CMOS compatible all-silicon TM pass polarizer based on highly doped silicon waveguide

We propose and analyze via simulation a novel approach to implement a complementary metal-oxide-semiconductor compatible and high extinction ratio transverse magnetic pass polarizer on the silicon-on-insulator platform with a 340 nm thick silicon core. The TM-pass polarizer utilizes a highly doped p-silicon waveguide as the transverse hybrid plasmonic waveguide. We observed an extinction ratio of 30.11 dB and an insertion loss of 3.08 dB for a device length of 15 µm. The fabrication process of the proposed TM-pass polarizer is simpler compared to the state-of-the-art since it only uses silicon waveguides and does not require any special material or feature size

Broadband all-silicon hybrid plasmonic TM-pass polarizer using bend waveguides

A complementary–metal–oxide semiconductor (CMOS) compatible all-silicon TM-pass polarizer using plasmonic bends is proposed. To simplify the fabrication and be compatible with the CMOS process, we employ only two materials: silicon and silicon dioxide. Highly doped silicon is used to support the plasmons. We obtain an extinction ratio and an insertion loss of 45.4 and 1.7 dB, respectively, at 1550 nm and a maximum extinction ratio of 58 dB. This is the highest reported extinction ratio for a TM-pass polarizer to the best of our knowledge. Furthermore, we achieved >20 dB of extinction ratio and <2 dB of insertion loss over 72 nm bandwidth for a device footprint <8.8 × 5.4 μm2. To achieve this, we exploit the properties of tight bends in plasmonic waveguides. Another advantage of the device is that it is robust against fabrication variations

CMOS-compatible multi-band plasmonic TE-pass polarizer

A CMOS-compatible plasmonic TE-pass polarizer capable of working in the O, E,S, C, L, and U bands is numerically analyzed. The device is based on an integrated hybrid plasmonic waveguide (HPW) with a segmented metal design. The segmented metal will avoid the propagation of the TM mode, confined in the slot of the HPW, while the TE fundamental mode will pass. The TE mode is not affected by the metal segmentation since it is confined in the core of the HPW. The concept of the segmented metal can be exploited in a plasmonic circuit with HPWs as the connecting waveguides between parts of the circuit and in a silicon photonics circuit with strip or slab waveguides connecting the different parts of the circuit. Using 3D FDTD simulations, it is shown that for a length of 5.5 μm the polarization extinction ratios are better than 20 dB and the insertion losses are less than 1.7dB over all the optical communication bands

A CMOS compatible ultracompact silicon photonic optical add-drop multiplexer with misaligned Sidewall Bragg gratings

We experimentally and via simulations demonstrate ultracompact single-stage and cascaded optical add-drop multiplexers using misaligned sidewall Bragg grating in a Mach-Zehnder interferometer for the silicon-on-insulator platform. The single-stage configuration has a device footprint of 400 μm × 90 μm, and the cascaded configuration has a footprint of 400 μm × 125 μm. The proposed designs have 3-dB bandwidths of 6 nm and extinction ratios of 25 dB and 51 dB, respectively, and have been fabricated for the transverse electric mode. A minimum lithographic feature size of 80 nm is used in our design, which is within the limitation of 193 nm deep ultraviolet lithography

Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BACKGROUND Regular, detailed reporting on population health by underlying cause of death is fundamental for public health decision making. Cause-specific estimates of mortality and the subsequent effects on life expectancy worldwide are valuable metrics to gauge progress in reducing mortality rates. These estimates are particularly important following large-scale mortality spikes, such as the COVID-19 pandemic. When systematically analysed, mortality rates and life expectancy allow comparisons of the consequences of causes of death globally and over time, providing a nuanced understanding of the effect of these causes on global populations. METHODS The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 cause-of-death analysis estimated mortality and years of life lost (YLLs) from 288 causes of death by age-sex-location-year in 204 countries and territories and 811 subnational locations for each year from 1990 until 2021. The analysis used 56 604 data sources, including data from vital registration and verbal autopsy as well as surveys, censuses, surveillance systems, and cancer registries, among others. As with previous GBD rounds, cause-specific death rates for most causes were estimated using the Cause of Death Ensemble model-a modelling tool developed for GBD to assess the out-of-sample predictive validity of different statistical models and covariate permutations and combine those results to produce cause-specific mortality estimates-with alternative strategies adapted to model causes with insufficient data, substantial changes in reporting over the study period, or unusual epidemiology. YLLs were computed as the product of the number of deaths for each cause-age-sex-location-year and the standard life expectancy at each age. As part of the modelling process, uncertainty intervals (UIs) were generated using the 2·5th and 97·5th percentiles from a 1000-draw distribution for each metric. We decomposed life expectancy by cause of death, location, and year to show cause-specific effects on life expectancy from 1990 to 2021. We also used the coefficient of variation and the fraction of population affected by 90% of deaths to highlight concentrations of mortality. Findings are reported in counts and age-standardised rates. Methodological improvements for cause-of-death estimates in GBD 2021 include the expansion of under-5-years age group to include four new age groups, enhanced methods to account for stochastic variation of sparse data, and the inclusion of COVID-19 and other pandemic-related mortality-which includes excess mortality associated with the pandemic, excluding COVID-19, lower respiratory infections, measles, malaria, and pertussis. For this analysis, 199 new country-years of vital registration cause-of-death data, 5 country-years of surveillance data, 21 country-years of verbal autopsy data, and 94 country-years of other data types were added to those used in previous GBD rounds. FINDINGS The leading causes of age-standardised deaths globally were the same in 2019 as they were in 1990; in descending order, these were, ischaemic heart disease, stroke, chronic obstructive pulmonary disease, and lower respiratory infections. In 2021, however, COVID-19 replaced stroke as the second-leading age-standardised cause of death, with 94·0 deaths (95% UI 89·2-100·0) per 100 000 population. The COVID-19 pandemic shifted the rankings of the leading five causes, lowering stroke to the third-leading and chronic obstructive pulmonary disease to the fourth-leading position. In 2021, the highest age-standardised death rates from COVID-19 occurred in sub-Saharan Africa (271·0 deaths [250·1-290·7] per 100 000 population) and Latin America and the Caribbean (195·4 deaths [182·1-211·4] per 100 000 population). The lowest age-standardised death rates from COVID-19 were in the high-income super-region (48·1 deaths [47·4-48·8] per 100 000 population) and southeast Asia, east Asia, and Oceania (23·2 deaths [16·3-37·2] per 100 000 population). Globally, life expectancy steadily improved between 1990 and 2019 for 18 of the 22 investigated causes. Decomposition of global and regional life expectancy showed the positive effect that reductions in deaths from enteric infections, lower respiratory infections, stroke, and neonatal deaths, among others have contributed to improved survival over the study period. However, a net reduction of 1·6 years occurred in global life expectancy between 2019 and 2021, primarily due to increased death rates from COVID-19 and other pandemic-related mortality. Life expectancy was highly variable between super-regions over the study period, with southeast Asia, east Asia, and Oceania gaining 8·3 years (6·7-9·9) overall, while having the smallest reduction in life expectancy due to COVID-19 (0·4 years). The largest reduction in life expectancy due to COVID-19 occurred in Latin America and the Caribbean (3·6 years). Additionally, 53 of the 288 causes of death were highly concentrated in locations with less than 50% of the global population as of 2021, and these causes of death became progressively more concentrated since 1990, when only 44 causes showed this pattern. The concentration phenomenon is discussed heuristically with respect to enteric and lower respiratory infections, malaria, HIV/AIDS, neonatal disorders, tuberculosis, and measles. INTERPRETATION Long-standing gains in life expectancy and reductions in many of the leading causes of death have been disrupted by the COVID-19 pandemic, the adverse effects of which were spread unevenly among populations. Despite the pandemic, there has been continued progress in combatting several notable causes of death, leading to improved global life expectancy over the study period. Each of the seven GBD super-regions showed an overall improvement from 1990 and 2021, obscuring the negative effect in the years of the pandemic. Additionally, our findings regarding regional variation in causes of death driving increases in life expectancy hold clear policy utility. Analyses of shifting mortality trends reveal that several causes, once widespread globally, are now increasingly concentrated geographically. These changes in mortality concentration, alongside further investigation of changing risks, interventions, and relevant policy, present an important opportunity to deepen our understanding of mortality-reduction strategies. Examining patterns in mortality concentration might reveal areas where successful public health interventions have been implemented. Translating these successes to locations where certain causes of death remain entrenched can inform policies that work to improve life expectancy for people everywhere. FUNDING Bill & Melinda Gates Foundation

