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Chalcogenide semiconductors offer a unique compositionally-controllable material base for reconfigurable metamaterial applications. They present high and low-index dielectric, low-epsilon and plasmonic properties across UV to IR wavelengths, in addition to fast, non-volatile, electrically/optically induced phase-change capability between states with markedly different properties. We present our recent advances in their application to non-volatile reconfiguration in metamaterials, including: switchable ‘colors’ through reversible dielectric-plasmonic transitions; the first reconfigurable UV/HEV dielectric metamaterials, wherein the chalcogenide is hybridized with a high-index dielectric supporting the resonant mode; and the integration of such materials on the tip and side of optical fibres for dynamic dispersion control.

We report recent breakthroughs in nanomechanical metamaterials including (i) a giant acousto-optical effect, (ii) on/off switching of metasurfaces, (iii) selective electrical and optical actuation of metamaterials elements with sub-wavelength spatial resolution, (iv) phase-change metasurfaces with bistable optical and mechanical properties and (v) metamaterials tuned by electrostriction.

We utilize compositionally controlled low refractive index (n

This paper evaluates and compares two randomized interventions in Tonga, one targeting the home environment of children up to age 5 and one targeting the school environment for first and second grade students. The first intervention supports communities to set up and run playgroups that aim to improve caregiver-child interaction at home and ultimately improve children's readiness for school. Among children of mothers without high school education, being in a treatment community positively affects the school readiness literacy domains and overall score by 0.19 and 0.2 standard deviation, respectively, for girls and the literacy domains for boys by 0.17 standard deviation. The second intervention provides teachers with training, materials, and coaching to improve reading instruction practices and students’ reading ability. It increased average early grade reading scores by approximately 0.18 standard deviation per year of exposure. Two cohorts of children were potentially exposed to both interventions, providing an opportunity to compare, for the same population of children, the effects of an early childhood intervention with a school-based intervention using a common measure of learning achievement. The school readiness intervention is found to have positive effects on early grade reading scores only among children in the reading intervention’s control group; effect sizes of approximately 0.29 standard deviation were found at the end of second grade for children exposed to one year of the school readiness intervention and at the end of first grade for girls exposed to two years of the intervention.

Fascinating opportunities are offered by metamaterial nanostructures fabricated from materials with highly-dispersive optical properties, between those of ideally plasmonic (e.g. noble metal) and transparent dielectric media. Chalcogenide semiconductors are excellent examples – their optical properties can be engineered by controlling alloy composition and phase state to provide high and low refractive indices, plasmonic, dielectric and epsilon-near-zero characteristics at near-ultraviolet to near-infrared wavelengths. We report here on the application of chalcogenide materials to photonic metasurfaces.

Automation will be a boon or a catastrophe depending on whom you listen to. This paper proposes an overlapping-generations model with endogenous school choice in which the quality of a country's education system determines how well skill supply can respond to increased demand from automation and subsequently whether automation will be beneficial or detrimental. In this sense, education quality in the model offers a bridge between the optimistic and pessimistic perspectives on automation. In testing the model's assumptions, the paper finds evidence that educational attainment, cognitive skills, and select noncognitive skills are associated with avoiding automation-prone occupations. Consistent with the model's predictions, census data indicate that countries have historically relied most on these types of occupations at middle-income status. The model and empirical findings suggest that it is middle-income countries that are most vulnerable to automation if their education systems are unable to affect cognitive and noncognitive skills sufficiently. As a result, automation may herald a much different growth model for developing countries: one in which developing these skills is central.

Digital imaging has been steadily improving over the past decades and we are moving towards a wide use of multi- and hyperspectral cameras. A key component of such imaging systems are color filter arrays, which define the spectrum of light detected by each camera pixel. Hence, it is essential to develop a variable, robust and scalable way for controlling the transmission of light. Nanostructured surfaces, also known as metasurfaces, offer a promising solution as their transmission spectra can be controlled by shaping the wavelength-dependent scattering properties of their constituting elements. Here we present, metasurfaces based on silicon nanodisks, which provide filter functions with amplitudes reaching 70-90% of transmission, and well suitable for RGB and CMY color filter arrays, the initial stage towards the further development of hyperspectral filters. We suggest and discuss possible ways to expand the color gamut and improve the color values of such optical filters.

Early grade literacy skills are crucial for children's future education and ultimately their contribution to human capital formation and economic development. A significant challenge in development is identifying low-cost interventions to improve early literacy skills in contexts characterized by varying teacher ability and severe budget constraints. This paper evaluates the impact of Papua New Guinea's randomized Reading Booster Programme, which was conducted in Madang and Western Highlands Province in 2013 and 2014, respectively. The program provided teachers with training on a highly structured teaching method that they could apply one hour per day within the teaching time allocated to reading. Using the randomized assignment of schools into the program, the paper shows that it had a substantial impact on the reading skills targeted by the program for third grade students, ranging from 0.6 to 0.7 standard deviation. Large effects on other reading skills were found for girls but not boys. The program's cost per student was approximately US$60.

In this oral presentation, we demonstrate using two coherent light beams to measure the thickness of absorptive thin films and selectively excite plasmonic resonances at the surface of transparent bulk substrates.