[Show abstract][Hide abstract]ABSTRACT: We developed an apparatus to couple a 50-μm diameter whispering-gallery silica microtoroidal res- onator in a helium-4 cryostat using a straight optical tapered-fiber at 1550 nm wavelength. On a top- loading probe specifically adapted for increased mechanical stability, we use a specifically-developed “cryotaper” to optically probe the cavity, allowing thus to record the calibrated mechanical spectrum of the optomechanical system at low temperatures. We then demonstrate excellent thermalization of a 63-MHz mechanical mode of a toroidal resonator down to the cryostat’s base temperature of 1.65 K, thereby proving the viability of the cryogenic refrigeration via heat conduction through static low-pressure exchange gas. In the context of optomechanics, we therefore provide a versatile and powerful tool with state-of-the-art performances in optical coupling efficiency, mechanical stability, and cryogenic cooling.
Full-text Article · Apr 2013 · Review of Scientific Instruments
[Show abstract][Hide abstract]ABSTRACT: We present optical measurements of the photothermal response of a whispering-gallery silica microresonator in a helium-4 exchange gas cryostat. Using transient-mode numerical simulations, we discuss the various heat propagation mechanisms.
[Show abstract][Hide abstract]ABSTRACT: 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.
[Show abstract][Hide abstract]ABSTRACT: A micromechanical oscillator is cooled close to the quantum ground state using a laser tuned to its lower mechanical sideband. This highly coupled system allows to optically control the transmission of a weak probe beam.
[Show abstract][Hide abstract]ABSTRACT: Cooling a mesoscopic mechanical oscillator to its quantum ground state is
elementary for the preparation and control of low entropy quantum states of
large scale 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 3He gas. Two-level system induced damping via structural defect states is
shown to be strongly reduced, and simultaneously serves as novel thermometry
method to independently quantify excess heating due to the cooling laser. We
demonstrate that dynamical backaction 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.
[Show abstract][Hide abstract]ABSTRACT: 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. OCIS codes: (020.3320) Laser cooling; (140.3945) Microcavities; (230.4685) Optical microelectromechanical devices The control of low-entropy quantum states of a micro-oscillator could not only allow researchers to probe quantum mechanical 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, two challenges have to be met: its effective temperature
[Show abstract][Hide abstract]ABSTRACT: 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.
[Show abstract][Hide abstract]ABSTRACT: We present the dynamic optical response of silica microcavities in a4He environment. Dispersive properties of silica and external detection of a superfluid sound are characterized, due to accurate temperature tuning of the cryodevice.
[Show abstract][Hide abstract]ABSTRACT: We present the optical and mechanical properties of toroidal optomechanical resonators thermalized to Helium-3 (600 mK) temperatures. Dramatic improvements of mechanical quality factors are reported and evidence for direct phonon absorption is presented.
[Show abstract][Hide abstract]ABSTRACT: Using resolved-sideband laser cooling, a micromechanical oscillator is cooled to an average occupation of 63 quanta, and simultaneously measured close to the limit imposed by the Heisenberg uncertainty principle.
Article · Oct 2009 · Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS
[Show abstract][Hide abstract]ABSTRACT: We present the optical and mechanical properties of high-Q fused silica
microtoroidal resonators at cryogenic temperatures (down to 1.6 K). A thermally
induced optical multistability is observed and theoretically described; it
serves to characterize quantitatively the static heating induced by light
absorption. Moreover the influence of structural defect states in glass on the
toroid mechanical properties is observed and the resulting implications of
cavity optomechanical systems on the study of mechanical dissipation discussed.
[Show abstract][Hide abstract]ABSTRACT: Exploring quantum effects in mesoscopic mechanical oscillators as palpable as a pendulum or a cantilever has been a subject of long-standing interest in Quantum Physics and in the context of gravitational wave detection, and has recently - within the setting of cavity optomechanics - received significant interest. Studying non-classical aspects however requires the ability to both prepare and probe the mechanical degree of freedom at the quantum level. Classical thermal noise, and the tiny displacements associated with quantum signatures, pose two of the main experimental challenges. Up to now, they have been thought to be most easily addressed with nanomechanical oscillators cooled in dilution refrigerators, and probed with nanoelectronic motion transducers. This paper demonstrates that cooling and monitoring of a mechanical device with only a few thermal quanta is possible with objects discernable to the bare eye, in the present case given by a high-quality on-chip silica oscillator. These advances are afforded by two key properties of cavity optomechanics: optical interferometric monitoring of mechanical displacement with sensitivity at the attometer level, and resolved sideband laser cooling of a mechanical mode in addition to cryogenic pre-cooling of the optomechanical system. To probe the fluctuations of the mechanical radial breathing mode (RBM) in the silica oscillator, a high Q mode is excited using a continuous-wave Tksapphire laser. Fluctuations of the cavity radius (as induced by thermal excitation of the RBM) thus induce fluctuations in the WGM resonance frequency. A homodyne detection scheme allows measuring the mechanical fluctuations at a sensitivity of ca. 10<sup>-18</sup> m/Hz<sup>1/2</sup>. From the measured phase fluctuation spectrum, resonance frequency, damping rate and occupation number of the RBM can be derived.
