We calculate the spectrum of a beam of atoms output from a single mode atomic cavity. The output coupling uses an internal state change to an untrapped state. We present an analytical solution for the output energy spectrum from a broadband coupler of this type. An example of such an output coupler, which we discuss in detail uses a Raman transition to produce a non-trapped state.
We have observed the intensity fluctuations of the F=2 87Rb atom laser at low output coupling rate. Theoretically, we find that the atom loss of the condensate due to the output of atom laser leads to fluctuations of the laser pulses, which is inherent in all state changing out-coupling such as rf and Raman. Another reason leading to large fluctuations is the interference of output pulses.
We investigated the two-dimensional electron momentum distributions of atomic negative ions in an intense laser field by solving the time-dependent Schrodinger equation (TDSE) and using the first- and 2nd-order strong-field approximations (SFA). We showed that photoelectron energy distributions and low-energy photoelectron momentum spectra predicted from SFA are in reasonable agreement with the solutions from the TDSE. More importantly, we showed that accurate electron-atom elastic scattering cross sections can be retrieved directly from high-energy electron momentum spectra of atomic negative…
We propose a scheme based on a heterodyne laser link that allows for long baseline gravitational wave detection using atom interferometry. While the baseline length in previous atom-based proposals is constrained by the need for a reference laser to remain collimated as it propagates between two satellites, here we circumvent this requirement by employing a strong local oscillator laser near each atom ensemble that is phase locked to the reference laser beam. Longer baselines offer a number of potential advantages, including enhanced sensitivity, simplified atom optics, and reduced atomic sour…
We present a theoretical analysis of high-order harmonic generation from ion-atom collisions in the presence of linearly polarized intense laser pulses. Photons with frequencies significantly higher than in standard atomic high-harmonic generation are emitted. These harmonics are due to two different mechanisms: (i) collisional electron capture and subsequent laser-driven transfer of an electron between projectile and target atom; (ii) reflection of a laser-driven electron from the projectile leading to recombination at the parent atom.
We report 2D confinement of Rb 87 atoms in a Laguerre-Gaussian laser beam. Changing of the sign of the detuning from the atomic resonance dramatically alters the geometry of the confinement. With the laser detuned to the blue, the atoms are confined to the dark, central node of the Laguerre-Gaussian laser mode. This trapping method leads to low ac Stark shifts to the atomic levels. Alternatively, by detuning the laser to the red of the resonance, we confine atoms to the high intensity outer ring in a multiply-connected, toroidal configuration. We model the confined atoms to determine azimuthal…
We propose a new laser cooling method for atomic species whose level structure makes traditional laser cooling difficult. For instance, laser cooling of hydrogen requires single-frequency vacuum-ultraviolet light, while multielectron atoms need single-frequency light at many widely separated frequencies. These restrictions can be eased by laser cooling on two-photon transitions with ultrafast pulse trains. Laser cooling of hydrogen, antihydrogen, and many other species appears feasible, and extension of the technique to molecules may be possible.
A compact and robust laser system for atom interferometry based on a frequency-doubled telecom laser is presented. Thanks to an original stabilization architecture on a saturated absorption setup, we obtain a frequency-agile laser system allowing fast tuning of the laser frequency over 1 GHz in few ms using a single laser source. The different laser frequencies used for atom interferometry are generated by changing dynamically the frequency of the laser and by creating sidebands using a phase modulator. A laser system for Rubidium 87 atom interferometry using only one laser source based on a f…
Based on the Rb$^+$-Rb hybrid trap, we investigate the effect of ion-atom elastic collisions on the number and temperature of the remaining atoms. We measured the remaining atomic number and temperature as a function of the wavelength and intensity of the ionization laser, and whether the ion trap was turned on. Fittings with a single exponential decay function plus an offset to the number and radius of the remaining atoms are found to be in good agreement. We found a difference in the exponential factor of different wavelengths of ionization laser with the ion trap on or off. We suppose that …
We present here a simple laser system for a laser cooled atom interferometer, where all functions (laser cooling, interferometry and detection) are realized using only two extended cavity laser diodes, amplified by a common tapered amplifier. One laser is locked by frequency modulation transfer spectroscopy, the other being phase locked with an offset frequency determined by an Field-Programmable Gate Array (FPGA) controlled Direct Digital Synthesizer (DDS), which allows for efficient and versatile tuning of the laser frequency. Raman lasers are obtained with a double pass acousto-optic modula…
In atom interferometers based on two photon transitions, the delay induced by the difference of the laser beams paths makes the interferometer sensitive to the fluctuations of the frequency of the lasers. We first study, in the general case, how the laser frequency noise affects the performance of the interferometer measurement. Our calculations are compared with the measurements performed on our cold atom gravimeter based on stimulated Raman transitions. We finally extend this study to the case of cold atom gradiometers.
