12 results on '"MacDonald, Kevin"'
Search Results
2. Color filter arrays based on dielectric metasurface elements
- Author
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Berzins, Jonas, Silvestri, Fabrizio, Gerini, Giampiero, Setzpfandt, Frank, Pertsch, Thomas, Bäumer, Stefan M.B., Boardman, Allan D., Zayats, Anatoly V., MacDonald, Kevin F., and Electromagnetics
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Silicon ,Hyperspectral imaging ,Computer science ,Dependent scatterings ,FOS: Physical sciences ,High Tech Systems & Materials ,Applied Physics (physics.app-ph) ,02 engineering and technology ,01 natural sciences ,Nanodisks ,010309 optics ,Gamut ,Optics ,Wave filters ,Color gel ,0103 physical sciences ,Optical filter ,RGB ,color filter array ,CMY ,Industrial Innovation ,Pixel ,business.industry ,silicon ,Physics - Applied Physics ,Hyper-spectral cameras ,Cameras ,021001 nanoscience & nanotechnology ,metasurfaces ,Color filter arrays ,Metasurfaces ,color filter ,Filter (video) ,nanodisk ,Metamaterials ,Light transmission ,RGB color model ,Nanostructured surface ,Color filter array ,Transmission spectrums ,Electronics ,0210 nano-technology ,business ,Optics (physics.optics) ,Physics - Optics - Abstract
Digital imaging has been steadily improving over the past decades and we are moving towards a wide use of multi- and hyperspectral cameras. A key component of such imaging systems are color filter arrays, which define the spectrum of light detected by each camera pixel. Hence, it is essential to develop a variable, robust and scalable way for controlling the transmission of light. Nanostructured surfaces, also known as metasurfaces, offer a promising solution as their transmission spectra can be controlled by shaping the wavelength-dependent scattering properties of their constituting elements. Here we present, metasurfaces based on silicon nanodisks, which provide filter functions with amplitudes reaching 70-90% of transmission, and well suitable for RGB and CMY color filter arrays, the initial stage towards the further development of hyperspectral filters. We suggest and discuss possible ways to expand the color gamut and improve the color values of such optical filters.
- Published
- 2018
3. Metasurface Enhanced AFM Cantilevers
- Author
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Speet, B., Silvestri, F., Gerini, G., Mashaghi Tabari, S., Sadeghian, H., Boardman, Allan D., Zayats, Anatoly V., MacDonald, Kevin F., Electromagnetics, and Dynamics and Control
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Materials science ,Cantilever ,Polarization rotator ,Industrial Innovation ,Optical Metasurface ,business.industry ,Stray light ,Detector ,High Tech Systems & Materials ,Polarization (waves) ,Ellipse ,AFM probe ,Atomic Force Microscopy ,Resonator ,Optics ,Orthogonal coordinates ,Electronics ,business - Abstract
In this contribution, we present the application of an optical metasurface polarization rotator in an Atomic Force Microscopy (AFM) setup. In AFM, the laser beam used to measure the cantilever deflection is not entirely intercepted by the cantilever surface. Consequently, the remainder of the beam illuminates part of the surface under measurement. Part of the light scattered by the surface is intercepted by the Position Sensitive Detector (PSD), interfering with the measurement of the light that is directly reflected by the cantilever. This reduces the measurement Signal-to-Noise Ratio (SNR), decreasing the AFM accuracy and generating artefacts. To enhance the SNR we propose a metasurface reflective polarization rotator, directly integrated on the cantilever. The metasurface elliptical resonators, oriented at a certain angle with respect to the incoming polarization state, will induce different phase shifts on the two components parallel to the orthogonal axes of the ellipse. By properly tuning the dimensions of the resonators, a 90° rotation of the reflected light polarization with respect to the incident polarization is realized. We arrive at three designs with cross-polar reflectivities of 0.82, 0.86 and 0.66 and total reflectivities of 0.83, 0.87 and 0.68 correspondingly. The metasurface allows to discriminate the desired light, reflected by the cantilever, from stray light from the sample surface, which maintains mostly the original polarization. In this paper, performance of the different configurations will be presented and discussed together with other considerations relative to the mechanical performances of the enhanced cantilever.
