Photonic crystal polarizers and polarizing beam splitters

We have experimentally demonstrated polarizers and polarizing beam splitters based on microwave-scale two-dimensional photonic crystals. Using polarized microwaves within certain frequency bands, we have observed a squared-sinusoid (Malus) transmission law when using the photonic crystal as a polarizer. The photonic crystal also functions as a polarizing beamsplitter; in this configuration it can be engineered to split incident polarizations in either order, making it more versatile than conventional, Brewster-angle beamsplitters.Comment: 7 pages, 3 figures, published Journal Applied Physics 93, 9429 (2003

Weak-wave advancement in nearly collinear four-wave mixing

We identify a new four-wave mixing process in which two nearly collinear pump beams produce phase-dependent gain into a weak bisector signal beam in a self-defocusing Kerr medium. Phase matching is achieved by weak-wave advancement caused by cross-phase modulation between the pump and signal beams. We relate this process to the inverse of spatial modulational instability and suggest a time-domain analog.Comment: 7 pages, 3 figure

Microwave measurements of the photonic bandgap in a two-dimensional photonic crystal slab

We have measured the photonic bandgap in the transmission of microwaves through a two-dimensional photonic crystal slab. The structure was constructed by cementing acrylic rods in a hexagonal closed-packed array to form rectangular stacks. We find a bandgap centered at approximately 11 GHz, whose depth, width and center frequency vary with the number of layers in the slab, angle of incidence and microwave polarization.Comment: 8 pages, 3 figures, submitted to Journal of Applied Physic

Atributos físicos e químicos de um argissolo vermelho-amarelo submetido a diferentes manejos de um experimento de longa duração.

Neste trabalho objetivou-se avaliar a alteração de algumas propriedades físicas e químicas do solo sob diferentes sistemas de preparo, num experimento de longa duração, após 23 anos de instalação. Foram coletadas amostras de solo para avaliar os atributos químicos e físicos do solo. Os tratamentos foram: plantio direto, arado de disco, arado de disco + grade pesada, grade pesada e mata secundária, como referência. Com os dados obtidos, foi possível observar que a mata secundária apresentou os maiores teores de carbono total e acidez. Já os teores de nutrientes P, K+, Ca2+ e Mg2+, foram mais elevados nos sistemas de preparo do solo, destacando o P na camada superficial do sistema Plantio direto. A densidade de solo também foi maior na camada superficial neste tratamento, diminuindo em profundidade, enquanto se verificou o inverso nos preparos convencionais. Concluiu-se que o maior conteúdo de carbono total na mata secundária se deve ao acúmulo de resíduos vegetais na superfície, aportados pela vegetação natural. Já os maiores teores de P, K, Ca2+ e Mg2+ nos solos agricultáveis deve-se a aplicação de fertilizantes e corretivos e, o aumento da densidade de solo na superfície é devido ao tráfego de máquinas e implementos agrícolas durante o manejo

Demonstration of superluminal effects in an absorptionless, non-reflective system

We present an experimental and theoretical study of a simple, passive system consisting of a birefringent, two-dimensional photonic crystal and a polarizer in series, and show that superluminal dispersive effects can arise even though no incident radiation is absorbed or reflected. We demonstrate that a vector formulation of the Kramers-Kronig dispersion relations facilitates an understanding of these counter-intuitive effects.Comment: 6 pages, 3 figures, accepted on Physical Review Letter

Fast light, slow light, and phase singularities: a connection to generalized weak values

We demonstrate that Aharonov-Albert-Vaidman (AAV) weak values have a direct relationship with the response function of a system, and have a much wider range of applicability in both the classical and quantum domains than previously thought. Using this idea, we have built an optical system, based on a birefringent photonic crystal, with an infinite number of weak values. In this system, the propagation speed of a polarized light pulse displays both superluminal and slow light behavior with a sharp transition between the two regimes. We show that this system's response possesses two-dimensional, vortex-antivortex phase singularities. Important consequences for optical signal processing are discussed.Comment: 9 pages, 4 figures, accepted in Physical Review Letters (2003

Disponibilidade de nitrogênio mineral decorrente da aplicação de uréias tratadas em solo com alta umidade superficial.

Fertbio 2012