We describe an optical bench in which we lock the relative frequencies or phases of a set of three lasers in order to use them in a cold atoms interferometry experiment. As a new feature, the same two lasers serve alternately to cool atoms and to realize the atomic interferometer. This requires a fast change of the optical frequencies over a few GHz. The number of required independent laser sources is then only 3, which enables the construction of the whole laser system on a single transportable optical bench. Recent results obtained with this optical setup are also presented.
The parity of atomic wave functions prevents neutral atoms from having permanent electric-dipole moment. Electric-dipole moment is induced in an atom when exposed to strong light, the electric field of the light. Hence the optical trapping of neutral atoms relies on the induced dipole moment. Here we present the calculated numerical values of the detuning, potential depth, minimum laser power required to trap $^{87}$Rb ($D_2$ line) atoms using lasers of wavelength 1064 nm, 850 nm, 820 nm and 800 nm and beam waists 50$μ$m, 100$μ$m and 200$μ$m.
We present a novel and simple method of stabilizing the laser phase and frequency by polarization spectroscopy of an atomic vapor. In analogy to the Pound-Drever-Hall method, which uses a cavity as a memory of the laser phase, this method uses atomic coherence (dipole oscillations) as a phase memory of the transmitting laser field. A preliminary experiment using a distributed feedback laser diode and a rubidium vapor cell demonstrates a shot-noise-limited laser linewidth reduction (from 2 MHz to 20 kHz). This method would improve the performance of gas-cell-based optical atomic clocks and magn…
We observe bimodal fluorescence patterns from atoms in a fast atomic beam when the laser excitation occurs in the presence of a magnetic field and the atoms sample only a portion of the laser profile. The behavior is well explained by competition between the local intensity of the laser, which tends to generate a coherent-population-trapping (CPT) dark state in the $J=1$ to $J'=0$ system, and the strength of an applied magnetic field that can frustrate the CPT process. This work is relevant for understanding and optimizing the detection process for clocks or other coherent systems utilizing th…
We present the experimental realization of a pumped atom laser. We demonstrate the pumping through measurements of the source and laser-mode atom numbers, making a rate equation study of the pumping process.
We demonstrate a 1.4 W continuous wavelength (CW) laser at 243.1 nm. The radiation is generated through frequency quadrupling the output of a ytterbium-doped fiber amplifier system which produces $>$ 10 W of CW power at 972.5 nm. We demonstrate absolute frequency control by locking the laser to an optical frequency comb and exciting the 1S-2S transition in atomic hydrogen. This frequency-stabilized, high-power deep-UV laser should be of significant interest for precision spectroscopy of simple and exotic atoms, two-photon laser cooling of hydrogen, and Raman spectroscopy.
We present an innovative fiber laser system for both cesium and rubidium manipulation. The architecture is based on frequency conversion of two lasers at 1560 nm and 1878 nm. By taking advantage of existing fiber components at these wavelengths, we demonstrate an all fiber laser system delivering 350 mW at 780 nm for rubidium and 210 mW at 852 nm for cesium. This result highlights the promising nature of such laser system especially for Cs manipulation for which no fiber laser system has been reported. It offers new perspectives for the development of atomic instruments dedicated to onboard ap…
We consider electron-atom scattering in a circularly polarized laser field at sufficiently high electron energies, permitting to describe the scattering process by the first order Born approximation. Assuming the radiation field has sufficiently moderate intensities, the laser-dressing of the hydrogen target atom in its ground state will be treated in second order perturbation theory. Within this approximation scheme, it is shown that the nonlinear differential cross sections of free-free transitions do neither depend on the {\it dynamical phase} $ϕ$ of the radiative process nor on the {\it he…
Optical dipole traps and fractional Talbot optical lattices based on the interference between multiple co-propagating laser beams are proposed. The variation of relative amplitudes and phases of the interfering light beams of these traps makes it possible to manipulate the spatial position of trapped atoms. Examples of spatial translation and splitting of atoms between a set of the interference traps are considered. The prospect of constructing all-light atom chips based on the proposed technique is presented.
