Contra-directional couplers as optical filters on the silicon on insulator platform

Ce mémoire vise à étudier la conception, la fabrication et la caractérisation de filtres à base de coupleurs contra-directionels en silicium. Ceux-ci sont un type de filtre optique encore peu connu, semblable à des réseaux de Bragg, mais réfléchissant dans un autre guide d'onde. Afin de comprendre pourquoi les filtres optiques sont importants à améliorer, ce mémoire commence en expliquant la base des communications optiques. Sont ensuite expliqués les principes de la photonique sur silicium, et comment arriver à manipuler la lumière à l'aide des matériaux utilisés en électronique. Les différents dispositifs existants en silicium sont énumérés, avec une attention particuliére portée aux filtres optiques. Le principe de fonctionnement des coupleurs contra-directionels est expliqué en détail au chapitre 2. Celui-ci reformule les principes de base connus, en rajoutant des détails sur la simulation de l'apodization et du bruit de phase. La recherche originale en laboratoire à ce sujet est exposée dans les chapitres 3 et 4. Le premier article démontre qu'il est possible de fabriquer des coupleurs contra-directionels avec un processus de photolithographie malgré la précision requise. Le deuxième utilise des coupleurs contra-directionels pour créer un filtre accordable ayant la plus grande plage d'accordabilité mesurée sur silicium. Tester ces dispositifs fut une part importante du travail et de l'apprentissage. Ainsi, le dernier chapitre est consacré à la caractérisation des dispositifs sur silicium à l'aide d'un montage automatisé. Ce chapitre a pour but d'expliquer en détail toutes les étapes du design, de l'alignement et des tests afin de documenter la procédure pour les nouveaux étudiants. Au final, ce travail démontre que les coupleurs contra-directionels en silicium sont une solution envisageable pour plusieurs applications nécessitant des filtres optiques, tel que les réseaux reconfigurables et les canaux de communication large bande.This memoir aims to study the design, fabrication and characterization of filters based on contra-directional couplers on silicon. These are a type of filter still little known, similar to Bragg gratings, but reflecting the light in an other waveguide. To understand why optical filters are important to improve, this memoir starts by introducing the basis of optical communications. The principles of silicon photonics are then explained, to understand how to manipulate light using micro-electronics materials. The devices available on silicon are enumerated, with a special attention given to optical filters. Contra-directional couplers are explained in detail in chapter 2. This chapter explains the known principles, adapting them to be able to simulate apodization and phase noise in these devices. The original laboratory research is shown in chapters 3 and 3. The first article demonstrates that it is possible to fabricate contra-directional couplers using photolithography despite the small features required. The second one uses contra-directional couplers to create a tunable filter displaying the greatest tunable bandwidth range measured in silicon filters. Testing these devices has been an important part of the work. The last chapter is about the characterization of silicon devices using an automated setup. This chapter aims to explain all the details of the design, alignment and test to document the procedure for future students. In sum, this work shows that silicon contra-directional couplers are an appealing solution for many applications which require optical filters such as reconfigurable networks and broadband channels

Polarization-insensitive silicon nitride arrayed waveguide grating

Next-generation passive optical networks require integrated, polarization-insensitive wavelength-division multiplexing solutions, for which the recently emerging low-loss silicon nitride nanophotonic platforms hold great potential. A novel polarization-insensitive arrayed waveguide grating (AWG) built with silicon nitride waveguides is presented in this Letter. Polarization insensitivity is obtained when both the channel spacing and the center wavelength of the two orthogonal polarization states (i.e., the TE and TM waveguide modes) are simultaneously aligned. In our design, the channel spacing alignment between the polarization states is obtained by optimizing the geometry of the arrayed waveguides, whereas the central wavelength polarization insensitivity is obtained by splitting the two polarization states and adjusting their angle of incidence at the input star coupler to compensate for the polarization mode dispersion of the AWG. A 100 GHz 1×8 wavelength-division multiplexer with crosstalk levels below −16  dB is demonstrated experimentally

Analytical modeling of silicon microring and microdisk modulators with electrical and optical dynamics

We propose an analytical time-domain model for microring and microdisk modulators, which considers both their electrical and optical properties. Theory of the dynamics of microring/microdisk is discussed, and general solutions to the transfer matrix representation are presented. Both static and dynamic predictions from the model are compared to measurement results to demonstrate the accuracy of our model. Static predictions and measurements are presented for power and phase responses, whereas dynamic predictions and measurements are presented for small-signal and large-signal operations. The model verifies that the chirping and modulation bandwidth of the modulators depend on the detuning state. Finally, the accuracy and scalability of several techniques employed in the model are discussed

