[Show abstract][Hide abstract] ABSTRACT: Quantum information processing holds great promise for communicating and
computing data efficiently. However, scaling current photonic implementation
approaches to larger system size remains an outstanding challenge for realizing
disruptive quantum technology. Two main ingredients of quantum information
processors are quantum interference and single-photon detectors. Here we
develop a hybrid superconducting-photonic circuit system to show how these
elements can be combined in a scalable fashion on a silicon chip. We
demonstrate the suitability of this approach for integrated quantum optics by
interfering and detecting photon pairs directly on the chip with
waveguide-coupled single-photon detectors. Using a directional coupler
implemented with silicon nitride nanophotonic waveguides, we observe 97%
interference visibility when measuring photon statistics with two
monolithically integrated superconducting single photon detectors. The photonic
circuit and detector fabrication processes are compatible with standard
semiconductor thin-film technology, making it possible to implement more
complex and larger scale quantum photonic circuits on silicon chips.
[Show abstract][Hide abstract] ABSTRACT: We propose and demonstrate a dispersion control technique by combination of
different waveguide cross sections in an aluminum nitride micro-ring resonator.
Narrow and wide waveguides with normal and anomalous dispersion, respectively,
are linked with tapering waveguides and enclosed in a ring resonator to produce
a total dispersion near zero. The mode-coupling in multimoded waveguides is
also effectively suppressed. This technique provides new degrees of freedom and
enhanced flexibility in engineering the dispersion of microcomb resonators.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate broadband, low loss optical waveguiding in single crystalline GaN grown epitaxially on c-plane sapphire wafers through a buffered metal-organic chemical vapor phase deposition process. High Q optical microring resonators are realized in near infrared, infrared, and near visible regimes with intrinsic quality factors exceeding 50000 at all the wavelengths we studied. TEM analysis of etched waveguide reveals growth and etch-induced defects. Reduction of these defects through improved material and device processing could lead to even lower optical losses and enable a wideband photonic platform based on GaN-on-sapphire material system.
[Show abstract][Hide abstract] ABSTRACT: Using a stabilizing quadrature-feedback scheme the thermal motion of an on-chip opto-electromechanical resonator is squeezed far beyond the limit of classical parametric squeezing. It is shown that feedback on the Y quadrature by itself can already squeeze the thermal motion of the resonator, but the maximum achievable squeezing level is limited by the imprecision noise. By combining the feedback and parametric pumping a record of 15.1 dB of classical noise squeezing is demonstrated. This not only largely exceeds the 3 dB limit for regular squeezing, but is also deeper than ever can be achieved with feedback cooling. The detector-resonator interaction is analyzed within the semi-classical framework and it is shown that using this feedback-stabilized parametric pumping technique true quantum-squeezed states can be prepared when the resonator starts off close to its ground state, and that the ultimate amount of squeezing depends on the minimum detuning that can be achieved.
New Journal of Physics 04/2015; 17(4). DOI:10.1088/1367-2630/17/4/043056 · 3.56 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Operation of nanomechanical devices in water environment has been challenging
due to the strong viscous damping that greatly impedes the mechanical motion.
Here we demonstrate an optomechanical micro-wheel resonator integrated in
microfluidic system that supports low-loss optical resonances at near-visible
wavelength with quality factor up to 1.5 million. The device can be operated in
self-oscillation mode in air with low threshold power of 45 uW. The very high
optical Q allows the observation of the thermal Brownian motion of the
mechanical mode in both air and water environment with high
signal-to-background ratio. A numerical model is developed to calculate the
hydrodynamic effect on the device due to the surrounding water, which agrees
well with the experimental results. With its very high resonance frequency (170
MHz) and small loaded mass (75 pg), the present device is estimated to have
mass sensitivity of attogram level in liquid environment with bandwidth of 1
[Show abstract][Hide abstract] ABSTRACT: Electromagnetically induced transparency has great theoretical and
experimental importance in many physics subjects, such as atomic physics,
quantum optics, and more recent cavity optomechanics. Optical delay is the most
prominent feature of electromagnetically induced transparency, and in cavity
optomechanics optical delay is limited by mechanical dissipation rate of
sideband-resolved mechanical modes. Here we demonstrate a cascaded optical
transparency scheme by leveraging the parametric phonon-phonon coupling in a
multimode optomechanical system, where a low damping mechanical mode in the
unresolved-sideband regime is made to couple to an intermediate, high frequency
mechanical mode in the resolved-sideband regime of an optical cavity. Extended
optical delay and higher transmission, as well as optical advancing are
demonstrated. These results provide a route to realize ultra-long optical
delay, indicating a significant step toward integrated classical and quantum
information storage devices.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate squeezing of a strongly interacting opto-electromechanical
system using a parametric drive. By employing real-time feedback on the phase
of the pump at twice the resonance frequency the thermo-mechanical noise is
squeezed beyond the 3 dB instability limit. Surprisingly, this method can also
be used to generate highly nonlinear states. We show that using the parametric
drive with feedback on, classical number-like and cat-like states can be
prepared. This presents a valuable electro-optomechanical state-preparation
protocol that is extendable to the quantum regime.
