Distribution Of Scattered Light Research Articles

Wide edge state supercontinuum in a Floquet–Lieb topological photonic insulator

Conventional topological photonic insulators typically have narrow nontrivial band gaps truncated by broad dispersive bulk bands, resulting in limited edge mode transmission bandwidths that can be exploited for potential applications. Here, we demonstrate a Floquet–Lieb topological photonic insulator with all flat bands that can support continuous edge mode transmission across multiple Floquet–Brillouin zones. This supercontinuum of edge states results from the coexistence and orthogonality of the localized flat-band modes and the edge states, allowing for continuous excitation of the latter without scattering into the bulk modes. Moreover, we show that these flat bands are perfectly immune to random variations in the on-site potential, regardless of how large the perturbations are, thus ensuring complete robustness of the edge modes to this type of disorder. We realized Floquet–Lieb insulators using 2D microring resonator lattices with perfect nearest-neighbor couplings. Transmission measurements and direct imaging of the scattered light distributions showed an edge mode supercontinuum spanning more than three microring free spectral ranges. The proposed Floquet–Lieb insulator can potentially be used to realize topological photonic devices with wide bandwidths and super robustness for applications in integrated quantum photonics and programmable photonic circuits.

Diffuse light around cities: New perspectives in satellite remote sensing of nighttime aerosols

Satellite remote sensing of nighttime aerosols in the lower atmosphere poses additional challenges in comparison with daytime sensing, due to the specific features of the available light sources and the different scattering geometries. In this work we develop a detailed quantitative model for the top-of-atmosphere radiance of the halos of diffuse light observed around cities in satellite nighttime imagery. It is shown that these scattered light distributions contain relevant information about the aerosol properties, and that under some basic assumptions they can be used to estimate them. We formalize the basis of a method for retrieving the aerosol particle size number distribution function based on inverting the angular dependence of the radiance detected in near-nadir remote sensing observations. The results stress the convenience of endowing future night Earth observation missions with enhanced angular detection capabilities.

Inflow nano-optics from the near-to the far-field detection based on Metal-Enhanced Fluorescence signaling

In this communication we evaluated the detection and tracking of Ultraluminescent gold core–shell nanoplatforms based on Metal-Enhanced Fluorescence (MEF) within colloidal dispersion by In-Flow Cytometry and Imaging Flow Cytometry (IFC). The enhanced properties were developed by the incorporation of Rhodamine B (RhB) as a laser dye reporter at variable controlled silica spacer lengths (Au@SiO2-RhB) from a gold core template. Thus, SiO2 was varied from 6 to 7 nm to 25 nm in order to place the laser dye sensitizer at different lengths of the higher electromagnetic fields surrounding the 45-nm gold core diameter. By Laser Fluorescence Microscopy, high intense emissions were shown at shorter SiO2 lengths, while lower emissions were found towards longer ones. These characteristics related to MEF were evaluated by in-flow cytometry with dual laser excitation and fluorescence detection, and by an IFC set-up. By In-flow cytometry, different scattered-light distributions were shown, depending on the nanoparticle concentrations in the colloidal dispersion and size of the Au@SiO2-RhB. Moreover, varied fluorescent event detections and counting were recorded according to the SiO2 lengths applied. A ratio of fluorescent event detection counting of core–shell/core-less of 40–42 was established for optimal MEF Enhancement Factors (MEFEF) of 41–43 determined by Laser Fluorescence Microscopy. Core-less nanoparticles showed a marked decrease of fluorescent event detection counting caused by higher photobleaching and absence of the MEF effect. Hence, an improved detection effect was shown within in-flow based on MEF from single nanoplatforms. Therefore, the Ultraluminescence emission of core–shell nanoarchitectures within in-flow techniques was shown and discussed. A non-classical light in real time within colloidal gold core–shell nanoparticles was generated by accurate control of their architectures.

Reference Star Differential Imaging of Close-in Companions and Circumstellar Disks with the NIRC2 Vortex Coronagraph at the W. M. Keck Observatory

Abstract Reference star differential imaging (RDI) is a powerful strategy for high-contrast imaging. Using example observations taken with the vortex coronagraph mode of Keck/NIRC2 in L′ band, we demonstrate that RDI provides improved sensitivity to point sources at small angular separations compared to angular differential imaging (ADI). Applying RDI to images of the low-mass stellar companions HIP 79124 C (192 mas separation, ΔL′ = 4.01) and HIP 78233 B (141 mas separation, ΔL′ = 4.78), the latter a first imaging detection, increases the significance of their detections by up to a factor of 5 with respect to ADI. We compare methods for reference frame selection and find that pre-selection of frames improves detection significance of point sources by up to a factor of 3. In addition, we use observations of the circumstellar disks around MWC 758 and 2MASS J16042165−2130284 to show that RDI allows for accurate mapping of scattered light distributions without self-subtraction artifacts.

