4,761 research outputs found
Infrared Phase-Change Meta-Devices with In-Situ Switching
This is the author accepted manuscript. The final version is available from the European Phase Change and Ovonics Symposium via the link in this recordWe describe a possible device design approach and an experimental test platform suitable for the
realization and characterization of phase-change based meta-devices incorporating in-situ
switching and operating at infrared wavelengths. Measurements on such a prototype device
working at 1.55 µm are presented.US Naval Research LaboratoriesEngineering and Physical Sciences Research Council (EPSRC
A behavioural model for integrated phase-change photonics
This is the author accepted manuscript. The final version is available from the European Phase Change and Ovonics Symposium via the link in this recordThe use of phase-change materials in integrated photonics applications has enabled the development
of new types of all-optical devices, including multilevel photonic memories, arithmetic and logic
processors and synaptic and neuron mimics. In order to design, optimise and understand the
performance of large-scale systems, fast and accurate material and device models are needed. Here we
present a behavioural model for phase-change photonic devices that can simulate the write, erase and
readout operations in timespans compatible with system level performance evaluation.European Union Horizon 2020Engineering and Physical Sciences Research Council (EPSRC
Phase-change meta-photonics
We combine phase-change materials and metamaterial arrays (metasurfaces) to create new forms of dynamic, tuneable and reconfigurable photonic devices including ‘perfect’ absorbers, infra-red light modulators, optical beam steerers and enhanced phase-change optoelectronic displays
Reconfigurable multilevel control of hybrid all-dielectric phase-change metasurfaces
This is the final version. Available from Optical Society of America via the DOI in this record. All-dielectric metasurfaces comprising arrays of nanostructured high-refractive-index materials are re-imagining what is achievable in terms of the manipulation of light. However, the functionality of conventional dielectric-based metasurfaces is fixed by design; thus, their optical response is locked in at the fabrication stage. A far wider range of applications could be addressed if dynamic and reconfigurable control were possible. We demonstrate this here via the novel concept of hybrid metasurfaces, in which reconfigurability is achieved by embedding sub-wavelength inclusions of chalcogenide phase-change materials within the body of silicon nanoresonators. By strategic placement of an ultra-thin Ge 2 Sb 2 Te 5
Ge2Sb2Te5
layer and reversible switching of its phase-state, we show individual, multilevel, and dynamic control of metasurface resonances. We showcase our concept via the design, fabrication, and characterization of metadevices capable of dynamically filtering and modulating light in the near infrared (O and C telecom bands), with modulation depths as high as 70% and multilevel tunability. Finally, we show numerically how the same approach can be re-scaled to shorter wavelengths via appropriate material selection, paving the way to additional applications, such as high-efficiency vivid structural color generators in the visible spectrum. We believe that the concept of hybrid all-dielectric/phase-change metasurfaces presented in this work could pave the way for a wide range of design possibilities in terms of multilevel, reconfigurable, and high-efficiency light manipulation.Engineering and Physical Sciences Research Council (EPSRC)Russian Science FoundationRussian Foundation for Basic Researc
Performance characteristics of phase-change integrated silicon nitride photonic devices in the O and C telecommunications bands
This is the final version. Available on open access from the Optical Society via the DOI in this recordData Availability:
Data relating to this manuscript can be obtained from the authors.The evaluation and comparison of the optical properties in the O and C bands of silicon nitride rib waveguides with integrated Ge2Sb2Te5 phase-change cells is reported. In straight rib waveguides, a high transmission contrast is observed in both bands when the Ge2Sb2Te5 cell is switched between states, being up to 2.5 dB/μm in the C-band and 6.4 dB/μm in the O-band. In the case of silicon nitride ring resonator waveguides, high quality factor resonances (Q ∼ 105) are found in both bands, leading to the provision of an ON-OFF switch characterized by an extinction ratio of 12 and 18 dB in O and C bands respectively. Finally, with the view to provide a comparison of the wavelength-dependent optical switching of the phase-change cell, a 3-dimensional finite-element method simulation is performed and a comparison of the optical-to-thermal energy conversion in both bands given.European Union Horizon 2020Engineering and Physical Sciences Research Council (EPSRC
