High frequency electro-optic measurement of strained silicon racetrack resonators

The observation of the electro-optic effect in strained silicon waveguides has been considered as a direct manifestation of an induced $\chi^{(2)}$ non-linearity in the material. In this work, we perform high frequency measurements on strained silicon racetrack resonators. Strain is controlled by a mechanical deformation of the waveguide. It is shown that any optical modulation vanishes independently of the applied strain when the applied voltage varies much faster than the carrier effective lifetime, and that the DC modulation is also largely independent of the applied strain. This demonstrates that plasma carrier dispersion is responsible for the observed electro-optic effect. After normalizing out free carrier effects, our results set an upper limit of $8\,pm/V$ to the induced high-speed $\chi^{(2)}_{eff,zzz}$ tensor element at an applied stress of $-0.5\,GPa$. This upper limit is about one order of magnitude lower than the previously reported values for static electro-optic measurements

Power efficiency estimation of silicon nanocrystals based light emitting devices in alternating current regime

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Probing the Spontaneous Emission Dynamics in Si-Nanocrystals-Based Microdisk Resonators

As a possible cavity quantum electrodynamical system, unlike III-V quantum dots, Si-NCs are not considered ideal emitters for emission rate enhancement observations (Purcell effect). Here, we report on direct measurements of spontaneous emission rate enhancement of Si-NCs embedded in a whispering-gallery mode resonator at room temperature. Using time-resolved microphotoluminescence experiments, we demonstrate important lifetime reductions ( ∼ 70 % ) for Si-NCs coupled to cavity modes with respect to uncoupled ones. Comparing experiments with the theoretical Purcell enhancement in a bad emitter regime, we estimate effective linewidths of ∼ 10     meV through which Si-NC emitters are coupled to cavity photons. Finally, our study provides an alternative method for the estimation of subnatural linewidths of quantum dots at room temperature

Graded-size Si quantum dot ensembles for efficient light-emitting diodes

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Photon recycling in Fabry-Perot micro-cavities based on Si3_3N4_4 waveguides

We present a numerical analysis and preliminary experimental results on one-dimensional Fabry-Perot micro-cavities in Si$_3$N$_4$ waveguides. The Fabry-Perot micro-cavities are formed by two distributed Bragg reflectors separated by a straight portion of waveguide. The Bragg reflectors are composed by a few air slits produced within the Si$_3$N$_4$ waveguides. In order to increase the quality factor of the micro-cavities, we have minimized, with a multiparametric optimization tool, the insertion loss of the reflectors by varying the length of their first periods (those facing the cavity). To explain the simulation results the coupling of the fundamental waveguide mode with radiative modes in the Fabry-Perot micro-cavities is needed. This effect is described as a recycling of radiative modes in the waveguide. To support the modelling, preliminary experimental results of micro-cavities in Si$_3$N$_4$ waveguides realized with Focused Ion Beam technique are reported.Comment: 5 pages, 5 figure

Oscillatory coupling between a monolithic whispering-gallery resonator and a buried bus waveguide

We report on a combined theoretical and experimental study of the optical coupling between a microdisk resonator and a waveguide laying on different planes. While the lateral coupling between a planar resonator and a waveguide is characterized by a unique distance at which the resonant waveguide transmission vanishes because of destructive interference, the vertical coupling geometry exhibits an oscillatory behavior in the coupling amplitude as a function of the vertical gap. This effect manifests experimentally as oscillations in both the waveguide transmission and the mode quality factor. An analytical description based on coupled-mode theory and a two-port beam-splitter model of the waveguide-resonator coupling is developed, which compares successfully both to experimental data and numerical simulations.Comment: 5 pages, 3 figure

