Wide-angle reflection-mode spatial filtering and splitting with photonic crystal gratings and single-layer rod gratings

Cataloged from PDF version of article.New diffractive optical elements offering a frequency tolerant, very efficient, high-pass and bandpass spatial filtering over a broad range of incidence angles are demonstrated by numerical simulations. The device operates in reflection mode owing to the (nearly) perfect blazing. It relies on two-dimensional square-lattice photonic crystals composed of dielectric rods with simple corrugations at the interface. Similar performance can be obtained with gratings composed of a single rod layer placed in the near field of a metal mirror, indicating a route to geometries that can be easily fabricated with modern nanotechnologies. Also equal splitting between zero and first negative orders can be obtained for incidence-angle variations that are wider than 60 degrees. (C) 2014 Optical Society of Americ

The MESANGE model: re-estimation on National Accounts base 2000 / Part 2 Version with chained-linked volumes

Mesange is a medium-size quarterly macro-econometric model of the French economy (about 500 equations, three sectors). The model describes short-term Keynesian dynamics and its long-term equilibrium is driven by supply-side determinants. Its reestimation on data from the national accounts base 2000 with fixed-base volumes is presented in a recent working paper (Klein and Simon, 2010). This first version of the model has been optimized for simulation use. Other applications of the Mesange model (short-term forecasting, analyses of the past) required its adaptation to the published data from the quarterly accounts with chained-linked volumes, as well as the integration of the recent crisis episode. A second version of the Mesange model has, therefore, been developed for this purpose. This version is presented in this working paper. First, the problems raised for macroeconomic modelling by national accounts with chained-linked volumes are explained and the solutions chosen to adapt the model to these new conventions are discussed. The applications of the version of the model with chained-linked volumes are, then, explained and illustrated with examples. Last, the main reestimated equations are detailed. The differences with respect to the version of the model with fixed-base volumes are commented. They stem from estimations based on non-identical data, but also from the different uses made of the two versions of Mesange and the resulting various needs and constraints that have conditioned the methodological choices that have been made. As for the version of the model with chained-linked volumes, priority has been given to the quality of the adjustment to the data rather than to the underlying theoretical framework. Nonetheless, the philosophy and general structure of the two versions of the model remain very much alike.macroeconometric model, estimation, chained-linked volumes, short-term forecasting, contribution analysis

Degeneracy analysis for a super cell of a photonic crystal and its application to the creation of band gaps

A method is introduced to analyze the degeneracy properties of the band structure of a photonic crystal making use of the super cells. The band structure associated with a super cell of a photonic crystal has degeneracies at the edge of the Brillouin zone if the photonic crystal has some kind of point group symmetry. Both E-polarization and H-polarization cases have the same degeneracies for a 2-dimensional (2D) photonic crystal. Two theorems are given and proved. These degeneracies can be lifted to create photonic band gaps by changing the transform matrix between the super cell and the smallest unit cell. The existence of the photonic band gaps for many known 2D photonic crystals is explained through the degeneracy analysis.Comment: 19 pages, revtex4, 14 figures, p

Experimental verification of the "rainbow" trapping effect in plasmonic graded gratings

We report the first experimental observation of trapped rainbow1 in graded metallic gratings2-4, designed to validate theoretical predictions for this new class of plasmonic structures. One-dimensional tapered gratings were fabricated and their surface dispersion properties tailored by varying the grating period and depth, whose dimensions were confirmed by atomic force microscopy. Reduced group velocities and the plasmonic bandgap were observed. Direct measurements on graded grating structures show that light of different wavelengths in the 500-700nm region is "trapped" at different positions along the grating, consistent with computer simulations, thus verifying the "rainbow" trapping effect. The trapped rainbow effect offers exciting pathways for optical information storage and optical delays in photonic circuits at ambient temperature

Modelling of photonic wire Bragg Gratings

Some important properties of photonic wire Bragg grating structures have been investigate. The design, obtained as a generalisation of the full-width gap grating, has been modelled using 3D finite-difference time-domain simulations. Different types of stop-band have been observed. The impact of the grating geometry on the lowest order (longest wavelength) stop-band has been investigated - and has identified deeply indented configurations where reduction of the stop-bandwidth and of the reflectivity occurred. Our computational results have been substantially validated by an experimental demonstration of the fundamental stop-band of photonic wire Bragg gratings fabricated on silicon-on-insulator material. The accuracy of two distinct 2D computational models based on the effective index method has also been studied - because of their inherently much greater rapidity and consequent utility for approximate initial designs. A 2D plan-view model has been found to reproduce a large part of the essential features of the spectral response of full 3D models

