Showing papers by "Nader Engheta published in 2010"
TL;DR: By properly loading and matching nanoantenna pairs with optical nanocircuits, this work theoretically demonstrate a complete optical wireless link that, in spite of some radiation loss and mismatch factors, may exhibit much less absorption loss, largely outperforming regular plasmonic waveguide links.
Abstract: Optical waveguide interconnects are a major component of chip-scale data processing and computational systems. Here, we propose an alternative mechanism based on optical wireless broadcasting links using nanoantennas, which may overcome some of the limitations of nanoscale waveguide interconnects. By properly loading and matching nanoantenna pairs with optical nanocircuits, we theoretically demonstrate a complete optical wireless link that, in spite of some radiation loss and mismatch factors, may exhibit much less absorption loss, largely outperforming regular plasmonic waveguide links.
249 citations
TL;DR: In this article, the authors clarified the nature of this apparent paradox and the limitations of this anomalous phenomenon in terms of particle size, identifying relevant missteps in some of their physical interpretation, and considering the general possibility of verifying these effects.
Abstract: A few decades ago, Kerker et al. [J. Opt. Soc. Am. 73, 765-767 (1983)] theoretically pointed out the interesting possibility of conceiving small magnetodielectric spheres that may provide zero scattering in the forward direction, despite significantly larger scattering in any other direction. Recent experimental and theoretical papers on the topic have further discussed this possibility in more realistic scenarios. Inspecting some of their analyses, it seems indeed possible to conceive nanoparticles characterized by a scattering pattern with a sharp minimum, although not zero, in the forward direction. From a theoretical standpoint, however, it is well known that the total scattered power from any object has to be proportional to a portion of the scattered field in the forward direction, implying that very small or zero forward scattering should be synonymous to even smaller or zero total scattering, regardless of the nature of the object and of its design. Using analytical theory and an accurate scattering formulation, we clarify the nature of this apparent paradox and the limitations of this anomalous phenomenon in terms of particle size. In this way, we shed some new light on theoretical and experimental papers on the topic, identifying relevant missteps in some of their physical interpretation, and considering the general possibility of verifying these effects. This discussion may also be relevant to some cloaking applications using exotic artificial materials.
109 citations
TL;DR: Here, the recent concept of a "cloaked sensor" to an NSOM device in collection mode is applied, showing theoretically how a proper plasmonic cover applied to anNSOM tip may drastically improve its overall measurement capabilities.
Abstract: Near-field imaging is a well-established technique in biomedical measurements, since closer to the detail of interest it is possible to resolve subwavelength details otherwise unresolved by regular lenses. A near-field scanning optical microscope (NSOM) tip may indeed overcome the resolution limits of far-field optics, but its proximity inherently perturbs the measurement. Here, we apply the recent concept of a "cloaked sensor" to an NSOM device in collection mode, showing theoretically how a proper plasmonic cover applied to an NSOM tip may drastically improve its overall measurement capabilities.
87 citations
TL;DR: A novel, low power imaging sensor capable of recording the optical properties of partially linearly polarized light in real-time is presented.
Abstract: Traditional imaging systems capture and replicate the imaged environment in terms of color and intensity. One important property of light, which the human eye is blind to and is ignored by traditional imaging systems, is polarization. In this paper we present a novel, low power imaging sensor capable of recording the optical properties of partially linearly polarized light in real-time. The imaging sensor combines polymer polarization filters with a CMOS image sensor in order to compute the first three Stokes parameters at the focal plane. The imaging array contains 100 x 100 pixels and consumes 48 mW at 30 fps.
85 citations
TL;DR: In this paper, the use of metamaterial-inspired ultranarrow channels at cutoff is proposed to realize an interesting matching between a coaxial antenna and a waveguide, independent of the relative position of the antenna and possible bending and abruptions along the channel.
