Spectral Engineering with Coupled Microcavities: Active Control of Resonant Mode-Splitting

Optical mode-splitting is an efficient tool to shape and fine-tune the spectral response of resonant nanophotonic devices. The active control of mode-splitting, however, is either small or accompanied by undesired resonance shifts, often much larger than the resonance-splitting. We report a control mechanism that enables reconfigurable and widely tunable mode-splitting while efficiently mitigating undesired resonance shifts. This is achieved by actively controlling the excitation of counter-traveling modes in coupled resonators. The transition from a large splitting (80 GHz) to a single-notch resonance is demonstrated using low power microheaters (35 mW). We show that the spurious resonance-shift in our device is only limited by thermal crosstalk and resonance-shift-free splitting control may be achieved.Comment: 4 pages, 3 figure

Comparative study between wet and dry etching of silicon for microchannels fabrication

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOIn this work we present a comparative study of two processes for the fabrication of an array of microchannels for microfluidics applications, based on integrated-circuit technology process steps, such as lithography and dry etching. Two different methods were investigated in order to study the resulting microstructures: wet and dry deep etching of silicon substrate. The typical etching depth necessary to the target application is 50 mu m.1093015FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO2016/09509-112. Conference on Advanced Fabrication Technologies for Micro/Nano Optics and Photonics3 a 5 de Fevereiro de 2019San Francisco, CA, Estados UnidosSPIE; Nanoscribe Gmb

Pseudo-Unitary Operators and Pseudo-Unitary Quantum Dynamics

We consider pseudo-unitary quantum systems and discuss various properties of pseudo-unitary operators. In particular we prove a characterization theorem for block-diagonalizable pseudo-unitary operators with finite-dimensional diagonal blocks. Furthermore, we show that every pseudo-unitary matrix is the exponential of $i=\sqrt{-1}$ times a pseudo-Hermitian matrix, and determine the structure of the Lie groups consisting of pseudo-unitary matrices. In particular, we present a thorough treatment of $2\times 2$ pseudo-unitary matrices and discuss an example of a quantum system with a $2\times 2$ pseudo-unitary dynamical group. As other applications of our general results we give a proof of the spectral theorem for symplectic transformations of classical mechanics, demonstrate the coincidence of the symplectic group $Sp(2n)$ with the real subgroup of a matrix group that is isomorphic to the pseudo-unitary group U(n,n), and elaborate on an approach to second quantization that makes use of the underlying pseudo-unitary dynamical groups.Comment: Revised and expanded version, includes an application to symplectic transformations and groups, accepted for publication in J. Math. Phy

Effects of Ga+ milling on InGaAsP Quantum Well Laser with mirrors etched by Focused Ion Beam

InGaAsP/InP quantum wells (QW) ridge waveguide lasers were fabricated for the evaluation of Ga+ Focused Ion Beam (FIB) milling of mirrors. Electrical and optical proprieties were investigated. A 7% increment in threshold current, a 17% reduction in external quantum efficiency and 15 nm blue shift in the emission spectrum were observed after milling as compared to the as cleaved facet result. Annealing in inert atmosphere partially revert these effects resulting in 4% increment in threshold current, 11% reduction in external efficiency and 13 nm blue shift with the as cleaved result. The current-voltage behavior after milling and annealing shows a very small increase in leakage current indicating that optical damage is the main effect of the milling process.Comment: 12 pages, 4 figure

MapOrgânico: mapeamento participativo de circuitos curtos de comercialização na região de Campinas (SP).

Um diagnóstico de demandas para a ampliação da comercialização e do acesso a produtos orgânicos em Campinas e região indicou o mapeamento de pontos de venda como fundamental para fomentar a consolidação de mercados regionais. Neste Contexto, foi criado o MapOrgânico, uma ferramenta para mapeamento participativo de pontos de comercialização, produzido a partir da aplicação My Maps, do Google. Na interface criada, os usuários podem cadastrar unidades de produção, feiras, grupos de consumo, entre outros. A inserção dos pontos ocorre por meio de um formulário eletrônico, preenchido pelo interessado. Posteriormente, o pedido e os dados são validados pela equipe do projeto e disponibilizados para acesso público. O mapa, além da identificação geográfica, comporta informações como local, horário de funcionamento, certificação, tipo de produto oferecido. Em seis meses foram cadastrados 31 pontos de comercialização, agregados em 11 diferentes categorias, em 9 municípios da região

Quantum Time and Spatial Localization: An Analysis of the Hegerfeldt Paradox

Two related problems in relativistic quantum mechanics, the apparent superluminal propagation of initially localized particles and dependence of spatial localization on the motion of the observer, are analyzed in the context of Dirac's theory of constraints. A parametrization invariant formulation is obtained by introducing time and energy operators for the relativistic particle and then treating the Klein-Gordon equation as a constraint. The standard, physical Hilbert space is recovered, via integration over proper time, from an augmented Hilbert space wherein time and energy are dynamical variables. It is shown that the Newton-Wigner position operator, being in this description a constant of motion, acts on states in the augmented space. States with strictly positive energy are non-local in time; consequently, position measurements receive contributions from states representing the particle's position at many times. Apparent superluminal propagation is explained by noting that, as the particle is potentially in the past (or future) of the assumed initial place and time of localization, it has time to propagate to distant regions without exceeding the speed of light. An inequality is proven showing the Hegerfeldt paradox to be completely accounted for by the hypotheses of subluminal propagation from a set of initial space-time points determined by the quantum time distribution arising from the positivity of the system's energy. Spatial localization can nevertheless occur through quantum interference between states representing the particle at different times. The non-locality of the same system to a moving observer is due to Lorentz rotation of spatial axes out of the interference minimum.Comment: This paper is identical to the version appearing in J. Math. Phys. 41; 6093 (Sept. 2000). The published version will be found at http://ojps.aip.org/jmp/. The paper (40 page PDF file) has been completely revised since the last posting to this archiv