- Published
- 2018
4. Polycarboxylate ether and slabs: understanding how they work in floor construction
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MacDonald, Kevin
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Floors -- Design and construction ,Floors -- Materials ,Concrete slabs -- Design and construction ,Concrete slabs -- Materials ,Cement -- Additives ,Cement -- Usage ,Cement -- Properties ,Business ,Construction and materials industries - Published
- 2009
5. MacDonald on ... celebrating the past with an eye to the future
- Author
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MacDonald, Kevin
- Subjects
Business ,Government - Abstract
It is symptomatic of my inability to meet deadlines that l should have missed my own anniversary. Thus it is a quarter of a century and one month since an [...]
- Published
- 2002
6. The man who listened to Britain
- Author
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MacDonald, Kevin
- Subjects
Filmmakers -- Influence ,Business ,Business, international ,Retail industry - Abstract
The influence of Humphrey Jennings on filmmaking in the UK is often overlooked. He made a small number of films, mainly shorts, between 1938 and 1945. These had a unique cinematic style and very unusual effects.
- Published
- 2000
7. Hot electron generation via internal surface photo-effect in structures with quantum well
- Author
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Jacob B. Khurgin, Igor V. Smetanin, Igor E. Protsenko, Fedor A. Shuklin, Alexander V. Uskov, MacDonald, Kevin F., Staude, Isabelle, and Zayats, Anatoly V.
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Work (thermodynamics) ,Materials science ,Condensed matter physics ,business.industry ,Orders of magnitude (temperature) ,Schottky barrier ,Hot electron generation ,Dielectric ,Electron ,Threshold energy ,Photo-effect ,Semiconductor ,Metal-semiconductor interface ,Water splitting ,business ,Quantum well - Abstract
It was recently demonstrated in the experiments [1,2] that the internal photoemission efficiency can reach several tens of percents because of "coherent" or, "surface" photoemission. In present work we provide theoretical description of this effect assuming the surface photoemissionin the structureconsisting ofthe Schottky-barrier metal-semiconductor interface with the Quantum Well (QW) inside. We take into account the difference of dielectric permittivities for the metal and the semiconductor which strongly affects the photoemission efficiency. We show that QW inside the Schottky-barrier can lead to (a) lowering the threshold energy of the photoemission due to resonance tunneling of electrons through the intermediate quasi-level of energy in QW; (b) the photoemission efficiency can be increased by several orders of magnitude.
- Published
- 2020
8. Near-field phase characterization of gradient gap plasmon-based metasurfaces
- Author
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Sergey I. Bozhevolnyi, Vladimir A. Zenin, Fei Ding, Rucha Anil Deshpande, Niels Asger Mortensen, Zayats, Anatoly V., Boardman, Allan D., and MacDonald, Kevin F.
- Subjects
Coupling ,Fabrication ,Materials science ,gap surface plasmons ,business.industry ,Phase (waves) ,s-SNOM ,Near and far field ,02 engineering and technology ,021001 nanoscience & nanotechnology ,metasurfaces ,01 natural sciences ,010309 optics ,Wavelength ,Near-field ,Transmission (telecommunications) ,0103 physical sciences ,Reflection (physics) ,Optoelectronics ,0210 nano-technology ,business ,Plasmon - Abstract
Metasurface studies have demonstrated vast applications to control optical properties of light based on the ability to design unit cells with desired phase and reflectivity in 2D subwavelength periodic arrays. The simplified design strategy is only an approximation since the unit cells can be subject to near-field coupling effects due to influence from neighbor unit cells. In this work, we try to investigate this effect by numerically and experimentally studying the near-field response from gold nanobricks of varied length, fabricated in both quasi-periodic and periodic configuration on top of dielectric-coated (SiO2) layer and gold layer at telecommunication wavelength (1500 nm), which is the commonly used gap plasmon configuration for efficient metasurfaces. The experimental near-field investigation is performed using a phase-resolved scattering-type scanning near-field optical microscopy (s-SNOM) in the transmission mode. We demonstrate that near-field coupling becomes significant when edge-to-edge separation between GSP elements goes below ∼200-250 nm. We also show that the reflection phase of any GSP element is approximately equal to its doubled near-field phase. Thus, our studies provide a direct explanation of a reduced performance of a densely-packed GSP metasurfaces. This technique can accurately predict the performance of different types of metasurfaces by observing their near-field response in different periodic configurations by considering factors ignored in the design stage, which include fabrication uncertainties, wrong design considerations along with near-field coupling effects.
- Published
- 2018
9. Bifunctional metamirrors for simultaneous polarization splitting and focusing
- Author
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Rucha Anil Deshpande, N. Asger Mortensen, Sergejs Boroviks, Sergey I. Bozhevolnyi, Boardman, Allan D., Zayats, Anatoly V., and MacDonald, Kevin F.
