Effects of substrate and deposition method onto the mirror scattering

The effect of surface roughness onto the mirror scattering has been studied. Five kinds of substrates with different surface roughness were fabricated. On those substrates, dielectric multilayer coating for high reflectivity was deposited by ion-beam sputtering (IBS) and by electron-beam (EB) evaporation. Total integrated scattering (TIS) measurement setup was built for the evaluation of deposited samples. Most of the IBS mirrors showed lower scattering than the EB mirrors, which were deposited on the similar substrates in surface roughness. The ratio of substrate TIS to mirror TIS was defined for evaluation. It increased abruptly at approximately 2A in surface roughness, which indicated that to make low-loss mirrors, the substrate roughness should be less than 2A in rms.     

Improved algorithm for electromagnetic scattering of plane waves and shaped beams by multilayered spheres

An efficient numerical procedure for computing the scattering coefficients of a multilayered sphere is discussed. The stability of the numerical scheme allows us to extend the feasible range of computations, both in size parameter and in number of layers for a given size, by several orders of magnitude with respect to previously published algorithms. Exemplifying results, such as scattering diagrams and cross-sectional curves, including the case of Gaussian beam illumination, are provided. Particular attention is paid to scattering at the rainbow angle for which approaches based on geometrical optics might fail to provide accurate enough results.     

Measurement of Infrared Spectral Directional Hemispherical Reflectance and Emissivity at BNM-LNE

An infrared reflectometer has been designed by BNM-LNE (Bureau National de Métrologie–Laboratoire National d’Essais) to measure the spectral directional hemispherical reflectance of solid materials at ambient temperature. For opaque materials, the spectral directional emissivity can be calculated from the measured reflectance. The reflectance can be measured from 0.8 to 14 μm in five directions with an angle of 12°, 24°, 36°, 48°, and 60° with respect to the normal to the surface of the sample. The optical arrangement to collect the reflected flux is based on the Coblentz arrangement (hemispherical mirror). In fact, four mirrors cut in an hemisphere are used to collect the flux reflected by the sample. This optical arrangement was chosen to limit the angle of incidence of rays on the detector (38° instead of 90° for the Coblentz arrangement). The final expanded uncertainty (level of confidence 95%) of the reflectance is estimated to be about ±0.03 for wavelengths between 0.8 and 10 μm and ±0.04 for wavelengths over 10 μm. The values of the spectral reflectance measured on a black paint and on a white ceramic tile are compared to those measured by the two laboratories PTB (Physikalisch Technische Bundesanstalt) and NIST (National Institute of Standards and Technology). The results validate the measurements performed at BNM-LNE. Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A.     

Fabrication of hemispherical nano structure on a curved Al surface using low-temperature and high-voltage anodizing method

A simple method of fabricating hemispherical nanostructures on a curved aluminum rod surface was presented. In conventional methods of fabricating nanopatterns on a curved aluminum surface, mechanical or chemical processes have been widely used for the lens technologies. Such processes are not only expensive with long processing times, however, but they also involve local fabrication and are limited in the dimension size. In this paper, a method of fabricating hemispherical nanostructures on a curved aluminum surface is suggested for a functional three-dimensional (3D) master using a low-temperature and high-voltage (LTHV) anodizing method. By reducing the aluminum reaction rate under a low-temperature environment, the reaction current density can be remarkably reduced even though a high voltage was induced. Using the LTHV anodizing method, the hemispherical pattern size can be easily controlled with respect to voltage variations. The sizes of the hemispherical nanopatterns were about 150-300 nm. Using the LTHV anodizing process, hemispherical nanostructures can be obtained on a curved aluminum surface with controllable pattern sizes of 150-300 nm without defects such as burring from Joule's heat, micro-scratches, and cracks. A curved 3D hemispherical nanostructure may be used as a master in the roll-to-roll process.     

