Universal lineshapes at the crossover between weak and strong critical coupling in Fano-resonant coupled oscillators

In this article we discuss a model describing key features concerning the lineshapes and the coherent absorption conditions in Fano-resonant dissipative coupled oscillators. The model treats on the same footing the weak and strong coupling regimes, and includes the critical coupling concept, which is of great relevance in numerous applications; in addition, the role of asymmetry is thoroughly analyzed. Due to the wide generality of the model, which can be adapted to various frameworks like nanophotonics, plasmonics, and optomechanics, we envisage that the analytical formulas presented here will be crucial to effectively design devices and to interpret experimental results

Coherent perfect absorption in photonic structures

The ability to drive a system with an external input is a fundamental aspect of light-matter interaction. The coherent perfect absorption (CPA) phenomenon extends to the general multibeam interference phenomenology the well known critical coupling concepts. This interferometric control of absorption can be employed to reach full delivery of optical energy to nanoscale systems such as plasmonic nanoparticles, and multi-port interference can be used to enhance the absorption of a nanoscale device when it is embedded in a strongly scattering system, with potential applications to nanoscale sensing. Here we review the two-port CPA in reference to photonic structures which can resonantly couple to the external fields. A revised two-port theory of CPA is illustrated, which relies on the Scattering Matrix formalism and is valid for all linear two-port systems with reciprocity. Through a semiclassical approach, treating two-port critical coupling conditions in a non-perturbative regime, it is demonstrated that the strong coupling regime and the critical coupling condition can indeed coexist; in this situation, termed strong critical coupling, all the incoming energy is converted into polaritons. Experimental results are presented, which clearly display the elliptical trace of absorption as function of input unbalance in a thin metallo-dielectric metamaterial, and verify polaritonic CPA in an intersubband-polariton photonic-crystal membrane resonator. Concluding remarks discuss the future perspectives of CPA with photonic structures.Comment: arXiv admin note: substantial text overlap with arXiv:1605.0890

Office Buildings Cooling Need in the Italian Climatic Context: Assessing the Performances of Typical Envelopes☆

Abstract This study assesses the cooling thermal energy need of office buildings that can represent typical cases within the Italian context, in particular defined by the envelope solutions that belong to three main construction ages, including new solutions that meet the current requirements for the envelope thermal properties. The results show that the large-glazed and lighter solutions (also newly built, consistent with the recent standards) reveal the worst behavior, while the buildings characterized by the lowest needs are the old conventional ones, even though they do not comply with the recent requirements for the envelope components. The same cooling performances are achieved by newly built insulated envelopes if they are "conventionally-glazed", but only when a strategy to loose the heat stored by the massive internal surfaces is adopted

Structured Optical Materials Controlled by Light

Materials of which the optical response is determined by their structure are of much interest both for their fundamental properties and applications. Examples range from simple gratings to photonic crystals. Obtaining control over the optical properties is of crucial importance in this context, and it is often attempted by electro-optical effect or by using magnetic fields. In this paper, we introduce the use of light to switch and tune the optical response of a structured material, exploiting a physical deformation induced by light itself. In this new strategy, light drives an elastic reshaping, which leads to different spectral properties and hence to a change in the optical response. This is made possible by the use of liquid crystalline networks structured by Direct Laser Writing. As a proof of concept, a grating structure with sub-millisecond time-response is demonstrated for optical beam steering exploiting an optically induced reversible shape-change. Experimental observations are combined with finite-element modeling to understand the actuation process dynamics and to obtain information on how to tune the time and the power response of this technology. This optical beam steerer serves as an example for achieving full optical control of light in broad range of structured optical materials

Avaliação em larga escala e BNCC: estratégias para o gerencialismo na educação

This article has the purpose to analyze the relation between policies of large-scale evaluation and the National Curricular Common Base (BNCC), in the sense of identifying the managerialism’s elements in the dimensions of educational control and results. We presented the following question: what are the contents present in the large-scale evaluation policies and curricular that are close to the management perspective in the dimensions of control and results in education? We developed a qualitative research, using bibliographic and documental sources. Upon the methodological procedures, we divided the study into two stages: we analyzed bibliographies regarding the State, evaluation’s public policies, curricular policies and the management perspective in education; in the BNCC’s content, we identified managerialism elements and we related them to the large-scale evaluation policies. In the article, we systematized these methodological steps into two sections. In the final considerations, we indicated as our studies’ main results that the creation of a National Curricular Common Base is justified by the necessity of intensification on State’s control of the pedagogic work developed at school, and of the content to be taught to students, in order to adjust the teaching and learning to the competencies and abilities’ list demanded by the indicators of the large-scale evaluations. From the BNCC’s perspective, the basic education’s purpose becomes the measurement of results via evaluation processes as the Students International Evaluation Program and the national large-scale evaluations, like Prova Brasil.O artigo tem o objetivo de analisar a relação entre políticas de avaliação em larga escala e a Base Nacional Comum Curricular - BNCC, no sentido de identificar elementos do gerencialismo, nas dimensões do controle e dos resultados educacionais. Apresentamos a seguinte problemática: quais os conteúdos presentes nas políticas de avaliação em larga escala e curriculares que se aproximam da perspectiva gerencial, nas dimensões do controle e dos resultados da educação? Desenvolvemos uma pesquisa qualitativa, com a utilização de fontes bibliográficas e documentais. Sobre os procedimentos metodológicos, dividimos o estudo em dois momentos: analisamos bibliografias referentes ao Estado, políticas públicas de avaliação, políticas curriculares e perspectiva gerencial na educação; identificamos no conteúdo da BNCC, elementos do gerencialismo e os relacionamos com as políticas de avaliação em larga escala. No artigo, sistematizamos essas etapas metodológicas em duas seções. Nas considerações finais, indicamos como principais resultados do nosso estudo, que a criação de uma base curricular se justifica pela necessidade de intensificação do controle, por parte do Estado, do trabalho pedagógico desenvolvido na escola e do conteúdo a ser ensinado aos alunos, a fim de ajustar o ensino e aprendizagem ao rol de competências e habilidades solicitadas pelos indicadores das avaliações em larga escala. Sob a ótica da BNCC, a finalidade da educação básica passa a ser a mensuração de resultados via processos de avaliações como o Programa Internacional de Avaliação de Estudantes e as avaliações nacionais em larga escala, como a Prova Brasil

Metamaterial-enabled asymmetric negative refraction of GHz mechanical waves

Wave refraction at an interface between different materials is a basic yet fundamental phenomenon, transversal to several scientific realms – electromagnetism, gas and fluid acoustics, solid mechanics, and possibly also matter waves. Under specific circumstances, mostly enabled by structuration below the wavelength scale, i.e., through the metamaterial approach, waves undergo negative refraction, eventually enabling superlensing and transformation optics. However, presently known negative refraction systems are symmetric, in that they cannot distinguish between positive and negative angles of incidence. Exploiting a metamaterial with an asymmetric unit cell, we demonstrate that the aforementioned symmetry can be broken, ultimately relying on the specific shape of the Bloch mode isofrequency curves. Our study specialized upon a mechanical metamaterial operating at GHz frequency, which is by itself a building block for advanced technologies such as chip-scale hybrid optomechanical and electromechanical devices. However, the phenomenon is based on general wave theory concepts, and it applies to any frequency and time scale for any kind of linear waves, provided that a suitable shaping of the isofrequency contours is implemented