Design rules and optimization of electro-optic modulators based on coplanar waveguides

Electro-optical traveling wave modulators (EO-TWM) are basic building blocks of the optical communications industry which is leading a revolution in the way we communicate, work and live. As a result, the demand for high-speed data transmission with low driving voltage is continuously growing up with costs that should be kept below a minimum. Besides communications, a growing number of applications for EO-TWM is continuously emerging with equally stringent requirements. This Thesis is concerned with advances in the eld of systematic design and optimization of EO-TWM for coping inverse of the velocity matching constant has been shown to govern the low-loss limit (LL), while in the velocity matching limit (VM), a constant bandwidth times squared-length rule proportional to the inverse of the squared loss constant has been found more appropriate. In this work we provide insights into the trade-o issue in EO-TWM, and a complete picture of the applicable gures of merit for every operative range. Besides the known LL and VM gures of merit, two intermediate ranges, the quasi-low loss (QLL) and the quasi-velocity matching (QVM), have been identi ed. Also novel closed-forms expressions fully accounting for the e ffects of the skin-e ffect electrode loss and optical-electrical wave velocity mismatch, explicitly relating the operative bandwidth and the electrode length in EO-TWM, have been found. Novel bandwidth and electrode-length charts have been created, which constitute a useful tool for the optimization and design of this modulators. A graphical interface tool called MZM-GIT has been built integrating the analytical optimization and design strategies developed throughout the Thesis. With the aid of the MZM-GIT, several proposals of optimized MZM designs based on practical structures described in literature, and also based on the industry trends, are made and analyzed. with the industrial demands. In EO-TWM, the accumulated electro-optic e ect over the optical wave grows with the co-propagated traveling wave (TW) length, allowing to reduce the required RF driving power. However, in typical electro-optic materials for modulators, among which LiNbO3 stands up, due to the natural mismatch between the velocity of the RF and the optical waves, the modulation bandwidth decreases with the TW length, giving place to a well-known trade-o ff. In typical LiNbO3 substrates, in which this Thesis is focused, this trade-off is seen to mainly depend on the values of the electrical loss constant and the e ective wave velocity mismatch in the TW structure that forms the electrodes, usually a coplanar waveguide (CPW). Special emphasis has historically been placed on the optimized design of the CPW in EO-TWM. In this Thesis the study of closed-form expressions for the propagation parameters of CPW as a function of the geometry, has proven useful for the design and optimization procedures sought. Although some interesting approaches to closed-form formulations have been found in literature, none of them completely ful lls the desired requirements of providing a reliable yet simple description of propagation in CPW, appropriate to systematic and easy to follow design rules for EO-TWM, and therefore new simpli ed closed-form expressions for the CPW transmission parameters have been developed. In a second part of the Thesis, the bandwidth-length trade-off has been examined. To date, two bandwidth-length rules have been proposed: a constant bandwidth-length product proportional to the inverse of the velocity matching constant has been shown to govern the low-loss limit (LL), while in the velocity matching limit (VM), a constant bandwidth times squared-length rule proportional to the inverse of the squared loss constant has been found more appropriate. In this work we provide insights into the trade-off issue in EO-TWM, and a complete picture of the applicable fi gures of merit for every operative range. Besides the known LL and VM gures of merit, two intermediate ranges, the quasi-low loss (QLL) and the quasi-velocity matching (QVM), have been identi ed. Also novel closed-forms expressions fully accounting for the e ffects of the skin-eff ect electrode loss and optical-electrical wave velocity mismatch, explicitly relating the operative bandwidth and the electrode length in EO-TWM, have been found. Novel bandwidth and electrode-length charts have been created, which constitute a useful tool for the optimization and design of this modulators. A graphical interface tool called MZM-GIT has been built integrating the analytical optimization and design strategies developed throughout the Thesis. With the aid of the MZM-GIT, several proposals of optimized MZM designs based on practical structures described in literature, and also based on the industry trends, are made and analyzed

Encomio de los ingenios sevillanos

Reproducción facs. de la portada de la ed. de: Sevilla: Francisco de Lyra, 162

Protective Role of the Immune System in Spinal Cord Injury: Immunomodulation with Altered Peptide Ligands

