5 research outputs found
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
Tristable and multiple bistable activity in complex random binary networks of two-state units
A História da Alimentação: balizas historiogråficas
Os M. pretenderam traçar um quadro da HistĂłria da Alimentação, nĂŁo como um novo ramo epistemolĂłgico da disciplina, mas como um campo em desenvolvimento de prĂĄticas e atividades especializadas, incluindo pesquisa, formação, publicaçÔes, associaçÔes, encontros acadĂȘmicos, etc. Um breve relato das condiçÔes 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 biolĂłgica, a econĂŽmica, a social, a cultural e a filosĂłfica!, assim como da identificação das contribuiçÔes mais relevantes da Antropologia, Arqueologia, Sociologia e Geografia. A fim de comentar a multiforme e volumosa bibliografia histĂłrica, foi ela organizada segundo critĂ©rios morfolĂłgicos. A seguir, alguns tĂłpicos importantes mereceram tratamento Ă parte: a fome, o alimento e o domĂnio religioso, as descobertas europĂ©ias e a difusĂŁo mundial de alimentos, gosto e gastronomia. O artigo se encerra com um rĂĄpido balanço crĂtico 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