Using direct-write atom lithography, Fe nanolines are deposited with a pitch of 186 nm, a full width at half maximum (FWHM) of 50 nm, and a height of up to 6 nm. These values are achieved by relying on geometrical collimation of the atomic beam, thus without using laser collimation techniques. This opens the way for applying direct-write atom lithography to a wide variety of elements.
We present measurements of the velocity distribution of calcium atoms in an atomic beam generated using a dual-stage laser back-ablation apparatus. Distributions are measured using a velocity selective Doppler time-of-flight technique. They are Boltzmann-like with rms velocities corresponding to temperatures above the melting point for calcium. Contrary to a recent report in the literature, this method does not generate a sub-thermal atomic beam.
A new version of the R-matrix Floquet theory for laser-assisted electron-atom scattering is presented. The theory is non-perturbative and applicable to a non-relativistic many-electron atom or ion in a homogeneous linearly polarized field. It is based on the use of channel functions built from field-dressed target states, which greatly simplifies the general formalism.
A laser-cooled neutral-atom beam from a low-velocity intense source is split into two beams while guided by a magnetic-field potential. We generate our multimode-beamsplitter potential with two current-carrying wires on a glass substrate combined with an external transverse bias field. The atoms bend around several curves over a $10$-cm distance. A maximum integrated flux of $1.5\cdot10^{5} \mathrm{atoms/s}$ is achieved with a current density of $5\cdot10^{4} \mathrm{Ampere/cm^{2}}$ in the 100-$\mathrm{μm}$ diameter wires. The initial beam can be split into two beams with a 50/50 splitting rat…
We analyze the dynamics of atom-laser interactions for atoms having multiple, closely spaced, excited-state hyperfine manifolds. The system is treated fully quantum mechanically, including the atom's center-of-mass degree of freedom, and motion is described in a polarization gradient field created by a three-dimensional laser configuration. We develop the master equation describing this system, and then specialize it to the low-intensity limit by adiabatically eliminating the excited states. We show how this master equation can be simulated using the Monte Carlo wave function technique, and we…
High sensitivity differential atom interferometers are promising for precision measurements in science frontiers in space, including gravity field mapping for Earth science studies and gravitational wave detection. We propose a new configuration of twin atom interferometers connected by a laser ranging interferometer (LRI-AI) to provide precise information of the displacements between the two AI reference mirrors and a means to phase-lock the two independent interferometer lasers over long distances, thereby further enhancing the feasibility of long baseline differential atom interferometers. …
We demonstrate experimentally the generation of one-dimensional cold gases of $^{87}$Rb atoms by diffuse laser cooling (DLC). A horizontal slender vacuum glass tube with length of 105~cm and diameter of 2~cm is used in our experiment. The diffuse laser light inside the tube, which is generated by multi-reflection of injected lasers, cools the background vapor atoms. With 250~mW of cooling light and 50~mW of repumping light, an evenly distributed meter-long profile of atom cloud is obtained. We observe a factor 4 improvement on the atomic OD for a typical cooling duration of 170~ms and a sub-Do…
In the recent work of Vanne and Saenz [Phys. Rev. A 75, 063403 (2007)] the quasistatic limit of the velocity gauge strong-field approximation describing the ionization rate of atomic or molecular systems exposed to linearly polarized laser fields was derived. It was shown that in the low-frequency limit the ionization rate is proportional to the laser frequency (for a constant intensity of the laser field). In the present work I show that for circularly polarized laser fields the ionization rate is proportional to higher powers of the laser frequency for hydrogenic atoms. The new analytical ex…
We present the accurate measurement of the frequency of the $7S-7P$ laser-trapping transition for three francium isotopes. Our approach is based on an interferometric comparison to deduce the unknown laser frequency from a secondary laser frequency-standard. After careful investigation of systematics, with samples of about 100 atoms the final accuracy reaches 8 MHz, an order of magnitude better than the best previous measurement for $^{210}$Fr, and opens the way to improved tests of the theoretical computation of Fr atomic structure.