Abstract: We propose the use of metamaterial-inspired ultranarrow channels at cutoff to realize an interesting matching between a coaxial antenna and a waveguide. The anomalous properties of a channel at cutoff, analogous to those of zero permittivity materials, allow a simple matching design, valid for arbitrary waveguides, with large degrees of freedom in terms of geometry, length and possible bending of the connecting channel. Moreover, the static-like properties of the channel allow such matching, independent of the relative position of the antenna and possible bending and abruptions along the channel.
50 citations
TL;DR: In this paper, the effect of a small disorder on the guidance properties of plasmonic nanoparticles is quantitatively taken into account, and the main effect of the small disorder consists of additional radiation losses for the guided mode.
Abstract: In this paper, we formulate an analytical theory that quantifies the first-order effect of a small random uncontrollable disorder that is due to limitations in the realization of periodic arrays of plasmonic nanoparticles. In particular, we show how the effect of a small disorder may be quantitatively taken into account when evaluating the guidance properties of these otherwise periodic chains, and how the main effect of the small disorder consists of additional radiation losses for the guided mode. Similar quantitative analyses may be extended to the general class of periodic metamaterials, providing an idea of how disorder affects their electromagnetic response, and which types of disorder have the most effect.
45 citations
TL;DR: In this paper, the authors pointed out that "Look around, and you will probably see numerous electronic and optical gadgets, such as mobile phones, personal digital assistants, laptops, TVs and digital cameras".
Abstract: Look around, and you will probably see numerous electronic and optical gadgets, such as mobile phones, personal digital assistants, laptops, TVs and digital cameras.
42 citations
TL;DR: In this paper, the authors discuss the possibility of applying the scattering-cancellation-based plasmonic cloaking technique to reduce the scattering from a sensing device, lowering its disturbance on sensing without affecting its ability to measure and sense the external world.
39 citations
TL;DR: In this paper, transformation-based optics is applied to the derivation of a general class of transparent metamaterial slabs, and the authors explore their image-displacement/formation capabilities and establish intriguing connections with configurations already known in the literature.
Abstract: In this paper, we apply transformation-based optics to the derivation of a general class of transparent metamaterial slabs. By means of analytical and numerical full-wave studies, we explore their image-displacement/formation capabilities, and establish intriguing connections with configurations already known in the literature. Starting from these revisitations, we develop a number of nontrivial extensions, and illustrate their possible applications to the design of perfect radomes, anticloaking devices, and focusing devices based on double-positive (possibly nonmagnetic) media. These designs show that such anomalous features may be achieved without necessarily relying on negative-index or strongly resonant metamaterials, suggesting more practical venues for the realization of these devices.
36 citations
TL;DR: Analytically and numerically, it is shown that in a TiO(2) double-groove grating with two different groove widths per period attached on the SiO( 2) substrate, the normally incident light couples to the +1st-order transmission with 96.9% efficiency and with a 50° diffraction angle that is larger than the Si O(2)-air interface critical angle.
Abstract: Here we show, analytically and numerically, that in a TiO(2) double-groove grating with two different groove widths per period attached on the SiO(2) substrate, the normally incident light couples to the +1st-order transmission with 96.9% efficiency and with a 50° diffraction angle that is larger than the SiO(2)-air interface critical angle. Modal analysis reveals that three propagating modes for the +1st diffraction order reach the grating back end in phase, while the corresponding propagating modes for the -1st and zeroth orders are added destructively at the grating end. Four optical devices based on this grating characteristic are numerically demonstrated.
22 citations
TL;DR: In this article, the authors explore an alternative transformation-optics-based route, which relies on the recently introduced concept of anti-cloaking, which is a suitable tailoring of the competing cloaking and anti cloaking mechanisms interacting in a two-dimensional cylindrical scenario.