Physical Review A 11/2014; 90(6). DOI:10.1103/PhysRevA.90.063809 · 2.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this paper we present a theory that predicts the phase noise
characteristics of self-sustained optomechanical oscillators. By treating the
cavity optomechanical system as a feedback loop consisting of an optical cavity
and a mechanical resonator, we analytically derive the transfer functions
relating the amplitude/phase noise of all the relevant dynamical quantities
from the quantum Langevin equations, and obtain a closed-form expressions for
the phase noise spectral densities contributed from thermomechanical noise,
photon shot noise, and low-frequency technical laser noise. We numerically
calculate the phase noise for various situations and perform a sample
calculation for an experimentally demonstrated system. We also show that the
presented model reduces to the well-known Leeson's phase noise model when the
amplitude noise and the amplitude/phase noise inter-transfers are ignored.
Physical Review A 04/2014; 90(2). DOI:10.1103/PhysRevA.90.023825 · 2.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We demonstrate an optomechanical phase shifter. By electrostatically deflecting the nanofabricated mechanical structure, the effective index of a nearby waveguide is changed and the resulting phase shift is measured using an integrated Mach-Zehnder interferometer. Comparing to thermo-optical phase shifters, our device does not consume power in static operation and also it can operate over large frequency, wavelength, and power ranges. Operation in the MHz range and sub-μs pulses is demonstrated.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate an optomechanical phase shifter. By electrostatically
deflecting the nanofabricated mechanical structure, the effective index of a
nearby waveguide is changed and the resulting phase shift is measured using an
integrated Mach-Zehnder interferometer. Comparing to thermo-optical phase
shifters, our device does not consume power in static operation and also it can
operate over large frequency, wavelength, and power ranges. Operation in the
MHz range and sub-$\mu$s pulses are demonstrated.
[Show abstract][Hide abstract] ABSTRACT: Synchronization in oscillatory systems is a frequent natural phenomenon and is becoming an important concept in modern physics. Nanomechanical resonators are ideal systems for studying synchronization due to their controllable oscillation properties and engineerable nonlinearities. Here we demonstrate synchronization of two nanomechanical oscillators via a photonic resonator, enabling optomechanical synchronization between mechanically isolated nanomechanical resonators. Optical backaction gives rise to both reactive and dissipative coupling of the mechanical resonators, leading to coherent oscillation and mutual locking of resonators with dynamics beyond the widely accepted phase oscillator (Kuramoto) model. In addition to the phase difference between the oscillators, also their amplitudes are coupled, resulting in the emergence of sidebands around the synchronized carrier signal.
[Show abstract][Hide abstract] ABSTRACT: A nanoelectromechanical resonator is used as an on-chip phase shifter. Unprecedentedly strong electrostatic effects are observed and using real-time parametric feedback the thermal motion of the resonator is squeezed below 3dB.
[Show abstract][Hide abstract] ABSTRACT: Parametric squeezing can reduce the uncertainty in one quadrature of the
position of a mechanical resonator, even below the standard quantum
limit, and it can improve measurement sensitivity. Here we demonstrate
squeezing of the thermal motion of a 570 kHz opto-electromechanical
resonator made out of high-stress SiN by modulating its spring constant
at twice the resonance frequency. Parametric and direct actuation are
achieved by applying a.c. voltages between strongly coupled electrodes
on the resonator and a fixed one. It is well know that using this method
the motion of one quadrature cannot be decreased more than 3 dB below
the undriven case before instabilities kick in. However, by measuring
the phase-space trajectory of the resonator and adjusting the phase of
the parametric drive in real-time we achieve a stationary reduction in
both quadratures that is far beyond this limit. Finally, due to the
strong coupling between the drive electrodes, the nonlinearity of the
resonator can be tuned all the way from a stiffening spring to a
[Show abstract][Hide abstract] ABSTRACT: We present the design and experimental comparison of femtogram L3-nanobeam photonic crystal cavities for optomechanical studies. Two symmetric nanobeams are created by placing three air slots in a silicon photonic crystal slab where three holes are removed. The nanobeams' mechanical frequencies are higher than 600 MHz with ultrasmall effective modal masses at approximately 20 femtograms. The optical quality factor (Q) is optimized up to 53,000. The optical and mechanical modes are dispersively coupled with a vacuum optomechanical coupling rate g<sub>0</sub>/2? exceeding 200 kHz. The anchor-loss-limited mechanical Q of the differential beam mode is evaluated to be greater than 10,000 for structures with ideally symmetric beams. The influence of variations on the air slot width and position is also investigated. The devices can be used as ultrasensitive sensors of mass, force, and displacement.