Spinal cord injury (SCI) is a phenomenon characterized by damage to the spinal cord and nerve roots, resulting in loss of physiological activity below the lesion. Injury to the spinal cord activates a cascade of cellular and molecular reactions in which the immune system plays an essential role, as there is an uncontrolled immune response that endows further damage to neural tissue. However, the activity of immune system at the site of injury can be modified in order to obtain a neuroprotective environment and promote SCI recovery. This strategy has been designed under the light of the innovative concept “protective autoimmunity” (PA) and can be stimulated with the use of altered peptide ligands (APL). Adequate immunomodulation with APL can be obtained with the peptide A91, which is a safe synthetic peptide derived from the myelin basic protein (MBP) that has proven to be effective in preclinical research. Immunization with A91 is carried out with the objective of preventing further damage and promoting neuroprotection. This peptide has direct influence over SCI secondary mechanisms such as inflammation, lipid peroxidation, and apoptosis. Preclinical results suggest that immunization with A91 could be an effective treatment in the clinical field, providing a better quality of life to SCI patients

Aplicación de los modelos de crisis financiera de primera y segunda generación a la crisis financiera en Ecuador en el año 1999

The contemporary history of the Republic of Ecuador was marked undoubtedly by the financial crisis that hit the country in the last years of the 90s. This recession was characterized by a poor management of public policies and the deteriorating macroeconomic conditions, linked to the lack of confidence of economic agents that precipitated the withdrawal of the financial sector deposits. The economic literature on the origins and causes of financial crises and currency crisis is wide and is divided into three generations. The practical application of crisis models first and second generation 1999 Ecuador crisis allows us to understand the causes of it.La historia contemporánea de la República del Ecuador estuvo marcada sin duda alguna por la crisis financiera que azotó al país en los últimos años de la década de los 90s. Esta recesión estuvo marcada por un mal manejo de las políticas públicas y el deterioro de las condiciones macroeconómicas que, ligadas a la falta de confianza de los agentes económicos, precipitaron el retiro de los depósitos del sector financiero. La literatura económica sobre los orígenes y causas de las crisis financieras y cambiarias es amplia y está dividida en tres generaciones. La aplicación práctica de los modelos de crisis de primera y segunda generación a la crisis ecuatoriana de 1999 nos permite entender las causas de la misma

Arthroscopic Technique to Treat Articular Cartilage Lesions in the Patellofemoral Joint

Cartilage lesions are frequent in routine knee arthroscopy (63%). Among these injuries, 11–23% are located in patella and 6–15% in the trochlea. Treatment of cartilage lesions in patellofemoral joint (PFJ) represents a challenge because of its complex access, high axial loading, and shearing forces. These factors explain the 7% of good results in the PFJ versus 90% in femoral condyles for autologous chondrocyte implantation (ACI). Microfracture (MF) as the first line of treatment has revealed limited hyaline-like cartilage formation in comparison to ACI. This fibrocartilage deteriorates with the time resulting in inferior biomechanical properties. Important issues that enhance the results of cartilage repair procedures in PFJ are associated with the restoration of the joint balance as unloading/realigning techniques. In the literature, there is no description of any convenient arthroscopic technique for ACI. The reported techniques usually require to set up the patient in prone position to perform the arthroscopy making it difficult to treat associated knee malalignment or instability. Others are open techniques with more risk of morbidities, pain, and complications and longer recovery time. In this chapter, we will describe a novel all-arthroscopic technique to treat cartilage lesions in the patella that permits the correction and treatment of associated lesions in the same patient position

Estimating Regional Poverty Lines With Scarce Data: An Application to Brazilian Regions

The recent emphasis on fighting poverty in Brazil makes the determination of the size of the targeted population an important issue (What is the right poverty line? What is the real size of the poor population? How much money should be given to each poor family?). The application of poverty lines based on national income levels tends to produce important distortions at the regional level. Using data from a Household Expenditure Survey (HES) that covered some regions in Brazil, the paper develops and applies a methodology to define poverty lines for all regions and urban areas. These lines are based on nutritional requirements, thus avoiding the purchasing power parity problem, and take into account non-monetary income and in-kind consumption, aspects that are very important at the rural level. The HES results are matched with Census data, allowing for the estimation of rural and urban poverty lines for Brazilian regions.