Abstract: The suggestive idea of “cloaking” an electromagnetic sensor, i.e., strongly reducing its visibility (scattering) while maintaining its field-sensing (absorption) capabilities, has recently been proposed in the literature, based on scattering-cancellation, Fano-resonance, or transformation-optics approaches. In this paper, we explore an alternative transformation-optics-based route, which relies on the recently introduced concept of “anti-cloaking.” More specifically, our proposed approach relies on a suitable tailoring of the competing cloaking and anti-cloaking mechanisms, interacting in a two-dimensional cylindrical scenario. Via analytical and parametric studies, we illustrate the underlying phenomenology, identify the critical design parameters, and address the relevant optimality and trade-off issues, taking also into account the effect of material losses. Our results confirm the envisaged potentials of the proposed transformation-optics approach as an attractive alternative route to sensor cloaking.
TL;DR: In this article, a TiO2 grating beam splitter on the SiO2 layer is designed using the modal analysis, which achieves a 49.6% efficiency for each and a 50° refraction angle that is larger than the critical angle for the siO2-air interface.
Abstract: A TiO2 grating beam splitter on the SiO2 layer is designed using the modal analysis. Normal incident light couples to the −1st/+1st-order transmission diffraction with a 49.6% efficiency for each and with a 50° refraction angle that is larger than the critical angle for the SiO2-air interface. The SiO2 interlayer is sandwiched between the two gratings. The finite-integration-technique investigation shows its switching capability due to the quarter-period shift between the gratings, with the zeroth-order transmission smaller than 5% for the “off” state and larger than 95% for the “on” state from 553 to 654 nm wavelength regime.
01 Jan 2010
15 Nov 2010
TL;DR: In this paper, a transformation-optics-based approach to cloaking an electromagnetic sensor is proposed, which reduces its visibility while maintaining its field-sensing capabilities. But the proposed approach relies on a judicious tailoring of the interactions between the competing effects of invisibility cloaking and anti-cloaking and constitutes an attractive alternative to other approaches.
Abstract: In this paper, we introduce and explore a transformation-optics-based approach to “cloaking” an electromagnetic sensor, i.e., strongly reducing its visibility while maintaining its field-sensing capabilities. The proposed approach relies on a judicious tailoring of the interactions between the competing effects of invisibility cloaking and “anti-cloaking,” and constitutes an attractive alternative to other approaches (e.g., scattering cancellation, or Fano-resonance-based) recently proposed in the literature.
TL;DR: The 13 papers in this special issue describe some of the most remarkable work in the field of metamaterials and outline a number of exciting future research directions as discussed by the authors, which can be found in the special issue.
Abstract: The 13 papers in this special issue describe some of the most remarkable work in the field of metamaterials and outline a number of exciting future research directions.
TL;DR: In this paper, the role of the incident angle of incoming light on the excited modes in rectangular grating at the interface of air and fused silica in Littrow mounting is investigated by the modal analysis.
Abstract: The role of the incident angle of incoming light on the excited modes in rectangular grating at the interface of air and fused silica in Littrow mounting is investigated by the modal analysis.The analysis points out that the optimum effective refractive index difference for two propagating modes varies with the angle of incidence. In polarization-independent −1st order diffraction, effective refractive index difference has the same value for the p- and s-polarizations for incident angles from 30° to 37.5°, and a ratio of one-third with the further increase of incident angle, to select the minimum aspect ratio of the grating dimensions. On the other hand, polarization splitting condition has a change of ratio of effective refractive index difference from a half to zero at an incident angle of 45.3°, where the coupling order of diffraction for p- or s-polarization is also swapped. Such ratio of effective refractive index differences are seen as the ratio of modal periods in the variation of diffraction efficiency with the grating height. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1362–1369, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25163
TL;DR: By properly designing pairs of nanoantennas, the authors theoretically showed that the second-harmonic generation in nonlinear media can be enhanced by combining field enhancement at the fundamental frequency and the Purcell effect at the second harmonics.
Abstract: By properly designing pairs of nanoantennas, we theoretically show that the second-harmonic generation in nonlinear media can be enhanced by combining field enhancement at the fundamental frequency and the Purcell effect at the second harmonics.
TL;DR: In this article, the manipulation, routing, waveguiding and scattering of surface-plasmon polaritons along graphene at IR wavelengths were investigated, exploiting the dependence of graphene conductivity on the electric bias field.