Global, regional, and national burden of disorders affecting the nervous system, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BackgroundDisorders affecting the nervous system are diverse and include neurodevelopmental disorders, late-life neurodegeneration, and newly emergent conditions, such as cognitive impairment following COVID-19. Previous publications from the Global Burden of Disease, Injuries, and Risk Factor Study estimated the burden of 15 neurological conditions in 2015 and 2016, but these analyses did not include neurodevelopmental disorders, as defined by the International Classification of Diseases (ICD)-11, or a subset of cases of congenital, neonatal, and infectious conditions that cause neurological damage. Here, we estimate nervous system health loss caused by 37 unique conditions and their associated risk factors globally, regionally, and nationally from 1990 to 2021.MethodsWe estimated mortality, prevalence, years lived with disability (YLDs), years of life lost (YLLs), and disability-adjusted life-years (DALYs), with corresponding 95% uncertainty intervals (UIs), by age and sex in 204 countries and territories, from 1990 to 2021. We included morbidity and deaths due to neurological conditions, for which health loss is directly due to damage to the CNS or peripheral nervous system. We also isolated neurological health loss from conditions for which nervous system morbidity is a consequence, but not the primary feature, including a subset of congenital conditions (ie, chromosomal anomalies and congenital birth defects), neonatal conditions (ie, jaundice, preterm birth, and sepsis), infectious diseases (ie, COVID-19, cystic echinococcosis, malaria, syphilis, and Zika virus disease), and diabetic neuropathy. By conducting a sequela-level analysis of the health outcomes for these conditions, only cases where nervous system damage occurred were included, and YLDs were recalculated to isolate the non-fatal burden directly attributable to nervous system health loss. A comorbidity correction was used to calculate total prevalence of all conditions that affect the nervous system combined.FindingsGlobally, the 37 conditions affecting the nervous system were collectively ranked as the leading group cause of DALYs in 2021 (443 million, 95% UI 378–521), affecting 3·40 billion (3·20–3·62) individuals (43·1%, 40·5–45·9 of the global population); global DALY counts attributed to these conditions increased by 18·2% (8·7–26·7) between 1990 and 2021. Age-standardised rates of deaths per 100 000 people attributed to these conditions decreased from 1990 to 2021 by 33·6% (27·6–38·8), and age-standardised rates of DALYs attributed to these conditions decreased by 27·0% (21·5–32·4). Age-standardised prevalence was almost stable, with a change of 1·5% (0·7–2·4). The ten conditions with the highest age-standardised DALYs in 2021 were stroke, neonatal encephalopathy, migraine, Alzheimer's disease and other dementias, diabetic neuropathy, meningitis, epilepsy, neurological complications due to preterm birth, autism spectrum disorder, and nervous system cancer.InterpretationAs the leading cause of overall disease burden in the world, with increasing global DALY counts, effective prevention, treatment, and rehabilitation strategies for disorders affecting the nervous system are needed

