B. K. Teo

Autler-Townes spectroscopy of the 5 S 1 / 2 − 5 P 3 / 2 − 44 D cascade of cold 85 Rb atoms

We study nonlinear optical effects in the laser excitation of Rydberg states. 5S 1 / 2 and 5 P 3 / 2 levels of 8 5 Rb are coupled by a strong laser field and probed by a weak laser tuned to the 5P 3 / 2 -44D Rydberg resonance. We observe high contrast Autler-Townes spectra which are dependent on the pump polarization, intensity, and detuning. The observed behavior agrees with calculations, which include the effect of optical pumping.

A slow and dark atomic beam

We demonstrate a method to produce a very slow atomic beam from a vapor cell magneto-optical trap. Atoms are extracted from the trap using the radiation pressure imbalance caused by a push beam. An additional transfer beam placed near the center of the trap transfers the atomic beam into an off-resonant state. The velocity of the atomic beam has been varied by changing the intensity of the push beam or the position of the transfer beam. The method can be used to generate a continuous, magnetically guided atomic beam in a dark state.

Time averaging of multimode optical fiber output for a magneto-optical trap

We demonstrate a method for increasing the amount of power available for laser cooling applications by using a multimode optical fiber. Through randomization of phase shifts of modes within the fiber on time scales faster than the center-of-mass response time of the atoms, a smooth time-averaged trapping beam is generated. The principle has been demonstrated in a pyramidal magneto-optical trap. The method is particularly suitable for the harnessing of the high output power of broad-area diode lasers for laser cooling.

Coherent population transfer of ground state atoms into Rydberg states

We demonstrate experimentally and theoretically an efficiency of /spl sime/70%for excitation from the /sup 85/Rb 5S ground state to the 44D Rydberg state, using the technique of stimulated Raman adiabatic passage (STIRAP).

Loading mechanism for atomic guides

Summary form only given. Small guides can produce very strong confining fields but the transfer of cold atoms from a magneto optical trap (MOT) into such guides present a problem. This is because MOTs require a fixed trapping volume of /spl sim/ 1 cm/sup 3/ and cannot be miniaturized in the same way as atom guides. We demonstrate the loading of atoms from a cycled MOT into a tapered magnetic atom guide that overlaps with the MOT. This integrated loading strategy involves the formation of a MOT directly inside the atom guide.

Gauge potentials and tunneling dynamics in optical lattices

Summary form only given. It has been predicted that topological potentials play a significant role in gray optical lattices. However, so far there has been no direct experimental demonstration of their existence. Unlike light-shift potentials, which, in the case of low saturation, scale as the laser intensity, topological (or gauge) potentials are intensity independent and solely depend on the topology of the lattice, which is determined by the detuning, beam geometry and magnetic fields. In our experiment, /sup 87/Rb atoms are collected in a standard magneto-optic trap and loaded into a 1D optical lattice. The lattice is formed by counterpropagating, orthogonally polarized laser beams. The minima of the trapping potential form at the antinodes of the standing waves and, as a result of optical pumping, the wells are alternately occupied. When an atom tunnels from one type of well to another, it must then flip its magnetic spin state. The gauge potential is associated with the energy needed for this change. In this gray lattice, the potential wells are shallow due to the weak interaction with the light field. Shallow potentials are necessary for tunneling. We use two schemes to observe tunneling. In the first, we use an auxiliary weak laser pulse to selectively depopulate one of the two types of wells. We observe tunneling by measuring the population in each type of well as a function of time. The second way we study tunneling is to create atomic wave-packets within the wells and to observe their motion as they oscillate. The wave-packets are created by diabatically displacing the trapped atoms in either position or momentum space. Tunneling occurs when the wave-packets run against barriers provided by the maxima of the trapping potential.