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Optical fiber ,Materials science ,gap surface plasmons ,Extinction ratio ,business.industry ,gradient metasurfaces ,Physics::Optics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Polarization (waves) ,Ray ,plasmonics ,law.invention ,Numerical aperture ,at optics ,020210 optoelectronics & photonics ,law ,0202 electrical engineering, electronic engineering, information engineering ,Optoelectronics ,Focal length ,Photonics ,0210 nano-technology ,business ,Electron-beam lithography - Abstract
Metasurfaces - artificial 2D sheet structures with sub-wavelength periodicity and dimensions of elements - are paving the way to improve traditional optical components by integrating multiple functionalities into one optically flat device. With the progress in nano-fabrication methods, different applications of metasurfaces were demonstrated experimentally, ranging from artificial plasmonic colouring to flat optical components. In this work, we demonstrate implementation of a bifunctional gap-surface-plasmon-based metasurface which, in reflection mode, splits orthogonal linear light polarizations and focuses into different focal spots. The fabricated configuration consists of 50 nm thick gold nanobricks with different lateral dimensions, organized in an array of 240 nm x 240 nm unit cells on the top of a 50 nm thick silicon dioxide layer, which is deposited on an optically thick reflecting gold substrate. Structure is fabricated using standard electron beam lithography and lift-off techniques. Characterization is performed using scanning electron microscopy and optical measurements, including investigation of wavelength dependence of efficiency, focal length and polarization extinction ratio. Our device features high efficiency (up to ∼65%) and polarization extinction ratio (up to ∼30 dB), exhibiting broadband response in the near-infrared band (750 950 nm wavelength) with the focal length and numerical aperture dependent on the wavelength of incident light. The proposed optical component can be straightforwardly integrated into photonic circuits or fiber optic devices which employ polarization multiplexing.
- Published
- 2018
10. Gold Asymmetric-Split Ring Resonators (A-SRRs) for Proteins Sensing
- Author
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Nigel P. Johnson, Jharna Paul, Richard M. De La Rue, Boardman, Allan D., Johnson, Nigel P., MacDonald, Kevin F., and Özbay, Ekmel
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Materials science ,business.industry ,High-refractive-index polymer ,Self-assembled monolayer ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Spectral line ,0104 chemical sciences ,chemistry.chemical_compound ,Resist ,chemistry ,Monolayer ,Optoelectronics ,Zinc selenide ,Fourier transform infrared spectroscopy ,0210 nano-technology ,business ,Plasmon - Abstract
In this paper, gold asymmetric-split ring resonators (A-SRRs) are used for proteins sensing in the mid-infrared (IR) spectral region. Self-assembled monolayers (SAMs) of octadecanethiol (ODT) in ethanolic solution were deposited on the resonator surfaces to immobilise protein molecules for their detection. Different diameters ASRRs were fabricated on zinc selenide (ZnSe) substrates using electron-beam lithography technique. Their plasmonic responses appear in the mid-IR spectral region and match with the vibrational responses of many organic molecules. After the formation of SAMs layer, one sample was immersed in bovine serum albumin (BSA) solution for proteins adsorption while other sample was immersed in hydroxyl terminated hexa-ethylene glycol (EG6-OH) solution to modify SAMs surfaces to resist immobilisation of proteins. The vibrational responses of these organic molecules, all samples were excited using an incident broadband mid-IR light source and their reflectance spectra were measured at normal incidence using a microscope coupled Fourier Transform Infrared (FTIR) spectrometer. This study highlights the capability of plasmonic structures (A-SRRs) fabricated on transparent and high refractive index ZnSe substrates allows the detection of BSA proteins with enhanced detection in the mid-IR spectral range, demonstrating their potential for a wide range of sensing applications, e.g. in biomedical engineering and food industries.
