RESUMO
The holographic recording of gratings that have very large diffraction angles and/or slants is challenging because recording requires beam angles that are not possible without the use of prisms. However, by using a recording wavelength that is different from (usually shorter than) the intended operating wavelength, it is possible to record with less challenging beam angles. In this paper, a recently developed model that allows systematic investigation of the potential and limits of this wavelength-shift recording technique is extended to include a reflection format. Transmission and reflection recording options are compared systematically for the first time, and it is shown that in reflection recording, some couplers can be recorded more easily when the recording wavelength is longer than the operating wavelength. This opens up new design options for previously challenging regions of the spectrum. Experimental validation of the reflection version of the model is carried out by holographic recording in reflection mode at 532â nm in Bayfol HX 200 photopolymer, demonstrating the coupling of blue light.
RESUMO
Quantum dots consisting of an axial Zn0.97Mg0.03Te insertion inside a large-bandgap Zn0.9Mg0.1Te nanowire core are fabricated in a molecular-beam epitaxy system by employing the vapor-liquid-solid growth mechanism. In addition, this structure is coated with a thin ZnSe radial shell that forms a type-II interface with the dot semiconductor. The resulting radial electron-hole separation is evidenced by several distinct effects that occur in the presence of the ZnSe shell, including the optical emission redshift of about 250 meV, a significant decrease in emission intensity, an increase in the excitonic lifetime by one order of magnitude, and an increase in the biexciton binding energy. The type-II nanowire quantum dots where electrons and holes are radially separated constitute a promising platform for potential applications in the field of quantum information technology.
RESUMO
Thin films with nanometer thicknesses in the range 100-400 nm are prepared from double hydrophilic copolymers of complex branched structures containing poly(N,N-dimethyl acrylamide) and poly(ethylene oxide) blocks and are used as humidity sensitive media. Instead of using glass or opaque wafer for substrates, polymer thin films are deposited on Bragg stacks and thin (30 nm) sputtered Au-Pd films thus bringing color for the colorless polymer/glass system and enabling transmittance measurements for humidity sensing. All samples are characterized by transmittance measurements at different humidity levels in the range from 5% to 90% relative humidity. Additionally, the humidity induced color change is studied by calculating the color coordinates at different relative humidity using measured spectra of transmittance or reflectance. A special attention is paid to the selection of wavelength(s) of measurements and discriminating between different humidity levels when sensing is performed by measuring transmittance at fixed wavelengths. The influence of initial film thickness, sensor architecture, and measuring configuration on sensitivity is studied. The potential and advantages of using top covered Bragg stacks and polymer/metal thin film structures as humidity sensors with simple optical read-outs are demonstrated and discussed.
RESUMO
Advanced therapy medicinal products (ATMPs), which include gene therapy medicinal products, somatic cell therapy medicinal products and tissue-engineered products, are at the cutting edge of innovation and offer a major hope for various diseases for which there are limited or no therapeutic options. They have therefore been subject to considerable interest and debate. Following the European regulation on ATMPs, a consolidated regulatory framework for these innovative medicines has recently been established. Central to this framework is the Committee for Advanced Therapies (CAT) at the European Medicines Agency (EMA), comprising a multidisciplinary scientific expert committee, representing all EU member states and European Free Trade Association countries, as well as patient and medical associations. In this article, the CAT discusses some of the typical issues raised by developers of ATMPs, and highlights the opportunities for such companies and research groups to approach the EMA and the CAT as a regulatory advisor during development.
