597 research outputs found
Optical spin-to-orbital angular momentum conversion in ultra-thin metasurfaces with arbitrary topological charges
Orbital angular momentum associated with the helical phase-front of optical
beams provides an unbounded \qo{space} for both classical and quantum
communications. Among the different approaches to generate and manipulate
orbital angular momentum states of light, coupling between spin and orbital
angular momentum allows a faster manipulation of orbital angular momentum
states because it depends on manipulating the polarisation state of light,
which is simpler and generally faster than manipulating conventional orbital
angular momentum generators. In this work, we design and fabricate an
ultra-thin spin-to-orbital angular momentum converter, based on plasmonic
nano-antennas and operating in the visible wavelength range that is capable of
converting spin to an arbitrary value of OAM . The nano-antennas are
arranged in an array with a well-defined geometry in the transverse plane of
the beam, possessing a specific integer or half-integer topological charge .
When a circularly polarised light beam traverses this metasurface, the output
beam polarisation switches handedness and the OAM changes in value by per photon. We experimentally demonstrate values ranging
from to with conversion efficiencies of . Our
ultra-thin devices are integratable and thus suitable for applications in
quantum communications, quantum computations and nano-scale sensing.Comment: 4 pages, 3 figures - submitted
Finding in Commercial-Engineer Controversy
Finding concerning a controversy between the commercial and engineer departments at Utah Agricultural College
Photon Number Resolving Detection with a Single-Photon Detector and Adaptive Storage Loop
Photon number resolving (PNR) measurements are beneficial or even necessary
for many applications in quantum optics. Unfortunately, PNR detectors are
usually large, slow, expensive, and difficult to operate. However, if the input
signal is multiplexed, photon "click" detectors, that lack an intrinsic photon
number resolving capability, can still be used to realize photon number
resolution. Here, we investigate the operation of a single click detector,
together with a storage line with tunable outcoupling. Using adaptive feedback
to adjust the storage outcoupling rate, the dynamic range of the detector can
in certain situations be extended by up to an order of magnitude relative to a
purely passive setup. An adaptive approach can thus allow for photon number
variance below the quantum shot noise limit under a wider range of conditions
than using a passive multiplexing approach. This can enable applications in
quantum enhanced metrology and quantum computing.Comment: 16 pages, 8 figure
Generating optical orbital angular momentum at visible wavelengths using a plasmonic metasurface
The authors acknowledge the support of the Canada Excellence Research Chairs Program.Light beams with a helical phase-front possess orbital angular momentum along their direction of propagation in addition to the spin angular momentum that describes their polarisation. Until recently, it was thought that these two ‘rotational’ motions of light were largely independent and could not be coupled during light–matter interactions. However, it is now known that interactions with carefully designed complex media can result in spin-to-orbit coupling, where a change of the spin angular momentum will modify the orbital angular momentum and vice versa. In this work, we propose and demonstrate that the birefringence of plasmonic nanostructures can be wielded to transform circularly polarised light into light carrying orbital angular momentum. A device operating at visible wavelengths is designed from a space-variant array of subwavelength plasmonic nano-antennas. Experiment confirms that circularly polarised light transmitted through the device is imbued with orbital angular momentum of ±2ħ (with conversion efficiency of at least 1%). This technology paves the way towards ultrathin orbital angular momentum generators that could be integrated into applications for spectroscopy, nanoscale sensing and classical or quantum communications using integrated photonic devices.Publisher PDFPeer reviewe
Strong, spectrally-tunable chirality in diffractive metasurfaces
The authors acknowledge the support of the Canada Excellence Research Chairs Program. P.B. acknowledges the support from the Alexander von Humboldt Foundation.Metamaterials and metasurfaces provide a paradigm-changing approach for manipulating light. Their potential has been evinced by recent demonstrations of chiral responses much greater than those of natural materials. Here, we demonstrate theoretically and experimentally that the extrinsic chiral response of a metasurface can be dramatically enhanced by near-field diffraction effects. At the core of this phenomenon are lattice plasmon modes that respond selectively to the illumination’s polarization handedness. The metasurface exhibits sharp features in its circular dichroism spectra, which are tunable over a broad bandwidth by changing the illumination angle over a few degrees. Using this property, we demonstrate an ultra-thin circular-polarization sensitive spectral filter with a linewidth of ~10 nm, which can be dynamically tuned over a spectral range of 200 nm. Chiral diffractive metasurfaces, such as the one proposed here, open exciting possibilities for ultra-thin photonic devices with tunable, spin-controlled functionality.Publisher PDFPeer reviewe
Adaptive immunity to rhinoviruses: sex and age matter
Background: Rhinoviruses (RV) are key triggers in acute asthma exacerbations. Previous studies suggest that men suffer from infectious diseases more frequently and with greater severity than women. Additionally, the immune response to most infections and vaccinations decreases with age. Most immune function studies do not account for such differences, therefore the aim of this study was to determine if the immune response to rhinovirus varies with sex or age
Short courses of antibiotics for children and adults with bronchiectasis (Review)
BackgroundBronchiectasis is an important cause of respiratory morbidity in both developing and developed countries. Antibiotics are considered standard therapy in the treatment of this condition but it is unknown whether short courses (four weeks or less) are efficacious.ObjectivesTo determine whether short courses of antibiotics (i.e. less than or equal to four weeks) for treatment of acute and stable state bronchiectasis, in adults and children, are efficacious when compared to placebo or usual care.Search methodsThe Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), MEDLINE, EMBASE, OLDMEDLINE, CINAHL, AMED and PsycINFO and handsearching of respiratory journals and meeting abstracts were performed by the Cochrane Airways Group up to February 2011.Selection criteriaOnly randomised controlled trials were considered. Adults and children with bronchiectasis (defined clinically or radiologically) were included. Patients with cystic fibrosis were excluded.Data collection and analysisTwo review authors independently reviewed the titles, abstracts and citations to assess eligibility for inclusion. Only one study fulfilled the inclusion criteria and thus meta-analysis could not be performed.Main resultsThe single eligible study showed a small benefit, when compared to placebo, of four weeks of inhaled antibiotic therapy in adults with bronchiectasis and pseudomonas in their sputum. There were no studies in children and no studies on oral or intravenous antibiotics.Authors\u27 conclusionsThere is insufficient evidence in the current literature to make reasonable conclusions about the efficacy of short course antibiotics in the management of adults and children with bronchiectasis. Until further evidence is available, adherence to current treatment guidelines is recommended
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