RNF8 ubiquitylation of XRN2 facilitates R-loop resolution and restrains genomic instability in BRCA1 mutant cells

Breast cancer linked with BRCA1/2 mutations commonly recur and resist current therapies, including PARP inhibitors. Given the lack of effective targeted therapies for BRCA1-mutant cancers, we sought to identify novel targets to selectively kill these cancers. Here, we report that loss of RNF8 significantly protects Brca1-mutant mice against mammary tumorigenesis. RNF8 deficiency in human BRCA1-mutant breast cancer cells was found to promote R-loop accumulation and replication fork instability, leading to increased DNA damage, senescence, and synthetic lethality. Mechanistically, RNF8 interacts with XRN2, which is crucial for transcription termination and R-loop resolution. We report that RNF8 ubiquitylates XRN2 to facilitate its recruitment to R-loop-prone genomic loci and that RNF8 deficiency in BRCA1-mutant breast cancer cells decreases XRN2 occupancy at R-loop-prone sites, thereby promoting R-loop accumulation, transcription-replication collisions, excessive genomic instability, and cancer cell death. Collectively, our work identifies a synthetic lethal interaction between RNF8 and BRCA1, which is mediated by a pathological accumulation of R-loops

DMTs and Covid-19 severity in MS: a pooled analysis from Italy and France

We evaluated the effect of DMTs on Covid-19 severity in patients with MS, with a pooled-analysis of two large cohorts from Italy and France. The association of baseline characteristics and DMTs with Covid-19 severity was assessed by multivariate ordinal-logistic models and pooled by a fixed-effect meta-analysis. 1066 patients with MS from Italy and 721 from France were included. In the multivariate model, anti-CD20 therapies were significantly associated (OR = 2.05, 95%CI = 1.39–3.02, p < 0.001) with Covid-19 severity, whereas interferon indicated a decreased risk (OR = 0.42, 95%CI = 0.18–0.99, p = 0.047). This pooled-analysis confirms an increased risk of severe Covid-19 in patients on anti-CD20 therapies and supports the protective role of interferon

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Penilaian Kinerja Keuangan Koperasi di Kabupaten Pelalawan

This paper describe development and financial performance of cooperative in District Pelalawan among 2007 - 2008. Studies on primary and secondary cooperative in 12 sub-districts. Method in this stady use performance measuring of productivity, efficiency, growth, liquidity, and solvability of cooperative. Productivity of cooperative in Pelalawan was highly but efficiency still low. Profit and income were highly, even liquidity of cooperative very high, and solvability was good

Juxtaposing BTE and ATE – on the role of the European insurance industry in funding civil litigation

One of the ways in which legal services are financed, and indeed shaped, is through private insurance arrangement. Two contrasting types of legal expenses insurance contracts (LEI) seem to dominate in Europe: before the event (BTE) and after the event (ATE) legal expenses insurance. Notwithstanding institutional differences between different legal systems, BTE and ATE insurance arrangements may be instrumental if government policy is geared towards strengthening a market-oriented system of financing access to justice for individuals and business. At the same time, emphasizing the role of a private industry as a keeper of the gates to justice raises issues of accountability and transparency, not readily reconcilable with demands of competition. Moreover, multiple actors (clients, lawyers, courts, insurers) are involved, causing behavioural dynamics which are not easily predicted or influenced. Against this background, this paper looks into BTE and ATE arrangements by analysing the particularities of BTE and ATE arrangements currently available in some European jurisdictions and by painting a picture of their respective markets and legal contexts. This allows for some reflection on the performance of BTE and ATE providers as both financiers and keepers. Two issues emerge from the analysis that are worthy of some further reflection. Firstly, there is the problematic long-term sustainability of some ATE products. Secondly, the challenges faced by policymakers that would like to nudge consumers into voluntarily taking out BTE LEI

Search for stop and higgsino production using diphoton Higgs boson decays

Results are presented of a search for a "natural" supersymmetry scenario with gauge mediated symmetry breaking. It is assumed that only the supersymmetric partners of the top-quark (stop) and the Higgs boson (higgsino) are accessible. Events are examined in which there are two photons forming a Higgs boson candidate, and at least two b-quark jets. In 19.7 inverse femtobarns of proton-proton collision data at sqrt(s) = 8 TeV, recorded in the CMS experiment, no evidence of a signal is found and lower limits at the 95% confidence level are set, excluding the stop mass below 360 to 410 GeV, depending on the higgsino mass