[Show abstract][Hide abstract]ABSTRACT: Using resolved-sideband laser cooling, a micromechanical oscillator is cooled to an average occupation of 63 quanta, and simultaneously measured close to the limit imposed by the Heisenberg uncertainty principle. Extending cavity optomechanics to the nanoscale is demonstrated using a nanomechanical oscillator dispersively coupled to an optical microresonator.
[Show abstract][Hide abstract]ABSTRACT: The theory of quantum measurement of mechanical motion, describing the mutual coupling of a meter and a measured object, predicts a variety of phenomena such as quantum backaction, quantum correlations and non-classical states of motion. In spite of great experimental efforts, mostly based on nano-electromechanical systems, probing these in a laboratory setting has as yet eluded researchers. Cavity optomechanical systems, in which a high-quality optical resonator is parametrically coupled to a mechanical oscillator, hold great promise as a route towards the observation of such effects with macroscopic oscillators. Here, we present measurements on optomechanical systems exhibiting radiofrequency (62-122 MHz) mechanical modes, cooled to very low occupancy using a combination of cryogenic precooling and resolved-sideband laser cooling. The lowest achieved occupancy is n similar to 63. Optical measurements of these ultracold oscillators' motion are shown to perform in a near-ideal manner, exhibiting an imprecision-backaction product about one order of magnitude lower than the results obtained with nano-electromechanical transducers.
[Show abstract][Hide abstract]ABSTRACT: We report the study of the optical and mechanical properties of high-Q fused silica microtoroidal resonators at cryogenic temperatures (down to 1.6 K). A thermally induced optical multistability is observed and theoretically described, originating from the reverse thermally induced optical frequency shift. Moreover the influence of structural defect states (two level fluctuators) on their mechanical properties is observed and probed at an unprecedentedly achieved low phonon number. The resulting implications for cavity optomechanics and studies of mechanical decoherence are also discussed.
[Show abstract][Hide abstract]ABSTRACT: We show that evanescent fields of microresonators can be employed for cavity-enhanced high-sensitivity monitoring of nanomechanical motion. This novel scheme opens the path to observing backaction effects using optical gradient forces in the resolved-sideband regime.
[Show abstract][Hide abstract]ABSTRACT: The observation of quantum phenomena in macroscopic mechanical oscillators has been a subject of interest since the inception of quantum mechanics. Prerequisite to this regime are both preparation of the mechanical oscillator at low phonon occupancy and a measurement sensitivity at the scale of the spread of the oscillator's ground state wavefunction. It has been widely perceived that the most promising approach to address these two challenges are electro nanomechanical systems. Here we approach for the first time the quantum regime with a mechanical oscillator of mesoscopic dimensions--discernible to the bare eye--and 1000-times more massive than the heaviest nano-mechanical oscillators used to date. Imperative to these advances are two key principles of cavity optomechanics: Optical interferometric measurement of mechanical displacement at the attometer level, and the ability to use measurement induced dynamic back-action to achieve resolved sideband laser cooling of the mechanical degree of freedom. Using only modest cryogenic pre-cooling to 1.65 K, preparation of a mechanical oscillator close to its quantum ground state (63+-20 phonons) is demonstrated. Simultaneously, a readout sensitivity that is within a factor of 5.5+-1.5 of the standard quantum limit is achieved. The reported experiments mark a paradigm shift in the approach to the quantum limit of mechanical oscillators using optical techniques and represent a first step into a new era of experimental investigation which probes the quantum nature of the most tangible harmonic oscillator: a mechanical vibration.
[Show abstract][Hide abstract]ABSTRACT: We expose low temperature optomechanical properties of toroidal silica microcavities and report on low phonon occupation number achieved when combining standard cryogenic operation and optical cooling.
[Show abstract][Hide abstract]ABSTRACT: Cavity-enhanced radiation-pressure coupling of optical and mechanical degrees of freedom gives rise to a range of optomechanical phenomena, in particular providing a route to the quantum regime of mesoscopic mechanical oscillators. A prime challenge in cavity optomechanics has been to realize systems that simultaneously maximize optical finesse and mechanical quality. Here we demonstrate, for the first time, independent control over both mechanical and optical degrees of freedom within the same on- chip resonator. The first direct observation of mechanical normal mode coupling in a micromechanical system allows for a quantitative understanding of mechanical dissipation. Subsequent optimization of the resonator geometry enables intrinsic material loss limited mechanical Q-factors, rivalling the best values reported in the high megahertz frequency range, while simultaneously preserving the resonators’ ultrahigh optical finesse. As well as providing a complete understanding of mechanical dissipation in microresonator-based optomechanical systems, our results provide a promising setting for cavity optomechanics.