171 research outputs found
Applications of Integrated Magnetic Microtraps
Lithographically fabricated circuit patterns can provide magnetic guides and
microtraps for cold neutral atoms. By combining several such structures on the
same ceramic substrate, we have realized the first ``atom chips'' that permit
complex manipulations of ultracold trapped atoms or de Broglie wavepackets. We
show how to design magnetic potentials from simple conductor patterns and we
describe an efficient trap loading procedure in detail. Applying the design
guide, we describe some new microtrap potentials, including a trap which
reaches the Lamb-Dicke regime for rubidium atoms in all three dimensions, and a
rotatable Ioffe-Pritchard trap, which we also demonstrate experimentally.
Finally, we demonstrate a device allowing independent linear positioning of two
atomic clouds which are very tightly confined laterally. This device is well
suited for the study of one-dimensional collisions.Comment: 10 pages, 17 figure
Optimal transport of ultracold atoms in the non-adiabatic regime
We report the transport of ultracold atoms with optical tweezers in the
non-adiabatic regime, i.e. on a time scale on the order of the oscillation
period. We have found a set of discrete transport durations for which the
transport is not accompanied by any excitation of the centre of mass of the
cloud. We show that the residual amplitude of oscillation of the dipole mode is
given by the Fourier transform of the velocity profile imposed to the trap for
the transport. This formalism leads to a simple interpretation of our data and
simple methods for optimizing trapped particles displacement in the
non-adiabatic regime
Attosecond control of electrons emitted from a nanoscale metal tip
Attosecond science is based on steering of electrons with the electric field
of well-controlled femtosecond laser pulses. It has led to, for example, the
generation of XUV light pulses with a duration in the sub-100-attosecond
regime, to the measurement of intra-molecular dynamics by diffraction of an
electron taken from the molecule under scrutiny, and to novel ultrafast
electron holography. All these effects have been observed with atoms or
molecules in the gas phase. Although predicted to occur, a strong light-phase
sensitivity of electrons liberated by few-cycle laser pulses from solids has
hitherto been elusive. Here we show a carrier-envelope (C-E) phase-dependent
current modulation of up to 100% recorded in spectra of electrons laser-emitted
from a nanometric tungsten tip. Controlled by the C-E phase, electrons
originate from either one or two sub-500as long instances within the 6-fs laser
pulse, leading to the presence or absence of spectral interference. We also
show that coherent elastic re-scattering of liberated electrons takes place at
the metal surface. Due to field enhancement at the tip, a simple laser
oscillator suffices to reach the required peak electric field strengths,
allowing attosecond science experiments to be performed at the 100-Megahertz
repetition rate level and rendering complex amplified laser systems
dispensable. Practically, this work represents a simple, exquisitely sensitive
C-E phase sensor device, which can be shrunk in volume down to ~ 1cm3. The
results indicate that the above-mentioned novel attosecond science techniques
developed with and for atoms and molecules can also be employed with solids. In
particular, we foresee sub-femtosecond (sub-) nanometre probing of (collective)
electron dynamics, such as plasmon polaritons, in solid-state systems ranging
in size from mesoscopic solids via clusters to single protruding atoms.Comment: Final manuscript version submitted to Natur
Carrier-envelope phase effects on the strong-field photoemission of electrons from metallic nanostructures
Sharp metallic nanotapers irradiated with few-cycle laser pulses are emerging
as a source of highly confined coherent electron wavepackets with attosecond
duration and strong directivity. The possibility to steer, control or switch
such electron wavepackets by light is expected to pave the way towards direct
visualization of nanoplasmonic field dynamics and real-time probing of electron
motion in solid state nanostructures. Such pulses can be generated by
strong-field induced tunneling and acceleration of electrons in the near-field
of sharp gold tapers within one half-cycle of the driving laser field. Here, we
show the effect of the carrier-envelope phase of the laser field on the
generation and motion of strong-field emitted electrons from such tips. This is
a step forward towards controlling the coherent electron motion in and around
metallic nanostructures on ultrashort length and time scales
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