9 research outputs found
Bichromatic Slowing of Metastable Helium
We examine two approaches for significantly extending the velocity range of
the optical bichromatic force (BCF), to make it useful for laser deceleration
of atomic and molecular beams. First, we present experimental results and
calculations for BCF deceleration of metastable helium using very large BCF
detunings, and discuss the limitations of this approach. We consider in detail
the constraints, both inherent and practical, that set the usable upper limit
of the BCF. We then show that a more promising approach is to utilize a BCF
profile with a relatively small velocity range in conjunction with chirped
Doppler shifts, to keep the force resonant with the atoms as they are slowed.
In an initial experimental test of this chirped BCF method, helium atoms are
slowed by m/s using a BCF profile with a velocity width of m/s. Straightforward scaling of the present results indicates that a
decelerator for He* capable of loading a magneto-optical trap (MOT) can yield a
brightness comparable to a much larger Zeeman slower.Comment: 11 pages, 9 figures. Published in Phys. Rev.
Prospects for rapid deceleration of small molecules by optical bichromatic forces
We examine the prospects for utilizing the optical bichromatic force (BCF) to
greatly enhance laser deceleration and cooling for near-cycling transitions in
small molecules. We discuss the expected behavior of the BCF in near-cycling
transitions with internal degeneracies, then consider the specific example of
decelerating a beam of calcium monofluoride molecules. We have selected CaF as
a prototype molecule both because it has an easily-accessible near-cycling
transition, and because it is well-suited to studies of ultracold molecular
physics and chemistry. We also report experimental verification of one of the
key requirements, the production of large bichromatic forces in a multi-level
system, by performing tests in an atomic beam of metastable helium.Comment: 11 pages, 6 figures, revised version, to be published in Physical
Review
Continuous all-optical deceleration and single-photon cooling of molecular beams
Ultracold molecular gases are promising as an avenue to rich many-body physics, quantum chemistry, quantum information, and precision measurements. This richness, which flows from the complex internal structure of molecules, makes the creation of ultracold molecular gases using traditional methods (laser plus evaporative cooling) a challenge, in particular due to the spontaneous decay of molecules into dark states. We propose a way to circumvent this key bottleneck using an all-optical method for decelerating molecules using stimulated absorption and emission with a single ultrafast laser. We further describe single-photon cooling of the decelerating molecules that exploits their high dark state pumping rates, turning the principal obstacle to molecular laser cooling into an advantage. Cooling and deceleration may be applied simultaneously and continuously to load molecules into a trap. We discuss implementation details including multilevel numerical simulations of strontium monohydride. These techniques are applicable to a large number of molecular species and atoms with the only requirement being an electric dipole transition that can be accessed with an ultrafast laser. © 2014 American Physical Society
Atoms in the counter-propagating frequency-modulated waves: splitting, cooling, confinement
We show that the counter-propagating frequency-modulated (FM) waves of the same intensity can split an orthogonal atomic beam into two beams. We calculate the temperature of the atomic ensemble for the case when the atoms are grouped around zero velocity in the direction of the waves propagation. The high-intensity laser radiation with a properly chosen carrier frequency can form a one-dimensional trap for atoms. We carry out the numerical simulation of the atomic motion (two-level model of the atom-field interaction) using parameters appropriate for sodium atoms and show that sub-Doppler cooling can be reached. We suppose that such a cooling is partly based on the cooling without spontaneous emission in polychromatic waves [H. Metcalf, Phys. Rev. A 77, 061401 (2008)]. We calculate the state of the atom in the field by the Monte Carlo wave-function method and describe its mechanical motion by the classical mechanics