Stress induced effects for advanced polarization control in silicon photonics components

We review the use of the oxide cladding stress-induced photoelastic effect to modify the polarization dependent properties in silicon-on-insulator (SOI) waveguide components, and highlight characteristics particular to this high index contrast (HIC) systems. The birefringence in SOI waveguides has its origin in the electromagnetic boundary conditions at the waveguide boundaries, and can be further modified by the presence of stress in the waveguiding materials. With typical stress levels in SiO2 films, which are often used as the upper cladding, the waveguide effective index can be altered anisotropically up to the order of 10−3 for ridges with heights ranging from 1 μm to 5 μm. This effect can be used effectively to counter the waveguide geometrical birefringence, allowing the waveguide cross-section profiles to be optimized for design criteria other than null geometrical birefringence. Design strategies are developed for using stress engineering to achieve a variety of functions. Polarization insensitive arrayed waveguide gratings (AWGs), polarization insensitive ring resonators, and polarization splitters and filters are demonstrated using these design principles

Tilted fiber Bragg grating sensor interrogation system using a high-resolution silicon-on-insulator arrayed waveguide grating

We report a compact high-resolution arrayed waveguide grating (AWG) interrogator system designed to measure the relative wavelength spacing between two individual resonances of a tilted fiber Bragg grating (TFBG) refractometer. The TFBG refractometer benefits from an internal wavelength and power reference provided by the core mode reflection resonance that can be used to determine cladding mode perturbations with high accuracy. The AWG interrogator is a planar waveguide device fabricated on a silicon-on-insulator platform, having 50 channels with a 0.18 nm wavelength separation and a footprint of 8 mm × 8 mm. By overlaying two adjacent interference orders of the AWG we demonstrate simultaneous monitoring of two widely separated resonances in real time with high wavelength resolution. The standard deviation of the measured wavelength shifts is 1.2 pm, and it is limited by the resolution of the optical spectrum analyzer used for the interrogator calibration measurements

Genome-wide association analyses for lung function and chronic obstructive pulmonary disease identify new loci and potential druggable targets

Chronic obstructive pulmonary disease (COPD) is characterized by reduced lung function and is the third leading cause of death globally. Through genome-wide association discovery in 48,943 individuals, selected from extremes of the lung function distribution in UK Biobank, and follow-up in 95,375 individuals, we increased the yield of independent signals for lung function from 54 to 97. A genetic risk score was associated with COPD susceptibility (odds ratio per 1 s.d. of the risk score (∼6 alleles) (95% confidence interval) = 1.24 (1.20-1.27), P = 5.05 × 10‾⁴⁹), and we observed a 3.7-fold difference in COPD risk between individuals in the highest and lowest genetic risk score deciles in UK Biobank. The 97 signals show enrichment in genes for development, elastic fibers and epigenetic regulation pathways. We highlight targets for drugs and compounds in development for COPD and asthma (genes in the inositol phosphate metabolism pathway and CHRM3) and describe targets for potential drug repositioning from other clinical indications.This work was funded by a Medical Research Council (MRC) strategic award to M.D.T., I.P.H., D.S. and L.V.W. (MC_PC_12010). This research has been conducted using the UK Biobank Resource under application 648. This article presents independent research funded partially by the National Institute for Health Research (NIHR). The views expressed are those of the author(s) and not necessarily those of the NHS, the NIHR or the UK Department of Health. This research used the ALICE and SPECTRE High-Performance Computing Facilities at the University of Leicester. Additional acknowledgments and funding details can be found in the Supplementary Note

WSES guidelines for management of Clostridium difficile infection in surgical patients

In the last two decades there have been dramatic changes in the epidemiology of Clostridium difficile infection (CDI), with increases in incidence and severity of disease in many countries worldwide. The incidence of CDI has also increased in surgical patients. Optimization of management of C difficile, has therefore become increasingly urgent. An international multidisciplinary panel of experts prepared evidenced-based World Society of Emergency Surgery (WSES) guidelines for management of CDI in surgical patients.Peer reviewe

Oxidation of Silicon Promoted by Alkali Metals.

Oxidation of Silicon Promoted by Alkali Metals. K.F. FRENETTE, L. LEVESQUE, B. LAMONTAGNE, D. ROY. LP AM. Département-, de Physique. Université Laval. - The study of the Si/Si02 interface is of great fundamental and technological interest. High quality oxide films of less than 100 A in thickness will be soon required to reach higher integration in microelectonics devices. To avoid excessive diffusion of impurities and dopants in these thin interfaces, silicon oxidation must be performed at temperature below 1300 K. Alkali metals are known to increase oxidation rate and then might be used to circumvent thermal oxidation. The present work dwells on simultaneous adsorption of oxygen and alkali atoms (K or Cs) on Si (111)7x7. Simultaneous adsorption was performed at different O2 pressures. XPS was used to study the evolution of alkali oxides under X-rays and thermal treatment. It was observed that X-rays affect oxygen diffusion through the K-multilayers. The formation of silicon oxide was also investigated. Finally, SIMS depth profiles and RBS measurements were made in order to monitor traces of cesium left in the substrate after its desorption at moderate temperature

The next generation of switchable glass : the micro-blinds

Switchable glass or smart windows have been developed and discussed for decades. They have bright futures in applications such as vehicle, architecture, privacy and energy efficient glazing among others. The existing technologies seriously suffer from customer acceptance. The next generation of switchable glass based on micro-blinds might help the incursion of smart windows to the market, or at least to some niche markets. The micro-blinds are composed of invisible and electrostatically activated curling electrodes of 100 micrometers size. They can be deposited on flat glass by magnetron sputtering like regular low-E coatings, and then patterned by laser. They possess several advantages such as switching speed, UV durability, customized appearance and transmission, and do not employ costly ITO, relative to the current smart windows technologies: electrochromic, suspended particles and liquid crystals. Several groups have successfully developed curling electrodes for small area devices; the novelty of the proposed technology lies in the revolutionary and cost-effective processing scheme for large areas. This paper presents the status of our R&D project.NRC publication: Ye

Controlling the selfassembly of InAs/InP Quantum Dots

NRC publication: Ye