Two-dimensional photonic crystal slabs (PCS) offer an appealing alternative to distributed Bragg reflectors or filters for various applications. Indeed, their scattering properties, governed by Fano-resonances, have been used in areas as diverse as optical wavelength and polarization filters, reflectors, semiconductor lasers, photodetectors, bio-sensors, or non-linear optical components. Suspended PCSs also find natural applications in the field of optomechanics, where the mechanical modes of a suspended slab interact via radiation pressure with the optical field of a high finesse cavity. The reflectivity and transmission properties of a defect-free suspended PCS around normal incidence can be used to couple out-of-plane mechanical modes to an optical field by integrating it in a free space cavity. We have demonstrated the successful implementation of a PCS reflector on a high-tensile stress Si3N4 nanomembrane. We could measure the photonic crystal band diagram with a spectrally, angular, and polarization resolved setup. Moreover, a cavity with a finesse as high as 12 000 was formed using the suspended membrane as end-mirror of a Fabry-Perot cavity. These achievements allow us to operate in the resolved sideband regime where the optical storage time exceeds the mechanical period of low-order mechanical drum modes. This condition is a prerequisite to achieve quantum control of the mechanical resonator with light.
Radiation pressure exerted by light in interferometric measurements is responsible for displacements of mirrors
which appear as an additional back-action noise and limit the sensitivity of the measurement. We experimentally
study these effects by monitoring in a very high-finesse optical cavity the displacements of a mirror with a
sensitivity at the 10-20m/√Hz level. This unique sensitivity is a step towards the first observation of the
fundamental quantum effects of radiation pressure and the resulting standard quantum limit in interferometric
measurements. Our experiment may become a powerful facility to test quantum noise reduction schemes, and
we already have demonstrated radiation-pressure induced correlations between two optical beams sent into the
same moving mirror cavity. Our scheme can be extended down to the quantum level and has applications both
in high-sensitivity measurements and in quantum optics.
Recent progress in high-finesse optical cavities and micro-mechanical resonators allows one to reach a new regime in which both mechanical and optical dynamics are governed by the radiation pressure exerted by light on mirrors. This optomechanical coupling leads to the existence of fundamental quantum limits in ultrasensitive interferometric measurements, and also to very efficient cooling mechanisms of micromirrors. We experimentally study these effects by monitoring in a very high-finesse cavity the displacements of a mirror coated on a microresonator. Directs effects of intracavity radiation pressure are experimentally demonstrated: we have observed a self-cooling of the resonator induced by the intracavity radiation pressure, to effective emperature in the 10K range. Further experimental progress and cryogenic operation may allow for quantum optics experiments and lead to the experimental observation of the quantum ground state of a mechanical resonator.
Radiation pressure exerted by light in interferometric measurements is responsible for displacements of mirrors
which appear as an additional back-action noise and limit the sensitivity of the measurement. We experimentally
study these effects by monitoring in a very highfinesse optical cavity the displacements of a mirror with
a sensitivity at the 10-20 m/√Hz level. This unique sensitivity is a step towards the first observation of the
fundamental quantum effects of radiation pressure and the resulting standard quantum limit in interferometric
measurements. Our experiment may become a powerful facility to test quantum noise reduction schemes,
and we already report the first experimental demonstration of a back-action noise cancellation. Using a classical
radiation-pressure noise to mimic the quantum noise of light, we have observed a drastic improvement of
sensitivity both in position and force measurements.
We have developed an experiment of ultrasensitive interferometric measurement of small displacements based
on a high-finesse Fabry-Perot cavity. We describe recent progress in our experimental setup in order to reach a
sensitivity better than 10-20 m/√Hz. This unique sensitivity is a step towards the first observation of radiation
pressure effects and the resulting standard quantum limit in interferometric measurements. Our experiment
may become a powerful facility to test quantum noise reduction schemes, and we already report the first experimental
demonstration of a back-action noise cancellation. Using a classical radiation-pressure noise to mimic
the quantum noise of light, we have observed a drastic improvement of sensitivity either in position or force
measurements.
We present an experiment where the motion of a silicon micro-mechanical resonator is optically monitored with
a very high-finesse optical cavity, down to a quantum-limited sensitivity at the 10-19m/√Hz level. We have
observed the thermal noise of the resonator at room temperature over a wide frequency range, and fully characterized
its optomechanical behaviour, in good agreement with theoretical models. We have also demonstrated a
direct effect of intracavity radiation pressure upon the dynamics of the micro-resonator in a detuned high-finesse
optical cavity: depending on the sign of the detuning, we have obtained both cooling and heating, with an
effective temperature ranging from 10 to 2000 K. We have also observed a related radiation-pressure induced
instability of the resonator. This experiment opens the way to radiation pressure-driven quantum optics effects,
with silicon resonators offering high resonance frequencies, low effective masses, and a high displacement sensitivity.
