474,512 research outputs found
Fabrication and deterministic transfer of high quality quantum emitter in hexagonal boron nitride
Color centers in solid state crystals have become a frequently used system
for single photon generation, advancing the development of integrated photonic
devices for quantum optics and quantum communication applications. In
particular, defects hosted by two-dimensional (2D) hexagonal boron nitride
(hBN) are a promising candidate for next-generation single photon sources, due
to its chemical and thermal robustness and high brightness at room temperature.
The 2D crystal lattice of hBN allows for a high extraction efficiency and easy
integration into photonic circuits. Here we develop plasma etching techniques
with subsequent high temperature annealing to reliably create defects. We show
how different fabrication parameters influence the defect formation probability
and the emitter brightness. A full optical characterization reveals the higher
quality of the created quantum emitters, represented by a narrow spectrum,
short excited state lifetime and high single photon purity. We also
investigated the photostability on short and very long timescales. We utilize a
wet chemically-assisted transfer process to reliably transfer the single photon
sources onto arbitrary substrates, demonstrating the feasibility for the
integration into scalable photonic quantum information processing networks.Comment: revised versio
Hybrid Group IV Nanophotonic Structures Incorporating Diamond Silicon-Vacancy Color Centers
We demonstrate a new approach for engineering group IV semiconductor-based
quantum photonic structures containing negatively charged silicon-vacancy
(SiV) color centers in diamond as quantum emitters. Hybrid SiC/diamond
structures are realized by combining the growth of nanoand micro-diamonds on
silicon carbide (3C or 4H polytype) substrates, with the subsequent use of
these diamond crystals as a hard mask for pattern transfer. SiV color
centers are incorporated in diamond during its synthesis from molecular diamond
seeds (diamondoids), with no need for ionimplantation or annealing. We show
that the same growth technique can be used to grow a diamond layer controllably
doped with SiV on top of a high purity bulk diamond, in which we
subsequently fabricate nanopillar arrays containing high quality SiV
centers. Scanning confocal photoluminescence measurements reveal optically
active SiV lines both at room temperature and low temperature (5 K) from
all fabricated structures, and, in particular, very narrow linewidths and small
inhomogeneous broadening of SiV lines from all-diamond nano-pillar arrays,
which is a critical requirement for quantum computation. At low temperatures (5
K) we observe in these structures the signature typical of SiV centers in
bulk diamond, consistent with a double lambda. These results indicate that high
quality color centers can be incorporated into nanophotonic structures
synthetically with properties equivalent to those in bulk diamond, thereby
opening opportunities for applications in classical and quantum information
processing
Optical polarization of nuclear ensembles in diamond
We report polarization of a dense nuclear-spin ensemble in diamond and its
dependence on magnetic field and temperature. The polarization method is based
on the transfer of electron spin polarization of negatively charged nitrogen
vacancy color centers to the nuclear spins via the excited-state level
anti-crossing of the center. We polarize 90% of the 14N nuclear spins within
the NV centers, and 70% of the proximal 13C nuclear spins with hyperfine
interaction strength of 13-14 MHz. Magnetic-field dependence of the
polarization reveals sharp decrease in polarization at specific field values
corresponding to cross-relaxation with substitutional nitrogen centers, while
temperature dependence of the polarization reveals that high polarization
persists down to 50 K. This work enables polarization of the 13C in bulk
diamond, which is of interest in applications of nuclear magnetic resonance, in
quantum memories of hybrid quantum devices, and in sensing.Comment: 8 pages, 5 figure
Visible Light Fluorescence Switching in Dye-Doped Conjugated Polymer Nanoparticles
Conjugated polymer nanoparticles (CPNs) harvest energy from photons and transfer it efficiently to dye molecules in their proximity. My research focuses on a kind of photochromic dye that harnesses the transferred energy to perform its photochromic conversion, resulting in fluorescence switching of the CPN. My system features PFBT nanoparticles and a class of merocyanine dyes. The fluorescence of the system can be activated and detected using single color visible light by modulating the energy transfer pathway between the CPN and the dye. Kinetic analysis and modeling explains the accelerated fluorescence switching observed in the system, producing new insights that will both contribute to more structural understanding of similar systems and lead to potential applications that harness similar effects
Scan and paint: theory and practice of a sound field visualization method
Sound visualization techniques have played a key role in the development of acoustics throughout history. The development of measurement apparatus and techniques for displaying sound and vibration phenomena has provided excellent tools for building understanding about specific problems. Traditional methods, such as step-by-step measurements or simultaneous multichannel systems, have a strong tradeoff between time requirements, flexibility, and cost. However, if the sound field can be assumed time stationary, scanning methods allow us to assess variations across space with a single transducer, as long as the position of the sensor is known. The proposed technique, Scan and Paint, is based on the acquisition of sound pressure and particle velocity by manually moving a P-U probe (pressure-particle velocity sensors) across a sound field whilst filming the event with a camera. The sensor position is extracted by applying automatic color tracking to each frame of the recorded video. It is then possible to visualize sound variations across the space in terms of sound pressure, particle velocity, or acoustic intensity. In this paper, not only the theoretical foundations of the method, but also its practical applications are explored such as scanning transfer path analysis, source radiation characterization, operational deflection shapes, virtual phased arrays, material characterization, and acoustic intensity vector field mapping
Recycled plastics as fillers in polymer cement concrete composites
How to handle the plastic waste is a big task for the modern society in environmental protection. People already focus on it, especially in PET soft drink bottles. Although PET bottle can be reclaimed, its usages are restricted due to the limitation in color and difficulty in purification.
On the other side, concrete is the most common material for human beings to used [sic] in construction. Concrete has good compressive strength, but poor [sic] in flexural and tensile strengths, which limits its applications. So, scientists try to improve its properties by adding the polymer into the conventional concrete, to enhance its strengths, chemical resistance and ductility.
In this study, the behaviors of the PPCC in corporation [sic] of the recycled plastics as filler, without causing any problem of color and purity, has been investigated on tensile, flexural and compressive strengths, weight reduction and weathering test. The reason to chose [sic] the unsaturated polyester polymer Portland cement concrete (UP-PPCC) is to develop a novel method to transfer the plastics waste to valuable product and to solve the problem about dumping the million tons of plastic waste.
The results of experiments show that UP-PPCC system has very good adhesive ability to bind the flakes of plastics with polymer-concrete matrix and the light-weighing [sic] plastic concrete can cut down the cost of transportation
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