Calculation of fully anisotropic liquid crystal waveguide modes

The accurate analysis of optical waveguides is an important issue when designing devices for optical communication. Waveguides combined with liquid crystals have great potential because they allow waveguide tuning over a wide range using low voltages. In this paper, we present calculations that combine an advanced algorithm for calculating liquid crystal behavior and a finite-element mode solver that is able to incorporate the full anisotropy of the materials. Calculation examples demonstrate the validity of our program

A finite element beam propagation method for simulation of liquid crystal devices

An efficient full-vectorial finite element beam propagation method is presented that uses higher order vector elements to calculate the wide angle propagation of an optical field through inhomogeneous, anisotropic optical materials such as liquid crystals. The full dielectric permittivity tensor is considered in solving Maxwell's equations. The wide applicability of the method is illustrated with different examples: the propagation of a laser beam in a uniaxial medium, the tunability of a directional coupler based on liquid crystals and the near-field diffraction of a plane wave in a structure containing micrometer scale variations in the transverse refractive index, similar to the pixels of a spatial light modulator. (C) 2009 Optical Society of Americ

Microstrip Device for Broadband (15–65 GHz) Measurement of Dielectric Properties of Nematic Liquid Crystals

The essential dielectric properties, the basic alignment techniques, and the common measurement methods of the nematic liquid crystal (LC) at RF are briefly reviewed. A new device for the broadband measurement of the dielectric constants and loss tangents of nematic LCs at microwave and millimeter-wave frequencies is presented. This device whose specification and fabrication are outlined is essentially a two dielectric layer microstrip structure with coplanar-waveguide terminals, which is easy to fabricate. Compared to previous structures, the proposed device is extremely broadband with 15-65-GHz bandwidth, benefits from a solid exposed ground plane for easy temperature test, and operates under bias voltage. The technique for the extraction of the dielectric parameters of the nematic LC analyzed by this device is explained and the sources imposing the frequency limits on the device performance are identified. Two different nematic LCs, MDA-00-3506 and GT3-23001, are characterized and the results are shown to compare well with those available in the literature. In the comparisons, the maximum difference found for the dielectric constants for MDA-00-3506 is 5% and for GT3-23001 is 5.3%

Tuning silicon-on-insulator ring resonators with in-plane switching liquid crystals

We show that the resonance wavelength of silicon-on-insulator ring resonators can be tuned when a top cladding of liquid crystal is present. In-plane strip electrodes are used to generate an electric field that reorients the liquid crystal director in the plane parallel to the chip surface. This causes the resonance wavelength to shift toward longer wavelengths. The magnitude of this shift is about 1 nm, which is twice as large as previously reported shifts. The experimental results are verified extensively with our simulation tools, where a calculation of the director orientation is combined with a fully anisotropic mode solver. From this, we get a clear view of the mechanism behind the tuning. (C) 2010 Optical Society of Americ

Efectos de diferentes prácticas de preparación del terreno y fertilización sobre el crecimiento inicial del Pinus spp en el NE argentino

Se presentan los resultados de crecimiento obtenidos, a los seis meses de efectuada la plantación, cuyos objetivos son evaluar la respuesta de Pinus taeda L. y de Pinus elliottii E. frente a diversas prácticas de establecimiento en el noreste de la provincia de Corrientes, Argentina. Sobre un Kandiudalf se evaluó la respuesta del Pinus taeda a la aplicación de 0, 22.5 y 45 g de N pl-1; 0, 45 y 90 g P2O5 pl-1 y 0, 36 y 72 g K2O pl-1 . Se observaron diferencias estadísticas entre las distintas dosis de N, de P y la interacción de NxK. La aplicación de fósforo se tradujo en un efecto positivo, mientras que la aplicación de nitrógeno muestra una tendencia inversa. También se evaluó la respuesta del Pinus taeda y Pinus elliottii, implantados en sitios con drenaje deficiente preparados mediante rastra y camellones, en los cuales fueron aplicados, además, 0, 100 y 200 g pl-1 de NPK 15-30-12. Los mayores crecimientos se presentaron cuando ambas especies fueron implantadas en camellones. Para el Pinus taeda se detectó una tendencia positiva ante la aplicación del fertilizante.Growth results of two experiments, obtained six months after plantation are presented. The objective was to evaluate the response of Pinus taeda L. and Pinus elliottii E. under different silvicultural treatments in Corrientes, northeastern Argentina. Response of Pinus taeda, applying 0, 22.5 and 45 g N pl-1; 0, 45 and 90 g P2O5 pl-1; also 0,36 and 72 g K2O pl-1, on Kandiudalf soil was evaluated. Statistical differences were observed between N, P and NxP interaction. P doses had a positive effect, while N doses presented a negative effect. Response of Pinus taeda and Pinus elliottii on deficient drainage sites prepared with disk ploughs or mounding with applications of NPK 15-30-12, at 0, 100 and 200 g pl-1 to both species was also evaluated. The best growth results were obtained when both species were planted on moundings. A positive trend was detected in Pinus taeda when fertilizer was applied.EEA MontecarloFil: Fernandez, Roberto Anibal. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Montecarlo; ArgentinaFil: Rodríguez Aspillaga, F. Productos Tissue S.A.; ArgentinaFil: Lupi, Ana María. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Montecarlo; ArgentinaFil: Hernández, A. Productos Tissue S.A.; ArgentinaFil: Reis, H. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Montecarlo; Argentin

Reconfigurable surfaces using fringing electric fields from nanostructured electrodes in nematic liquid crystals

Liquid crystals with a varying phase profile enable reconfigurable and intelligent devices to be designed, which are capable of manipulating incident electromagnetic fields in display, telecommunications as well as wearable applications. The active control of defects in these devices is becoming more important, especially since the electrodes used to manipulate them are shrinking to nanometer length scales. In this paper, a simple subwavelength, 1D, interdigitated metal electrode structure that can be reconfigured using nematic liquid crystals aligned in the homeotropic, planar, and hybrid methods are demonstrated. Accurate electro‐optic modeling of the directors and the defects are shown, which are induced by the fringing electric fields. Applied voltages result in liquid crystal reorientation near the bottom surface, such that defects are induced between the electrodes. The height of the electrodes does not affect the lateral position of these defects. Rather, this can be achieved by increasing the biasing voltage on the top electrode, which also leads to greater splay‐bend in the bulk of the material. These results therefore aim to generalize the control of defects in complex anisotropic nematic liquid crystals using simple interdigitated structures for a range of reconfigurable intelligent surface applications