L'analyse spectrale d'une scène infrarouge permet une meilleure identification des objets la composant. Il est possible d'obtenir du filtrage spectral grâce à des résonances optiques au sein de nanostructures. Cette thèse traite de l'utilisation de structures à réseau sub-longueur d'onde pour obtenir des filtres spectraux à l'échelle d'un pixel de détection. Je me suis concentré sur l'étude de filtres à résonance de mode guidé, constitué d'un réseau de couplage associé à une couche mince diélectrique, qui nécessite typiquement de grandes surfaces pour fonctionner. J'ai mené une étude numérique du comportement spectral et angulaire de ces structures et j'ai envisagé deux possibilités pour obtenir un filtrage sur de petites dimensions: l'utilisation d'une cavité résonante dans le guide d'onde à l'aide de miroirs latéraux et l'utilisation de réseaux métalliques.L'analyse numérique de la réponse optique des structures à réseau métallique montre qu'il est possible d'obtenir une extension spatiale limitée du champ électromagnétique dans le guide d'onde à la résonance. Grâce à cette faible extension, j'ai pu étudier numériquement des filtres à résonance de mode guidé foisonnants sur des longueurs aussi faibles que 30 µm. J'ai aussi pu établir un processus de fabrication en salle blanche puis caractériser des filtres de la taille d'un pixel de détection infrarouge.Finalement, j'ai étudié la possibilité de fabriquer des mosaïques de filtres à résonance de mode guidé pour le filtrage spectral à proximité d'un détecteur plan focal. J'ai pu démontrer que les dimensions, les transmissions résonantes et les tolérances angulaires de ces filtres les rendent compatibles avec une telle utilisation. J'ai alors pu montrer un exemple d'architecture simple de caméra multi-spectrale infrarouge mettant en jeu une mosaïque de filtres à résonance de mode guidé. / Spectral analysis of an infrared scene allows for a better identification of its components. Nanotechnologies offer new opportunities to achieve spectral filtering thanks to optical resonances. In this thesis, I use sub-wavelength gratings to achieve spectral filtering on areas as small as a pixel. I focused on the study of guided-mode resonance filters, made of a coupling grating and a thin dielectric layer acting as a waveguide. This structure typically needs large surfaces to filter infrared light. However, I proposed two possible modifications of this structure: either using a resonant cavity or using metallic gratings.Numerical analysis of the optical response of structures with a metallic grating showed that the spatial extension of the electromagnetic field is limited at the resonant wavelength. Thanks to this short extension, I is possible to achieve filtering with only 30 µm-long guided-mode resonance filters. I also fabricated and characterized those pixel-sized filters.Finally, I studied mosaics of small guided-mode resonance filters. I showed that the dimensions, the resonant transmissions and the angular acceptance of those mosaics are compatible with using them inside multi-spectral cameras. I also showed a sample architecture for an infrared multispectral-camera using a mosaics of guided-mode resonance filters.

A wide range of applications currently utilize conventional optical elements to individually transform the phase, polarization, and spectral transmission/reflection of the incident radiation to realize the desired system level function. The material properties and the feasibility of fabrication primarily impact the device and system functionality that can be realized. With the advancement in micro/nano patterning, growth, deposition and etching technology, devices with novel and multiplexed optical functionalities have become feasible. As a result, it has become possible to engineer the device response in the near and far field by controlling the phase, polarization or spectral response at the micro scale. One of the methods that have been explored to realize unique optical functionalities is by varying the structural properties of the device as a function of spatial location at the sub-micron scale across the device aperture. Spatially varying the structural parameters of these devices is analogous to local modifications of the material properties. In this dissertation, the optical response of interference transmission filters, guided mode resonance reflection filters, and diffraction gratings operated in Littrow condition with strategically introduced spatial variation have been investigated. Spatial variations in optical interference filters were used to demonstrate wavelength tunable spatial filters. The effect was realized by integrating diffractive and continuous phase functions on the defect layer of a one-dimensional photonic crystal structure. Guided mode resonance filters are free space optical filters that provide narrow spectral reflection by combining grating and waveguide dispersion effects. Frequency dependent spatial reflection profiles were achieved by spatially varying the grating fill fraction in designed contours. Diffraction gratings with space variant fill fractions operating in Littrow condition were used to provide graded feedback profiles to improve the beam quality and spatial brightness of broad area diode lasers. The fabrication of space variant structures is challenging and has been accomplished primarily by techniques such as ruling, electron beam writing or complex deposition methods. In order to vary the desired structural parameter in a designed manner, a novel technique for the fabrication of space variant structures using projection lithography with a fidelity that rivals any of the current technologies was also developed as a part of this work. The devices exhibit wavelength dependent beam shaping properties in addition to spatial and spectral filtering and have potential applications in advanced imaging systems, graded reflectivity laser mirrors, and engineered illumination. The design, modeling, microfabrication and experimental characterization of space variant micro optical elements with novel optical functionalities are presented.