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 $\ell$. 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 $q$. When a circularly polarised light beam traverses this metasurface, the output beam polarisation switches handedness and the OAM changes in value by $\ell = \pm2q\hbar$ per photon. We experimentally demonstrate $\ell$ values ranging from $\pm 1$ to $\pm 25$ with conversion efficiencies of $8.6\pm0.4~\%$. 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

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

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

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

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

MERAV: a tool for comparing gene expression across human tissues and cell types

The oncogenic transformation of normal cells into malignant, rapidly proliferating cells requires major alterations in cell physiology. For example, the transformed cells remodel their metabolic processes to supply the additional demand for cellular building blocks. We have recently demonstrated essential metabolic processes in tumor progression through the development of a methodological analysis of gene expression. Here, we present the Metabolic gEne RApid Visualizer (MERAV, http://merav.wi.mit.edu), a web-based tool that can query a database comprising ∼4300 microarrays, representing human gene expression in normal tissues, cancer cell lines and primary tumors. MERAV has been designed as a powerful tool for whole genome analysis which offers multiple advantages: one can search many genes in parallel; compare gene expression among different tissue types as well as between normal and cancer cells; download raw data; and generate heatmaps; and finally, use its internal statistical tool. Most importantly, MERAV has been designed as a unique tool for analyzing metabolic processes as it includes matrixes specifically focused on metabolic genes and is linked to the Kyoto Encyclopedia of Genes and Genomes pathway search.United States. National Institutes of Health (CA103866)United States. National Institutes of Health (AI47389)Life Sciences Research FoundationMassachusetts Institute of Technology. Ludwig Center for Molecular OncologyHoward Hughes Medical Institut