Possible experiments include QND measurement of light intensity or optomechanical squeezing of the
optical field, as well as the optical observation of the quantum ground state of a macroscopic oscillator.
Detecting quantum fluctuations of a mechanical resonator is a
long-standing goal of experimental physics. Recent progress has
been focussed on high frequency (MHz to GHz) resonators inserted
in a milli-Kelvin environment, with motion detection performed by
single electron transistor means. Here we propose a novel
experimental approach based on high-sensitivity optical monitoring
of the displacement of the resonator and feedback cooling. The
experimental setup is based on a micro-mechanical resonator
inserted in a high-finesse optical cavity and monitored by a
highly-stabilized laser system. Available optical technologies
provide an unequalled sensitivity, in the 1E-20 m/sqrt{Hz}
range. The displacement signal is used in real-time to perform a
feedback cooling in order to set the resonator's fundamental mode
of vibration in its quantum ground state. With the resonator at
cryogenic temperature, the feedback cooling mechanism should allow
to reach an effective temperature in the micro-Kelvin range.
Detecting quantum fluctuations of a mechanical resonator is a
long-standing goal of experimental physics. Recent progress has
been focussed on high frequency (MHz to GHz) resonators inserted
in a milli-Kelvin environment, with motion detection performed by
single electron transistor means. Here we propose a novel
experimental approach based on high-sensitivity optical monitoring
of the displacement of the resonator and feedback cooling. The
experimental setup is based on a micro-mechanical resonator
inserted in a high-finesse optical cavity and monitored by a
highly-stabilized laser system. Available optical technologies
provide an unequalled sensitivity, in the 10-20m/√Hz
range. The displacement signal is used in real-time to perform a
feedback cooling in order to set the resonator's fundamental mode
of vibration in its quantum ground state. With the resonator at
cryogenic temperature, the feedback cooling mechanism should allow
to reach an effective temperature in the micro-Kelvin range.
We discuss the use of active control to reduce mirrors position fluctuations at the quantum level. 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 an high-finesse optical cavity, and corrected by a feedback loop. We show that this approach can be extended to lock the mirror motion at the quantum level and we propose to use this quantum locking technique to reduce the noise in interferometric measurements such as gravitational-waves detectors. We analyze the back-action effects of the optomechanical sensor and show that quantum limits can be transferred from the sensor measurement to the interferometric one. This simple technique allows one to suppress the quantum effects of radiation pressure in the interferometer and to greatly enhance its sensitivity. The effect is furthermore insensitive to losses in the interferometer.
We have performed an experiment in order to measure the displacement of a mirror at the attometer level. The mirror is coated on a high-Q millimeter-sized mechanical resonator made of fused silica. Using a high-finesse optical cavity, a highly stabilized Ti:Sa laser source and a low-noise detection system allows us to reach a shot-noise limited sensitivity of 2.8 10-19m/√Hz at the resonator’s fundamental acoustic resonance frequency, about 2 MHz. We have also implemented a feedback scheme, where the information about the mirror's motion is used in a feedback loop to control the intensity of a radiation pressure force applied onto the mirror. This allows to reduce the thermal noise and to cool down the mirror well below its initial temperature. The effect of this cold damping mechanism is visualized both on the temporal evolution of the mirror displacement and on its distribution in phase-space, with a sensitivity of a few attometers.
We have also observed the thermal noise squeezing in the case of a parametrically-modulated feedback force, observing both the 50% theoretical limit of squeezing below the mirror’s parametric oscillation threshold, and the oscillation above threshold. Enhancement of the experimental setup, with the use of an optical cavity with a higher finesse inserted in a liquid helium cryostat, in order to observe quantum effects of radiation pressure such as the Standard Quantum Limit, will also be discussed.
Active control devices have long been proven effective in reducing the fluctuations of various physical parameters, both in electronics or in optics. In particular, systems controlling the intensity fluctuations of a laser beam by opto-electronic feedback are now widely used to reduce laser intensity noise. Such systems, make use of a beamsplitter (B), deviating part of the incoming beam onto a photodetector (PD). The resulting photocurrent, suitably amplified and filtered, is then fed into an intensity modulator (IM) which corrects the intensity fluctuations of the output beam. The correction can be applied either before the beamsplitter or after it.
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