Erbium compounds for light emission at 1.54[mu]m

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013.In title on title page, "[mu]" appear as lower case Greek letter. Cataloged from PDF version of thesis.Includes bibliographical references (p. 181-193).Silicon microphotonics has emerged as the leading technology to overcome the interconnect bottleneck that limits a further increase of computation power following Moore's law. Optical interconnects between different electronic microprocessors in an electronic-photonic integrated circuit (EPIC) can provide a fast, low-loss and high-bandwidth alternative to electrical interconnects, which suffer from issues such as resistive heating, RC delays and channel crosstalk at an increasing device density. A crucial device in such an electronic-photonic integrated circuit is a compact, high-gain and low power optical amplifier to compensate for signal attenuation due to propagation losses and to recover signal strength after subsequent 3dB splits during fanout of the optical signal to different microprocessors. Erbium ions (Er3+) are an excellent candidate to provide amplification around [lambda] = 1.54[mu]m for optical telecommunications. Erbium-doped fiber amplifiers (EDFAs) have already enabled long-haul optical data transmission through silica optical fibers, but scaling down a fiber amplifier to an on-chip erbium-doped waveguide amplifier (EDWA) brings along significant materials and device design challenges. In this thesis, erbium-ytterbium oxide (Er.Yb2.0 3) and erbium-ytterbium-yttrium silicate (ErxYbYY 2 ,ySi 2O7 ) compounds are investigated as novel materials systems for the development of EDWAs. The high erbium and ytterbium solubility (>1022 cm-3) and refractive index (1.71 < n < 1.92) make these materials excellent candidates for compact, low-power optical amplifiers. ErxYb2.xo 3 and ErxYb2 -. Si2O7 thin films were deposited on Si0 2 and analyzed structurally and optically. The role of ytterbium in these compounds is twofold. First, ytterbium can be used as an alternative to yttrium for dilution of the erbium concentration in order to mitigate parasitic concentration quenching effects. Second, ytterbium acts as a sensitizer for erbium during optical pumping at [lambda] = 980nm. Comparison of the different oxide and silicate thin films reveals that the a-disilicate phase is the best candidate for an EDWA gain medium pumped at [lambda] = 980nm. By means of rate and propagation equations, the composition of an ErxYbY 2 -x-ySi 2 07 gain medium was optimized for application as a 3dB EDWA. The optimal composition was found to be Ero.02 5Ybo.2 00 Y1 .7 75 Si2 07, which provides a 1.5dB/cm gain at only 3mW of pump power. In terms of the figure of merit 3dB gain/(device area - pump power), this material outperforms other EDWA materials reported in literature.by Michiel Vanhoutte.Ph.D

Flämischer Sprachnationalismus im Spannungsfeld zwischen kollektiver Identitätsstiftung und Rechtspopulismus

In der Arbeit wird die Entstehung Belgiens als Nationalstaat dargestellt. Da es sich bei den Flamen und Wallonen von Anfang um zwei unterschiedliche Kulturen mit unterschiedlichen Sprachen handelte, wurde es sehr schwer, zur Zufriedenheit beider eine Nationale Regierung zu bilden. Die Flamen waren in der Mehrheit aber die nationale Regierung war wallonisch dominiert und frankophon. Hierdurch war Nationalismus und gemeinsamer Habitus sehr schwer zu vereinen. Die Flamen mussten sich, von Anfang an, gegen den Vorwurf des Rechtextremismus und Rechtspopulismus als spezifischen Konfliktmodus wehren. Auch die Politisierung des flämischen Sprachnationalismus war immer ein Anlass für Auseinanderset-zungen zwischen Flamen und Wallonen. Erst in den siebziger Jahren haben Flandern und die Wallonie, zusätzlich zur nationalen Regierung, je eine eigene Regierung bekommen

Processing and properties of ytterbium-erbium silicate thin film gain media

The structural and photoluminescence properties of ytterbium-erbium silicate thin films have been investigated. The films were fabricated by RF-magnetron co-sputtering of Er[subscript 2]O[subscript 3], Yb[subscript 2]O[subscript 3] and SiO[subscript 2] on c-Si and subsequent annealing in N[subscript 2] or O[subscript 2] atmosphere.United States. Air Force Office of Scientific Research. Multidisciplinary University Research Initiativ