Silicon photonic devices and circuits for optical communication applications

Emerging applications such as cloud-based storage services, high definition streaming services, machine-to-machine communications, and 5G radio networks are fueling the need for faster and bandwidth-efficient optical networks. The requirements of these applications include increased capacity, and reduced cost, power consumption, footprint, and complexity. Therefore, there is a growing trend in developing integrated optoelectronic devices to meet the above mentioned requirements. Specifically, the silicon-on-insulator (SOI) platform has drawn huge research interest due to its low power operation, dense integration, and low-cost fabrication with relatively high yield using the existing complementary-metal-oxide-semiconductor (CMOS) foundries. Consequently, silicon photonics has recently entered the production phase of the technology development cycle. This thesis presents several silicon photonic devices and circuits for applications in different segments of the optical networks.In the first part of the thesis, we report several passive silicon photonic devices based on Bragg gratings, interference, and doping. First, two configurations (single-stage and cascaded) of the optical add-drop multiplexers (OADMs) are presented using Bragg gratings in a Mach-Zehnder interferometer. The single-stage and the cascaded OADMs achieved extinction ratios (ERs) of 25 and 51 dB, respectively. Second, we present two types of the transversely coupled Fabry-Perot resonators using Bragg gratings and loop mirrors. The Bragg grating-based designs offer maximum ER of 37.3 dB and maximum Q-factor of 23642 while the loop mirror-based designs offer maximum ER of 18.1 dB and maximum Q-factor of 28086. Third, we demonstrate a 120° optical hybrid using 3x3 multimode interference (MMI) coupler. The hybrid demonstrates measured excess loss of &lt;2.4 dB over 60 nm and phase deviations of ≤10° over 80 nm bandwidths. Finally, we report a hybrid plasmonic transverse magnetic (TM)-pass polarizer using highly doped silicon instead of metals achieving an ER of 30.1 dB and an insertion loss (IL) of 3.1 dB with a length of 15 μm near 1550 nm wavelength.In the last part of the thesis, we present bench-top and integrated solutions for applications in the high-speed passive optical networks (PONs). First, we report a bench-top simplified coherent receiver based on 120° hybrid using 4-level pulse amplitude modulation (PAM-4). This allows the use of low bandwidth optoelectronic components to achieve higher bit rate (e.g., 10G component for 25 Gb/s bit rate). Using the bulk optics based receiver we obtained 25 Gb/s PAM-4 transmission over 21 km of single-mode fiber (SMF) with a receiver sensitivity of -14.5 dBm. Second, we demonstrate a fully-integrated 120° hybrid based simplified coherent receiver on SOI achieving a sensitivity of -20.3 dBm after 21 km of propagation of 25 Gb/s PAM-2 signal. Third, the performance of the integrated coherent receiver is improved further by using a better transmitter and simple digital signal processing (DSP) at the receiver. We achieved -16.6 dBm of receiver sensitivity with 25 Gb/s (12.5 GBaud) PAM-4 after 21 km without any dispersion compensation and receiver equalizer, and -11.6 dBm of receiver sensitivity with 50 Gb/s (25 GBaud) PAM-4 after 21 km using 31-tap linear feed-forward equalizer (FFE) at the receiver.Les applications émergentes telles que les services de stockage en nuage, les services de streaming haute définition, les communications entre ordinateurs et les réseaux radio 5G sont des alimentant le besoin de réseaux optiques plus rapides et efficaces en bande passante. Les exigences de ces applications incluent une capacité accrue et une réduction des coûts, de la consommation d'énergie, de l'encombrement et de la complexité. Par conséquent, il existe une tendance croissante à développer des dispositifs optoélectroniques intégrés pour répondre aux exigences susmentionnées. Plus précisément, la plate-forme silicium sur isolant (SOI) a suscité un intérêt considérable en matière de recherche en raison de son fonctionnement à faible puissance, de son intégration dense et de sa fabrication à faible coût avec un rendement relativement élevé grâce aux fonderies existantes CMOS. En conséquence, la photonique sur silicium a récemment atteint la phase de production du cycle de développement technologique. Cette thèse présente plusieurs dispositifs et circuits photoniques en silicium pour des applications dans différents segments des réseaux optiques.Dans la première partie de la thèse, nous rapportons plusieurs dispositifs photoniques passifs au silicium basés sur les réseaux de Bragg, les interférences et le dopage. Premièrement, deux configurations (à une étape et en cascade) des multiplexeurs optiques add-drop (OADM) sont présentées à l'aide de réseaux de Bragg dans un interféromètre de Mach-Zehnder. Les OADM à une étape et en cascade ont atteint des taux d'extinction (ER) de 25 et 51 dB, respectivement. Deuxièmement, nous présentons deux types de résonateurs Fabry-Perot à couplage transversal utilisant des réseaux de Bragg et des miroirs à boucle. Les conceptions à base de réseau de Bragg offrent un ER maximal de 37,3 dB et un facteur Q maximal de 23642, tandis que les conceptions à base de miroirs en boucle offrent un ER maximal de 18,1 dB et un facteur Q maximal de 28086. Troisièmement, nous démontrons un hybride optique à 120 ° en utilisant 3 x 3 coupleur d'interférence multimode (MMI). L'hybride présente une perte d'excès mesurée &lt;2,4 dB sur 60 nm et des écarts de phase ≤ 10 ° sur des largeurs de bande de 80 nm. Enfin, nous rapportons un polariseur hybride transverse magnétique plasmonique (TM) utilisant du silicium hautement dopé au lieu de métaux atteignant un ER de 30,1 dB et une perte d’insertion (IL) de 3,1 dB avec une longueur de 15 µm aux alentours de 1550 nm.Dans la dernière partie de la thèse, nous présentons des solutions intégrées et de référence pour des applications dans les réseaux optiques passifs à grande vitesse (PON). Tout d'abord, nous rapportons un récepteur cohérent simplifié de table basé sur un hybride à 120 ° utilisant une modulation d'amplitude à 4 niveaux (PAM-4). Cela permet l'utilisation de composants optoélectroniques à faible bande passante pour atteindre un débit binaire plus élevé (par exemple, composant 10G pour un débit binaire de 25 Gb / s). En utilisant le récepteur basé optique en vrac, nous avons obtenu une transmission PAM-4 à 25 Gb / s sur 21 km de fibre monomode (SMF) avec une sensibilité de récepteur de -14,5 dBm. Deuxièmement, nous démontrons un récepteur cohérent simplifié basé sur l'hybride hybride à 120 ° entièrement intégré, atteignant une sensibilité de -20,3 dBm après 21 km de propagation du signal PAM-2 à 25 Gb / s. Troisièmement, les performances du récepteur cohérent intégré sont encore améliorées en utilisant un meilleur émetteur et un simple traitement du signal numérique (DSP) au niveau du récepteur. Nous avons atteint une sensibilité du récepteur de -16,6 dBm avec PAM-4 à 25 Gb / s (12,5 Gbaud) après 21 km sans compensation de dispersion ni égaliseur au niveau du récepteur, et une sensibilité de récepteur de -11,6 dBm avec PAM-4 de 50 Gb / s (25 Gbaud) après 21 km, en utilisant l’égaliseur linéaire à 31-tap de correction avancée (FFE) au niveau du récepteu

