Directional and singular surface plasmon generation in chiral and achiral nanostructures demonstrated by Leakage Radiation Microscopy

In this paper, we describe the implementation of leakage radiation microscopy (LRM) to probe the chirality of plasmonic nanostructures. We demonstrate experimentally spin-driven directional coupling as well as vortex generation of surface plasmon polaritons (SPPs) by nanostructures built with T-shaped and $\Lambda$- shaped apertures. Using this far-field method, quantitative inspections, including directivity and extinction ratio measurements, are achieved via polarization analysis in both image and Fourier planes. To support our experimental findings, we develop an analytical model based on a multidipolar representation of $\Lambda$- and T-shaped aperture plasmonic coupler allowing a theoretical explanation of both directionality and singular SPP formation. Furthermore, the roles of symmetry breaking and phases are emphasized in this work. This quantitative characterization of spin-orbit interactions paves the way for developing new directional couplers for subwavelength routing

From solid solution to cluster formation of Fe and Cr in α\alpha-Zr

To understand the mechanisms by which Fe and Cr additions increase the corrosion rate of irradiated Zr alloys, a combination of experimental (atom probe tomography, x-ray diffraction and thermoelectric power measurements) and modelling (density functional theory) techniques are employed to investigate the non-equilibrium solubility and clustering of Fe and Cr in binary Zr alloys. Cr occupies both interstitial and substitutional sites in the {\alpha}-Zr lattice, Fe favours interstitial sites, and a low-symmetry site that was not previously modelled is found to be the most favourable for Fe. Lattice expansion as a function of alloying concentration (in the dilute regime) is strongly anisotropic for Fe additions, expanding the $c$-axis while contracting the $a$-axis. Defect clusters are observed at higher solution concentrations, which induce a smaller amount of lattice strain compared to the dilute defects. In the presence of a Zr vacancy, all two-atom clusters are more soluble than individual point defects and as many as four Fe or three Cr atoms could be accommodated in a single Zr vacancy. The Zr vacancy is critical for the increased solubility of defect clusters, the implications for irradiation induced microstructure changes in Zr alloys are discussed.Comment: 15 pages including figure, 9 figures, 2 tables. Submitted for publication in Acta Mater, Journal of Nuclear Materials (2015

До питання моделювання механізмів лазерно-індукованого руйнування діелектри-ків та напівпровідників

Results of analysis of problem of mechanisms of laser-induced destruction in dielectrics, including polariton models, are discussed. These phenomena may be represented as effects of Relaxed Optics. The influence of dynamic and kinetic factors on these processes is shown. Some analogy of these mechanisms with microscopic mechanism of Cherenkov radiation is analyzed too. ; Наведено результати аналізу проблеми моделювання механізмів лазерно-індуко-ваного руйнування діелектриків, включаючи поляритонні моделі. Ці явища розглянуто як ефекти релаксаційної оптики. Показано, що поряд з динамічними чинниками в цих процесах вирішальну роль можуть відігравати і кінетичні чинники. Проаналізовано певну аналогію цих механізмів з мікроскопічним механізмом Черенковського випромінювання

A Broadly Tunable Surface Plasmon-Coupled Wavelength Filter for Visible and Near Infrared Hyperspectral Imaging

Hyperspectral imaging is a set of techniques that has contributed to the study of advanced materials, pharmaceuticals, semiconductors, ceramics, polymers, biological specimens, and geological samples. Its use for remote sensing has advanced our understanding of agriculture, forestry, the Earth, environmental science, and the universe. The development of ultra-compact handheld hyperspectral imagers has been impeded by the scarcity of small widefield tunable wavelength filters. The widefield modality is preferred for handheld imaging applications in which image registration can be performed to counter scene shift caused by irregular user motions that would thwart scanning approaches. In the work presented here an electronically tunable widefield wavelength filter has been developed for hyperspectral imaging applications in the visible and near-infrared region. Conventional electronically tunable widefield imaging filter technologies include liquid crystal-based filters, acousto-optic tunable filters, and electronically tuned etalons; each having its own set of advantages and disadvantages. The construction of tunable filters is often complex and requires elaborate optical assemblies and electronic control circuits. I introduce in the work presented here is a novel widefield tunable filter, the surface plasmon coupled tunable filter (SPCTF), for visible and near infrared imaging. The SPCTF is based on surface plasmon coupling and has simple optical design that can be miniaturized without sacrificing performance. The SPCTF provides diffraction limited spatial resolution with a moderately narrow nominal passband (\u3c10 \u3enm) and a large spurious free spectral range (450 nm-1000 nm). The SPCTF employs surface plasmon coupling of the π-polarized component of incident light in metal films separated by a tunable dielectric layer. Acting on the π-polarized component, the device is limited to transmitting 50 percent of unpolarized incident light. This is higher than the throughput of comparable Lyot-based liquid crystal tunable filters that employ a series of linear polarizers. In addition, the SPCTF is not susceptible to the unwanted harmonic bands that lead to spurious diffraction in Bragg-based devices. Hence its spurious free spectral range covers a broad region from the blue through near infrared wavelengths. The compact design and rugged optical assembly make it suitable for hand-held hyperspectral imagers. The underlying theory and SPCTF design are presented along with a comparison of its performance to calculated estimates of transmittance, spectral resolution, and spectral range. In addition, widefield hyperspectral imaging using the SPCTF is demonstrated on model sample

