Bulletin of the American Physical Society
38th Annual Meeting of the Division of Atomic, Molecular, and Optical Physics
Volume 52, Number 7
Tuesday–Saturday, June 5–9, 2007; Calgary, Alberta, Canada
Session Q4: Laser Cooling and Trapping |
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Chair: C. Monroe, University of Michigan Room: TELUS Convention Centre Macleod A1-A2 |
Friday, June 8, 2007 1:30PM - 1:42PM |
Q4.00001: A diode laser system for sideband cooling of Sr$^+$ Kenneth Brown, Jaroslaw Labaziewicz, Philip Richerme, Isaac Chuang Sideband cooling is performed on the 5S$_{1/2}$ to 4D$_{5/2}$ line of Sr$^+$ in an RF Paul trap using a diode laser system in which the linewidth is reduced by optical feedback and the frequency is stabilized to the ion. The diode laser system uses optical feedback from a filter cavity to narrow the linewidth of an external cavity diode laser to $\leq 30$ kHz.\footnote{J. Labaziewicz, P. Richerme, K. R. Brown, I. L. Chuang, and K.Hayasaka, ``Compact, filtered diode laser system for precision spectroscopy,'' Opt. Lett. 32, 572-574 (2007)} The frequencies of the sideband cooling (674 nm) and Doppler cooling (422 nm) lasers are stabilized by performing a shelving experiment on the 5S$_{1/2}$ to 4D$_{5/2}$ carrier transition. This stabilization feedback is included in the pulse sequence used for sideband cooling. Using this scheme, the axial motion is sideband cooled to an average quanta $\langle n_z \rangle \leq 0.11$ without stabilizing the lasers to a high-finesse cavity. [Preview Abstract] |
Friday, June 8, 2007 1:42PM - 1:54PM |
Q4.00002: Sideband cooling while preserving the nuclear spin state of alkaline-earth-like atoms Iris Reichenbach, Ivan Deutsch Alkaline-earth-like atoms in the ground state have a total electron angular momentum of zero, and therefore no hyperfine interaction which couples the nuclear spin to the angular momentum of the electrons. By applying a magnetic field in the Paschen-Back regime, it is possible to also decouple the nuclear spin of higher-lying states from the electron angular momentum. We propose a scheme which uses these features to perform resolved sideband cooling without changing the state of the nuclear spin, thus preserving coherences which are usually destroyed due to optical pumping during laser cooling. This makes it possible for the first time to laser-cool neutral atom qubits without destroying the quantum information, if the quantum information is stored in the nuclear spin of the atom. The cooling scheme is explained on the example of $^{171}$Yb and $^{87}$Sr. [Preview Abstract] |
Friday, June 8, 2007 1:54PM - 2:06PM |
Q4.00003: Cooling in a Bistable Optical Cavity Ilya Averbukh, Mark Vilensky, Yehiam Prior We propose a new approach to non-resonant laser cooling of atoms and molecules based on their interaction with a bistable cavity supporting a standing wave mode. The bistability may be induced by an external feedback loop, or by intaracavity nonlinear optical elements. The method exemplifies a photonic version of Sisyphus cooling, in which the matter-dressed cavity extracts energy from the particles and discharges it to the external field as a result of sudden transitions between two stable states. In contrast to the conventional cavity cooling, in which atoms experience a viscous-type force, the bistable cavity imitates ``dry friction'', and stops the atoms much faster. We provide an analytical estimate for the stopping force, consider numerically the cooling of an ensemble of particles in a bistable cavity, and discuss the prospects of our method for cooling micromechanical resonators. [Preview Abstract] |
Friday, June 8, 2007 2:06PM - 2:18PM |
Q4.00004: Prospects for cavity-assisted laser cooling of OH Benjamin Lev, Brian Sawyer, Josh Dunn, Chris Greene, Jun Ye The experimental realization of large samples of ultracold, ground state polar molecules would be a major breakthrough for research in ultracold collisions and chemistry, quantum information processing, and the study of novel states of matter. While many techniques for ultracold, ground state polar molecule production show promise, none so far have simultaneously yielded the low temperatures and high densities required to pursue these goals. The Stark decelerator provides a nice compromise between density and temperature. Electric and magnetic trapping of samples as cold as 10 mK at densities approaching $10^7$/cm$^3$ have been demonstrated. However, new cooling techniques are required if we hope to push well below the 1 mK regime. Unlike atoms, molecules typically have an enormous number of channels into which a given excited state can decay. This makes the efficient free-space laser cooling of molecules challenging. Cavity-assisted laser cooling is a promising solution in that it provides dissipative cooling largely independent of molecular structure. We discuss attainable cooling rates and suppression of deleterious Raman scattering given current experimental constraints on cavity design and the number of intracavity molecules obtainable from our OH Stark decelerator. [Preview Abstract] |
