Silicon Mie Resonators for Highly Directional Light Emission from monolayer MoS2

Controlling light emission from quantum emitters has important applications ranging from solid-state lighting and displays to nanoscale single-photon sources. Optical antennas have emerged as promising tools to achieve such control right at the location of the emitter, without the need for bulky, external optics. Semiconductor nanoantennas are particularly practical for this purpose because simple geometries, such as wires and spheres, support multiple, degenerate optical resonances. Here, we start by modifying Mie scattering theory developed for plane wave illumination to describe scattering of dipole emission. We then use this theory and experiments to demonstrate several pathways to achieve control over the directionality, polarization state, and spectral emission that rely on a coherent coupling of an emitting dipole to optical resonances of a Si nanowire. A forward-to-backward ratio of 20 was demonstrated for the electric dipole emission at 680 nm from a monolayer MoS2 by optically coupling it to a Si nanowire

Enhanced nonlinear optical response from individual silicon nanowires

cited By 10International audienceWe report about the experimental observation and characterization of nonlinear optical properties of individual silicon nanowires of different dimensions. Our results show that the nonlinear light has different components, with one of them corresponding to the second-harmonic generation (SHG). The SHG strongly depends on the polarization of the optical excitation and nanowire diameter, and gives access to the local electromagnetic field intensity distribution. Furthermore, we show that the second harmonic, when observed, is enhanced compared to bulk silicon and is sensitive to optical resonances supported by the nanowires. This offers different perspectives on the definition of silicon-based nonlinear photonic devices

Pushing the limits of optical information storage using deep learning

11 pages, 5 figures + supporting informations of 7 pages, 10 figuresDiffraction drastically limits the bit density in optical data storage. To increase the storage density, alternative strategies involving supplementary recording dimensions and robust read-out schemes must be explored. Here, we propose to encode multiple bits of information in the geometry of subwavelength dielectric nanostructures. A crucial problem in high-density information storage concepts is the robustness of the information readout with respect to fabrication errors and experimental noise. Using a machine-learning based approach in which the scattering spectra are analyzed by an artificial neural network, we achieve quasi error free read-out of 4-bit sequences, encoded in top-down fabricated silicon nanostructures. The read-out speed can further be increased exploiting the RGB values of microscopy images, and the information density could be increased beyond current state of the art. Our work paves the way towards high-density optical information storage using planar silicon nanostructures, compatible with mass-production ready CMOS technology

Impact of an Organizational Intervention Designed to Improve Snack and Beverage Quality in YMCA After-School Programs

Objectives. We evaluated the quality of snacks and beverages served at YMCA after-school programs before and after the programs' participation in a YMCA Learning Collaborative

Evolutionary multi-objective optimization of colour pixels based on dielectric nano-antennas

10 pages, 6 figures + 10 pages of supporting informations including 17 additional figuresInternational audienceThe rational design of photonic nanostructures consists of anticipating their optical response from systematic variations of simple models. This strategy, however, has limited success when multiple objectives are simultaneously targeted, because it requires demanding computational schemes. To this end, evolutionary algorithms can drive the morphology of a nano-object towards an optimum through several cycles of selection, mutation and cross-over, mimicking the process of natural selection. Here, we present a numerical technique that can allow the design of photonic nanostructures with optical properties optimized along several arbitrary objectives. In particular, we combine evolutionary multi-objective algorithms with frequency-domain electrodynamical simulations to optimize the design of colour pixels based on silicon nanostructures that resonate at two user-defined, polarization-dependent wavelengths. The scattering spectra of optimized pixels fabricated by electron-beam lithography show excellent agreement with the targeted objectives. The method is self-adaptive to arbitrary constraints and therefore particularly apt for the design of complex structures within predefined technological limits

The prevalence of eating behaviors among Canadian youth using cross-sectional school-based surveys

BACKGROUND: Obesity is a growing public health concern in Canada. Excess weight is particularly a concern among youth given that obesity in youth predicts obesity in adulthood. Eating behaviors, both inside and outside the home have been associated with increased risk of obesity; however, there is little data among Canadian youth to monitor trends. METHODS: The School Health Action, Planning and Evaluation Surveys (SHAPES) were administered in schools. Our study examined 20, 923 students (grades 5-12) from four regions in Canada. The regions were Hamilton and Thunder Bay (both in Ontario), the Province of Prince Edward Island, and the Province of Quebec. RESULTS: Consuming breakfast daily was reported by 70% of grade 5-8 students, and 51% of grade 9-12’s. Among students in grade 9-12, 52% reported eating with family members daily, compared with 68% in grade 5-8. Just over half of students in grade 5-8, and 70% in grade 9-12 reported eating at a fast-food place once a week or more. Among grade 5-8 students 68% reported eating in front of the television at least once per week, compared to 76% in grade 9-12. Obese students were more likely to watch TV while eating, and less likely to eat with a family member and eat breakfast. CONCLUSIONS: The findings suggest that only a modest proportion of youth report dietary patterns that have previously been associated with healthy eating and reduced risk of obesity. Later adolescence may be a critical time for intervention in health-related behaviors