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Providing antireflection in the visible spectrum is useful for a number of applications. Solar cells, LCD screens, optical lenses and stealth surfaces are a few examples of applications that can benefit from antireflection. In this work, maximizing the performance of a biomimetic motheye metamaterial antireflection layer via optimization of its design parameters was investigated. Additionally, case studies of designing optimized antireflection solutions were carried out for some of the most demanding applications such in solar cells and stealth coatings. More specifically, simulations of the moth-eye design parameters for feature period, height, density factor, shape and topology were carried out. For feature height, it was found that for a height larger than 400nm, the gains in providing antireflection for the visible spectrum are low, so it is not necessary to create features taller than this to achieve a good antireflection performance. For feature density factor an almost linear monotonic relationship was observed, so for this design parameter, maximization is necessary. For the feature period parameter, it was found that a simple rule could not be extracted and thus to optimize performance, a tailoring of the period for each application has to be done whilst taking into account the incident spectrum. An optimization of the feature period was carried out for monocrystalline silicon solar cells and the AM 1.5 solar spectrum and it was found that for this spectrum, the optimum period is 397nm. Feature topology was not found to provide a significant advantage to the antireflection behaviour of the metamaterial layer in terms of power, however it does provide a more diffuse scattering of the backscattering diffraction order which emanates from the structure at high angles of incidence, an attribute which is very useful for stealth applications. To verify simulation results, fabrication of moth-eye antireflection structures were carried out via nano-imprint, electron-beam and nanosphere lithography. The nanosphere lithography technique presented was optimized specifically for the samples required in this thesis. Complete monolayer coverage of large areas (2x2cm2) was accomplished and thus complex biomimetic feature topologies could be readily investigated. Optical experiments measuring specular reflectance and the backscattered diffraction orders were carried out both with readily available and custom built optical setups. The simulation trends were all verified successfully and a summary of suggested design parameters for a range of different applications has been suggested.

Dans le cadre de ses recherches menées sur la fusion par confinement inertiel, le Commissariat à l’énergie atomique et aux énergies alternatives met en œuvre un spectromètre X large bande étalonné en absolu et résolu en temps, appelé Diagnostic de Mesure du rayonnement X. Ce diagnostic, composé de 20 voies de mesure, permet de mesurer l’émissivité spectrale d’un plasma créé par laser entre 50 eV et 20 keV. Nous avons développé des voies de mesure complémentaires aux voies existantes, afin d’obtenir une redondance et une amélioration de la précision de la mesure. Le principe de ces nouvelles voies de mesure repose sur un concept original permettant d’obtenir des fonctions de transfert spectrales bornées et constantes. Deux voies ont été développées pour les gammes spectrales 2 – 4 keV et 4 – 6 keV, utilisant des miroirs multicouches apériodiques réalisés au Laboratoire Charles Fabry en Cr/Sc et Ni/W/SiC/W, respectivement. Ces miroirs ont ensuite été caractérisés sur synchrotrons puis intégrés dans le spectromètre. Les nouvelles voies ont été utilisées durant des campagnes d’expériences laser-Plasma sur l’installation laser OMEGA à Rochester (États-Unis). Elles ont permis de déterminer la puissance rayonnée directement avec une seule voie de mesure par bande spectrale et avec une meilleure précision qu’avec celles utilisées habituellement. Les résultats, en bon accord avec les voies de mesure classiques, permettent de valider l’utilisation des miroirs multicouches apériodiques pour la spectrométrie X large bande. / Within the framework of the research on inertial confinement fusion, the “Commissariat à l’énergie atomique et aux énergies alternatives” has studied and implemented an absolute calibrated time-Resolved broadband soft x-Ray spectrometer, called “Diagnostic de Mesure du rayonnement X”. This diagnostic, composed of 20 measurement channels, measures the emitted radiant power from a laser created plasma in the range from 50 eV to 20 keV. We have developed additional measurement channels to obtain redundancy and an improvement in measurement accuracy. The principle of these new channels is based on an original concept to obtain spectral bounded flat-Responses. Two channels have been developed for the 2 – 4 keV and 4 – 6 keV spectral ranges, using aperiodic multilayer mirrors made at the “Laboratoire Charles Fabry” with Cr/Sc and Ni/W/SiC/W layers respectively. These mirrors were characterized at synchrotron radiation facilities and integrated into the spectrometer. The two new channels were used during laser-Plasma experimental campaigns at the OMEGA laser facility in Rochester (USA). This allowed us to determine directly the radiant power with only one measurement within a certain spectral band, and with a better precision when compared with using standard channels. The results, in good agreement with the standard measurement channels, allowed us to validate the use of aperiodic multilayer mirrors for X-Ray broadband spectrometry.