Calculation of Mie derivatives

Analytical expressions are found for the derivatives of commonly used Mie scattering parameters, in particular the absorption and the scattering efficiencies, and for the angular intensity functions. These expressions are based on the analytical derivatives of the Mie scattering amplitudes a(n) and b(n) with respect to the particle size parameter and complex refractive index. In addition, analytical derivatives are found for the volume absorption and scattering coefficients, as well as for the intensity functions of a population of particles with log normal size distribution. These derivatives are given with respect to the total number density, to the median radius and spread of the distribution, and to the refractive index. Comparison between analytically and numerically computed derivatives showed the analytical version to be 2.5 to 6.5 times as fast for the single-particle and particle-distribution cases, respectively.     

Analysis of the resonant scattering of light by cylinders at oblique incidence

We study the resonant scattering of light at oblique incidence by dielectric uncoated and coated cylinders. We develop a stable algorithm that permits us to calculate the resonances of a single dielectric cylinder as the tilting angle varies. This algorithm is based on semiclassical formulas for the distance between resonances. Results show that the resonances and the resonant electromagnetic energy flux near and internal to the cylindrical surface are highly sensitive to variations in the tilting angle. In addition, the coating effects are studied for scattering of light at oblique incidence by an infinite, perfect cylindrical conductor coated by a dielectric layer. In this case the resonance calculations show a peculiar similarity between this light scattering and atomic-molecular scattering. A physical interpretation for these effects is given, based on an analogy of optics and quantum mechanics.     

Rarefaction of the spectrum of H-type whispering-gallery modes in a hemispherical dielectric resonator

A dense spectrum of H-type resonance oscillations (whispering-gallery modes) is observed in a hemispherical dielectric resonator excited by a capacitive slit situated on the equatorial metal mirror surface. The spectrum can be significantly rarefied by exciting the WG modes in the resonator by means of distributed coupling to a dielectric waveguide arranged in a certain special position relative to the hemisphere base.     

Extended bidirectional reflectance distribution function for polarized light scattering from subsurface defects under a smooth surface

By introducing the scattering probability of a subsurface defect (SSD) and statistical distribution functions of SSD radius, refractive index, and position, we derive an extended bidirectional reflectance distribution function (BRDF) from the Jones scattering matrix. This function is applicable to the calculation for comparison with measurement of polarized light-scattering resulting from a SSD. A numerical calculation of the extended BRDF for the case of p-polarized incident light was performed by means of the Monte Carlo method. Our numerical results indicate that the extended BRDF strongly depends on the light incidence angle, the light scattering angle, and the out-of-plane azimuth angle. We observe a 180 degrees symmetry with respect to the azimuth angle. We further investigate the influence of the SSD density, the substrate refractive index, and the statistical distributions of the SSD radius and refractive index on the extended BRDF. For transparent substrates, we also find the dependence of the extended BRDF on the SSD positions.     

Shape matters: plasmonic nanoparticle shape enhances interaction with dielectric substrate

Numerical analyses of the ultraviolet and visible plasmonic spectra measured from hemispherical gallium nanostructures on dielectric substrates reveal that resonance frequencies are quite sensitive to illumination angle and polarization in a way that depends on nanostructure size, shape, and substrate. Large, polarization-dependent splittings arise from the broken symmetry of hemispherical gallium nanoparticles on sapphire substrates, inducing strong interactions with the substrate that depend sensitively on the angle of illumination and the nanoparticle diameter.     

