P. Piron
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15 records found
1
One of the most ambitious goals of modern astronomy is to uncover signs of extraterrestrial biological activity, primarily achieved through spectroscopic analysis of light emitted by exoplanets to identify specific atmospheric molecules. Most exoplanets are indirectly identified through techniques like transit or Doppler shift of the host star's flux. Long-term surveys have yielded statistical insights into the occurrence rates of different planet types based on factors such as radius/mass, orbital period, and the spectral type of the host star, initial estimates of terrestrial planets within the habitable zone have also emerged. However, the difficulty of detecting light from these exoplanets leaves much unknown about their nature, formation, and evolution. As the number of rocky exoplanets around nearby stars rises, questions about their atmospheric composition, evolutionary trajectory, and habitability increase. Direct measurement of an cxoplanct's atmospheric composition through its spectral signature in the infrared can provide answers. Measuring the infrared spectrum of these planets poses significant challenges due to the star/planet contrast and very small angular separation from their host stars. Previous research showed that space-based telescopes are mandatory, and unless large primary mirrors (>30m in diameter) can be sent into space, intcrfcrometric techniques become essential. Combining light from distant telescopes with interferometric techniques allows access to information at minimal angular separation, operating within the diffraction limit of individual telescopes. Successful demonstrations of on-ground nulling interferometry open a new era for such space-based missions. They are vital to sidestep and tackle these scientific questions. We recently initiated a new study with the European Space Agency to explore the design parameters and the performances related to an interferometric concept based on a single spacecraft and sparse multiple sub-apertures. Launch constraints are linked to the use of an Ariane 6 launch vehicle. Our parametric study covers a range of 1-4 m for the diameter of the telescope and a 10-60 m baseline. The most promising concept working in the infrared range (3-20μm) will be highlighted. This study is conducted by TUDelft in cooperation with KULeuven, CSL/ULiege, and Amos with the support of the European Space Agency.
Mctamatcrials and mctasurfaccs hold significant promise for space applications due to their compactness and lightweight characteristics. These devices use nanostructures embedded in their flat surfaces to manipulate the electromagnetic field for various purposes. Among their potential applications, metalenses stand out for their prospective role in the next generation of optical instruments deployed in space. Specifically, they offer considerable advantages for free space optical and quantum communications terminals. In intersatellite free space optical communication links, transmitter pointing errors degrade the performance of the link. Nevertheless, optimizing the shape of the transmitted beam through a metalens can improve the communication link performance. In this study, we delve into the application of metalenses for shaping laser beams in intersatellite optical communication scenarios. We present the preliminary design of the metalens and analyze its performance through numerical simulations, analyzing its feasibility and potential in space-based optical communications.
In this paper, we propose the design of a reconfigurable metasurface filter incorporating phase change materials (PCMs). This filter is part of a novel spaceborne spectrometer concept for atmospheric monitoring. The metasurface filter consists of PCMs pillars embedded in a diamond matrix. The combination of shape and material properties results in resonances that give rise to specific spectral filtering functions. The optical properties of PCMs, and hence the transmission function, change when stimulated with a pulsed laser. In combination with a compressive sensing (CS) algorithm, a limited number of measurements with a single metasurface results in precise reconstructions of the Earth's atmospheric spectrum.
Photonic structuration is an efficient way to improve light harvesting in multiple optoelectronic applications. In this study, photonically structured TiO2 is considered as a photoanode layer for perovskite solar cells to enhance light absorption through the excitation of quasi-guided modes within the photoactive perovskite material, while optimizing the charge collection in the photovoltaic assembly and therefore its global efficiency. Practically, polystyrene beads of various diameters are used as hard templating sacrificial agents for the design of inverse-opal TiO2 through spin-coating protocols. The positive impact of the porous photonic structuration in comparison with compact, unstructured photoactive layers is demonstrated. An optimum of light absorption is shown for hybrid TiO2-perovskite structures composed of ∼400 nm diameter TiO2 hollow spheres filled with CH3NH3PbI3, confirming recent numerical predictions. However, electronic-related countereffects are observed in consecutively assembled solar cells when pore dimensions exceed the estimated diffusion length of electrons in the infiltrated perovskite material. Upper conversion efficiency is obtained with solar cells composed of ∼220 nm diameter large TiO2 pores filled with CH3NH3PbI3.
Light management is an important area of photovoltaic research, but little is known about it in perovskite solar cells. The present work numerically studies the positive effect of structuring the photo-active layer of perovskite material. This structuration consists of a hybrid absorbing layer made of an uniform part and an opal-like part. A genetic algorithm approach allows us to determine the optimal combination among more than 1.4 x 109 potential combinations. The optimal combination provides an internal quantum efficiency of 98.1%, nearly 2% higher than for an equivalent unstructured photo-active layer. The robustness of the optimum against potential experimental deviations, as well as the angular dependency of the proposed structure, are examined in the present study.
Perovskite solar cells have shown a tremendous interest for photovoltaics since the past decade. However, little is known on the influence of light management using photonic crystals inside such structures. We present here numerical simulations showing the effect of photonic crystal structuring on the integrated quantum efficiency of perovskite solar cells. The photo-active layer is made of an opal-like perovskite structure (monolayer, bilayer or trilayer of perovskite spheres) built in a TiO2 matrix. Fano resonances are exploited in order to enhance the absorption, especially near the bandgap of perovskite material. The excitation of quasi-guided modes inside the absorbing spheres enhances the integrated quantum efficiency and the photonic enhancement factor. More specifically, a photonic enhancement factor as high as 6.4% is predicted in the case of spheres monolayer compared to an unstructured perovskite layer. The influences of sphere’s radius and incident angle on the absorbing properties are also estimated. Those numerical results can be applied to the nascent field of photonic structuring inside perovskite solar cells.