Introduction to human-building interaction (HBI): Interfacing HCI with architecture and urban design

Buildings and urban spaces increasingly incorporate artificial intelligence and new forms of interactivity, raising a wide span of research questions about the future of human experiences with, and within, built environments. We call this emerging area Human-Building Interaction (HBI) and introduce it as an interdisciplinary domain of research interfacing Human-Computer Interaction (HCI) with Architecture and Urban Design. HBI seeks to examine the involvement of HCI in studying and steering the evolution of built environments. Therefore,we need to ask foundational questions such as the following:what are the specific attributes of built environments that HCI researchers should take into account when shifting attention and scale from "artefacts" to "environments"? Are architecture and interaction design methods and processes compatible? Concretely, how can a team of interaction designers bring their tools to an architectural project, and collaborate with other stakeholders? Can and will architecture change the theory and practice of HCI? Furthermore, research in HBI should produce knowledge and practical guidelines by experimenting novel design instances that combine architecture and digital interaction. The primary aim of this article is to specify the mission, vision, and scope of research in HBI. As the introductory article to the TOCHI special issue, it also provides a summary of published manuscripts and describes their collective contribution to the development of this field

Measurement of double beta decay of ¹⁰⁰Mo to excited states in the NEMO 3 experiment

The double beta decay of ¹⁰⁰Mo to the 0_{1}^{+} and 2_{1}^{+} excited states of ¹⁰⁰Ru is studied using the NEMO 3 data. After the analysis of 8024 h of data the half-life for the two-neutrino double beta decay of ¹⁰⁰Mo to the excited 0_{1}^{+} state is measured to be T_{1/2}^{2v} = [5.7_{-0.9}^{+1.3} (stat.) ± 0.8 (syst.)] x 10²⁰ y. The signal-to-background ratio is equal to 3. Information about energy and angular distributions of emitted electrons is also obtained. No evidence for neutrinoless double beta decay to the excited 0_{1}^{+} state has been found. The corresponding half-life limit is T_{1/2}^{0v} (0⁺→0_{1}^{+}) > 8.9 x 10²² y (at 90% C.L.). The search for the double beta decay to the 2_{1}^{+} excited state has allowed the determination of limits on the half-life for the two neutrino mode T_{1/2}^{0v} (0⁺→2_{1}^{+}) > 1.1 x 10²¹ y (at 90% C.L.) and for the neutrinoless mode T_{1/2}^{0v} (0⁺→2_{1}^{+}) > 1.6 x 10²³ y (at 90% C.L.)

On negative higher-order Kerr effect and filamentation

As a contribution to the ongoing controversy about the role of higher-order Kerr effect (HOKE) in laser filamentation, we first provide thorough details about the protocol that has been employed to infer the HOKE indices from the experiment. Next, we discuss potential sources of artifact in the experimental measurements of these terms and show that neither the value of the observed birefringence, nor its inversion, nor the intensity at which it is observed, appear to be flawed. Furthermore, we argue that, independently on our values, the principle of including HOKE is straightforward. Due to the different temporal and spectral dynamics, the respective efficiency of defocusing by the plasma and by the HOKE is expected to depend substantially on both incident wavelength and pulse duration. The discussion should therefore focus on defining the conditions where each filamentation regime dominates.Comment: 22 pages, 11 figures. Submitted to Laser physics as proceedings of the Laser Physics 2010 conferenc

Hyphal network whole field imaging allows for accurate estimation of anastomosis rates and branching dynamics of the filamentous fungus Podospora anserina

The success of filamentous fungi in colonizing most natural environments can be largely attributed to their ability to form an expanding interconnected network, the mycelium, or thallus, constituted by a collection of hyphal apexes in motion producing hyphae and subject to branching and fusion. In this work, we characterize the hyphal network expansion and the structure of the fungus Podospora anserina under controlled culture conditions. To this end, temporal series of pictures of the network dynamics are produced, starting from germinating ascospores and ending when the network reaches a few centimeters width, with a typical image resolution of several micrometers. The completely automated image reconstruction steps allow an easy post-processing and a quantitative analysis of the dynamics. The main features of the evolution of the hyphal network, such as the total length L of the mycelium, the number of "nodes" (or crossing points) N and the number of apexes A, can then be precisely quantified. Beyond these main features, the determination of the distribution of the intra-thallus surfaces (S; i; ) and the statistical analysis of some local measures of N, A and L give new insights on the dynamics of expanding fungal networks. Based on these results, we now aim at developing robust and versatile discrete/continuous mathematical models to further understand the key mechanisms driving the development of the fungus thallus