Monitoring the deflection of a membrane using direct UV written planar Bragg gratings

A thin (~100 µm thick) silica-on-silicon square membrane (10 mm x 10 mm) has been fabricated and its deflection monitored through a 100 Bragg grating array defined within the membrane

Terahertz bandwidth photonic Hilbert transformers and implementations in ultra wideband single-sideband filters

Planar Bragg grating based photonic Hilbert transformers (PHTs) with THz bandwidths are proposed and practically demonstrated. An X-coupler, PHT, and a flat-top reflector are incorporated, demonstrating 2THz all-optical single-sideband filters. Devices are fabricated via a direct UV grating writing technique on a silica-on-silicon platform

Facet machining of silica waveguides with nanoscale roughness without polishing or lapping

To achieve low-loss free space coupling for integrated optics, device facets need to be smooth, free of chips and flat. The typical route for accomplishing these requirements is by traditional lapping and polishing. We report that high quality optical quality facets with a Sa = 4.9 nm can be machined using a simple dicing technique. In order to directly measure the scatter loss a device with a series of Bragg gratings is used to characterise the average interface loss per facet

Integrated temperature compensated Bragg grating refractometer

UV written planar Bragg grating sensors have been shown to form effective refractometers. Here we show that by using the birefringence of an integrated waveguide a temperature insensitive Bragg grating refractometer can be realised

Planarised optical fiber composite using flame hydrolysis deposition demonstrating an integrated FBG anemometer

This paper reports for the first time a planarised optical fiber composite formed using Flame Hydrolysis Deposition (FHD). As a way of format demonstration a Micro-Opto-Electro-Mechanical (MOEMS) hot wire anemometer is formed using micro-fabrication processing. The planarised device is rigidly secured to a silicon wafer using optical quality doped silica that has been deposited using flame hydrolysis and consolidated at high temperature. The resulting structure can withstand temperatures exceeding 580K and is sensitive enough to resolve free and forced convection interactions at low fluid velocity

Ultra-wide detuning planar Bragg grating fabrication technique based on direct UV grating writing with electro-optic phase modulation

A direct UV grating writing technique based on phase-controlled interferometry is proposed and demonstrated in a silica-on-silicon platform, with a wider wavelength detuning range than any previously reported UV writing technology. Electro-optic phase modulation of one beam in the interferometer is used to manipulate the fringe pattern and thus control the parameters of the Bragg gratings and waveguides. Various grating structures with refractive index apodization, phase shifts and index contrasts of up to 0.8×10-3 have been demonstrated. The method offers significant time/energy efficiency as well as simplified optical layout and fabrication process. We have shown Bragg gratings can be made from 1200 nm to 1900 nm exclusively under software control and the maximum peak grating reflectivity only decreases by 3dB over a 250 nm (~32THz) bandwidth

Simple planar Bragg grating devices for photonic Hilbert transform

Hilbert transformers are important devices widely used in information processing and signal analysis in the electronic domain. For example, for spectral efficiency improvement, it is used to construct the analytic signal for single sideband (SSB) modulation from a real signal. Photonic Hilbert transformers (PHTs) are proposed for a similar range of applications and would allow the direct processing of optical signals at bandwidths far beyond current electronic technologies

Effect of a short message service intervention on excessive gestational weight gain in a low-income population: a randomized controlled trial

Objectives: The objective of this trial was to investigate the effect of educational short message service (SMS), or text messages, on excessive gestational weight gain (GWG) in a low-income, predominantly overweight/obese population. Methods: Participants (n = 83) were mostly overweight/obese women recruited at Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) clinics on the island of O’ahu, Hawai’i at 15–20 weeks gestational age. The intervention group received SMS on nutrition and physical activity during pregnancy designed to help them meet Institute of Medicine (IOM) guidelines for GWG and American College of Obstetricians and Gynecologists guidelines for exercise, respectively. The control group received SMS about general health topics during pregnancy, excluding nutrition and physical activity. Both groups received one text message per week for eighteen weeks. GWG was defined as the difference between the last self-reported weight taken before delivery and participants’ self-reported weight before pregnancy. Differences between study groups were examined using t-tests and Chi-square tests. Linear regression models were used to examine association of GWG with study group and other factors. Results: GWG was similar (p = 0.58) in the control group (14.1 ± 11.4 kg) and the intervention group (15.5 ± 11.6 kg). The percentage of participants exceeding IOM guidelines for GWG was similar (p = 0.51) in the control group (50.0%, n = 17) and the intervention group (60.5%, n = 23). Conclusions: GWG was not significantly different between intervention and control groups. Trials that begin earlier in pregnancy or before pregnancy with longer intervention durations and varying message frequency as well as personalized or interactive messages may be needed to produce significant improvements

Meningococcal core and accessory phasomes vary by clonal complex

Neisseria meningitidis is a Gram-negative human commensal pathogen, with extensive phenotypic plasticity afforded by phase-variable (PV) gene expression. Phase variation is a stochastic switch in gene expression from an ON to an OFF state, mediated by localized hypermutation of simple sequence repeats (SSRs). Circulating N. meningitidis clones vary in propensity to cause disease, with some clonal complexes (ccs) classified as hypervirulent and others as carriage-associated. We examined the PV gene repertoires, or phasome, of these lineages in order to determine whether phase variation contributes to disease propensity. We analysed 3328 genomes representative of nine circulating meningococcal ccs with PhasomeIt, a tool that identifies PV genes by the presence of SSRs and homologous gene clusters. The presence, absence and functions of all identified PV gene clusters were confirmed by annotation or blast searches within the Neisseria PubMLST database. While no significant differences were detected in the number of PV genes or the core, conserved phasome content between hypervirulent and carriage lineages, individual ccs exhibited major variations in PV gene numbers. Phylogenetic clusters produced by phasome or core genome analyses were similar, indicating co-evolution of PV genes with the core genome. While conservation of PV clusters is high, with 76 % present in all meningococcal isolates, maintenance of an SSR is variable, ranging from conserved in all isolates to present only in a single cc, indicating differing evolutionary trajectories for each lineage. Diverse functional groups of PV genes were present across the meningococcal lineages; however, the majority directly or indirectly influence bacterial surface antigens and could impact on future vaccine development. Finally, we observe that meningococci have open pan phasomes, indicating ongoing evolution of PV gene content and a significant potential for adaptive changes in this clinically relevant genus

Phase modulation technique for high modulation wide band planar Bragg grating fabrication

Direct UV Grating Writing (DGW) is effective route for fabricating high quality Bragg gratings, similar to fiber Bragg gratings, in a planar geometry. We will present a phase modulation controlled DGW method using an Electro-Optical Modulator for planar Bragg grating fabrication that offers improved performance. This new approach not only provides much greater modulation depths for stronger and shorter Bragg gratings but also offers greater fabrication speed and a higher fidelity of control than previous amplitude modulation methods