920 research outputs found
A micropillar for cavity optomechanics
We present a new micromechanical resonator designed for cavity optomechanics.
We have used a micropillar geometry to obtain a high-frequency mechanical
resonance with a low effective mass and a very high quality factor. We have
coated a 60-m diameter low-loss dielectric mirror on top of the pillar and
are planning to use this micromirror as part of a high-finesse Fabry-Perot
cavity, to laser cool the resonator down to its quantum ground state and to
monitor its quantum position fluctuations by quantum-limited optical
interferometry
Radiation-pressure cooling and optomechanical instability of a micro-mirror
Recent experimental progress in table-top experiments or gravitational-wave
interferometers has enlightened the unique displacement sensitivity offered by
optical interferometry. As the mirrors move in response to radiation pressure,
higher power operation, though crucial for further sensitivity enhancement,
will however increase quantum effects of radiation pressure, or even jeopardize
the stable operation of the detuned cavities proposed for next-generation
interferometers. The appearance of such optomechanical instabilities is the
result of the nonlinear interplay between the motion of the mirrors and the
optical field dynamics. In a detuned cavity indeed, the displacements of the
mirror are coupled to intensity fluctuations, which modifies the effective
dynamics of the mirror. Such "optical spring" effects have already been
demonstrated on the mechanical damping of an electromagnetic waveguide with a
moving wall, on the resonance frequency of a specially designed flexure
oscillator, and through the optomechanical instability of a silica
micro-toroidal resonator. We present here an experiment where a
micro-mechanical resonator is used as a mirror in a very high-finesse optical
cavity and its displacements monitored with an unprecedented sensitivity. By
detuning the cavity, we have observed a drastic cooling of the micro-resonator
by intracavity radiation pressure, down to an effective temperature of 10 K. We
have also obtained an efficient heating for an opposite detuning, up to the
observation of a radiation-pressure induced instability of the resonator.
Further experimental progress and cryogenic operation may lead to the
experimental observation of the quantum ground state of a mechanical resonator,
either by passive or active cooling techniques
Endogenous Retroviruses: Thierry Heidmann wins the 2009 Retrovirology prize
Thierry Heidmann wins the 2009 Retrovirology prize
High-sensitivity optical monitoring of a micro-mechanical resonator with a quantum-limited optomechanical sensor
We experimentally demonstrate the high-sensitivity optical monitoring of a
micro-mechanical resonator and its cooling by active control. Coating a
low-loss mirror upon the resonator, we have built an optomechanical sensor
based on a very high-finesse cavity (30000). We have measured the thermal noise
of the resonator with a quantum-limited sensitivity at the 10^-19 m/rootHz
level, and cooled the resonator down to 5K by a cold-damping technique.
Applications of our setup range from quantum optics experiments to the
experimental demonstration of the quantum ground state of a macroscopic
mechanical resonator.Comment: 4 pages, 5 figure
Quantum noise in the position measurement of a cavity mirror undergoing Brownian motion
We perform a quantum theoretical calculation of the noise power spectrum for
a phase measurement of the light output from a coherently driven optical cavity
with a freely moving rear mirror. We examine how the noise resulting from the
quantum back action appears among the various contributions from other noise
sources. We do not assume an ideal (homodyne) phase measurement, but rather
consider phase modulation detection, which we show has a different shot noise
level. We also take into account the effects of thermal damping of the mirror,
losses within the cavity, and classical laser noise. We relate our theoretical
results to experimental parameters, so as to make direct comparisons with
current experiments simple. We also show that in this situation, the standard
Brownian motion master equation is inadequate for describing the thermal
damping of the mirror, as it produces a spurious term in the steady-state phase
fluctuation spectrum. The corrected Brownian motion master equation [L. Diosi,
Europhys. Lett. {\bf 22}, 1 (1993)] rectifies this inadequacy.Comment: 12 pages revtex, 2 figure
Free-space cavity optomechanics in a cryogenic environment