Friday, June 8, 2007 2:18PM - 2:30PM |
Q4.00005: Optical Stark deceleration of cold molecules P.F. Barker Our work in this rapidly developing field of cold molecules has centered on the development of optical Stark deceleration, which momentarily traps and brings molecules to rest, initially with a molecular beam. This is done utilizing the large optical potentials that result from the interaction between an induced dipole moment and the intense optical field (10$^{12}$ W/cm$^{2})$ that induced it. As all molecules are polarizable, in principle any molecule or atom can be manipulated and slowed in the same manner, opening up the capability of creating essentially any cold molecular species. We describe our experiments, where we have successfully slowed every species that we have so far placed within the molecular beam[1-3]. This includes the organic molecule benzene (non-polar) and nitric oxide (weakly polar), as well as ground state xenon, the inert buffer gas used to form the molecular beam. Benzene, at a density of 10$^{11}$ cm$^{-3}$, has been brought to rest using a pulsed optical lattice created by two near counter-propagating optical fields. [1] R. Fulton, A.I. Bishop, P.F. Barker, Phys. Rev. Lett. \textbf{93}, 243004 (2004) [2] R. Fulton, A. Bishop, M.N. Shneider, P.F. Barker, Nature Physics \textbf{2}, 465 (2006) [3] R. Fulton, A.I. Bishop, M.N. Shneider, P.F. Barker, J. Phys. B: At. Mol. Opt. Phys. \textbf{39,} S1097 (2006) [Preview Abstract] |
Friday, June 8, 2007 2:30PM - 2:42PM |
Q4.00006: Loading Dynamics and Characteristics of a Far Off-Resonance Optical Dipole Trap Y.N. Martinez, P.G. Mickelson, S.B. Nagel, T.C. Killian We implement an optical dipole trap in a crossed beam configuration for experiments with ultracold strontium. Strontium atoms cooled to nearly 1 $\mu$K are loaded into the optical dipole trap from a magneto-optical trap operating on the 689 nm intercombination line. Loading dynamics and characteristics of the far off-resonance dipole trap are explored as part of our group's study of ultracold collisions in strontium. [Preview Abstract] |
Friday, June 8, 2007 2:42PM - 2:54PM |
Q4.00007: Realization of a Magneto-Optical Trap for Cadmium Atoms Mark Acton, Kathy-Anne Brickman, Ming-Shien Chang, Dzimitry Matsukevich, Paul Haljan, Vanderlei Bagnato, Christopher Monroe We report the confinement of cadmium atoms in a vapor cell magneto-optical trap (MOT). Using the closed $^{1}$S$_{0}-^{1}$P$_{1}$ transition ($\lambda $=229 nm, $\gamma $=2$\pi $*90.9 MHz), we are able to trap neutral cadmium atoms and examine the dependence of loss mechanisms, atomic density, and atom number on trapping parameters. This represents the trapping of a new atomic species and the shortest wavelength MOT produced to date. We anticipate that cold Cd atoms will be interesting for future studies in at least two directions: First, the $^{1}$S$_{0}-^{3}$P intercombination lines ($\lambda $=325 nm) could be useful for optical cooling to very low temperatures ($^{1}$S$_{0}-^{3}$P$_{1})$ and for high resolution optical spectroscopy ($^{1}$S$_{0}-^{3}$P$_{0})$. Second, combining cold Cd atoms with individual laser-cooled Cd$^{+}$ ions in a nearby ion trap may allow for studies of cold ion/neutral interactions such as charge-exchange, the transport of a charged ``hole'' through a gas, and perhaps the transfer of coherence from hyperfine states in the ion to pure nuclear spins in the neutral gas. [Preview Abstract] |
Friday, June 8, 2007 2:54PM - 3:06PM |
Q4.00008: Measurement of Population Dynamics in STIRAP M.A. Gearba, M.L. Trachy, G. Veshapidze, M.H. Shah, H.A. Camp, H.U. Jang, B.D. DePaola A tremendous amount of work, both theoretical and experimental, has recently been invested in finding efficient coherent excitation techniques to control the population transfer between specified energy states. Measuring the population changes in real time and probing all levels involved during coherent excitation are some of the challenges that most experiments have had to face. Our experiment overcomes these difficulties by employing a modern diagnostic technique, known as Magneto-Optical Trap Recoil Ion Momentum Spectroscopy (MOTRIMS), which makes use of an ion beam as a non-intrusive probe of a three-level rubidium ladder system, coherently excited via the standard STIRAP (stimulated Raman adiabatic passage) method. Several cases are investigated, in which the temporal delay between the two laser pulses is varied, ranging from the so-called counter-intuitive order to the intuitive order. The population dynamics of all three levels involved in the STIRAP process is measured with a resolution of a few nanoseconds. Experimental results are compared with predictions of theory. [Preview Abstract] |