- Published
- 2016
11. Conjugate-impedance matched metamaterials for super-Planckian radiative heat transfer
- Author
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Stanislav I. Maslovski, Constantin Simovski, Sergei A. Tretyakov, Boardman, Allan D., Johnson, Nigel P., Macdonald, Kevin, Ozbay, Ekmel, Universidade de Coimbra, Department of Radio Science and Engineering, Aalto-yliopisto, and Aalto University
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Physics ,Spectral index ,ta114 ,business.industry ,Impedance matching ,02 engineering and technology ,super-Planckian radiative heat transfer ,Effective radiated power ,thermal emission ,021001 nanoscience & nanotechnology ,01 natural sciences ,Computational physics ,Radiative flux ,metamaterials ,Atmospheric radiative transfer codes ,Optics ,Heat flux ,black body ,0103 physical sciences ,Heat transfer ,Radiative transfer ,010306 general physics ,0210 nano-technology ,business - Abstract
A problem of maximization of the radiative heat transfer (at a given wavelength) between a body and its environment is considered theoretically. It is shown that the spectral density of the radiative heat flux is maximized under the formulated conjugate impedance matching condition, in which case the spectral density of radiated power can exceed the black body limit, resulting in a super-Planckian heat exchange at characteristic distances significantly greater than the wavelength. It is demonstrated that the material parameters of the optimal emitters can be deduced from the known material parameters of the environment and represented by closed-form relations, thus, enabling a way for physical realization of such far-field super-Planckian emitters.
- Published
- 2016
12. Gap plasmon-based metasurfaces: fundamentals and applications (Conference Presentation)
- Author
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Anders Pors, Boardman, Allan D., Johnson, Nigel P., MacDonald, Kevin F., and Özbay, Ekmel
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Physics ,business.industry ,Surface plasmon ,Metamaterial ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Polarization (waves) ,01 natural sciences ,Surface plasmon polariton ,Ray ,010309 optics ,symbols.namesake ,Optics ,0103 physical sciences ,Reflection (physics) ,symbols ,Optoelectronics ,Stokes parameters ,0210 nano-technology ,business ,Plasmon - Abstract
Plasmonic metasurfaces, which can be considered as the two-dimensional analog of metal-based metamaterials, have recently attracted considerable attention due to the possibility to fully control the reflected or transmitted light, while featuring relatively low losses even at optical wavelengths and being suitable for planar fabrication techniques. Among all the different design approaches, one particular configuration, consisting of a subwavelength thin dielectric spacer sandwiched between an optically thick metal film and an array of metal nanobricks (also known as nanopatches), has gained awareness from researchers working in practical any frequency regime as its realization only requires on step of lithography, yet with the possibility to fully control the amplitude and phase of the reflected light. At optical wavelengths, the full control of the reflected light is closely associated with gap surface plasmon (GSP) resonances and, hence, the configuration is also known as GSP-based metasurface. In this work, we highlight the connection between the properties of GSP modes and the optical response of GSP-based metasurfaces, particularly discussing the possibility to independently control either the reflection phases for two orthogonal polarizations or both the amplitude and phase of the reflected light for one polarization by proper choice of geometrical and material parameters [1]. Having obtained thorough insight into the optical response of GSP-based metasurfaces, we design and realize at optical and near-infrared wavelengths a broad range of inhomogeneous metasurfaces targeting different applications. For example, we exemplify the control of reflection amplitude by performing plasmonic color printing on a subwavelength scale [2], while full control of reflection phases for orthogonal polarizations are illustrated by the realization of unidirectional polarization-controlled surface plasmon polariton couplers [3] and compact polarimeters [4]. Finally, the simultaneous control of the amplitude and phase of reflected light allow us to perform calculus operations, such as differentiation and integration, on the incident light [5], which signifies the possibility to do optical signal processing using GSP-based metasurfaces. References: 1. A. Pors and S. I. Bozhevolnyi, “Gap plasmon-based phase-amplitude metasurfaces: material constraints”, Opt. Mater. Express 5, 2448-2458 (2015). 2. A. S. Roberts, A. Pors, O. Albrektsen, and S. I. Bozhevolnyi, “Subwavelength plasmonic color printing for ambient use”, Nano Lett. 14, 783-787 (2014). 3. A. Pors, M. G. Nielsen, T. Bernardin, J.-C. Weeber, and S. I. Bozhevolnyi, “Efficient unidirectional polarization-controlled excitation of surface plasmon polaritons”, Light: Sci. Applications 3, e197 (2014). 4. A. Pors, M. G. Nielsen, and S. I. Bozhevolnyi, “Plasmonic metagratings for simultaneous determination of Stokes parameters”, Optica 2, 716-723 (2015). 5. A. Pors, M. G. Nielsen, and S. I. Bozhevolnyi, “Analog computing using reflective plasmonic metasurfaces”, Nano Lett. 15, 791-797 (2015).
- Published
- 2016
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