Ultra-broadband photon pair preparation by spontaneous four wave mixing in dispersion-engineered optical fiber

We present a study of the spectral properties of photon pairs generated through the process of spontaneous four wave mixing (SFWM) in single mode fiber. Our analysis assumes narrowband pumps, which are allowed to be frequency-degenerate or non-degenerate. Based on this analysis, we derive conditions on the pump frequencies and on the fiber dispersion parameters which guarantee the generation of ultra-broadband photon pairs. Such photon pairs are characterized by: i) a very large degree of entanglement, and ii) a very high degree of temporal synchronization between the signal and idler photons. Through a numerical exercise, we find that the use of photonic crystal fiber (PCF) facilitates the fulfilment of the conditions for ultra-broadband photon pair generation; in particular, the spectral region in which emission occurs can be adjusted to particular needs through an appropriate choice of the PCF parameters. In addition, we present a novel quantum interference effect, resulting from indistinguishable pathways to the same outcome, which can occur when pumping a SFWM source with multiple spectral lines.Comment: 15 pages, 10 figures. To be published in Phys. Rev.

Photon pair-state preparation with tailored spectral properties by spontaneous four-wave mixing in photonic-crystal fiber

We study theoretically the generation of photon pairs by spontaneous four-wave mixing (SFWM) in photonic crystal optical fiber. We show that it is possible to engineer two-photon states with specific spectral correlation (``entanglement'') properties suitable for quantum information processing applications. We focus on the case exhibiting no spectral correlations in the two-photon component of the state, which we call factorability, and which allows heralding of single-photon pure-state wave packets without the need for spectral post filtering. We show that spontaneous four wave mixing exhibits a remarkable flexibility, permitting a wider class of two-photon states, including ultra-broadband, highly-anticorrelated states.Comment: 17 pages, 7 figures, submitte

Development of Optical Waveguides Through Multiple-Energy Ion Implantations

In this chapter, we present information about the design, fabrication and characterization of optical waveguides obtained by using a protocol of multiple energy ion implantations. This protocol must provide an approach to produce optical waveguides with adequate features, such as dimensions, evanescent field and optical confinement. In general, optical waveguides can be improved by widening the optical barrier or waveguide core through multiple energy ion implantations. Design of optical waveguides must consider effects induced by the ion implantation process, such as modification of substrate density, polarizability and structure. Information will be presented about optical waveguides formed mainly in laser crystals (i.e., Nd:YAG, Nd:YVO4) using light ions such as H and He+ and heavy ions such as C2+. In general, these ions decrease the refractive index in the implanted area, producing a barrier that permits guiding in the region near the surface. Furthermore, information about nonlinear optical properties of channel waveguides containing metallic nanoparticles is presented. Composite materials containing metallic nanoparticles embedded in a dielectric matrix such as silica possess interesting properties due to surface plasmon resonance absorption features and the enhancement of the third-order nonlinear optical response. Therefore, nonlinear optical properties in composite waveguides can be used in all-optical switching devices

Effect of natural zeolite on live weight changes, ruminal fermentation and nitrogen metabolism of ewe lambs

The objective of this study was to evaluate the effects of natural zeolite on the performance and nitrogen metabolism of Rambouillet ewe lambs. Forty Rambouillet ewe lambs with an initial weight of 41.06 ± 3.9 kg were randomly assigned to one of four experimental diets, namely 0, 20, 40 and 60 g of natural zeolite (Comercializadora Omega® México) per kg dietary dry matter in a completely randomized design and sixteen ewe lambs were used in a 4 x 4 Latin square metabolism study. Performance was not modified by natural zeolite levels in the diet, and daily gain showed a quadratic response. Ammonia concentration at 8 and 12 hours increased linearly with zeolite. Zeolite increased ruminal pH linearly at 8 and 12 hours. Acetate and butyrate presented a quadratic response, and total ruminal volatile fatty acid concentration was linearly increased by zeolite. Nitrogen retention showed a linear and quadratic response to zeolite. The estimated fractions of protein digested in the small intestine, when rumen-fermentable energy was limiting (PDIE) and when rumen-fermentable nitrogen was limiting, showed a linear and quadratic response to zeolite. PDIE was positively correlated (r = 0.96) with average daily gain.Keywords: Sheep, ammonium, ruminal fermentation, productive, soluble nitroge

In vitro gas production of foliage from three browse tree species treated with different dose levels of exogenous fibrolytic enzymes

