971 research outputs found
Quantum limits of cold damping with optomechanical coupling
Thermal noise of a mirror can be reduced by cold damping. The displacement is
measured with a high-finesse cavity and controlled with the radiation pressure
of a modulated light beam. We establish the general quantum limits of noise in
cold damping mechanisms and we show that the optomechanical system allows to
reach these limits. Displacement noise can be arbitrarily reduced in a narrow
frequency band. In a wide-band analysis we show that thermal fluctuations are
reduced as with classical damping whereas quantum zero-point fluctuations are
left unchanged. The only limit of cold damping is then due to zero-point energy
of the mirrorComment: 10 pages, 3 figures, RevTe
Beating quantum limits in optomechanical sensor by cavity detuning
We study the quantum limits in an optomechanical sensor based on a detuned
high-finesse cavity with a movable mirror. We show that the radiation pressure
exerted on the mirror by the light in the detuned cavity induces a modification
of the mirror dynamics and makes the mirror motion sensitive to the signal.
This leads to an amplification of the signal by the mirror dynamics, and to an
improvement of the sensor sensitivity beyond the standard quantum limit, up to
an ultimate quantum limit only related to the mechanical dissipation of the
mirror. This improvement is somewhat similar to the one predicted in detuned
signal-recycled gravitational-waves interferometers, and makes a high-finesse
cavity a model system to test these quantum effect
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
Beating quantum limits in interferometers with quantum locking of mirrors
The sensitivity in interferometric measurements such as gravitational-wave
detectors is ultimately limited by quantum noise of light. We discuss the use
of feedback mechanisms to reduce the quantum effects of radiation pressure.
Recent experiments have shown that it is possible to reduce the thermal motion
of a mirror by cold damping. The mirror motion is measured with an
optomechanical sensor based on a high-finesse cavity, and reduced by a feedback
loop. We show that this technique can be extended to lock the mirror at the
quantum level. In gravitational-waves interferometers with Fabry-Perot cavities
in each arms, it is even possible to use a single feedback mechanism to lock
one cavity mirror on the other. This quantum locking greatly improves the
sensitivity of the interferometric measurement. It is furthermore insensitive
to imperfections such as losses in the interferometer
Mechanical loss in state-of-the-art amorphous optical coatings
We present the results of mechanical characterizations of many different
high-quality optical coatings made of ion-beam-sputtered titania-doped tantala
and silica, developed originally for interferometric gravitational-wave
detectors. Our data show that in multi-layer stacks (like high-reflection Bragg
mirrors, for example) the measured coating dissipation is systematically higher
than the expectation and is correlated with the stress condition in the sample.
This has a particular relevance for the noise budget of current advanced
gravitational-wave interferometers, and, more generally, for any experiment
involving thermal-noise limited optical cavities.Comment: 31 pages, 14 figure
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
Material loss angles from direct measurements of broadband thermal noise
International audienceWe estimate the loss angles of the materials currently used in the highly reflective test-mass coatings of interferometric detectors of gravitational waves, namely Silica, Tantala, and Ti-doped Tantala, from direct measurement of coating thermal noise in an optical interferometer testbench, the Caltech TNI. We also present a simple predictive theory for the material properties of amorphous glassy oxide mixtures, which gives results in good agreement with our measurements on Ti-doped Tantala. Alternative measurement methods and results are reviewed, and some critical issues are discussed
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