Various aspects of the phase dynamics of an atom laser scheme based on binary collisions are investigated. Analytical estimates of the influence of elastic atom-atom collisions on the laser linewidth are given, and linewidths achievable in a recently proposed atom laser scheme [Phys. Rev. A 56, 2989 (1997)] are evaluated explicitly. The extent to which a relative phase can be established between two interfering atom lasers, as well as the properties of that phase, are also investigated.
We deduce the coherent backscattering signal from two distant laser-driven atoms using single-atom equations. In contrast to the standard master equation treatment, this new approach is suitable for the generalization to a large number of atomic scatterers.
The use of Raman laser generated by modulation for light-pulse atom interferometer allows to have a laser system more compact and robust. However, the additional laser frequencies generated can perturb the atom interferometer. In this article, we present a precise calculation of the phase shift induced by the additional laser frequencies. The model is validated by comparison with experimental measurements on an atom gravimeter. The uncertainty of the phase shift determination limits the accuracy of our compact gravimeter at 8.10^-8 m/s^2. We show that it is possible to reduce considerably this…
Atom interferometry is the most successful technique for precision metrology. However, current interferometers using ultracold atoms allows one to probe the interference pattern only momentarily and has finite duty cycle, resulting in an aliasing effect and a low-bandwidth measurement -- also known as Dick effect. Interferometry with a continuous-wave atom laser shows promise in overcoming these limitations due a continuous monitoring of the interference pattern. In this work, we demonstrate a key step towards such an interferometry by demonstrating a diffraction of an `atom laser' in the Rama…
We measure the angular divergence of a quasi-continuous, rf-outcoupled, free-falling atom laser as a function of the outcoupling frequency. The data is compared to a Gaussian-beam model of laser propagation that generalizes the standard formalism of photonic lasers. Our treatment includes diffraction, magnetic lensing, and interaction between the atom laser and the condensate. We find that the dominant source of divergence is the condensate-laser interaction.
We have constructed a solid-state light source for experiments with laser cooled lithium atoms based on a Nd:YVO$_4$ ring laser with second-harmonic generation. Unidirectional lasing, an improved mode selection, and a high output power of the ring laser was achieved by weak coupling to an external cavity which contained the lossy elements required for single frequency operation. Continuous frequency tuning is accomplished by controlling two PZTs in the internal and the external cavities simultaneously. The light source has been utilized to trap and cool fermionic lithium atoms into the quantum…
The impact of a laser field on the process of photon radiation by an ultra-relativistic electron in an atomic field is investigated. The angular distribution and the spectrum of the radiated photon are derived. By means of the quasiclassical approximation, the obtained results are exact in the parameters of the laser field and the atomic field. It is shown that the impact of the laser field is significant even for fairly average values of the laser field parameters routinely achievable nowadays. Therefore, an experimental observation of the influence of the laser field on bremsstrahlung in the…
We demonstrate an atom laser using all-optical techniques. A Bose-Einstein condensate of rubidium atoms is created by direct evaporative cooling in a quasistatic dipole trap realized with a single, tightly focused CO$_{2}$-laser beam. An applied magnetic field gradient allows formation of the condensate in a field-insensitive $m_{F} = 0$ spin projection only, which suppresses fluctuations of the chemical potential from stray magnetic fields. A collimated and monoenergetic beam of atoms is extracted from the Bose-Einstein condensate by continuously lowering the dipole trapping potential in a co…
We discuss the role of light absorption by pairs of atoms (radiative collisions) in the context of a model for an atom laser. The model is applied to the case of VSCPT cooling of metastable triplet helium. We show that, because of radiative collisions, for positive detuning of the driving light fields from an atomic resonance the operating conditions for the atom laser can only be marginally met. It is shown that the system only behaves as an atom laser if a very efficient sub-Doppler precooling mechanism is operative. In the case of negative frequency detuning the requirements on this sub-Dop…
We study the propagation of a non-interacting atom laser distorted by the strong lensing effect of the Bose-Einstein Condensate (BEC) from which it is outcoupled. We observe a transverse structure containing caustics that vary with the density within the residing BEC. Using WKB approximation, Fresnel-Kirchhoff integral formalism and ABCD matrices, we are able to describe analytically the atom laser propagation. This allows us to characterize the quality of the non-ideal atom laser beam by a generalized M$^2$ factor defined in analogy to photon lasers. Finally we measure this quality factor for…
We experimentally investigate the generation of above-threshold harmonics completely from argon atoms on an excited state using mid-infrared femtosecond laser pulses. The highly nonlinear dependences of the observed signal on the pulse energy and polarization of the driver laser pulses indicate its non-perturbative characteristic.
