1,024 research outputs found
A Single Atom as a Mirror of an Optical Cavity
By tightly focussing a laser field onto a single cold ion trapped in front of
a far-distant dielectric mirror, we could observe a quantum electrodynamic
effect whereby the ion behaves as the optical mirror of a Fabry-P\'erot cavity.
We show that the amplitude of the laser field is significantly altered due to a
modification of the electromagnetic mode structure around the atom in a novel
regime in which the laser intensity is already changed by the atom alone. e
propose a direct application of this system as a quantum memory for single
photons.Comment: 7 pages, 3 figures, to appear in Physical Review Letter
Infrared spectroscopic studies on unoriented single-walled carbon nanotube films under hydrostatic pressure
The electronic properties of as-prepared and purified unoriented
single-walled carbon nanotube films were studied by transmission measurements
over a broad frequency range (far-infrared up to visible) as a function of
temperature (15 K - 295 K) and external pressure (up to 8 GPa). Both the
as-prepared and the purified SWCNT films exhibit nearly temperature-independent
properties. With increasing pressure the low-energy absorbance decreases
suggesting an increasing carrier localization due to pressure-induced
deformations. The energy of the optical transitions in the SWCNTs decreases
with increasing pressure, which can be attributed to pressure-induced
hybridization and symmetry-breaking effects. We find an anomaly in the
pressure-induced shift of the optical transitions at 2 GPa due to a
structural phase transition.Comment: 13 pages, 15 figure
Vacuum-Stimulated Raman Scattering based on Adiabatic Passage in a High-Finesse Optical Cavity
We report on the first observation of stimulated Raman scattering from a
Lambda-type three-level atom, where the stimulation is realized by the vacuum
field of a high-finesse optical cavity. The scheme produces one intracavity
photon by means of an adiabatic passage technique based on a counter-intuitive
interaction sequence between pump laser and cavity field. This photon leaves
the cavity through the less-reflecting mirror. The emission rate shows a
characteristic dependence on the cavity and pump detuning, and the observed
spectra have a sub-natural linewidth. The results are in excellent agreement
with numerical simulations.Comment: 4 pages, 5 figure
Quantum Beat of Two Single Photons
The interference of two single photons impinging on a beam splitter is
measured in a time-resolved manner. Using long photons of different frequencies
emitted from an atom-cavity system, a quantum beat with a visibility close to
100% is observed in the correlation between the photodetections at the output
ports of the beam splitter. The time dependence of the beat amplitude reflects
the coherence properties of the photons. Most remarkably, simultaneous
photodetections are never observed, so that a temporal filter allows one to
obtain perfect two-photon coalescence even for non-perfect photons.Comment: 4 pages, 3 figure
QED with a spherical mirror
We investigate the Quantum-Electro-Dynamic properties of an atomic electron
close to the focus of a spherical mirror. We first show that the spontaneous
emission and excited state level shift of the atom can be fully suppressed with
mirror-atom distances of many wavelengths. A three-dimensional theory predicts
that the spectral density of vacuum fluctuations can indeed vanish within a
volume around the atom, with the use of a far distant mirror
covering only half of the atomic emission solid angle. The modification of
these QED atomic properties is also computed as a function of the mirror size
and large effects are found for only moderate numerical apertures. We also
evaluate the long distance ground state energy shift (Casimir-Polder shift) and
find that it scales as at the focus of a hemi-spherical mirror
of radius , as opposed to the well known scaling law for an
atom at a distance from an infinite plane mirror. Our results are relevant
for investigations of QED effects, and also free space coupling to single atoms
using high-numerical aperture lenses.Comment: 12 pages, 4 figure
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