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Material nanostructuring and optical phenomena on a nanoscale such as plasmonic effects and light scattering have been widely studied for improving the solar-to-hydrogen efficiency of photoelectrochemical (PEC) water-splitting electrodes. In this work, we report a method for analyzing the contributions of optical effects from nanostructures for enhancing the PEC performances. Electromagnetic simulations are performed for the precise calculation of generated power density in a semiconductor material. In addition, the transport and transfer of photogenerated charges to the electrolyte are modeled by using the conservation of minority carriers. The surface loss parameter, diffusion length, and doping density of the semiconductor material are determined by fitting the model to an incident photon to current efficiency (IPCE) curve experimentally measured on the bare reference photoelectrode. These parameters are then used to compute the IPCE spectra of the photoelectrode for which an optical enhancement strategy is used, such as nanostructuring or plasmonics. The method is validated using published experimental data. The calculated IPCE enhancement ratio originating from optical effects is in quantitative agreement with experimental observations for both periodic and random optical structures. The model can be used to study in detail the key enhancement mechanisms for the IPCE from optical nanostructures and, in particular, discriminate between optical and nonoptical (e.g., catalytic) enhancement.

Bioelectronic and neuroprosthetic interfaces rely on implanted microelectrode arrays (MEAs) to interact with the human body. Printing techniques, such as inkjet and screen printing, are attractive methods for the manufacturing of MEAs because they allow flexible, room‐temperature, scalable, and cost‐effective fabrication processes. Herein, the fabrication of all‐printed electrocorticography arrays made by inkjet printing of platinum and screen printing of polyimide is shown. Next, mechanical and electrochemical characterizations are performed. As a proof of concept, in vivo visually evoked cortical potentials are recorded in rabbits upon flash stimulation. Lastly, it is shown that the all‐printed electrocorticography arrays are not cytotoxic. Altogether, the results enable the use of printed MEAs for neurological applications.

The optoelectronic properties of image sensors, among which are the photosensitivity and resolution, are key to the quality factors for imaging as well as spectrometry in Earth observation and scientific space exploration missions. Microlens arrays (MLAs) further improve state-of-the-art CMOS image sensors (CIS) by redirecting more photons into the photosensitive surface/volume of each pixel. This paper reports the design, deposition, optical characterization, and reliability assessment of such an MLA made from a UV-curable hybrid polymer and replicated on a packaged back-illuminated CIS having a pixel pitch of 15.5 µm. We find that such MLAs are highly stable to temperature variations, exposure to humidity, mechanical shocks and vibrations, as well as irradiation by gamma rays, while improving the parasitic light sensitivity by a factor of 1.8. Such MLAs can be applied on a large variety of image sensors, back-illuminated but mostly front-illuminated, with pixel pitches ranging from a few to several hundreds of micrometers, making them suitable for most specifications of the space industry.

In next generation space instrumentation for Earth and Universe Observation, new instrument concepts include often non planar gratings. Their realization is complex and costly. We propose a new technology for designing and realizing convex blazed gratings for high throughput spectrographs. For this purpose, our requirements are driven by a Digital-Micromirror-Device-based (DMD) MOS instrument to be mounted on the Telescopio Nazionale Galileo (TNG) and called BATMAN. The two-arm instrument is providing in parallel imaging and spectroscopic capabilities. The objects/field selector is a 2048 x 1080 micromirrors DMD, placed at the focal plane of the telescope; it is used as a programmable multi-slit mask at the entrance of the spectrograph. The compact Offner-type spectrograph design contains a low density convex grating to disperse light. For optimization of the spectrograph efficiency, this convex grating must be blazed. A blazed reflective grating has been designed with a period of 3300 nm and a blaze angle of 5.04°, and fabricated into convex substrates with 225 mm radius of curvature and a footprint diameter of 63.5 mm. The blaze is optimized for the center wavelength of 580 nm within the spectral range of 400 -800 nm. Convex blazed gratings have been fabricated and coated with protected silver, with a final 5.7° blaze angle over the whole surface. Efficiency close to 90% on the 1st diffraction order at 700nm has been obtained. This new type of non-planar reflective gratings will be the key component for future high throughput spectrographs in space missions.