The aim of this study was to evaluate the effect of different dose levels of exogenous fibrolytic enzymes (EFE) on in vitro ruminal fermentation kinetics and energy utilization of foliages from three browse trees (Pithecellobium dulce, Heliocarpus velutinus and Guazuma ulmifolia). Mixture of EFE product was added to the leaves of the three browse tree species at three dose levels: 0 (control), 3.5 and 7.0 mg/g of DM. Chemical composition of the foliages, including plant secondary metabolites such as total phenolics (TP), saponins (SAP) and aqueous fraction (AF), was determined. In addition, in vitro assaying of ruminal gas production kinetics was determined for the three browse three foliages treated with EFE. P. dulce had the highest crude protein content (p < 0.05), whereas G. ulmifolia had the highest content of neutral detergent fibre and SAP (p < 0.05) and H. velutinus had the lowest content of TP (p < 0.05). The interaction between tree species and dose level of EFE was significant (p < 0.05) for gas production (GP) at 24 h of incubation, parameters b and c of the accumulated GP curve, short-chain fatty acids (SCFA) and metabolizable energy (ME). The lowest (p < 0.01) extent of accumulated GP as well as the b and c values occurred in G. ulmifolia at 0 mg EFE/g DM. P. dulce had the highest (p < 0.05) values for ME and SCFA at the highest dose of EFE. Tree species and dose level had significant (p < 0.05) effects on all parameters describing in vitro ruminal fermentation kinetics and energy utilization. Addition of EFE improved the fermentation kinetics of the browse species considered in this study.UAE

Efecto del propionato de calcio en la fermentación in vitro de dietas a base de sorgo

The objective of the present study was to evaluate the effect of calcium propionate (CaPr) on in vitro ruminal fermentation using a factorial arrangement 2 x 2 evaluating CaPr (0 vs. 1%) and grain level (55 vs. 65%). There was a CaPr x Grain interaction in the volume of gas produced (V; p = 0.04). Addition of CaPr prolonged Lag time (1.4 vs. 1.04 h; P&lt;0.01), and increasing the grain level also prolonged Lag time (1.56 vs. 0.89 h; p &lt; 0.03) and gas production rate (0.046 vs. 0.041 h-1; P&lt;0.04). However, there were no differences in CH4, CO2, acetate, propionate and butyrate concentrations. Therefore, the addition of calcium propionate in a diet with 55 or 66% of grain increased Lag phase but it is not affected fermentation pattern or methane losses.El objetivo de este estudio fue evaluar in vitro el efecto de la adición de propionato de Ca (PrCa). El diseño experimental fue completamente al azar con un arreglo factorial 2x2; PrCa (0 o 1%) y grano (55 o 65%). Se encontró diferencias (p&gt;0,05) entre tratamientos para volumen de gas, pero la tasa de producción de gas no fue diferente (p&lt;0,05), se observó un efecto por parte del grano (p&lt;0,04). La adición de PrCa prolongó el tiempo Lag (1,4 vs. 1.04 h; P&lt;0,01) y aumentando el nivel de grano también prolongó la fase Lag (1,56 vs. 0,89 h; P&lt;0,03) y la tasa de producción de gas (0,046 vs. 0,041 h-1; P &lt;0,04). Sin embargo, no hubo diferencias en la concentración de CH4 y CO2, ni de propionato, acetato y butirato. La adición de propionato de calcio a una dieta con 55 o 65% de grano prolonga la fase Lag pero no afecta el patrón de fermentación o las pérdidas de metano.Fil: Miranda, Luis Alberto. Universidad Autónoma Chapingo (México)Fil: Lee-Rangel, Héctor Aarón. Universidad Autónoma de San Luis Potosí. Facultad de AgronomíaFil: Mendoza-Martínez, Germán David.Fil: Crosby-Galván, María Magdalena. Colegio de Postgraduados. Campus Montecillo (México)Fil: Relling, Alejandro Enrique. Universidad Nacional de la Plata. Facultad de Ciencias VeterinariasFil: Pinos-Rodríguez, Juan Manuel. Universidad Autónoma de San Luis Potosí. Facultad de AgronomíaFil: Rojo Rubio, Rolando . Universidad Autónoma del Estado de MéxicoFil: González Hernandez, Milagros. Universidad Autónoma de San Luis Potosí. Facultad de Agronomí