Abstract: Exploiting the dependence of graphene conductivity on the electric bias field, we theoretically investigate the manipulation, routing, waveguiding and scattering of surface-plasmon polaritons along graphene at IR wavelengths, proposing a “flatland” paradigm for optical metamaterials.
Proceedings Article•
12 Apr 2010TL;DR: In this article, the e-near zero (ENZ) tunneling phenomenon has been applied to realistic 3D cylindrical antenna geometries, with the purpose of realizing a frequency-hopping multi-band radiator working in a 5:1 bandwidth in the millimeter-wave regime.
Abstract: The e-near-zero (ENZ) tunneling phenomenon has been shown to allow full transmission of waves through narrow channels, even in the presence of a strong geometric mismatch. Here we propose an application of this principle to realistic 3D cylindrical antenna geometries, with the purpose of realizing a frequency-hopping multi-band radiator working in a 5:1 bandwidth in the millimetre-wave regime, of interest for a variety of real-life antenna applications.
TL;DR: In this article, the authors theoretically investigate the interaction of propagating waves in one-way waveguides with terminal loads and cavities, showing that the impedance mismatch between the load and the waveguide has no effect on energy propagation through the structure.
Abstract: We theoretically investigate interaction of propagating waves in one-way waveguides with terminal loads and cavities, showing that the impedance mismatch between the load and the waveguide has no effect on energy propagation through the structure.
Proceedings Article•
12 Apr 2010TL;DR: In this paper, the authors explore how geometry, size and loading techniques may affect and improve efficiency, bandwidth and sensitivity of various optical nanoantennas, and show how it may be possible to operate various nanoantenna geometries as efficient optical nanoradiators, and how their tuning and matching properties may be tailored with large degrees of freedom by designing suitable nanoloads placed at their gap.
Abstract: Following our recent results on plasmonic nanoantennas of different geometry and shape, here we explore how geometry, size and loading techniques may affect and improve efficiency, bandwidth and sensitivity of various optical nanoantennas. We show how it may be possible to operate various nanoantenna geometries as efficient optical nanoradiators, and how their tuning and matching properties may be tailored with large degrees of freedom by designing suitable nanoloads placed at their gap. In this way, we successfully apply nanocircuit concepts to model the loading nanoparticles and in matching them to suitable optical lines. High levels of optical radiation efficiency may be achieved, even considering the realistic absorption of optical metals, by properly selecting specific geometries, size and design.
TL;DR: In this paper, the authors present a concise summary of selected results from their recent and ongoing studies on transformation electromagnetics, focusing on cloak/anti-cloak interactions and on some general classes of metamaterial slabs with interesting image displacing/reconstruction capabilities.
Abstract: In this paper, we present a concise summary of selected results from our recent and ongoing studies on transformation electromagnetics. Specifically, we focus on cloak/anti-cloak interactions (with possible application to sensor invisibility), and on some general classes of metamaterial slabs (made of double positive, double negative or single negative media) with interesting image displacing/reconstruction capabilities.
TL;DR: In this article, a technique for light trapping into the SiO2 substrate using a TiO2 grating was presented, and the switching capability of the double-sided gratings with the horizontal quarter-period shift between the top and bottom gratings was investigated.
Abstract: We present a technique for light trapping into the SiO2substrate using a TiO2grating, and the switching capability of the double-sided gratings with the horizontal quarter-period shift between the top and bottom gratings.
TL;DR: Metamaterials with extreme parameter values can manipulate electromagnetic fields and waves at various length scales, providing a platform for metatronic circuits, optical wires, plasmonic cloaking, enhanced emission at extended regions, and supercoupling in narrow channels as discussed by the authors.
Abstract: Metamaterials with extreme parameter values can manipulate electromagnetic fields and waves at various length scales, providing a platform for metatronic circuits, optical wires, plasmonic cloaking, enhanced emission at extended regions, and supercoupling in narrow channels