The effect of collectivity on the loading of an atom laser via optical pumping is discussed. In our model, atoms in a beam are laser-excited and subsequently spontaneously decay into a trapping state. We consider the case of sufficiently high particle density in the beam such that the spontaneous emission is modified by the particle interaction. We show that the collective effects lead to a better population of the trapping state over a wide range of system parameters, and that the second order correlation function of the atoms can be controlled by the applied laser field.
We report on theoretical and numerical study of propagation of atomic beams crossing a detuned standing-wave laser beam in the geometric optics limit. The interplay between external and internal atomic degrees of freedom is used to manipulate the atomic motion along the optical axis by light. By adjusting the atom-laser detuning, we demonstrate how to focus, split and scatter atomic beams in a real experiment. The novel effect of chaotic scattering of atoms at a regular near-resonant standing wave is found numerically and explained qualitatively. Some applications of the effects found are disc…
Hyperfine and Zeeman Optical Pumping and Transverse Laser Cooling of a Thermal Atomic Beam of Dysprosium Using a Single 421 nm Laser
Johannes Gutenberg-Universität Mainz(约翰内斯·古腾堡美因茨大学);Helmholtz-Institut Mainz, GSI Helmholtzzentrum für Schwerionenforschung(亥姆霍兹美因茨研究所,GSI重离子研究中心);Department of Physics, Indian Institute of Technology Tirupati(蒂鲁帕蒂印度理工学院物理系);Korea National University of Education(韩国国立教育大学);Department of Physics, University of California, Berkeley(加州大学伯克利分校物理系)
We report on the generation of 500 mW of spectrally pure laser light at the 460.86 nm transition used for laser cooling of strontium atoms. To this end we inject a high power single mode laser diode with light from a stabilized extended cavity diode laser. To optimize and monitor the injection status and the spectral purity of the slave diode we developed a novel technique that uses a single passive optical element. A narrow band interference filter generates a suitable monitoring signal without any additional electronics for post processing of the data. Our method greatly simplifies the daily…
We describe measurements demonstrating laser cooling of an atomic gas by means of collisional redistribution of radiation. The experiment uses rubidium atoms in the presence of several hundred bar of argon buffer gas pressure. Frequent collisions in the dense gas transiently shift a far red detuned optical field into resonance, while spontaneous emission occurs close to the unperturbed atomic transition frequency. Evidence for the cooling is obtained both via thermographic imaging and via thermographic deflection spectroscopy. The cooled gas has a density above 10$^{21}$ atoms/cm$^3$, yielding…
We study the properties of an atom laser beam derived from a Bose-Einstein condensate using three different outcouplers, one based on multi-state radio frequency transitions and two others based on Raman transitions capable of imparting momentum to the beam. We first summarize the differences that arise in such systems, and how they may impact on the use of an atom laser in interferometry. Experimentally, we examine the formation of a bound state in all three outcouplers, a phenomenon which limits the atom laser flux, and find that a two-state Raman outcoupler is the preferred option for high …
We present a diagrammatic derivation of the coherent backscattering spectrum from two two-level atoms using the pump-probe approach, wherein the multiple scattering signal is deduced from single-atom responses, and provide a physical interpretation of the single-atom building blocks.
