Rémi Rivière

Optomechanically induced transparency

Mechanical Transparency In atomic gases and other solid-state systems with appropriate energy levels, manipulation of the optical properties can be induced with a control pulse, allowing the system to transmit light of specific wavelengths that would otherwise have been absorbed. Weis et al. (p. 1520, published online 11 November) now report electromagnetically induced transparency in an optomechanical system whereby the coupling of a cavity to a light pulse is used to control the transmission of light through the cavity. This approach may help to allow the engineering of light storage and routing on an optical chip. Radiation pressure is used to manipulate the optical properties of an optomechanical system. Electromagnetically induced transparency is a quantum interference effect observed in atoms and molecules, in which the optical response of an atomic medium is controlled by an electromagnetic field. We demonstrated a form of induced transparency enabled by radiation-pressure coupling of an optical and a mechanical mode. A control optical beam tuned to a sideband transition of a micro-optomechanical system leads to destructive interference for the excitation of an intracavity probe field, inducing a tunable transparency window for the probe beam. Optomechanically induced transparency may be used for slowing and on-chip storage of light pulses via microfabricated optomechanical arrays.

Resolved-sideband cooling of a micromechanical oscillator

In atomic laser cooling, preparation of the motional quantum ground state has been achieved using resolved-sideband cooling of trapped ions. Here, we report the first demonstration of resolved-sideband cooling of a mesoscopic mechanical oscillator, a key step towards ground-state cooling as quantum back-action is sufficiently suppressed in this scheme. A laser drives the first lower sideband of an optical microcavity resonance, the decay rate of which is twenty times smaller than the eigenfrequency of the associated mechanical oscillator. Cooling rates above 1.5 MHz are attained, three orders of magnitude higher than the intrinsic dissipation rate of the mechanical device that is independently monitored at the level. Direct spectroscopy of the motional sidebands of the cooling laser confirms the expected suppression of motional increasing processes during cooling. Moreover, using two-mode pumping, this regime could enable motion measurement beyond the standard quantum limit and the concomitant generation of non-classical states of motion. Laser-driven resolved sideband cooling of the resonant vibrational mode of a toroidal microcavity represents another step towards reaching the quantum ground state.

Optomechanically Induced Transparency

In analogy to electromagnetically induced transparency observed in atomic systems, we demonstrate that the transmission of a probe laser beam through an optomechanical device can be modulated using a second, “control” laser beam.

Resolved-sideband cooling and position measurement of a micromechanical oscillator close to the Heisenberg uncertainty limit

Optomechanical systems in which a high-quality optical resonator is coupled to a mechanical oscillator hold great promise for examining quantum effects in relatively large structures. As a step towards this, a silica microtoroid has now been cooled to the point that it has just 63 thermal quanta.

High-sensitivity monitoring of micromechanical vibration using optical whispering gallery mode resonators

The inherent coupling of optical and mechanical modes in high finesse optical microresonators provides a natural, highly sensitive transduction mechanism for micromechanical vibration. Using homodyne and polarization spectroscopy techniques, we achieve shot-noise limited displacement sensitivities of . In an unprecedented manner, this enables the detection and study of a variety of mechanical modes, which are identified as radial breathing, flexural and torsional modes using three-dimensional finite element modeling. Furthermore, a broadband equivalent displacement noise is measured and found to agree well with models for thermorefractive noise in silica dielectric cavities. Implications for ground-state cooling, displacement sensing and Kerr squeezing are discussed.

Optomechanical sideband cooling of a micromechanical oscillator close to the quantum ground state

Cooling a mesoscopic mechanical oscillator to its quantum ground state is elementary for the preparation and control of quantum states of mechanical objects. Here, we pre-cool a 70-MHz micromechanical silica oscillator to an occupancy below 200 quanta by thermalizing it with a 600-mK cold He-3 gas. Two-level-system induced damping via structural defect states is shown to be strongly reduced and simultaneously serves as a thermometry method to independently quantify excess heating due to the cooling laser. We demonstrate that dynamical back action optical sideband cooling can reduce the average occupancy to 9 +/- 1 quanta, implying that the mechanical oscillator can be found (10 +/- 1)% of the time in its quantum ground state.

Cryogenic properties of optomechanical silica microcavities

We expose cryogenic (1.6 K) optomechanical properties of high-Q toroidal silica microcavities. A thermally induced optical multistability and the influence of structural defects of amorphous materials on phonon propagation are described.

Ultralow dissipation optomechanical resonators on a chip

Over recent years it has become experimentally possible to study the coupling of optical and mechanical modes by means of cavity-enhanced radiation pressure[1] which might enable ground state-cooling of macroscopic mechanical oscillators. For achieving this major goal in the field of cavity-optomechanics and for applications such as low-loss, narrowband ‘photonic clocks’ a combination of high optical finesse and high mechanical quality factors at mechanical oscillation frequencies exceeding the optical cavitys linewidth[1] is desirable. It has, however, so far not been possible to combine mechanical Q-factors comparable to those achieved in the field of nano- and microelectromechanical systems (e.g. [2]) with state-of-the-art values of optical finesse[3]. Here we show independent control over both optical and mechanical degrees of freedom in the same microscale optomechanical resonator[4].

Cavity optomechanics: Cooling of a micromechanical oscillator into the quantum regime

Using optical sideband cooling, a micromechanical oscillator is cooled to a phonon occupancy below 10 phonons, corresponding to a probability of finding it in its quantum ground state more than 10% of the time.

Cooling of a mechanical oscillator close to the quantum regime

The control of low-entropy quantum states of a micro-oscillator could not only allow researchers to probe quantum phenomena—such as entanglement and decoherence—at an unprecedentedly large scale, but also enable their use as interfaces in hybrid quantum systems. Preparing and probing an oscillator in the conceptually simplest low-entropy state, its quantum ground state, has now become a major goal in Cavity Optomechanics [1]. However, to experimentally achieve this goal, its effective temperature T<inf>eff</inf> has to be reduced sufficiently so that ħΩ<inf>m</inf> >>s k<inf>B</inf>T<inf>eff</inf> (ħ is the reduced Planck constant, k<inf>B</inf> the Boltzman constant, and Ω<inf>m</inf> the mechanical resonance pulsation). Using conventional cryogenic refrigeration, a nanomechanical oscillator has recently been cooled to the quantum regime and probed by a superconducting qubit to which it was piezoelectrically coupled [2].