378 research outputs found
Simulation and Fabrication of Three Novel Micromechanical Sensors
This work focuses on the simulation, fabrication and characterization of novel microdevices for chemical and biological sensors for improved sensitivity, enhanced performance and applicability. Specifically, microbridge and microcoil sensors have been fabricated via advanced microfabrication technologies. Due to the potential application in chemical and biological sensing, the growth of gold and platinum nanowires during an electrolysis process have also been investigated.
A microbridge can be considered as the head-to-head fusion of two cantilevers and the middle of the bridge would deform in a way similar to a microcantilever. The microbridge sensing device is more stable than the microcantilever, especially in turbulent or vibrational conditions, since both ends are fixed. The trade-off is the low ΔR/R change (sensitivity) of the microbridge compared to that of the microcantilever. Simulation of the microbridge has been conducted via Finite Element Analysis (FEA). The width, thickness and doping level of the piezoresistor play an important part in the sensitivity of the microbridge. Based on the simulation results and following standard microfabrication technology, microbridges have been fabricated. The detection of Hg2+ based on the microbridge platform was investigated for sensor validation.
The microcoil hygrometer can be used as a universal tool for the detection of chemical species by depositing a chemical specific coating on one side of the coil. The coil movement can be readily observed by the human eye and it advances as a cost-effective and power-free device. A micro- or nano-scale sized coil provides an outstanding sensor platform with improved dynamic response, greatly reduced size, and the integration of micromechanical components with on-chip electronic circuitry. Following standard microfabrication techniques, an SiO2/Si/SU-8 microcoil has been fabricated. After surface modification by treating the coil with aminopropyltriethoxysilane (APS), the microcoil was exposed to acetic acid vapor in air for characterization. This microcoil device has a potential to be used as a novel microsensor for the detection of chemical and biological species both in air and in solutions.
A self-assembled approach to grow gold and platinum nanowires across the gap of two electrodes on a surface using an electrolysis process has been investigated. In this process, the anode electrode is oxidized to form nanowires on the cathode. The DC offset, AC signal frequency and the space between the two electrodes all play important roles in the growth of the nanowires
On-chip generation and collectively coherent control of the superposition of the whole family of Dicke states
Integrated quantum photonics has recently emerged as a powerful platform for
generating, manipulating, and detecting entangled photons. Multipartite
entangled states lie at the heart of the quantum physics and are the key
enabling resources for scalable quantum information processing. Dicke state is
an important class of genuinely entangled state, which has been systematically
studied in the light-matter interactions, quantum state engineering and quantum
metrology. Here, by using a silicon photonic chip, we report the generation and
collectively coherent control of the entire family of four-photon Dicke states,
i.e. with arbitrary excitations. We generate four entangled photons from two
microresonators and coherently control them in a linear-optic quantum circuit,
in which the nonlinear and linear processing are achieved in a chip-scale
device. The generated photons are in telecom band, which lays the groundwork
for large-scale photonic quantum technologies for multiparty networking and
metrology.Comment: 19 pages, 4 figures in the main text and 13 figures in the
Supplemental Materia
Polarization-entangled quantum frequency comb
Integrated micro-resonator facilitates the realization of quantum frequency
comb (QFC), which provides a large number of discrete frequency modes with
broadband spectral range and narrow linewidth. However, all previous
demonstrations have focused on the generation of energy-time or time-bin
entangled photons from QFC. Realizing polarization-entangled quantum frequency
comb, which is the important resource for fundamental study of quantum
mechanics and quantum information applications, remains challenging. Here, we
demonstrate, for the first time, a broadband polarization-entangled quantum
frequency comb by combining an integrated silicon nitride micro-resonator with
a Sagnac interferometer. With a free spectral range of about 99 GHz and a
narrow linewidth of about 190 MHz, our source provides 22 polarization
entangled photons pairs with frequency covering the whole telecom C-band. The
entanglement fidelities for all 22 pairs are above 81%, including 17 pairs with
fidelities higher than 90%. Our demonstration paves the way for employing the
polarization-entangled quantum frequency comb in quantum network using CMOS
technology as well as standard dense wavelength division multiplexing
technology.Comment: 11 pages, 9 figure
Sound non-reciprocity based on synthetic magnetism
Synthetic magnetism has been recently realized using spatiotemporal
modulation patterns, producing non-reciprocal steering of charge-neutral
particles such as photons and phonons. Here, we design and experimentally
demonstrate a non-reciprocal acoustic system composed of three compact cavities
interlinked with both dynamic and static couplings, in which phase-correlated
modulations induce a synthetic magnetic flux that breaks time-reversal
symmetry. Within the rotating wave approximation, the transport properties of
the system are controlled to efficiently realize large non-reciprocal acoustic
transport. By optimizing the coupling strengths and modulation phases, we
achieve frequency-preserved unidirectional transport with 45-dB isolation ratio
and 0.85 forward transmission. Our results open to the realization of acoustic
nonreciprocal technologies with high efficiency and large isolation, and offer
a route towards Floquet topological insulators for sound.Comment: 13 pages, 4 figure
All-optical spatio-temporal metrology for isolated attosecond pulses
Characterizing an isolated attosecond pulse (IAP) is essential for its
potential applications. A complete characterization of an IAP ultimately
requires the determination of its electric field in both time and space
domains. However, previous methods, like the widely-used RABBITT and attosecond
streaking, only measure the temporal profile of the attosecond pulse. Here we
demonstrate an all-optical method for the measurement of the space-time
properties of an IAP. By introducing a non-collinear perturbing pulse to the
driving field, the process of IAP generation is modified both spatially and
temporally, manifesting as a spatial and a frequency modulation in the harmonic
spectrum. By using a FROG-like retrieval method, the spatio-spectral phases of
the harmonic spectrum are faithfully extracted from the induced spatio-spectral
modulations, which allows a thoroughgoing characterization of the IAP in both
time and space. With this method, the spatio-temporal structures of the IAP
generated in a two-color driving field in both the near- and far-field are
fully reconstructed, from which a weak spatio-temporal coupling in the IAP
generation is revealed. Our approach overcomes the limitation in the temporal
measurement in conventional in situ scheme, providing a reliable and holistic
metrology for IAP characterization.Comment: 18 pages, 5 figure
Effect of hydrodynamic heterogeneity on particle dispersion in a Taylor-Couette flow reactor with variable configurations of inner cylinder
BackgroundEffect of hydrodynamic heterogeneity on particle dispersion in a Taylor-Couette flow (TC) reactor with variable configurations of inner cylinder has been investigated using CFD modelling.MethodsParticle dispersion was tracked based on the Eulerian-Lagrangian approach, where the reactant solution phase was solved in the Eulerian reference frame, while the particle dispersion was calculated by tracking a large number of particles with consideration of the hydrodynamic forces acting on particles and adopting actual particle properties measured from the particle synthesis experiments.Significant FindingsThe simulation reveals that particle dispersion is significantly enhanced by increasing the inner cylinder rotational speed, characterized by particle distribution for both circular inner cylinder Taylor-Couette flow reactor (CTC) and lobed cross-section inner cylinder Taylor-Couette flow reactor (LTC). Particle trajectories or dispersion are influenced by the turbulent Taylor vortices. Particle radial dispersion affects the particle classification by presenting different particle axial velocities in radial direction, while particle axial dispersion can be seen as an indicator for global mixing occurring in the TC reactor, which is enhanced at high rotational speed, especially in the LTC. The calculated dispersion coefficient is found to be similar to the shape of particle size distribution found in the experiments
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