Classification and Size Estimation of Wafer Defects by Using Scattered Light Distribution

SUMMARYUsually, wafer inspection is a two‐step process. The first step, which is very important, consists of detection of defects on the wafer. The second step classification of the detected defects, which is done after defect detection as necessary. Recently, it has become necessary to perform simultaneous detection and classification of wafer defects in order to reduce the wafer inspection time while maintaining high resolution of inspection. Optical wafer inspection is the most effective method for detecting and classifying defects and estimating their size in a short time. In this method, the scattered light distribution is compared with a database of previous scattered light distributions and pattern matching is used to classify defects and estimate their size. Therefore, to achieve optical wafer inspection based on scattered light distribution, it is necessary to gather scattered light distribution data for many samples of various kinds. The first aim of this study is to develop a defect classification and size estimation method utilizing the scattered light distribution. We propose a method of classifying defects on wafers and estimating their size. The proposed method is based on pattern matching utilizing a parametric eigenspace. The second aim of the paper is to validate the proposed method by applying it to scattered light distribution samples. The light scattering distribution samples were generated by discrete dipole approximation (DDA) simulation. A database of the light scattering distribution is easily created using the simulation.

Classification and Size Estimation of Wafer Defects by Using Scattered Light Distribution

SUMMARY Usually, wafer inspection is a two-step process. The first step, which is very important, consists of detection of defects on the wafer. The second step classification of the detected defects, which is done after defect detection as necessary. Recently, it has become necessary to perform simultaneous detection and classification of wafer defects in order to reduce the wafer inspection time while maintaining high resolution of inspection. Optical wafer inspection is the most effective method for detecting and classifying defects and estimating their size in a short time. In this method, the scattered light distribution is compared with a database of previous scattered light distributions and pattern matching is used to classify defects and estimate their size. Therefore, to achieve optical wafer inspection based on scattered light distribution, it is necessary to gather scattered light distribution data for many samples of various kinds. The first aim of this study is to develop a defect classification and size estimation method utilizing the scattered light distribution. We propose a method of classifying defects on wafers and estimating their size. The proposed method is based on pattern matching utilizing a parametric eigenspace. The second aim of the paper is to validate the proposed method by applying it to scattered light distribution samples. The light scattering distribution samples were generated by discrete dipole approximation (DDA) simulation. A database of the light scattering distribution is easily created using the simulation.

Using laser diffraction data to obtain accurate particle size distributions: the role of particle composition

Suspended particle composition has a large influence on light scattering by small (<20 µm) particles. Inorganic particles and organic phytoplankton cells, both common in natural waters, have very different indices of refraction. This can affect results from laser diffraction particle size analyzers, which measure light scattering and assume an index of refraction to calculate the particle size distribution. Here we examine the effect of the assumed index of refraction on laser diffraction data. A Laser In‐situ Scattering and Transmissometry (LISST) 100X instrument is used to record scattered light distributions from glass microspheres, phytoplankton monocultures, and natural particle samples of mixed composition. The scattering distributions are processed with kernel matrices, derived using Mie theory, assuming either organic or inorganic compositions. Resulting particle size distributions are compared against microscope images. Processing with an assumed inorganic index of refraction was found to produce the most accurate results over the majority of the samples tested. The effect of scattering by particles having diameters outside the instrument inversion range was also assessed. The presence of significant concentrations of particles exceeding the upper limit of the LISST range (>250 µm) produced little effect; however, particles smaller than the lower limit (<1.25 µm) influenced concentrations over the entire LISST size range and produced counterintuitive effects, such as increased concentrations in the largest size bins.

The Circumstellar Structure of the Class I Protostar TMC‐1 (IRAS 04381+2540) fromHubble Space TelescopeNICMOS Data

