Sol-gel Barium Titanate Nanohole Array as a Nonlinear Metasurface and a Photonic Crystal

The quest of a nonlinear optical material that can be easily nanostructured over a large surface area is still ongoing. Here, we demonstrate a nanoimprinted nonlinear barium titanate 2D nanohole array that shows optical properties of a 2D photonic crystal and metasurface, depending on the direction of the optical axis. The challenge of nanostructuring the inert metal-oxide is resolved by direct soft nanoimprint lithography with sol-gel derived barium titanate enabling critical dimensions of 120 nm with aspect ratios of 5. The nanohole array exhibits a photonic bandgap in the infrared range when probed along the slab axis while lattice resonant states are observed in out-of-plane transmission configuration. The enhanced light-matter interaction from the resonant structure enables to increase the second-harmonic generation in the near-UV by a factor of 18 illustrating the potential in the flexible fabrication technique for barium titanate photonic devices

Nanoscale Near-Field Tomography of Surface States on (Bi(0.5)b(0.5))(2)Te-3

Three-dimensional topological insulators (TIs) have attracted tremendous interest for their possibility to host massless Dirac Fermions in topologically protected surface states (TSSs), which may enable new kinds of high-speed electronics. However, recent reports have outlined the importance of band bending effects within these materials, which results in an additional two-dimensional electron gas (2DEG) with finite mass at the surface. TI surfaces are also known to be highly inhomogeneous on the nanoscale, which is masked in conventional far-field studies. Here, we use near-field microscopy in the mid infrared spectral range to probe the local surface properties of customtailored (Bi0.5Sb0.5)(2)Te-3 structures with nanometer precision in all three spatial dimensions. Applying nanotomography and nanospectroscopy, we reveal a few-nanometer-thick layer of high surface conductivity and retrieve its local dielectric function without assuming any model for the spectral response. This allows us to directly distinguish between different types of surface states. An intersubband transition within the massive 2DEG formed by quantum confinement in the bent conduction band manifests itself as a sharp, surface-bound, Lorentzian-shaped resonance. An additional broadband background in the imaginary part of the dielectric function may be caused by the TSS. Tracing the intersubband resonance with nanometer spatial precision, we observe changes of its frequency, likely originating from local variations of doping or/and the mixing ratio between Bi and Sb. Our results highlight the importance of studying the surfaces of these novel materials on the nanoscale to directly access the local optical and electronic properties via the dielectric function

Peri-operative red blood cell transfusion in neonates and infants: NEonate and Children audiT of Anaesthesia pRactice IN Europe: A prospective European multicentre observational study

BACKGROUND: Little is known about current clinical practice concerning peri-operative red blood cell transfusion in neonates and small infants. Guidelines suggest transfusions based on haemoglobin thresholds ranging from 8.5 to 12 g dl-1, distinguishing between children from birth to day 7 (week 1), from day 8 to day 14 (week 2) or from day 15 (≥week 3) onwards. OBJECTIVE: To observe peri-operative red blood cell transfusion practice according to guidelines in relation to patient outcome. DESIGN: A multicentre observational study. SETTING: The NEonate-Children sTudy of Anaesthesia pRactice IN Europe (NECTARINE) trial recruited patients up to 60 weeks' postmenstrual age undergoing anaesthesia for surgical or diagnostic procedures from 165 centres in 31 European countries between March 2016 and January 2017. PATIENTS: The data included 5609 patients undergoing 6542 procedures. Inclusion criteria was a peri-operative red blood cell transfusion. MAIN OUTCOME MEASURES: The primary endpoint was the haemoglobin level triggering a transfusion for neonates in week 1, week 2 and week 3. Secondary endpoints were transfusion volumes, 'delta haemoglobin' (preprocedure - transfusion-triggering) and 30-day and 90-day morbidity and mortality. RESULTS: Peri-operative red blood cell transfusions were recorded during 447 procedures (6.9%). The median haemoglobin levels triggering a transfusion were 9.6 [IQR 8.7 to 10.9] g dl-1 for neonates in week 1, 9.6 [7.7 to 10.4] g dl-1 in week 2 and 8.0 [7.3 to 9.0] g dl-1 in week 3. The median transfusion volume was 17.1 [11.1 to 26.4] ml kg-1 with a median delta haemoglobin of 1.8 [0.0 to 3.6] g dl-1. Thirty-day morbidity was 47.8% with an overall mortality of 11.3%. CONCLUSIONS: Results indicate lower transfusion-triggering haemoglobin thresholds in clinical practice than suggested by current guidelines. The high morbidity and mortality of this NECTARINE sub-cohort calls for investigative action and evidence-based guidelines addressing peri-operative red blood cell transfusions strategies. TRIAL REGISTRATION: ClinicalTrials.gov, identifier: NCT02350348

