Bruce G. Klappauf

Observation of quantum diffractive collisions using shallow atomic traps

We present measurements and calculations of the trap loss rate for laser-cooled

Compact laser cooling apparatus for simultaneous cooling of lithium and rubidium

^{87}\text{R}\text{b}

Doppler cooling to the Quantum limit

atoms confined in either a magneto-optic trap (MOT) or a magnetic quadrupole trap when exposed to a room-temperature background gas of Ar. We study the loss rate as a function of trap depth and find that copious glancing elastic collisions, which occur in the so-called quantum diffractive regime and impart very little energy to the trapped atoms, result in significant differences in the loss rate for the MOT compared to a pure magnetic trap due solely to the difference in potential depth. This finding highlights the importance of knowing the trap depth when attempting to infer the total collision cross section from measurements of trap loss rates. Moreover, this variation in trap loss rate with trap depth can be used to extract information about the differential cross section.

Amplification and front facet reflectivity of broad area lasers.

We report on a dual species laser cooling apparatus capable of collecting over 108 87Rb or 85Rb atoms from an atomic vapor or up to (8±2)×107 6Li atoms directly into a magneto-optic trap (MOT) from an effusive oven without the need for a Zeeman slower. The use of a miniature atomic oven placed close to the trapping region yields a compact vacuum system with a captured flux of more than 4×106 lithium atoms per second and a high quality vacuum in the 10−10 Torr range. The atomic sources, laser system, and vacuum system are described. In addition, we use this system to study atom loss from the MOT due to interspecies collisions between 6Li and 85Rb or 87Rb. We report for the first time the heteronuclear loss coefficients for 6Li-85Rb mixtures.

Giant Feshbach resonances in {sup 6}Li-{sup 85}Rb mixtures

Doppler cooling on a narrow transition is limited by the noise of single scattering events. It shows novel features, which are in sharp contrast with cooling on a broad transition, such as a non-gaussian momentum distribution, and divergence of its mean square value close to the resonance. We have observed those features using 1D cooling on an intercombination transition in strontium, and compared the measurements with theoretical predictions and Monte Carlo simulations. We also find that for very a narrow transition, cooling can be improved using a dipole trap, where the clock shift is canceled.

Giant Feshbach resonances in Li 6 - Rb 85 mixtures

The effect of front-facet reflectivity on the amplification performance of Broad Area Laser (BAL) diodes in a double-pass configurationis studied experimentally. A method to measure the front facet reflectivities of laser diodes is generalized to BALs. The method is based on fitting a model, with front facet reflectivity as a parameter, to the threshold current vs. external feedback of the diode. Reflectivities of three BAL diodes are measured, and their amplification abilities have been assessed. The tested diodes had amplification factors of 0, 1, and 10 and front facet reflectivities of 12.7 +/-1%, 4.6 +/-0.4%, and 1.2 +/-0.2% respectively. It is concluded that a front facet modal reflectivity of less than 4.6% is necessary for a BAL to function as an amplifier.

Method and device for accurately measuring the incident flux of ambient particles in a high or ultra-high vacuum environment

We report on the observation of six large Feshbach resonances in a Fermi-Bose mixture of

Giant Feshbach resonances in 6Li-85Rb mixtures

^{6}\mathrm{Li}

Absolute atomic collision cross section measurements using Rb atoms confined in magneto-optic and magnetic traps

and

Dual-channel amplification in a single-mode diode laser for multi-isotope laser cooling

^{85}\mathrm{Rb}