587 research outputs found
Optimized optomechanical crystal cavity with acoustic radiation shield
We present the design of an optomechanical crystal nanobeam cavity that
combines finite-element simulation with numerical optimization, and considers
the optomechanical coupling arising from both moving dielectric boundaries and
the photo-elastic effect. Applying this methodology results in a nanobeam with
an experimentally realized intrinsic optical Q-factor of 1.2x10^6, a mechanical
frequency of 5.1GHz, a mechanical Q-factor of 6.8x10^5 (at T=10K), and a
zero-point-motion optomechanical coupling rate of g=1.1MHz.Comment: 4 pages, 4 figure
Two-dimensional phononic-photonic bandgap optomechanical crystal cavity
We present the fabrication and characterization of an artificial crystal
structure formed from a thin-film of silicon which has a full phononic bandgap
for microwave X-band phonons and a two-dimensional pseudo-bandgap for
near-infrared photons. An engineered defect in the crystal structure is used to
localize optical and mechanical resonances in the bandgap of the planar
crystal. Two-tone optical spectroscopy is used to characterize the cavity
system, showing a large vacuum coupling rate of 220kHz between the fundamental
optical cavity resonance at 195THz and a co-localized mechanical resonance at
9.3GHz.Comment: 4 pages, 4 figure
Observation of Quantum Motion of a Nanomechanical Resonator
In this Letter we use resolved sideband laser cooling to cool a mesoscopic mechanical resonator to near its quantum ground state (phonon occupancy 2.6±0.2), and observe the motional sidebands generated on a second probe laser. Asymmetry in the sideband amplitudes provides a direct measure of the displacement noise power associated with quantum zero-point fluctuations of the nanomechanical resonator, and allows for an intrinsic calibration of the phonon occupation number
Nonlinear radiation pressure dynamics in an optomechanical crystal
Utilizing a silicon nanobeam optomechanical crystal, we investigate the
attractor diagram arising from the radiation pressure interaction between a
localized optical cavity at nm and a mechanical resonance at
GHz. At a temperature of K, highly nonlinear
driving of mechanical motion is observed via continuous wave optical pumping.
Introduction of a time-dependent (modulated) optical pump is used to steer the
system towards an otherwise inaccessible dynamically stable attractor in which
mechanical self-oscillation occurs for an optical pump red-detuned from the
cavity resonance. An analytical model incorporating thermo-optic effects due to
optical absorption heating is developed, and found to accurately predict the
measured device behavior.Comment: 5 pages, 3 figure
Highly efficient coupling from an optical fiber to a nanoscale silicon optomechanical cavity
We demonstrate highly efficient coupling of light from an optical fiber to a silicon photonic crystal optomechanical cavity. The fiber-to-cavity coupling utilizes a compact (L ≈ 25 µm) intermediate adiabatic coupler. The optical coupling is lithographically controlled, broadband, relatively insensitive to fiber misalignment, and allows for light to be transferred from an optical fiber to, in principle, any photonic chip with refractive index greater than that of the optical fiber. Here we demonstrate single-sided cavity coupling with a total fiber-to-cavity optical power coupling efficiency of 85%
Squeezed light from a silicon micromechanical resonator
Monitoring a mechanical object’s motion, even with the gentle
touch of light, fundamentally alters its dynamics. The experimental
manifestation of this basic principle of quantum mechanics, its
link to the quantum nature of light and the extension of quantum
measurement to the macroscopic realm have all received extensive
attention over the past half-century. The use of squeezed light, with
quantum fluctuations below that of the vacuum field, was proposed
nearly three decades ago
as a means of reducing the optical read-out
noise in precision force measurements. Conversely, it has also been proposed that a continuous measurement of a mirror’s position with
light may itself give rise to squeezed light. Such squeezed-light generation has recently been demonstrated in a system of ultracold
gas-phase atoms whose centre-of-mass motion is analogous to the
motion of a mirror. Here we describe the continuous position measurement of a solid-state, optomechanical system fabricated from a
silicon microchip and comprising a micromechanical resonator
coupled to a nanophotonic cavity. Laser light sent into the cavity is
used to measure the fluctuations in the position of the mechanical
resonator at a measurement rate comparable to its resonance frequency and greater than its thermal decoherence rate. Despite the
mechanical resonator’s highly excited thermal state (10^4
phonons),
we observe, through homodyne detection, squeezing of the reflected
light’s fluctuation spectrum at a level 4.5 ± 0.2 percent below that of
vacuum noise over a bandwidth of a few megahertz around the
mechanical resonance frequency of 28megahertz. With further
device improvements, on-chip squeezing at significant levels should
be possible, making such integrated microscale devices well suited
for precision metrology applications
Modeling Dispersive Coupling and Losses of Localized Optical and Mechanical Modes in Optomechanical Crystals
Periodically structured materials can sustain both optical and mechanical
excitations which are tailored by the geometry. Here we analyze the properties
of dispersively coupled planar photonic and phononic crystals: optomechanical
crystals. In particular, the properties of co-resonant optical and mechanical
cavities in quasi-1D (patterned nanobeam) and quasi-2D (patterned membrane)
geometries are studied. It is shown that the mechanical Q and optomechanical
coupling in these structures can vary by many orders of magnitude with modest
changes in geometry. An intuitive picture is developed based upon a
perturbation theory for shifting material boundaries that allows the
optomechanical properties to be designed and optimized. Several designs are
presented with mechanical frequency ~ 1-10 GHz, optical Q-factor Qo > 10^7,
motional masses meff 100 femtograms, optomechanical coupling length LOM < 5
microns, and a radiation-limited mechanical Q-factor Qm > 10^7.Comment: 25 pages, 9 figure
Laser noise in cavity-optomechanical cooling and thermometry
We review and study the roles of quantum and classical fluctuations in recent cavity-optomechanical experiments which have now reached the quantum regime (mechanical phonon occupancy ≾1) using resolved sideband laser cooling. In particular, both the laser noise heating of the mechanical resonator and the form of the optically transduced mechanical spectra, modified by quantum and classical laser noise squashing, are derived under various
measurement conditions. Using this theory, we analyze recent ground-state laser cooling and motional sideband asymmetry experiments with nanoscale optomechanical crystal resonators
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