Effect of beam parameters on the space charge wave modes in slow wave structures with semi-circular and trapezoidal corrugation

Corrugated waveguide with sinusoidal shape has long been used as slow wave structure (SWS) in backward wave oscillators (BWOs). Alternative SWSs with arbitrary geometries such as trapezoidal and semi-circular have drawn the attention of the researchers recently to be used as interaction regions in BWOs. In this work, the zero and non-zero beam dispersion characteristics of the axisymmetric transverse magnetic (TM) modes of semi-circularly and trapezoidally corrugated SWS (SCCSWS and TCSWS) have been studied numerically. The effect of variation of the electron beam parameters such as beam energy, current and radius on space charge wave modes (SCWM) and temporal growth rate (TGR) has also been investigated rigorously. The simulation results provide detail information regarding the unstable region where the resonant interaction occurs which is the requirement for microwave generation

Numerical study of the dispersion characteristics of a semi-circularly corrugated slow wave structure

The dispersion characteristics of the axisymmetric transverse magnetic (TM) modes of a semi-circularly corrugated periodic metallic slow wave structure (SCCSWS) have been analysed numerically by approximating the axial profile of the SWS using Fourier series. The theoretical results and some of their representative experimental counterpart revealed that, instead of using complex boundary conditions, the Fourier approximation of the axial profile can be used in deriving the dispersion relation using linear Rayleigh-Fourier (R-F) theory. An analytical equation has been derived in order to determine the Fourier constants of the approximated axial profile. Numerical technique has also been employed to calculate the Fourier constants. The dispersion relation for the SCCSWS is analysed for the cold structure which is characterized by the real value of frequency and wavenumber. The dispersion characteristics of the fundamental as well as higher order TM modes have been calculated using Fourier constants obtained by both analytical and numerical techniques. The SCCSWS analysed in this paper can be implemented in real experiments for the generation of high-power microwaves

Temporal growth rate study of a high power backward wave oscillator with semi-circularly corrugated slow wave structure

The dispersion properties and the temporal growth rate (TGR) of a high power backward wave oscillator (BWO) with a cylindrical metallic slow wave structure with semi-circular corrugation (SCCSWS) driven by an intense relativistic electron beam (IREB) are studied numerically. The IREB is assumed to be guided axially by an infinitely strong magnetic field. The semi-circular axial profile of the SWS is approximated by Fourier series and the study is carried out utilizing linear Rayleigh-Fourier (R-F) theory. The Fourier constants of the axial profile are determined numerically. The dispersion equation is solved numerically for the beam energy of 80–660 kV, beam current of 0.1–1.0 kA. When an electron beam with sufficient energy and current to produce instability propagates through the SWS, microwave radiation is generated. TGR which is obtained from the imaginary value of frequency and wavenumber can be used to qualitatively estimate the strength of the microwave radiation. The periodicity of the axial profile of SCCSWS is varied and the TGR for each case has been calculated by varying the beam parameters for TM01 mode. The proposed structure is comparatively easy to be fabricated and expected to be useful in BWO devices for generating high power microwaves for different applications