Search for the Higgs boson in events with missing transverse energy and b quark jets produced in proton-antiproton collisions at s**(1/2)=1.96 TeV
We search for the standard model Higgs boson produced in association with an
electroweak vector boson in events with no identified charged leptons, large
imbalance in transverse momentum, and two jets where at least one contains a
secondary vertex consistent with the decay of b hadrons. We use ~1 fb-1
integrated luminosity of proton-antiproton collisions at s**(1/2)=1.96 TeV
recorded by the CDF II experiment at the Tevatron. We find 268 (16) single
(double) b-tagged candidate events, where 248 +/- 43 (14.4 +/- 2.7) are
expected from standard model background processes. We place 95% confidence
level upper limits on the Higgs boson production cross section for several
Higgs boson masses ranging from 110 GeV/c2 to 140 GeV/c2. For a mass of 115
GeV/c2 the observed (expected) limit is 20.4 (14.2) times the standard model
prediction.Comment: 8 pages, 2 figures, submitted to Phys. Rev. Let
Evidence for t\bar{t}\gamma Production and Measurement of \sigma_t\bar{t}\gamma / \sigma_t\bar{t}
Using data corresponding to 6.0/fb of ppbar collisions at sqrt(s) = 1.96 TeV
collected by the CDF II detector, we present a cross section measurement of
top-quark pair production with an additional radiated photon. The events are
selected by looking for a lepton, a photon, significant transverse momentum
imbalance, large total transverse energy, and three or more jets, with at least
one identified as containing a b quark. The ttbar+photon sample requires the
photon to have 10 GeV or more of transverse energy, and to be in the central
region. Using an event selection optimized for the ttbar+photon candidate
sample we measure the production cross section of, and the ratio of cross
sections of the two samples. Control samples in the dilepton+photon and
lepton+photon+\met, channels are constructed to aid in decay product
identification and background measurements. We observe 30 ttbar+photon
candidate events compared to the standard model expectation of 26.9 +/- 3.4
events. We measure the ttbar+photon cross section to be 0.18+0.08 pb, and the
ratio of the cross section of ttbar+photon to ttbar to be 0.024 +/- 0.009.
Assuming no ttbar+photon production, we observe a probability of 0.0015 of the
background events alone producing 30 events or more, corresponding to 3.0
standard deviations.Comment: 9 pages, 3 figure
Search for Neutral Higgs Bosons in Events with Multiple Bottom Quarks at the Tevatron
The combination of searches performed by the CDF and D0 collaborations at the
Fermilab Tevatron Collider for neutral Higgs bosons produced in association
with b quarks is reported. The data, corresponding to 2.6 fb-1 of integrated
luminosity at CDF and 5.2 fb-1 at D0, have been collected in final states
containing three or more b jets. Upper limits are set on the cross section
multiplied by the branching ratio varying between 44 pb and 0.7 pb in the Higgs
boson mass range 90 to 300 GeV, assuming production of a narrow scalar boson.
Significant enhancements to the production of Higgs bosons can be found in
theories beyond the standard model, for example in supersymmetry. The results
are interpreted as upper limits in the parameter space of the minimal
supersymmetric standard model in a benchmark scenario favoring this decay mode.Comment: 10 pages, 2 figure
Precise measurement of the W-boson mass with the CDF II detector
We have measured the W-boson mass MW using data corresponding to 2.2/fb of
integrated luminosity collected in proton-antiproton collisions at 1.96 TeV
with the CDF II detector at the Fermilab Tevatron collider. Samples consisting
of 470126 W->enu candidates and 624708 W->munu candidates yield the measurement
MW = 80387 +- 12 (stat) +- 15 (syst) = 80387 +- 19 MeV. This is the most
precise measurement of the W-boson mass to date and significantly exceeds the
precision of all previous measurements combined
Precision Top-Quark Mass Measurements at CDF
We present a precision measurement of the top-quark mass using the full
sample of Tevatron TeV proton-antiproton collisions collected
by the CDF II detector, corresponding to an integrated luminosity of 8.7
. Using a sample of candidate events decaying into the
lepton+jets channel, we obtain distributions of the top-quark masses and the
invariant mass of two jets from the boson decays from data. We then compare
these distributions to templates derived from signal and background samples to
extract the top-quark mass and the energy scale of the calorimeter jets with
{\it in situ} calibration. The likelihood fit of the templates from signal and
background events to the data yields the single most-precise measurement of the
top-quark mass, \mtop = 172.85 \pm\pmComment: submitted to Phys. Rev. Let
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