We present experimental and theoretical results showing the improved beam quality and reduced divergence of an atom laser produced by an optical Raman transition, compared to one produced by an RF transition. We show that Raman outcoupling can eliminate the diverging lens effect that the condensate has on the outcoupled atoms. This substantially improves the beam quality of the atom laser, and the improvement may be greater than a factor of ten for experiments with tight trapping potentials. We show that Raman outcoupling can produce atom lasers whose quality is only limited by the wavefunctio…
We report on the observation of interference of a series of atom lasers. A comb-like array of coherent atomic beams is generated by outcoupling atoms from distinct Bose-Einstein condensates confined in the independent sites of a mesoscopic optical lattice. The observed interference signal arises from the spatial beating of the overlapped atom laser beams, which is sampled over a vertical region corresponding to 2 ms of free fall time. The average relative de Broglie frequency of the atom lasers was measured.
A pulsed atom laser derived from a Bose-Einstein condensate is used to probe a second target condensate. The target condensate scatters the incident atom laser pulse. From the spatial distribution of scattered atoms, one can infer important properties of the target condensate and its interaction with the probe pulse. As an example, we measure the s-wave scattering length that, in low energy collisions, describes the interaction between the |F=1,m_F=-1> and |F=2,m_F=0> hyperfine ground states in 87Rb.
Pulsed lasers offer significant advantages over CW lasers in the coherent control of qubits. Here we review the theoretical and experimental aspects of controlling the internal and external states of individual trapped atoms with pulse trains. Two distinct regimes of laser intensity are identified. When the pulses are sufficiently weak that the Rabi frequency $Ω$ is much smaller than the trap frequency $\otrap$, sideband transitions can be addressed and atom-atom entanglement can be accomplished in much the same way as with CW lasers. By contrast, if the pulses are very strong ($Ω\gg \otrap$),…
We present a new method of external-cavity diode laser grating stabilization which combines the high output power of the Littrow design with the fixed output pointing of the Littman-Metcalf design. Our new approach utilizes a Faraday-effect optical isolator inside the external cavity. Experimental testing and a model which describes the tuning range and optimal tuning parameters of the laser are described. Preliminary testing of this design has resulted in a short-term linewidth of 360 kHz and a side-mode suppression of 37 dB. The laser tunes mode-hop free over 7 GHz and we predict that much l…
In this paper, Bohmian mechanics is introduced to the intense laser-atom physics. The motion of atomic electron in intense laser field is obtained from the Bohm-Newton equation. We find the quantum potential that dominates the quantum effect of a physical system becomes negligible as the electron is driven far away from the parent ion by the intense laser field, i.e. the behavior of the electron smoothly trends to be classical soon after the electron was ionized. Our numerical calculations present a direct positive evidence for the semiclassical trajectory methods in the intense laser-atom phy…
We study Bessel beams of two-level atoms that are driven by a linearly polarized laser field. Starting from the Schroedinger equation, we determine the states of two-level atoms in a plane-wave field respecting propagation directions both of the atom and the field. For such laser-driven two-level atoms, we construct Bessel beams beyond the typical paraxial approximation. We show that the probability density of these atomic beams obtains a non-trivial, Bessel-squared-type behavior and can be tuned under the special choice of the atom and laser parameters, such as the nuclear charge, atom veloci…
To facilitate quantum simulation of open quantum systems at finite temperatures, an important ingredient is to achieve thermalization on a given time-scale. We consider a Rydberg aggregate (an arrangement of Rydberg atoms that interact via long-range interactions) embedded in a laser-driven atomic environment. For the smallest aggregate (two atoms), suitable laser parameters can be found by brute force scanning of the four tunable laser parameters. For more atoms, however, such parameter scans are too computationally costly. Here we apply Gaussian processes to predict the thermalization perfor…
We describe a scheme, operating in a manner analogous to a reversed Raman output coupler, for measuring the phase-sensitive quadrature statistics of an atom laser beam. This scheme allows for the transferral of the atomic field statistics to an optical field, for which the quantum statistics may then be measured using the well-developed technology of optical homodyne measurement.
We report the first realization of a guided quasicontinuous atom laser by rf outcoupling a Bose-Einstein condensate from a hybrid optomagnetic trap into a horizontal atomic waveguide. This configuration allows us to cancel the acceleration due to gravity and keep the de Broglie wavelength constant at 0.5 $μ$m during 0.1 s of propagation. We also show that our configuration, equivalent to pigtailing an optical fiber to a (photon) semiconductor laser, ensures an intrinsically good transverse mode matching.