112,925 research outputs found
Nanostructures + light = 'new optics'
No full textSuddenly, at the end of the last century, classical optics and classical electrodynamics became fashionable again. Fields that several generations of researchers thought were comprehensively covered by the famous Born and Wolf textbook and were essentially dead as research subjects were generating new excitement. In accordance with Richard Feynman's famous quotation on nano-science, the optical community suddenly discovered that 'there is plenty of room at the bottom'—mixing light with small, meso- and nano-structures could generate new physics and new mind-blowing applications. This renaissance began when the concept of band structure was imported from electronics into the domain of optics and led to the development of what is now a massive research field dedicated to two- and three-dimensional photonic bandgap structures. The field was soon awash with bright new ideas and discoveries that consolidated the birth of the 'new optics'. A revision of some of the basic equations of electrodynamics led to the suspicion that we had overlooked the possibility that the triad of wave vector, electric field and magnetic field, characterizing propagating waves, do not necessarily form a right-handed set. This brought up the astonishing possibilities of sub-wavelength microscopy and telescopy where resolution is not limited by diffraction. The notion of meta-materials, i.e. artificial materials with properties not available in nature, originated in the microwave community but has been widely adopted in the domain of optical research, thanks to rapidly improving nanofabrication capabilities and the development of sub-wavelength scanning imaging techniques. Photonic meta-materials are expected to open a gateway to unprecedented electromagnetic properties and functionality unattainable from naturally occurring materials. The structural units of meta-materials can be tailored in shape and size; their composition and morphology can be artificially tuned, and inclusions can be designed and placed at desired locations to achieve new functionality. Among important developments in the new optics was the discovery that a metal film with arrays of small holes in it could be transparent to light beyond any intuitive expectations and that a properly designed metallic structure could be made completely 'invisible' at certain wavelengths. A strong technological drive towards device miniaturization (or, perhaps we should say 'nanoturization'?) has breathed new life into plasmonics—a field many thought had matured some time ago. Surface plasmon polarition waves have come to be seen as potential broadband information carriers for highly integrated photonic devices with research now concentrating on routing and controlling plasmon–polariton signals. Among other new topics in optical electrodynamics are frequency selective surfaces, optical effects of low-dimensional chirality and electrodynamics of toroidal structures.This Special Issue of Journal of Optics A: Pure and Applied Optics on 'Nanostructured Optical Meta-Materials: Beyond Photonic Bandgap Effects' is a very representative cross-section of research in 'new optics', with papers covering essential issues in meta-materials research, surface plasmons, nanostructured surfaces, sub-wavelength imaging, nanostructured and random laser media and nonlinearities in nanostructured films.As the Guest Editors of this Special Issue, we are deeply grateful to all contributing authors for their efforts and their willingness to share recent results within the framework of what promises to be a landmark collection of papers in the field of 'new optics'. We are especially proud that the authorship includes pioneers and newcomers to this intriguing and fertile field of research
author-bios-SRD-19-0063.R1 – Supplemental material for The Network Structure of Police Misconduct
No full textSupplemental material, author-bios-SRD-19-0063.R1 for The Network Structure of Police Misconduct by George Wood, Daria Roithmayr and Andrew V. Papachristos in Socius</p
Bianisotropic Effective Parameters of Optical Metamagnetics and Negative-Index Materials
No full textApproaches to the adequate homogenization of optical metamaterials are becoming more and more complex, primarily due to an increased understanding of the role of asymmetric electrical and magnetic responses, in addition to the nonlocal effects of the surrounding medium, even in the simplest case of plane-wave illumination. The current trend in developing such advanced homogenization descriptions often relies on utilizing bianisotropic models as a base on top of which novel optical characterization techniques can be built. In this paper, we first briefly review general principles for developing a bianisotropic homogenization approach. Second, we present several examples validating and illustrating our approach using single-period passive and active optical metamaterials. We also show that the substrate may have a significant effect on the bianisotropic characteristics of otherwise symmetric passive and active metamaterials
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Laser assisted modification of poled silver-doped nanocomposite soda-lime glass
No full textThermal poling assisted homogenization of polydisperse Ag nanoparticles embedded in the soda-lime glass is demonstrated. The homogenization leads to the narrowing of the localized surface plasmon resonance. The subsequent irradiation with linearly polarized ultrashort laser pulses induces spectrally defined and three times larger dichroism than in non-poled sample