Direct demonstration of sensitization at 980nm optical excitation in erbium-ytterbium silicates

Sensitization of erbium by ytterbium in Er[subscript x]Yb[subscript 2-x]SiO[subscript 5] thin films at 980nm optical excitation is demonstrated by means of comparison of the 1.54μm photoluminescence intensities excited with 488nm and 980nm light. Additionally, it is shown that detrimental Er-Er interactions such as concentration quenching increase non-radiative decay rates at high erbium concentrations. Dilution of erbium by ytterbium reduces these interactions, leading to an increase of internal quantum efficiency.United States. Air Force Office of Scientific Research. Multidisciplinary University Research Initiative (Si-based Laser Initiative

Engineering broadband and anisotropic photoluminescence emission from rare earth doped tellurite thin film photonic crystals

Broadband and anisotropic light emission from rare-earth doped tellurite thin films is demonstrated using Er[superscript 3+]-TeO[subscript 2] photonic crystals (PhCs). By adjusting the PhC parameters, photoluminescent light can be efficiently coupled into vertical surface emission or lateral waveguide propagation modes. Because of the flexibility of light projection direction, Er[superscript 3+]-TeO[subscript 2] is a potential broadband light source for integration with three-dimensional photonic circuits and on-chip biochemical sensors

Synthesis and structure-activity relationship studies of benzo[b][1,4]oxazin-3(4H)-one analogues as inhibitors of mycobacterial thymidylate synthase

Since the discovery of a flavin-dependent thymidylate synthase (ThyX or FDTS) that is absent in humans but crucial for DNA biosynthesis in a diverse group of pathogens, the enzyme has been pursued for the development of new antibacterial agents against Mycobacterium tuberculosis, the causative agent of the widespread infectious disease tuberculosis (TB). In response to a growing need for more effective anti-TB drugs, we have built upon our previous screening efforts and report herein an optimization campaign of a novel series of inhibitors with a unique inhibition profile. The inhibitors display competitive inhibition toward the methylene tetrahydrofolate cofactor of ThyX, enabling us to generate a model of the compounds bound to their target, thus offering insight into their structure-activity relationships.status: Published onlin

Synthesis and Structure–Activity Relationship Studies of Benzo[ b ][1,4]oxazin‐3(4 H )‐one Analogues as Inhibitors of Mycobacterial Thymidylate Synthase X

International audienc

Implications of Genetic Testing in Dilated Cardiomyopathy

Background: Genetic analysis is a first-tier test in dilated cardiomyopathy (DCM). Electrical phenotypes are common in genetic DCM, but their exact contribution to the clinical course and outcome is unknown. We determined the prevalence of pathogenic gene variants in a large unselected DCM population and determined the role of electrical phenotypes in association with outcome. Methods: This study included 689 patients with DCM from the Maastricht Cardiomyopathy Registry, undergoing genetic evaluation using a 48 cardiomyopathy-associated gene-panel, echocardiography, endomyocardial biopsies, and Holter monitoring. Upon detection of a pathogenic variant in a patient with DCM, familial segregation was performed. Outcome was defined as cardiovascular death, heart transplantation, heart failure hospitalization, and/or occurrence of life-threatening arrhythmias. Results: A (likely) pathogenic gene variant was found in 19% of patients, varying from 36% in familial to 13% in nonfamilial DCM. Family segregation analysis showed familial disease in 46% of patients with DCM who were initially deemed nonfamilial by history. Overall, 18% of patients with a nongenetic risk factor had a pathogenic gene variant. Almost all pathogenic gene variants occurred in just 12 genes previously shown to have robust disease association with DCM. Genetic DCM was independently associated with electrical phenotypes such as atrial fibrillation, nonsustained ventricular tachycardia, and atrioventricular block and inversely correlated with the presence of a left bundle branch block (P Conclusions: One in 5 patients with an established nongenetic risk factor or a nonfamilial disease still carries a pathogenic gene variant. Genetic DCM is characterized by a profile of electrical phenotypes (atrial fibrillation, nonsustained ventricular tachycardia, and atrioventricular block), which carries increased risk for adverse outcomes. Based on these findings, we envisage a broader role for genetic testing in DCM