Modes of Parasitism between the Necrotrophic Fungus Botrytis cinerea and Trichoderma spp

This study aims to understand the differential antagonistic activity of the Trichoderma spp. against Botrytis cinerea (grey mould) on tomato plants. The antagonistic efficiency between Botrytis cinerea and Trichoderma spp. viz., Trichoderma reesei, Trichoderma viride, Trichoderma harzianum, Trichoderma hamatum, Trichoderma longibractum were studied in vitro using dual plate technique. The results revealed that all of the Trichoderma isolates had the ability to inhibit the mycelial growth of grey mould. The percentage reduction in the growth of B. cinerea after seven days of incubation at 23 ± 2ºC varied between 35-84%. The Trichoderma spp. such as T. reesei (A1) and T.harzianum (E1) showed the highest antagonistic activity (T. reesei (A1) – 84%; T. harzianum (E1) – 72.8%). SEM studies at cellular level have shown the collapse of hyphal wall of B. cinerea at an early stage. Clear evidence on direct parasitism was recorded on most of the Trichoderma spp. tested in this experiment. In bioassay experiments, B. cinerea applied alone was found throughout the leaf tissues in high densities after an incubation period of five days at 18°C in a moist chamber rather than when pathogen and antagonists were applied together. Based on previous records of Trichoderma spp., biocontrol potential and observations of its colonizing properties, it appears that          T. reesei can compete and reduce the growth of B. cinerea in tomato plants at an early stage and enhance the growth of the plants. Keywords: Biological control, antagonistic potential, cell damage, grey mould, Trichoderma spp

Pollen Rupture and Its Impact on Precipitation in Clean Continental Conditions

Pollen grains emitted from vegetation can rupture, releasing subpollen particles (SPPs) as fine atmospheric particulates. Previous laboratory research demonstrates potential for SPPs as efficient cloud condensation nuclei (CCN). We develop the first model of atmospheric pollen grain rupture and implement the mechanism in regional climate model simulations over spring pollen season in the United States with a CCN‐dependent moisture scheme. The source of SPPs (surface or in‐atmosphere) depends on region and sometimes season, due to the distribution of relative humidity and rain. Simulated concentrations of SPPs are approximately 1–10 or 1–1,000 cm−3, depending on the number of SPPs produced per pollen grain (nspg). Lower nspg (103) produces a negligible effect on precipitation, but high nspg (106) in clean continental CCN background concentrations (100 CCN per cubic centimeter) shows that SPPs suppress average seasonal precipitation by 32% and shift rates from heavy to light while increasing dry days. This effect is smaller (2% reduction) for polluted air.Plain Language SummaryPollen grains emitted by wind from a variety of plants can swell from exposure to high levels of humidity, creating internal pressure that may cause the grains to rupture. Particles that are 10 to a thousand times smaller than pollen grains are released in the process. These subpollen particles (SPPs) have been found in laboratory studies to efficiently collect water on their surfaces, making them potential cloud condensation nuclei (i.e., particles that may grow into cloud droplets). We have developed a numerical model of pollen rupture that interfaces with an atmosphere model to determine (1) how many SPPs are produced during the pollen season from two different sources: rupture of pollen at the surface and rupture of airborne pollen grains; (2) the geographic and vertical distribution of SPPs seasonally; and (3) the impact of SPPs on regional precipitation. We find that the strength of either source in any region or phase of season depends on rain and relative humidity. We also find that SPPs have the potential to suppress seasonal precipitation in clean conditions when anthropogenic pollution is not present depending on how many are released for each pollen grain that ruptures. The magnitude of suppression regionally is dependent on source magnitude of SPPs, as well as the availability of water vapor.Key PointsThe first model of moisture‐induced pollen rupture and release of subpollen particles (SPPs) is coupled to a regional climate modelDuring peak pollen season in the United States, simulated SPPs range from 1 to 1,000 cm−3, depending on the number produced per pollen grain rupturedSPP may have the ability to suppress precipitation regionally in clean continental CCN conditions and induce a negative feedback to SPP productionPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145502/1/grl57690_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/145502/2/grl57690.pd