Maximizing Photoluminescence Extraction in Silicon Photonic Crystal Slabs

Photonic crystal modes can be tailored for increasing light matter interactions and light extraction efficiencies. These PhC properties have been explored for improving the device performance of LEDs, solar cells and precision biosensors. Tuning the extended band structure of 2D PhC provides a means for increasing light extraction throughout a planar device. This requires careful design and fabrication of PhC with a desirable mode structure overlapping with the spectral region of emission. We show a method for predicting and maximizing light extraction from 2D photonic crystal slabs, exemplifiedby maximizing silicon photoluminescence PL . Systematically varying the lattice constant and filling factor, we predict the increases in PL intensity from band structure calculations and confirm predictions in micro PL experiments. With the near optimal design parameters of PhC, we demonstrate more than 500 fold increase in PL intensity, measured near band edge of silicon at room temperature, an enhancement by an order of magnitude more than what has been reporte

A História da Alimentação: balizas historiográficas

Os M. pretenderam traçar um quadro da História da Alimentação, não como um novo ramo epistemológico da disciplina, mas como um campo em desenvolvimento de práticas e atividades especializadas, incluindo pesquisa, formação, publicações, associações, encontros acadêmicos, etc. Um breve relato das condições em que tal campo se assentou faz-se preceder de um panorama dos estudos de alimentação e temas correia tos, em geral, segundo cinco abardagens Ia biológica, a econômica, a social, a cultural e a filosófica!, assim como da identificação das contribuições mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histórica, foi ela organizada segundo critérios morfológicos. A seguir, alguns tópicos importantes mereceram tratamento à parte: a fome, o alimento e o domínio religioso, as descobertas européias e a difusão mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rápido balanço crítico da historiografia brasileira sobre o tema

Influence of a nonradiative reservoir on polariton spin multistability

International audienceIn this work, we study the influence of the excitation conditions on power-dependent spin switching and spin multistability of exciton polaritons in planar semiconductor microcavities. We obtain experimental evidence for the influence of a reservoir of nonradiative states which make a determining contribution to the dynamics of polaritons. While the spinor Gross-Pitaevskii equation (SGPE) fails in reproducing some critical experimental trends, an extended set of equations including a nonradiative reservoir allows us to reproduce the experiments quantitatively. We find that the energy renormalization of the exciton field due to the reservoir is crucial to describe power-dependent spin switching. The reservoir is also responsible for the effective repulsive interactions between polaritons of opposite spin obtained in the framework of the SGPE. Two important parameters, the coupling of the spinor polariton fields to the reservoir and the decay of the reservoir, are determined experimentally. We present indications that the reservoir originates from the formation of biexcitons and is constituted of localized exciton states

Enhancement of microcavity polariton relaxation under confinement

International audienc