Lithium niobate on insulator from classical to quantum photonic devices

Integrated photonics is becoming more and more multifunctional thanks to the recent availability of an established material, lithium niobate, as thin films of less than 1 micron thickness. Overcoming key fabrication challenges has put this platform on its way to achieve scalability. Here, we show the performances of integrated and free space devices such as electrooptic modulators and active metasurfaces. Finally, we mention possible roles of lithium niobate on insulator in quantum photonics

Optically reconfigurable ferroelectric metasurfaces

We use ferroelectric-plasmonic metasurfaces to demonstrate volatile and non-volatile optical switching of near-infrared light. Plasmonic metasurfaces on lithium niobate enable high-contrast optical switching with ratios up to 2.37:1 (3.7 dB) due to photogalvanic and photorefractive effects, therefore rendering a compact platform for photonic computing

Photonic assemblies of randomly oriented nanocrystals for engineered nonlinear and electro-optic effects

Nonlinear crystals that have a noncentrosymmetric crystalline structure, such as lithium niobate (LiNbO3) and barium titanate (BaTiO3) exhibit nonzero second-order tensor susceptibilities (χ(2)) and linear electro-optic coefficients (rij). The constraints associated with top-down nanofabrication methods have led to bottom up approaches to harness the strong nonlinearities and electro-optical properties. Here, we present an overview of photonic assemblies made of randomly oriented noncentrosymmetric nanocrystals via bottom-up fabrication methods. In this configuration, nanocrystals can form objects with tunable dimensions, increased complexity, and a great span of symmetry level, ranging from thin layers to spheres. At the same time, according to their shape, photonic assemblies may support optical modes, that is, Mie or guided, which can tailor linear optical properties and enhance nonlinear and electro-optic responses. As a result, assemblies of noncentrosymmetric nanocrystals can form a disruptive platform to realize photonic integrated devices free of etching process and over large surface areas. Last, we foresee potential applications of noncentrosymmetric nanocrystals in various fields of nano-optics and sensing.ISSN:2330-402

Towards active electro-optic lithium niobate metasurfaces

We present the design and fabrication advances on active lithium niobate metasurfaces. We determine by numerical calculations a metasurface design with electro-magnetic resonances in the visible and near-infrared, by taking into account the constraints for fabrication on thin films of lithium niobate. We suggest that the optical properties of the metasurface can be switched using the electro-optical properties of lithium niobate

Towards active electro-optic lithium niobate metasurfaces

We present the design and fabrication advances on active lithium niobate metasurfaces. We determine by numerical calculations a metasurface design with electro-magnetic resonances in the visible and near-infrared, by taking into account the constraints for fabrication on thin films of lithium niobate. We suggest that the optical properties of the metasurface can be switched using the electro-optical properties of lithium niobate

Qualidade do preparado para bebida obtido a partir de polpa de juçara submetida ao tratamento térmico

Resumo As palmeiras do gênero Euterpe têm notável importância econômica e cultural, sendo que o seu valor se deve em parte às inúmeras formas de utilização, dentre as quais se destacam o consumo da bebida proveniente dos frutos e do palmito. Este estudo tem por objetivo avaliar a eficiência do tratamento térmico prévio nos frutos de juçara (E. edulis Martius) utilizados para o processamento da polpa de juçara, visando à obtenção de um preparado para bebida, com qualidade nutricional e segura para o consumo. Os frutos foram selecionados, higienizados com hipoclorito de sódio (200 ppm/15 min) e submetidos a três tratamentos térmicos (100 °C/5 s, 80 °C/10 s e 80 °C/30 s). Depois do tratamento foram realizados o despolpamento e o congelamento, seguidos de armazenamento. Os resultados das análises microbiológicas demonstram que é necessário o tratamento térmico a 100 °C/5 s para atender aos parâmetros microbiológicos exigidos pela legislação para polpa de açaí, além de preservar o conteúdo de antocianinas totais e atividade antioxidante. Desta forma, o tratamento térmico dos frutos apresenta-se como um método viável e de baixo custo, contribuindo para a produção da bebida com qualidade e segurança