Cost model for LIMA device

[EN] In this paper we show the results of the cost model developed in LIMA project (FP7-248909). The LIMA project is titled "Improve photovoltaic efficiency by applying novel effects at the limits of light to matter interaction". The project started in January 2010 and during this year a cost model of the device developed in the project has been developed to assess the industrial viability of this innovative approach to increase the efficiency and reduce the cost of photovoltaic solar cells. LIMA project exploits cutting edge photonic technologies to enhance silicon solar cell efficiencies with new concepts in nanostructured materials. It proposes nano-structured surface layers designed to increase light absorption in the solar cell while decreasing surface and interface recombination loss. Integration in a back contact design further reduces these interface losses and avoids shading. The project improves light-matter interaction by the use a surface plasmonic nanoparticle layer. This reduces reflection and efficiently couples incident radiation into the solar cell where it is trapped by internal reflection. Surface and interface recombination are minimized by using silicon quantum dot superlattices in a passivating matrix. The distance between quantum dots ensures wave-function overlap and good conductivity. © 2010 Published by Elsevier Ltd.This work has been carried out in the framework of the LIMA Project. The EC is gratefully acknowledged for financial support under Contract number FP7-248909.Vazquez, M.; Connolly, JP.; Cubero García, OJ.; Daly, G.; Halm, A.; Kopecek, R.; Mihailetchi, V.... (2011). Cost model for LIMA device. Energy Procedia. 8:443-448. https://doi.org/10.1016/j.egypro.2011.06.163S443448

Second-harmonic generation in silicon waveguides strained by silicon nitride

Silicon photonics meets the electronics requirement of increased speed and bandwidth with on-chip optical networks. All-optical data management requires nonlinear silicon photonics. In silicon only third-order optical nonlinearities are present owing to its crystalline inversion symmetry. Introducing a second-order nonlinearity into silicon photonics by proper material engineering would be highly desirable. It would enable devices for wideband wavelength conversion operating at relatively low optical powers. Here we show that a sizeable second-order nonlinearity at optical wavelengths is induced in a silicon waveguide by using a stressing silicon nitride overlayer. We carried out second-harmonic-generation experiments and first-principle calculations, which both yield large values of strain-induced bulk second-order nonlinear susceptibility, up to 40pm/V at 2.300 nm. We envisage that nonlinear strained silicon could provide a competing platform for a new class of integrated light sources spanning the near- to mid-infrared spectrum from 1.2 to 10 micron

Instalative art as a teaching resource for environmental education in Childhood Education

RESUMEN El niño aprende haciendo, manipulando los objetos y la realidad que se encuentra. Mediante la creación artística se puede abrir la puerta a nuevos aprendizajes, algunos de ellos pueden ser los siguientes: psicomotriz, emocional, cognitivo, artístico, lógico-matemático, lingüístico… Con el trabajo centrado en la instalación artística se le da al niño un espacio físico que le permite pensar mediante la actividad. De este modo, la manipulación de objetos durante el juego, ayuda al niño a descubrir y a experimentar a través del manejo de los materiales de dicha composición artística. La propuesta escogida en este caso ha sido la utilización de materiales presentes en la naturaleza. Con esta elección se intenta acercar la educación medioambiental a los niños a través del arte. Este trabajo, diseñado para aulas de educación infantil (2-6 años), consta de dos partes diferenciadas y relacionadas entre sí. Por un lado, se hace un recorrido teórico por los antecedentes del arte de la instalación enmarcada en el arte contemporáneo, donde se verán algunos de los autores que han contribuido al desarrollo de esta disciplina artística. De igual manera se revisa la importancia de la educación en contenidos de naturaleza y medio ambiente. En una segunda parte del trabajo, se desarrolla una parte más práctica para ilustrar a maestros y maestras acerca de cómo se lleva al espacio físico esta idea de instalación artística. Para ello, se mostrarán tres ejemplos de ellas y se llevará a cabo el análisis de su montaje, desarrollo y documentación de la actividad.ABSTRACT The child learns by doing, manipulating the objects and the reality arround them. Through artistic creation he will be able to access new learnings, such as: psychomotor, emotional, cognitive, artistic, logical-mathematical, linguistic,... Such work focused on the artistic installation, allows children to enjoy a place that gives them the chance to think while they are active. Thereby, object manipulation during the game helps them to learn through the handling of the materials of such artistic trend. The chosen approach in this case has been the usage of the materials which are found in nature. Along with this, we try to bring the environment friendly education close to the clindren through art. This work designed for preschool classrooms (2-6 years), consists of two different parts which are related to each other. The first one, consists in a theoretical journey through the background of the art of the installation framed in contemporary art, where we will talk about some of the authors who have contributed to the development of this artistic style. As well, the importance of education in content of nature and environment is reviewed. In the second part of the work, the development of a more practical part will be done to illustrate teachers about how the idea of artistic installation is taken to the physical space. Three examples of it will be shown and the analysis will be carried out, as well the development and the documentation of the activity.Grado en Magisterio en Educación Infanti