蒸发源位于半球面正下方膜厚分布理论研究

对蒸发源位于非平面基底一半球面正下方时膜厚均匀性进行了理论研究。通过建立无量纲模型计算了此种几何配置下,半球表面在两种常见理想蒸发源下各位置的膜厚公式以及膜厚分布方程。选择基底与蒸发源问较大的距离,可获得更大的可镀膜区域,同时该距离对基底上镀制的膜层厚度分布影响也较大。最后对实用蒸发源的发射系数,对该几何配置下半球面膜厚分布影响进行了理论研究。     

Camera for coherent diffractive imaging and holography with a soft-x-ray free-electron laser

We describe a camera to record coherent scattering patterns with a soft-x-ray free-electron laser (FEL). The camera consists of a laterally graded multilayer mirror, which reflects the diffraction pattern onto a CCD detector. The mirror acts as a bandpass filter for both the wavelength and the angle, which isolates the desired scattering pattern from nonsample scattering or incoherent emission from the sample. The mirror also solves the particular problem of the extreme intensity of the FEL pulses, which are focused to greater than 10(14) W/cm2. The strong undiffracted pulse passes through a hole in the mirror and propagates onto a beam dump at a distance behind the instrument rather than interacting with a beam stop placed near the CCD. The camera concept is extendable for the full range of the fundamental wavelength of the free electron laser in Hamburg (FLASH) FEL (i.e., between 6 and 60 nm) and into the water window. We have fabricated and tested various multilayer mirrors for wavelengths of 32, 16, 13.5, and 4.5 nm. At the shorter wavelengths mirror roughness must be minimized to reduce scattering from the mirror. We have recorded over 30,000 diffraction patterns at the FLASH FEL with no observable mirror damage or degradation of performance.     

Turning angle sensor based on a periodic optical raster and photodetector matrix in full-frame mode

A new principle for the construction of an angle sensor based on a periodic optical raster and a photodetector matrix is proposed. An algorithm for determining the angular position of the axis is considered. Theoretical and experimental estimates of the error in measurements of the angle and a comparison of the estimates are presented.     

Measurements of light scattering from glass substrates by total integrated scattering

A total integrated scattering (TIS) measurement was performed to investigate the surface and volume scattering of K9 glass substrates with low reflectance. Ag layers with thicknesses of 60 nm were deposited on the front and back surfaces of the K9 glass substrates by the magnetron sputtering technique. Surface scattering of the K9 glass substrate was obtained by the TIS measurement of the Ag layers on the assumption that the Ag layers and the K9 substrate had the same surface profile. Volume scattering of the substrates was deduced by subtracting the front and back surface scattering from the total scattering of the substrates.     

Fractal Web Design of a Hemispherical Photodetector Array with Organic-Dye-Sensitized Graphene Hybrid Composites

The vision system of arthropods consists of a dense array of individual photodetecting elements across a curvilinear surface. This compound-eye architecture could be a useful model for optoelectronic sensing devices that require a large field of view and high sensitivity to motion. Strategies that aim to mimic the compound-eye architecture involve integrating photodetector pixels with a curved microlens, but their fabrication on a curvilinear surface is challenged by the use of standard microfabrication processes that are traditionally designed for planar, rigid substrates (e.g., Si wafers). Here, a fractal web design of a hemispherical photodetector array that contains an organic-dye-sensitized graphene hybrid composite is reported to serve as an effective photoactive component with enhanced light-absorbing capabilities. The device is first fabricated on a planar Si wafer at the microscale and then transferred to transparent hemispherical domes with different curvatures in a deterministic manner. The unique structural property of the fractal web design provides protection of the device from damage by effectively tolerating various external loads. Comprehensive experimental and computational studies reveal the essential design features and optoelectronic properties of the device, followed by the evaluation of its utility in the measurement of both the direction and intensity of incident light.     

Calculation of the Optical Properties of Quartz Ceramics Based on Data on Its Structure

The optical parameters of quartz ceramics from a previously proposed identification method and simulation using different optical models of the material are compared. The identification method is based on deliberately measuring hemispherical spectral reflectances for layers of different thicknesses and solving the inverse problem using asymptotic formulas. Mathematical models are constructed based on the Mie theory on the assumption of independent scattering of electromagnetic radiation by fragments of the material. The material is considered as a polydisperse packing of spheres, the sizes of which are determined by data on the material structure. Both a grain surrounded by gas and a pore in monolithic material are considered as a scatterer. Data on the material structure were gathered using optical microscopy, static laser scattering, and mercury porosimetry. The best agreement with the results of the identification method is demonstrated by the model of ceramics in the form of a glass monolith with spherical voids. Comparative analysis eliminates uncertainty in the form of the scattering phase function and shows that the scattering is close to isotropic.     

