, 070404 (2002)] to a double-$\ensuremath{\Lambda}$ atomic system. We find that the intensity of the output matter waves is controlled by the relative phase of two coherent probe lights, which may provide an interesting method for the measurement of the initial relative phase of two independent light sources.

Solitonic transmission of Bose-Einstein matter waves

We consider a continuous atom laser propagating through a wave guide with a constriction. Two different types of transmitted stationary flow coexist. The first one coincides, at low incident current, with the non-interacting flow. As the incident flux increases, the repulsive interactions decrease the corresponding transmission coefficient. The second type only occurs for sufficiently large incident currents and has a solitonic structure. Remarkably, for any chemical potential there always exists a value of the incident flux at which the solitonic flow is perfectly transmitted.

A continuous source of Bose-Einstein condensed atoms.

A continuous source of Bose-Einstein condensed sodium atoms was created by periodically replenishing a condensate held in an optical dipole trap with new condensates delivered using optical tweezers. The source contained more than 1 x 10(6) atoms at all times, raising the possibility of realizing a continuous atom laser.

Continuous optical loading of a Bose-Einstein condensate

The continuous pumping of atoms into a Bose-Einstein condensate via spontaneous emission from a thermal reservoir is analyzed. We consider the case of atoms with a three-level $\Lambda$ scheme, in which one of the atomic transitions has a very much shorter life-time than the other one. We found that in such scenario the photon reabsorption in dense clouds can be considered negligible. If in addition inelastic processes can be neglected, we find that optical pumping can be used to continuously load and refill Bose-Einstein condensates, i.e. provides a possible way to achieve a continuous atom laser.

Reducing the linewidth of an atom laser by feedback.

A continuous atom laser will almost certainly have a linewidth dominated by the effect of the atomic interaction energy, which turns fluctuations in the condensate atom number into fluctuations in the condensate frequency. These correlated fluctuations mean that information about the atom number could be used to reduce the frequency fluctuations, by controlling a spatially uniform potential. We show that feedback based on a physically reasonable quantum nondemolition measurement of the atom number of the condensate in situ can reduce the linewidth enormously.

Coherence properties of a continuous atom laser

Coherence properties of a continuous atom laser

Coherence properties of a continuous atom laser

We investigate the coherence properties of an atomic beam evaporatively cooled in a magnetic guide, assuming thermal equilibrium in the quantum degenerate regime. The gas experiences two-dimensional, transverse Bose-Einstein condensation rather than a full three-dimensional condensation because of the very elongated geometry of the magnetic guide. First order and second order correlation functions of the atomic field are used to characterize the coherence properties of the gas along the axis of the guide. The coherence length of the gas is found to be much larger than the thermal de Broglie wavelength in the strongly quantum degenerate regime. Large intensity fluctuations present in the ideal Bose gas model are found to be strongly reduced by repulsive atomic interactions; this conclusion is obtained with a one-dimensional classical field approximation valid when the temperature of the gas is much higher than its chemical potential, k B T » |μ|.