International audienceWe present a free-space optomechanical system operating in the 1-K range. The device is made ofa high mechanical quality factor micropillar with a high-reflectivity optical coating atop, combinedwith an ultra-small radius-of-curvature coupling mirror to form a high-finesse Fabry-Perot cavityembedded in a dilution refrigerator. The cavity environment as well as the cryostat have beendesigned to ensure low vibrations and to preserve micron-level alignment from room temperatur
Nonclassical statistics of intracavity coupled waveguides: the quantum optical dimer
A model is proposed where two nonlinear waveguides are contained
in a cavity suited for second-harmonic generation. The evanescent wave coupling
between the waveguides is considered as weak, and the interplay between this
coupling and the nonlinear interaction within the waveguides gives rise to
quantum violations of the classical limit. These violations are particularly
strong when two instabilities are competing, where twin-beam behavior is found
as almost complete noise suppression in the difference of the fundamental
intensities. Moreover, close to bistable transitions perfect twin-beam
correlations are seen in the sum of the fundamental intensities, and also the
self-pulsing instability as well as the transition from symmetric to asymmetric
states display nonclassical twin-beam correlations of both fundamental and
second-harmonic intensities. The results are based on the full quantum Langevin
equations derived from the Hamiltonian and including cavity damping effects.
The intensity correlations of the output fields are calculated
semi-analytically using a linearized version of the Langevin equations derived
through the positive-P representation. Confirmation of the analytical results
are obtained by numerical simulations of the nonlinear Langevin equations
derived using the truncated Wigner representation.Comment: 15 pages, 8 figures, submitted to Phys. Rev.
Bright squeezing from self-induced transparencies in dressed three-level atoms
We investigate two schemes for the efficient conversion of coherent input light into bright-squeezed output light. Both schemes utilize strong signal and weak probe fields, interacting with three-level ladder-configuration atoms inside optical cavities. The schemes differ in the resonance requirements of the cavities and produce noise suppression for quite different tuning regimes. Quantum-noise reduction is a consequence of the dressing of the atoms with two coherent fields. By tuning the probe light in the right fashion, spontaneous emission from the excited state can be made to counteract signal-light intensity fluctuations
The Neutral Hydrogen Content of Fornax Cluster Galaxies
We present a new set of deep HI observations of member galaxies of the Fornax
cluster. We detected 35 cluster galaxies in HI. The resulting sample, the most
comprehensive to date, is used to investigate the distribution of HI in the
cluster galaxies. We compare the HI content of the detected cluster galaxies
with that of field galaxies by measuring HI mass-to-light ratios and the HI
deficiency parameter of Solanes et al. (1996). The mean HI mass-to-light ratio
of the cluster galaxies is 0.68+/-0.15, significantly lower than for a sample
of HI-selected field galaxies (1.15+/-0.10), although not as low as in the
Virgo cluster (0.45+/-0.03). The mean HI deficiency for the cluster is
0.38+/-0.09 (for T=1-6), significantly greater than for the field sample
(0.05+/-0.03). Both these tests show that Fornax cluster galaxies are
HI-deficient compared to field galaxies. The kinematics of the cluster galaxies
suggests that the HI deficiency may be caused by ram-pressure stripping of
galaxies on orbits that pass close to the cluster core.
We also derive the most complete B-band TF relation of inclined spiral
galaxies in Fornax. A subcluster in the South-West of the main cluster
contributes considerably to the scatter. The scatter for galaxies in the main
cluster alone is 0.50mag, which is slightly larger than the intrinsic scatter
of 0.4mag. We use the TF relation to derive a distance modulus of Fornax
relative to the Virgo cluster of -0.38+/-0.14mag. The galaxies in the
subcluster are 1.0+/-0.5mag brighter than the galaxies of the main cluster,
indicating that they are situated in the foreground. With their mean velocity
95km/s higher than that of the main cluster we conclude that the subcluster is
falling into the main Fornax cluster.Comment: 14 pages including 10 figures, plus 1 table. Accepted for publication
in A&
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