Holographic optical receiver front end for wireless infrared indoor communications

Multispot diffuse configuration (MSDC) for indoor wireless optical communications, utilizing multibeam transmitter and angle diversity detection, is one of the most promising ways of achieving high capacities for use in high-bandwidth islands such as classrooms, hotel lobbies, shopping malls, and train stations. Typically, the optical front end of the receiver consists of an optical concentrator to increase the received optical signal power and an optical bandpass filter to reject the ambient light. Using the unique properties of holographic optical elements (HOE), we propose a novel design for the receiver optical subsystem used in MSDC. With a holographic curved mirror as an optical front end, the receiver would achieve more than an 10-dB improvement in the electrical signal-to-noise ratio compared with a bare photodetector. Features such as multifunctionality of the HOE and the receiver's small size, light weight, and low cost make the receiver front end a promising candidate for a user's portable equipment in broadband indoor wireless multimedia access.     

Submonolayer adsorbate reference material based on a low alloy steel fracture sample for Auger electron spectroscopy Part 1 Characterisation

Abstract

A homogeneous set of Cr–3·5Ni low alloy steel samples has been made to enable laboratories studying grain boundary segregation by Auger electron spectroscopy to interrelate their studies. This steel has P, Sn, and Ni segregated at the grain boundaries. Data are provided of the effect of variation of signal intensities across a grain, on one grain as a function of the electron emission angle, on many grains, etc. for both unidirectional (concentric hemispherical) and multidirectional (cylindrical mirror) spectrometers. Reference spectra recorded from the sample allow the spectrometer transmission function to be calibrated so that data from all instruments may be interrelated. After correction for the transmission function, the Auger electron peak-to-peak height ratios, for a 5 eV Savitzky and Golay differentiation, are found to be P₁₂₀/Fe₇₀₃=0·33±0·06 and Sn₄₃₀/Fe₇₀₃=0·12±0·02. Calibrations from the literature show these signals can be attributed to 33 and 31% of a monolayer of P and Sn, respectively.

MST/1684a     

Methods,models, and budgets for estimation of measurement uncertainty during calibration

Basic models are given for the interaction of instruments to be calibrated and standard measuring instruments as a combination of two types of measuring instruments with three methods for transfer of the unit value. Model equations for additive correction, correction multipliers, and correction dividers (degrees of recovery) are written down. The uncertainty budgets are compared and formulas for the combined and expanded uncertainty for all these types of correction are derived.     

The theory of automatic beam scales with electrical balancing

Summary By means of the formulas derived in this article it is possible to determine the movement of the beam in a transient process, calculate the settling time of the beam oscillations and the angle of deviation of the beam at the instant of balancing, as well as the mechanical sensitivity of the scales for given beam parameters and those of the electrical regulator of the balance position.Above formulas can be used for designing scales with electrical regulators of the balance position.     

Real-time total integrated scattering measurements on the Mir spacecraft to evaluate sample degradation in space

An instrument to measure total integrated scattering (TIS) in space was built as part of the Optical Properties Monitor instrument package and flown on the Russian Mir Space Station in a low Earth orbit. TIS at two wavelengths was measured in space at approximately weekly intervals from 29 April to 26 December 1997 and telemetered to Earth during the mission. Of the 20 TIS samples, 13 are described here to illustrate the performance of the TIS instrument. These include ten optical samples and three thermal control samples. Two optical samples and one thermal control sample were severely degraded by atomic oxygen. All samples received a light dusting of particles during the mission and an additional heavier layer after the samples returned to Earth. The initial brassboard instrument and the validation tests of the flight instrument are also described.