The class I protostar TMC-1 (IRAS 04381+2540) is oriented favorably for determining the properties of its circumstellar envelope and outflow cavity. Deep, high spatial resolution Hubble Space Telescope (HST) NICMOS images at 1.6 μm exhibit both a narrow jet and a wide-angle conical outflow cavity. Model images of the scattered-light distribution fit the data well, reproducing the intensity level, cavity width, and observed limb brightening. The best-fit geometry for TMC-1 has a 45° ± 5° source inclination and an 80° ± 5° deprojected wind opening angle (full width). The age, normally a poorly known quantity, is well constrained; the protostar age, i.e., time since the onset of cloud collapse, is 1 × 105 yr to within a factor of 2. We offer a possible resolution to the well-known luminosity problem. By considering the efficiency of infall onto the protostar, we find that plausible parameters can give an efficiency, and hence accretion luminosity, as low as 10% of the value derived from the collapsing cloud core. The efficiency, together with a luminosity constraint, leads to a mass estimate that ranges from about 0.1 M☉ for high efficiency to 0.2 M☉ for low accretion efficiency onto the protostar. Similarly, the estimated mass accretion rate onto the protostar ranges over roughly (0.9-1.4) × 10-6 M☉ yr-1, which is smaller than the (1.6-3.5) × 10-6 M☉ yr-1 infall rate of the cloud. If low efficiency rates are prevalent for protostars, one important consequence is that it will take longer to assemble the central star than the time t = Min/in, a time that assumes all of the infalling material lands on the protostar.

Super Bright Light-Emitting Diode for Optical Roughness Characterization

A promising in-process roughness measuring technique is based on the detection of polychromatic scattered light Distributions and speckle correlation algorithms. The spectral light properties mainly influence the measuring range and the resolution. Further approaches use lasers, laser diodes, or a superluminescant diode (SLD), to produce light beams with a discrete or continuous spectrum and a sufficient temporal coherence to generate speckles. The presented approach investigates the suitability of a low-cost super bright light-emitting diode (SLED) for roughness characterization.

Defect characterization in natural diamonds by laser-light-scattering microtomography

Abstract Scanning microtomography using scattered laser light has been employed in a study of defects in small blocks of different types of diamond. Local changes in refractivity caused by various kinds of imperfections could be mapped. In relatively perfect yellow diamonds the scattered-light intensity distribution was related to growth zones, as was verified by stress-birefringence microscopy and cathodoluminescence. Scattered-light images of dislocation lines were also observed. In some diamonds it was found that {100} growth sectors showed a lower scattering intensity than the adjacent {111} sectors. Brown anisotropically scattering diamonds gave an inhomogeneous striated scattered-light distribution, not related to growth zones. A diamond with knots showed local differences in scattering intensity for the misoriented crystal volumes.

Interfacial scattering and electrodynamics due to roughness at silver surfaces

The effect of roughness on the reflectivity of metallic silver at various metal-liquid and metal-air boundaries is discussed. Experimental spectra are examined in cases of (1) roughened silver foils in contact with isopropanol and air; (2) electrochemically oxidized silver surfaces; and (3) small particle (latex sphere) roughened surfaces. Differences in scattered light distributions and changes in silver metal reflectance under these varied conditions have been analyzed, assuming the applicability of a classical first-order roughness theory. New information on the stochastic nature of either metallic or oxidized surface nonuniformities and on height and width correlations of surface corrugations is obtained.

Untersuchungen über den zusammenhang zwischen optischer und geometrischer grösse bei aerosolteilchen der bodennahen luft

This paper describes comparative measurements of the scattered light intensity and the “geometrical” size of atmospheric aerosol particles at the Earth's surface. Airborne particles were used to determine the scattered light distributions. Particles were also deposited on an impaction plate and prepared by a special deep-freeze-carbon-replica process. Their geometrical sizes were analysed by a scanning electron microscope. Comparison of the two methods shows that the investigated particles can, for size measurements, approximately be described as transparent spheres with refractive index 1.54 ± 0.02. The investigation refers to particles ranging between 0.3 and 2 μm and a relative humidity less than 60%.

Observation and Simulation of Effects on Parylene Disks Irradiated at High Intensities with a 1.06-μm Laser

Parylene (${\mathrm{C}}_{8}$${\mathrm{H}}_{8}$) disks have been irradiated with a 1.06-\ensuremath{\mu}m laser at fluxes of ${10}^{15}$-${10}^{17}$ W/${\mathrm{cm}}^{2}$. The spatial and temporal scattered light distributions, x-ray spatial and spectral emission properties, and ion spatial and energy distributions were measured. The results, together with two-dimensional magnetohydrodynamic code simulations, imply absorption via collective processes, laser generation of suprathermal electrons, and transport inhibition consistent with the presence of megagauss-level thermoelectric magnetic fields.

Theory of Scattering by Finite Dielectric Needles Illuminated Parallel to Their Axes

I derive the angular distribution of light scattered by parallel-illuminated dielectric needles (i.e., cylinders of radius r≪λ) of finite length L≫λ. The scattered light is found to be strongly peaked in the near-forward direction. As the needles get longer, they scatter more light, and the angular half-width decreases. The total light scattered at all angles is proportional to Lr4/λ3. This theory was developed to help interpret measured scattered-light distributions from low-loss optical-fiber waveguides.