Friday, June 8, 2007 3:06PM - 3:18PM |
Q4.00009: Zeeman Slower for Fermionic Potassium Atoms with Natural Abundance Sample Ye-ryoung Lee, Peter Zarth, Martin Weitz, Wolfgang Ketterle We present a new atomic source for $^{40}$K based on a Zeeman slower using natural abundance potassium. This method has practical and technical advantages over the conventional method of using enriched potassium. At the position of the $^{40}$K MOT, the Zeeman slower has a maximum flux of 2 $\cdot $ 10$^{7}$ atoms/s/cm$^{2}$, which is comparable to other techniques. This new atomic source saves expenses by not using enriched $^{40}$K samples and simplifies complications in other techniques. Our method serves as a simple and robust $^{40}$K source for the studies of fermionic atoms. [Preview Abstract] |
Friday, June 8, 2007 3:18PM - 3:30PM |
Q4.00010: Design and performance of an optimized dual-species Zeeman slower Ryan Olf, G. Edward Marti, Dan Stamper-Kurn An increasing number of experiments cool and trap multiple atomic species both simultaneously and alternatively. We present a Zeeman slower optimized for dual species operation via precise winding of multiple sections targeted at the individual species, with only marginally reduced performance than a slower designed for each species individually. The currently constructed slower is optimized for Li and Rb atoms emerging from a dual-species oven and eventually captured by a MOT, though other atomic mixtures are discussed. Design, construction, and performance results and considerations are shown. [Preview Abstract] |
Friday, June 8, 2007 3:30PM - 3:42PM |
Q4.00011: Velocity-selective two-photon resonances in a cold atomic sample with large one-photon blue detunings Matthew Terraciano, Spencer Olson, Mark Bashkansky, Zachary Dutton, Fredrik Fatemi We present experimental results on velocity-selective, magnetically-induced resonances in a cold Rb vapor. For small detuning from the D2 transition ($\vert \Delta \vert $ $<$ 50 MHz), we observe cooling only for negative $\Delta $ as expected, but at larger detuning ($\vert \Delta \vert $ $\approx $ 0.1-10 GHz) we find evidence for cooling with both blue- and red-detuning. To observe this effect, a freely expanding atom cloud is exposed to a $\sim $1-10 ms pulse from lin-perp-lin counterpropagating fields. The expanding cloud is later imaged and shows higher density for a narrow velocity class of atoms that is resonant with a two-photon transition whose Doppler shift corresponds to the Larmor precession frequency. We use this effect to demonstrate a simple technique for measuring (or zeroing) the magnetic field to within 1 mG, as verified by Faraday rotation. Furthermore, we cool several velocity classes simultaneously by imposing multiple frequency sidebands on one beam of the counterpropagating pair, and extend the experiments to two dimensions. [Preview Abstract] |
Friday, June 8, 2007 3:42PM - 3:54PM |
Q4.00012: Subnatural linewidth spectroscopy using a suppression and recovery of trapped Cs atoms Chin-Chun Tsai, Ray-Yuan Chang, Min-Da Tsai, Wei-Chia Fang, Yi-Chih Lee Subnatural linewidth in the \emph{8s} Rydberg state has been observed using a suppression and recovery of trapped Cs atoms. The suppression and recovery method has the advantages of requiring low light field for probing laser and providing a zero background. In our experiment, the Cs atoms in the magneto- optical trap (MOT) are radiated by a weak probe laser form $\mid$6S$_{1/2}$ F=4$\rangle$ to $\mid$6P$_{3/2}$ F=5$\rangle$ for 1000msec; then a coupling laser is superimposed with the probing laser to interact with the MOT atoms for 500msec by alternating the MOT lasers with the coupling laser at 70kHz to avoid the power broadening and the AC stark effect. The coupling laser is scanned from $\mid$6P$_{3/2}$ F=5$\rangle$ to $\mid$8S$_{1/2}$ F=4$\rangle$. If the coupling laser is off resonance, then the probe laser suppresses the atoms to be loaded into the MOT and results no background signal while probing the MOT florescence. If the coupling laser is on resonance, then the probe laser is induced to be transmitted and the MOT loading is recovered at the alternating stage. This transmitted probe laser field is due to quantum interference and is known as the electromagnetically induced transparency. A subnatural linewidth in the Cs(\emph{8s}) Rydberg state of 3.5MHz is obtained and the intensity dependence on the probing coupling lasers is discussed. [Preview Abstract] |
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