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International audience; Variable filters are key components for compact spectral imagers. In this paper, we present a method for the fabrication of linearly variable filters based on Bühler HELIOS machine (plasma assisted reactive magnetron sputtering). These filters are obtained by producing a variation of the thickness of all the layers of the coating, using adapted masks placed in between the sputtering targets for the low and high refractive index materials and the substrates. Variable band pass filter from 550 nm up to 1000 nm is demonstrated.

Protection from solar radiation is commonly achieved through the use of UV organic absorbers, such as benzophenones or benzotriazoles, often combined with inorganic materials such as TiO2 or ZnO2, supplied in the form of submicron size particles.[1] These compounds are usually dispersed in lotions or films,[2] the latter being typically made of polymers or inorganic glasses.[3,4] Lotions are mainly employed for skin protection, whilst solid state dispersions and coatings are typically used to improve the durability of plastics, whose mechanical stability is compromised by chain scissions, chain crosslinks and chain oxidations induced by UV absorption. Accordingly, these types of films are used in the fabrication of food packaging, to preserve containers and their edible contents from UV-induced damage, and also of glasses, to impede that UV rays reach, and harm, the eye. Solid state approaches to UV shielding might also find relevant applications in the field of skin protection, as they could be integrated in all sorts of screens or epidermal patches. However, a drawback of films like the above is that UV absorption induces the generation of free radicals, which not only reduce the mechanical stability of the polymer matrix progressively but also are toxic to cells.[5–7] Overcoming the problems associated to this inappropriate stability and biocompatibility may be possible using UV-reflecting films, which have been proposed recently as an alternative to traditional UV-absorbing-based materials.[8] There, the traditionally employed UV-absorption mechanism is substituted by radiation blockage, achieved as a result of the strong reflectance that arises from optical interference effects. This optical shielding has therefore a structural origin, rather than compositional, and has the advantage of preventing the undesired effects that highly reactive chemical species produced upon UV absorption have on the films themselves and on the tissues that they intend to protect. Besides all this, an appealing feature of UV-reflecting films is that their optical response can be tailored to measure, so that they block very efficiently any predetermined wavelength range.

A new type of nanostructured selective ultraviolet (UV) reflecting mirror is presented. Periodic porous multilayers with photonic crystal properties are built by spin-coating-assisted layer-by-layer deposition of colloidal suspensions of nanoparticles of ZrO2 and SiO2 (electronic band gap at λ < 220 nm). These optical filters are designed to block well-defined wavelength ranges of the UVA, UVB, and UVC regions of the electromagnetic spectrum while preserving transparency in the visible. The shielding against those spectral regions arises exclusively from optical interference phenomena and depends only on the number of stacked layers and the refractive index contrast between them. In addition, it is shown that the accessible pore network of the as-deposited multilayer allows preparing thin, flexible, self-standing, transferable, and adaptable selective UV filters by polymer infiltration, without significantly losing reflectance intensity, i.e., preserving the dielectric contrast. These films offer a degree of protection comparable to that of traditional ones, without any foreseeable unwanted secondary effects, such as photodegradation, increase of local temperature or, as is the case for organic absorbers, generation of free radicals, all of which are caused by light absorption.

We describe different use of photosensitivity for the realization of optical interference filters. We first realize a theoretical study of the programming of a multilayer Fabry-Perot filter, then of the programming of a cascaded solid-spaced Fabry-Perot filter ; finally of an ”hybrid” filter composed with a Bragg grating and a dielectric mirror. Secondly, we make a presentation of the realization of an absolute optical thickness measurement set-up of optical windows and we show the experimental results of the characterization of potentially photosensitive thin substrates. Finally, we describe the experimental manufacturing of a guided hybrid filter, and of the programming of a solid-spaced etalon., Nous presentons differentes applications de la photosensibilite a la realization de filtres optiques interferentiels. Nous commencons par une etude theorique de la programmation de la reponse spectrale d'un fabry-Perot multicouches et de celle d'un filtre a cavites-substrats tandem; enfin nous presentons le principe de fonctionnement d'un filtre dit ”hybride”, compose d'un miroir de Bragg et d'un miroir dielectrique. Nous presentons ensuite la realisation d'un montage de mesure absolue de l'epaisseur optique de cavites-substrats et les resultats experimentaux obtenus lors de la caracterisation de lames fines potentiellement photosensibles. Enfin, nous exposons les resultats obtenus lors de la realisation de filtres hybrids en espace guide et en espace libre puis lors de la structuration d'une cavite-substrat photosensible.