70 research outputs found
Solar cell Patent
Development and characteristics of solar cells with phosphors in cover glass to improve response to solar ultraviolet radiatio
Wavelength-Scale Imaging of Trapped Ions using a Phase Fresnel lens
A microfabricated phase Fresnel lens was used to image ytterbium ions trapped
in a radio frequency Paul trap. The ions were laser cooled close to the Doppler
limit on the 369.5 nm transition, reducing the ion motion so that each ion
formed a near point source. By detecting the ion fluorescence on the same
transition, near diffraction limited imaging with spot sizes of below 440 nm
(FWHM) was achieved. This is the first demonstration of imaging trapped ions
with a resolution on the order of the transition wavelength.Comment: 8 pages, 3 figure
High-Q measurements of fused-silica microspheres in the near infrared
Measurements of the quality factor Q ~ 8 x 10^9 are reported for the whispering-gallery modes (WGM’s) of quartz microspheres for the wavelengths 670, 780, and 850 nm; these results correspond to finesse F ~ 2.2 x 10^6. The observed independence of Q from wavelength indicates that losses for the WGM’s are dominated by a mechanism other than bulk absorption in fused silica in the near infrared. Data obtained by atomic force microscopy combined with a simple model for surface scattering suggest that Q can be limited by residual surface inhomogeneities. Absorption by absorbed water can also explain why the material limit is not reached at longer wavelengths in the near infrared
Continuous and Pulsed Quantum Zeno Effect
Continuous and pulsed quantum Zeno effects were observed using a Rb
Bose-Einstein condensate(BEC). Oscillations between two ground hyperfine states
of a magnetically trapped condensate, externally driven at a transition rate
, were suppressed by destructively measuring the population in one of
the states with resonant light. The suppression of the transition rate in the
two level system was quantified for pulsed measurements with a time interval
between pulses and continuous measurements with a scattering rate
. We observe that the continuous measurements exhibit the same
suppression in the transition rate as the pulsed measurements when
, in agreement with the predicted value of 4.
Increasing the measurement rate suppressed the transition rate down to
.Comment: 5 pages, 4 figure
Measurement of focusing properties for high numerical aperture optics using an automated submicron beamprofiler
The focusing properties of three aspheric lenses with numerical aperture (NA)
between 0.53 and 0.68 were directly measured using an interferometrically
referenced scanning knife-edge beam profiler with sub-micron resolution. The
results obtained for two of the three lenses tested were in agreement with
paraxial gaussian beam theory. It was also found that the highest NA aspheric
lens which was designed for 830nm was not diffraction limited at 633nm. This
process was automated using motorized translation stages and provides a direct
method for testing the design specifications of high numerical aperture optics.Comment: 6 pages 4 figure
Absorption imaging of a single atom
Absorption imaging has played a key role in the advancement of science from
van Leeuwenhoek's discovery of red blood cells to modern observations of dust
clouds in stellar nebulas and Bose-Einstein condensates. Here we show the first
absorption imaging of a single atom isolated in vacuum. The optical properties
of atoms are thoroughly understood, so a single atom is an ideal system for
testing the limits of absorption imaging. A single atomic ion was confined in
an RF Paul trap and the absorption imaged at near wavelength resolution with a
phase Fresnel lens. The observed image contrast of 3.1(3)% is the maximum
theoretically allowed for the imaging resolution of our setup. The absorption
of photons by single atoms is of immediate interest for quantum information
processing (QIP). Our results also point out new opportunities in imaging of
light-sensitive samples both in the optical and x-ray regimes.Comment: Accepted to Nature Commu
Atom trapping with a thin magnetic film
We have created a Rb Bose-Einstein condensate in a magnetic trapping
potential produced by a hard disk platter written with a periodic pattern. Cold
atoms were loaded from an optical dipole trap and then cooled to BEC on the
surface with radiofrequency evaporation. Fragmentation of the atomic cloud due
to imperfections in the magnetic structure was observed at distances closer
than 40 m from the surface. Attempts to use the disk as an atom mirror
showed dispersive effects after reflection.Comment: 4 pages, 5 figure
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