We demonstrate confinement of 85 Rb atoms in a dark, toroidal optical trap. We use a spatial light modulator to convert a single blue-detuned Gaussian laser beam to a superposition of Laguerre-Gaussian modes that forms a ring-shaped intensity null bounded harmonically in all directions. We measure a 1 / e spin-relaxation lifetime of Ϸ1.5 s for a trap detuning of 4.0 nm. For smaller detunings, a time-dependent relaxation rate is observed. We use these relaxation rate measurements and imaging diagnostics to optimize trap alignment in a programmable manner with the modulator. The results are compared with numerical simulations.

We demonstrate the continuous injection and propagation of a cold atomic beam in a high-gradient (up to 2.7 kGauss/cm) magnetic guide of 1.7 m length. Continuous injection is accomplished using a side-loading scheme that involves a sequence of two modified magneto-optic traps. Methods are developed to measure the atomic-flow temperatures and the flux under steady-state conditions. In the high-gradient portion of the guide, the guided atomic beam has a transverse temperature of 420 µK ± 40µK, a longitudinal temperature of 1 mK, and an average velocity of order 1 m/s. Using a radio-frequency (RF) current of a fixed frequency ν coupled directly into the guide wires, atoms exceeding a transverse energy of hν can be continuously and selectively removed from the atomic beam.

The mechanical behavior of cells offers insight into many aspects of their properties. We propose an approach to the mechanical analysis of cells that uses a combination of electromanipulation for stimulus and capacitance for sensing. To demonstrate this approach, polystyrene spheres and yeast cells flowing in a 25 m ϫ 100 m microfluidic channel were detected by a perpendicular pair of gold thin film electrodes in the channel, spaced 25 m apart. The presence of cells was detected by capacitance changes between the gold electrodes. The capacitance sensor was a resonant coaxial radio frequency cavity ͑2.3 GHz͒ coupled to the electrodes. The presence of yeast cells ͑Saccharomyces cerevisiae͒ and polystyrene spheres resulted in capacitance changes of approximately 10 and 100 attoFarad ͑aF͒, respectively, with an achieved capacitance resolution of less than 2 aF in a 30 Hz bandwidth. The resolution is better than previously reported in the literature, and the capacitance changes are in agreement with values estimated by finite element simulations. Yeast cells were trapped using dielectrophoretic forces by applying a 3 V signal at 1 MHz between the electrodes. After trapping, the cells were displaced using amplitude and frequency modulated voltages to produce modulated dielectrophoretic forces. Repetitive displacement and relaxation of these cells was observed using both capacitance and video microscopy.

We demonstrate a two dimensional grating magneto-optical trap (2D GMOT) with a single input cooling laser beam and a planar diffraction grating using 87 Rb. This configuration increases experimental access when compared with a traditional 2D MOT. As described in the paper, the output flux is several hundred million rubidium atoms/s at a mean velocity of 16.5(9) m/s and a velocity distribution of 4(3) m/s standard deviation. We use the atomic beam from the 2D GMOT to demonstrate loading of a three dimensional grating MOT (3D GMOT) with 2.46(7) × 10 8 atoms. Methods to improve output flux are discussed.

We present a method for generating precise, dynamically tunable magnetic potentials that can be described by a polynomial series along the axis of a cold-atom waveguide near the surface of an atom chip. With a single chip design consisting of several wire pairs, various axial potentials can be created by changing the ratio of the currents in the wires, including double wells, triple wells, and pure harmonic traps with suppression of higher-order terms. We use this method to design and fabricate a chip with modest experimental requirements. Finally, we use the chip to demonstrate a double-well potential.