Tunable Metasurface and Flat Optical Zoom Lens on a Stretchable Substrate

A mechanically reconfigurable metasurface that can continuously tune the wavefront is demonstrated in the visible frequency range by changing the lattice constant of a complex Au nanorod array fabricated on a stretchable polydimethylsiloxane substrate. It is shown that the anomalous refraction angle of visible light at 632.8 nm interacting with the tunable metasurface can be adjusted from 11.4° to 14.9° by stretching the substrate by ∼30%. An ultrathin flat 1.7× zoom lens whose focal length can continuously be changed from 150 to 250 μm is realized, which also demonstrates the potential of utilizing metasurfaces for reconfigurable flat optics

Factors used for assessing the annual incidence and 5-year period prevalence of chronic pulmonary aspergillosis (CPA) as a sequel to pulmonary tuberculosis.

<p>Factors used for assessing the annual incidence and 5-year period prevalence of chronic pulmonary aspergillosis (CPA) as a sequel to pulmonary tuberculosis.</p

Crystallographic Characterization of II–VI Semiconducting Nanostructures via Optical Second Harmonic Generation

We demonstrate the utility of optical second harmonic generation (SHG) polarimetry to perform structural characterization of noncentrosymmetric, single-crystalline II–VI semiconducting nanowires, nanobelts, and nanoflakes. By analyzing anisotropic SHG polarimetric patterns, we distinguish between wurtzite and zincblende II–VI semiconducting crystal structures and determine their growth orientation. The crystallography of these nanostructures was then confirmed via transmission electron microscopy measurements performed on the same system. In addition, we show that some intrinsic material properties such as nonlinear coefficients and geometry-dependent optical in-coupling coefficients can also be determined from the SHG experiments in WZ nanobelts. The ability to perform SHG-based structural characterization and crystallographic study of II–VI semiconducting single-crystalline nanomaterials will be useful to correlate structure–property relationships of nanodevices on which transmission electron microscopy measurements cannot be typically performed

Pulmonary tuberculosis (TB) estimates in the Indian population.

<p>CPA: chronic pulmonary aspergillosis.</p><p>Pulmonary tuberculosis (TB) estimates in the Indian population.</p

Estimated burden of allergic bronchopulmonary aspergillosis (ABPA) and severe asthma with fungal sensitization (SAFS) in adult Indian population with different rates of prevalence of ABPA in adult (≧15 years) asthmatic patients.

<p>Estimated burden of allergic bronchopulmonary aspergillosis (ABPA) and severe asthma with fungal sensitization (SAFS) in adult Indian population with different rates of prevalence of ABPA in adult (≧15 years) asthmatic patients.</p

Studies of Hot Photoluminescence in Plasmonically Coupled Silicon via Variable Energy Excitation and Temperature-Dependent Spectroscopy

By integrating silicon nanowires (∼150 nm diameter, 20 μm length) with an Ω-shaped plasmonic nanocavity, we are able to generate broadband visible luminescence, which is induced by high order hybrid nanocavity-surface plasmon modes. The nature of this super bandgap emission is explored via photoluminescence spectroscopy studies performed with variable laser excitation energies (1.959 to 2.708 eV) and finite difference time domain simulations. Furthermore, temperature-dependent photoluminescence spectroscopy shows that the observed emission corresponds to radiative recombination of unthermalized (hot) carriers as opposed to a resonant Raman process

Nanotwin Detection and Domain Polarity Determination via Optical Second Harmonic Generation Polarimetry

We demonstrate that optical second harmonic generation (SHG) can be utilized to determine the exact nature of nanotwins in noncentrosymmetric crystals, which is challenging to resolve via conventional transmission electron or scanned probe microscopies. Using single-crystalline nanotwinned CdTe nanobelts and nanowires as a model system, we show that SHG polarimetry can distinguish between upright (Cd–Te bonds) and inverted (Cd–Cd or Te–Te bonds) twin boundaries in the system. Inverted twin boundaries are generally not reported in nanowires due to the lack of techniques and complexity associated with the study of the nature of such defects. Precise characterization of the nature of defects in nanocrystals is required for deeper understanding of their growth and physical properties to enable their application in future devices

Strain-Induced Large Exciton Energy Shifts in Buckled CdS Nanowires

Strain engineering can be utilized to tune the fundamental properties of semiconductor materials for applications in advanced electronic and photonic devices. Recently, the effects of large strain on the properties of nanostructures are being intensely investigated to further expand our insights into the physics and applications of such materials. In this Letter, we present results on controllable buckled cadmium-sulfide (CdS) optical nanowires (NWs), which show extremely large energy bandgap tuning by >250 meV with applied strains within the elastic deformation limit. Polarization and spatially resolved optical measurements reveal characteristics related to both compressive and tensile regimes, while microreflectance spectroscopy clearly demonstrates the effect of strain on the different types of excitons in CdS. Our results may enable strained NWs-based optoelectronic devices with tunable optical responses

Uniform Bimetallic Nanocrystals by High-Temperature Seed-Mediated Colloidal Synthesis and Their Catalytic Properties for Semiconducting Nanowire Growth

A general procedure to prepare uniform gold-based bimetallic nanocrystals (NCs) is reported. The method relies on a seed-mediated approach in which deposition and <i>in-situ</i> alloying of a second metal (Ag, Pt, Hg, Sn, Cd) onto monodisperse Au seeds are performed at relatively high temperatures, giving access to bimetallic NCs of tunable compositions and properties. The position of the plasmon resonance in the original Au NCs is tunable over a wide range (∼300–520 nm) of the electromagnetic spectrum. We demonstrate the catalytic properties of these monodisperse NCs for growing single-crystalline semiconductor nanowires of uniform, small diameter (∼15–30 nm) via a vapor–liquid–solid (VLS) mechanism at low temperatures. This seeded-mediated approach is not restricted to Au but can be extended to several other combinations, making this procedure a straightforward method to prepare highly monodisperse and controllable multimetallic nanocrystals for optical and catalytic applications