9,445 research outputs found
All-optical atom surface traps implemented with one-dimensional planar diffractive microstructures
We characterize the loading, containment and optical properties of
all-optical atom traps implemented by diffractive focusing with one-dimensional
(1D) microstructures milled on gold films. These on-chip Fresnel lenses with
focal lengths of the order of a few hundred microns produce
optical-gradient-dipole traps. Cold atoms are loaded from a mirror
magneto-optical trap (MMOT) centered a few hundred microns above the gold
mirror surface. Details of loading optimization are reported and perspectives
for future development of these structures are discussed.Comment: 7 pages, 15 figure
Quantitative Determination of Enhanced and Suppressed Transmission through Subwavelength Slit Arrays in Silver Films
Measurement of the transmitted intensity from a coherent monomode light
source through a series of subwavelength slit arrays in Ag films, with varying
array pitch and number of slits, demonstrate enhancement (suppression) by as
much as a factor of 6 (9) when normalized to that of an isolated slit.
Pronounced minima in the transmitted intensity were observed at array pitches
corresponding to lambda_SPP, 2lambda_SPP, and 3lambda_SPP where lambda_SPP is
the wavelength of the surface plasmon polariton (SPP). Increasing the number of
slits to more than four does not increase appreciably the per-slit transmission
intensity. These results are consistent with a model for interference between
SPPs and the incident wave that fits well the measured transmitted intensity
profile.Comment: Figure 4 update
Study of high voltage solar array configurations with integrated power control electronics
Solar array electrical configurations for voltage regulatio
Controlling Condensate Collapse and Expansion with an Optical Feshbach Resonance
We demonstrate control of the collapse and expansion of an 88Sr Bose-Einstein
condensate using an optical Feshbach resonance (OFR) near the 1S0-3P1
intercombination transition at 689 nm. Significant changes in dynamics are
caused by modifications of scattering length by up to +- ?10a_bg, where the
background scattering length of 88Sr is a_bg = -2a0 (1a0 = 0.053 nm). Changes
in scattering length are monitored through changes in the size of the
condensate after a time-of-flight measurement. Because the background
scattering length is close to zero, blue detuning of the OFR laser with respect
to a photoassociative resonance leads to increased interaction energy and a
faster condensate expansion, whereas red detuning triggers a collapse of the
condensate. The results are modeled with the time-dependent nonlinear
Gross-Pitaevskii equation.Comment: 5 pages, 3 figure
Surface-wave interferometry on single subwavelength slit-groove structures fabricated on gold films
We apply the technique of far-field interferometry to measure the properties
of surface waves generated by two-dimensional (2D) single subwavelength
slit-groove structures on gold films. The effective surface index of refraction
measured for the surface wave propagating over a distance of more than 12
microns is determined to be 1.016 with a measurement uncertainty of 0.004, to
within experimental uncertainty of the expected bound surface plasmon-polariton
(SPP) value for a Au/Air interface of 1.018. We compare these measurements to
finite-difference-time-domain (FDTD) numerical simulations of the optical field
transmission through these devices. We find excellent agreement between the
measurements and the simulations for the surface index of refraction. The
measurements also show that the surface wave propagation parameter exhibits
transient behavior close to the slit, evolving smoothly from greater values
asymptotically toward the value expected for the SPP over the first 2-3 microns
of slit-groove distance. This behavior is confirmed by the FDTD simulations
Surface wave generation and propagation on metallic subwavelength structures measured by far-field interferometry
Transmission spectra of metallic films or membranes perforated by arrays of
subwavelength slits or holes have been widely interpreted as resonance
absorption by surface plasmon polaritons (SPPs). Alternative interpretations
involving evanescent waves diffracted on the surface have also been proposed.
These two approaches lead to divergent predictions for some surface wave
properties. Using far-field interferometry, we have carried out a series of
measurements on elementary one-dimensional (1-D) subwavelength structures with
the aim of testing key properties of the surface waves and comparing them to
predictions of these two points of view
Heteronuclear ionizing collisions between laser-cooled metastable helium atoms
We have investigated cold ionizing heteronuclear collisions in dilute
mixtures of metastable (2 3S1) 3He and 4He atoms, extending our previous work
on the analogous homonuclear collisions [R. J. W. Stas et al., PRA 73, 032713
(2006)]. A simple theoretical model of such collisions enables us to calculate
the heteronuclear ionization rate coefficient, for our quasi-unpolarized gas,
in the absence of resonant light (T = 1.2 mK): K34(th) = 2.4*10^-10 cm^3/s.
This calculation is supported by a measurement of K34 using magneto-optically
trapped mixtures containing about 1*10^8 atoms of each species, K34(exp) =
2.5(8)*10^-10 cm^3/s. Theory and experiment show good agreement.Comment: 8 pages, 6 figure
A mean field description of jamming in non-cohesive frictionless particulate systems
A theory for kinetic arrest in isotropic systems of repulsive,
radially-interacting particles is presented that predicts exponents for the
scaling of various macroscopic quantities near the rigidity transition that are
in agreement with simulations, including the non-trivial shear exponent. Both
statics and dynamics are treated in a simplified, one-particle level
description, and coupled via the assumption that kinetic arrest occurs on the
boundary between mechanically stable and unstable regions of the static
parameter diagram. This suggests the arrested states observed in simulations
are at (or near) an elastic buckling transition. Some additional numerical
evidence to confirm the scaling of microscopic quantities is also provided.Comment: 9 pages, 3 figs; additional clarification of different elastic moduli
exponents, plus typo fix. To appear in PR
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