[Show abstract][Hide abstract] ABSTRACT: The maximum amplitude of mechanical oscillators coupled to optical cavities
are studied both analytically and numerically. The optical backaction on the
resonator enables self-sustained oscillations whose limit cycle is set by the
dynamic range of the cavity. The maximum attainable amplitude and the phonon
generation quantum efficiency of the backaction process are studied for both
unresolved and resolved cavities. Quantum efficiencies far exceeding one are
found in the resolved sideband regime where the amplitude is low. On the other
hand the maximum amplitude is found in the unresolved system. Finally, the role
of mechanical nonlinearities is addressed.
Physical Review A 11/2012; 86(5). DOI:10.1103/PhysRevA.86.053826 · 2.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We develop an all-integrated optoelectromechanical system that operates in
the superhigh frequency band. This system is based on an ultrahigh-Q slotted
photonic crystal (PhC) nanocavity formed by two PhC membranes, one of which is
patterned with electrode and capacitively driven. The strong simultaneous
electromechanical and optomechanical interactions yield efficient electrical
excitation and sensitive optical transduction of the bulk acoustic modes of the
PhC membrane. These modes are identified up to a frequency of 4.20 GHz, with
their mechanical Q factors ranging from 240 to 1,730. Directly linking signals
in microwave and optical domains, such optoelectromechanical systems will find
applications in microwave photonics in addition to those that utilize the
electromechanical and optomechanical interactions separately.
[Show abstract][Hide abstract] ABSTRACT: We have studied the elastic deformation of freely suspended atomically thin
sheets of muscovite mica, a widely used electrical insulator in its bulk form.
Using an atomic force microscope, we carried out bending test experiments to
determine the Young's modulus and the initial pre-tension of mica nanosheets
with thicknesses ranging from 14 layers down to just one bilayer. We found that
their Young's modulus is high (190 GPa), in agreement with the bulk value,
which indicates that the exfoliation procedure employed to fabricate these
nanolayers does not introduce a noticeable amount of defects. Additionally,
ultrathin mica shows low pre-strain and can withstand reversible deformations
up to tens of nanometers without breaking. The low pre-tension and high Young's
modulus and breaking force found in these ultrathin mica layers demonstrates
their prospective use as a complement for graphene in applications requiring
flexible insulating materials or as reinforcement in nanocomposites.
Nano Research 08/2012; DOI:10.1007/s12274-012-0240-3 · 7.01 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We present the design of a femtogram L3-nanobeam photonic crystal cavity for
optomechanical studies. Two symmetric nanobeams are created by placing three
air slots in a silicon photonic crystal slab where three holes are removed. The
optical quality factor (Q) is optimized up to 52,000. The nanobeams' mechanical
frequencies are higher than 600 MHz due to their femtogram effective modal
masses. The optical and mechanical modes are dispersively coupled with a vacuum
optomechanical coupling rate g0/2pi exceeding 200 kHz. The anchor-loss-limited
mechanical Q of the differential beam mode is evaluated to be greater than
10,000 for structures with ideally symmetric beams. The influence of variations
on the air slot width and position is also investigated. The devices can be
used as ultrasensitive sensors of mass, force, and displacement.
[Show abstract][Hide abstract] ABSTRACT: We fabricate freely suspended nanosheets of molybdenum disulphide (MoS2) which are characterized by quantitative optical microscopy and high-resolution friction force microscopy. We study the elastic deformation of freely suspended nanosheets of MoS2 using an atomic force microscope. The Young's modulus and the initial pre-tension of the nanosheets are determined by performing a nanoscopic version of a bending test experiment. MoS2 sheets show high elasticity and an extremely high Young's modulus (0.30 TPa, 50% larger than steel). These results make them a potential alternative to graphene in applications requiring flexible semiconductor materials.
PACS, 73.61.Le, other inorganic semiconductors, 68.65.Ac, multilayers, 62.20.de, elastic moduli, 81.40.Jj, elasticity and anelasticity, stress-strain relations.
Nanoscale Research Letters 04/2012; 7(1):233. DOI:10.1186/1556-276X-7-233 · 2.78 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We demonstrate a new optomechanical device system which allows highly efficient transduction of femtogram nanobeam resonators. Doubly clamped nanomechanical resonators with mass as small as 25 fg are embedded in a high-finesse two-dimensional photonic crystal nanocavity. Optical transduction of the fundamental flexural mode around 1 GHz was performed at room temperature and ambient conditions, with an observed displacement sensitivity of 0.94 fm/Hz(1/2). Comparison of measurements from symmetric and asymmetric double-beam devices reveals hybridization of the mechanical modes where the structural symmetry is shown to be the key to obtain a high mechanical quality factor. Our novel configuration opens the way for a new category of "NEMS-in-cavity" devices based on optomechanical interaction at the nanoscale.