Challenges and prospects of plasmonic metasurfaces for photothermal catalysis
No full textSolar-thermal technologies for converting chemicals using thermochemistry require extreme light concentration. Exploiting plasmonic nanostructures can dramatically increase the reaction rates by providing more efficient solar-to-heat conversion by broadband light absorption. Moreover, hot-carrier and local field enhancement effects can alter the reaction pathways. Such discoveries have boosted the field of photothermal catalysis, which aims at driving industrially-relevant chemical reactions using solar illumination rather than conventional heat sources. Nevertheless, only large arrays of plasmonic nano-units on a substrate, i.e., plasmonic metasurfaces, allow a quasi-unitary and broadband solar light absorption within a limited thickness (hundreds of nanometers) for practical applications. Through moderate light concentration (∼10 Suns), metasurfaces reach the same temperatures as conventional thermochemical reactors, or plasmonic nanoparticle bed reactors reach under ∼100 Suns. Plasmonic metasurfaces, however, have been mostly neglected so far for applications in the field of photothermal catalysis. In this Perspective, we discuss the potentialities of plasmonic metasurfaces in this emerging area of research. We present numerical simulations and experimental case studies illustrating how broadband absorption can be achieved within a limited thickness of these nanostructured materials. The approach highlights the synergy among different enhancement effects related to the ordered array of plasmonic units and the efficient heat transfer promoting faster dynamics than thicker structures (such as powdered catalysts). We foresee that plasmonic metasurfaces can play an important role in developing modular-like structures for the conversion of chemical feedstock into fuels without requiring extreme light concentrations. Customized metasurface-based systems could lead to small-scale and low-cost decentralized reactors instead of large-scale, infrastructure-intensive power plants
Fabrication and realistic modeling of three-dimensional metal-dielectric composites
No full textHistorically, the methods used to describe the electromagnetic response of random, three-dimensional (3D), metal-dielectric composites (MDCs) have been limited to approximations such as effective-medium theories that employ easily-obtained, macroscopic parameters. Full-wave numerical simulations such as finite-difference time domain (FDTD) calculations are difficult for random MDCs due to the fact that the nanoscale geometry of a random composite is generally difficult to ascertain after fabrication. We have developed a fabrication method for creating semicontinuous metal films with arbitrary thicknesses and a modeling technique for such films using realistic geometries. We extended our two-dimensional simulation method to obtain realistic geometries of 3D MDC samples, and we obtained the detailed near-and far-field electromagnetic responses of such composites using FDTD calculations. Our simulation results agree quantitatively well with the experimentally measured far-field spectra of the real samples. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3590208
Highly efficient frequency shifting from temporally modulated epsilon-near-zero surfaces
No full textThe dynamical control of material electromagnetic (EM) properties has recently been attracting significant interest. While a static design of the optical properties can provide a complete control of the momentum of a propagating wave, time-dependent materials allow the manipulation of its optical frequency. For instance, suppose a laser pulse incident on the interface between two media where one of them is rapidly changing refractive index in time. The temporal modulation of the boundary between the two media leads to a backward and forward propagating wave with a shifted spectrum [1,2]. This phenomenon, called photon acceleration, has been theoretically investigated in the last century, whilst experimental proof is harder to achieve for homogenous materials or surfaces due to the extremely large and fast changes of the refractive index required
Growth and spectroscopic investigations of new crystal Er(3+),Ce(3+) : NaLa(MoO(4))(2) promising for 1.5 mu m solid-state lasers
No full textScheelite-like disordered double sodium-lanthanum molybdate NaLa(MoO(4))(2) single crystals co-doped with Er(3+) and different concentrations of Ce(3+) have been grown by Czochralski technique. The 300K spectroscopic properties of the excited states (4)S(3/2), (4)I(11/2) and (4)I(13/2) of Er(3+) ions in grown crystals as a function of Cerium concentration have been investigated. The lifetime of (4)I(11/2) have been found to reduce from 130 mu s in the solely Er-doped sample to approximately 3.5 mu s, when the concentration of Ce reaches 50 at. %. At the same time the lifetime of (4)I(13/2) level at 300 K remains unchanged (3.7 ms) up to the concentration of Ce in crystal equal to 10 at. %, and reduces by less than 30% (2.6 ms) in the 50 at. % Ce co-doped sample. This result looks very promising from point of view of obtaining low-threshold 1.5 mu m laser oscillation
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