Academic literature on the topic 'Holographic optical component'

Modelisation de la diffraction des reseaux de volume precisant les processus de codage et de selection de l'information caracterisant les fronts d'onde. Realisation d'un systeme multiplexeur/demultiplexeur de longueurs d'ondes

Analyse theorique des proprietes des reseaux de phase, conditions d'etude et de realisation des element optiques holographiques pour un certain nombre d'applications. Evaluation du materiau photosensible permettant d'atteindre des efficacites de diffraction tres proches de 100 %. Mise au point d'une methode de suivi de l'evolution du materiau durant le processus de fabrication des composants. Nous pouvons determiner separement les valeurs des indices de refraction et des epaisseurs par interferometrie mach-zehnder

Depuis de récentes années de nouveaux composants optiques ont fait leur apparition. Ces composants connus sous les noms de « Méta-optiques » ou encore « Métasurfaces », rendent possible le contrôle et la mise en forme du front d’onde de la lumière permettant alors de mettre en forme n’importe quel faisceau incident et ainsi créer des fonctionnalités optiques classiques telles que focaliser ou dévier la lumière, ou alors des fonctionnalités aux propriétés surprenantes telle que la réalisation de métahologramme dépendant en polarisation. En effet, grâce à l’arrangement périodique de résonateurs de dimensions géométriques sous-longueur d’onde, il est alors possible d’obtenir un contrôle local arbitraire du faisceau incident. Néanmoins, même si de nombreuses applications ont pu être démontré dans la communauté, seuls quelques matériaux se retrouvent être compatibles pour le développement industriel de ces composants. De plus, afin de passer de composant passif à actif, pour la réalisation de composant dynamique, il est nécessaire de passer de matériau diélectrique à matériau semi-conducteur. C’est pourquoi dans ces travaux, nous nous sommes intéressés à l’utilisation d’un matériau semi-conducteur qui est le Nitrure de Gallium pour la réalisation de composants métasurfaciques. Nous présentons alors dans un premier temps une étude numérique des nanostructures utilisées lors de ces travaux. Puis nous montrons comment est réalisée la conception de nos méta-optiques en présentant la méthode de design et les procédés de nanofabrications employés, notamment une nouvelle technique de gravure, compatible uniquement avec les matériaux cristallins et préservant leurs propriétés optiques. Nous exposons ensuite différentes applications où nos composants sont utilisés telles que : la réalisation de métalentilles de large ouverture numérique et de large surface, l’optimisation de réseaux métasurfaciques permettant d’atteindre des efficacités de diffraction supérieur à 80% ou encore la réalisation expérimentale de méta-hologramme permettant de conserver l’information du moment angulaire orbitale du faisceau incident<br>In the past years, new optical components have appeared. These components, known as "meta-optics" or "metasurfaces", made it possible to control and to shape the wavefront of the light. This allows the control of any incident beam and the creation of conventional optical functionalities, such as focusing or deflecting the light, or functionalities with additional features such as the possibility of creating polarization-dependent meta-holograms. Indeed, thanks to the periodic arrangement of resonators with sub-wavelength geometric dimensions, it is possible to obtain an arbitrary local control of the incident beam. Nevertheless, even though many applications have been demonstrated in the community, only a few materials are found to be compatible for the industrial development of these components. In addition, in order to pass from passive to active components for the fabrication of dynamic devices, it is necessary to switch from dielectric materials to semiconductor materials. For these reasons, we are interested in the use of a semiconductor material, Gallium Nitride, for the development of metasurface components. We first present a numerical study of the nanostructures used during this work. Then, we show how the design of our meta-optics is done by presenting the numerical conception method and nanofabrication processes used, which includes a new etching technique compatible only with crystalline materials while preserving their optical properties. Finally, we suggest different applications where our components can be used, such as: the development of metalenses with high numerical aperture and large surface; the optimization of metasurface high contrast gratings allowing to reach diffraction efficiencies higher than 80%; or the fabrication of meta-holograms preserving the information of the orbital angular momentum of the incident beam

博士<br>國防大學中正理工學院<br>國防科學研究所<br>99<br>The thesis presents how to apply the Digital Holographic Microscopy (DHM) with its non-contact, non-invasive and non-destructive characteristics to measure the physical characteristics of the optical components quantitively. In contrast with lensless digital holography, DHM uses an Objective Lens (OL) to collect the object wave and magnify the dimensions of object under test. When the object wavefront passes OL and propagates forward, then object wavefront will contain a quadratic phase term, the so called defocus aberration. The propagating object wavefront will interfere with the reference wave at the hologram plane and the interference pattern be captured by CCD. Thus the holograms recorded with DHM setup will not only the information of the zero order, object wavefront and its conjugate term, but also a quadratic phase term. Even the blur, i.e. zero order and wavefront conjugate terms, had been removed; if the hologram is directly reconstructed using numerical algorithms, then the reconstructed object wavefront will still include a quadratic phase term (defocus aberration). Since the phase information of the object wavefront contains a quadratic phase term, thus the absolute phase distribution of object wavefront had been masked, therefore the shape, profile and surface roughness of the object under test can not be reconstructed. To remove the defocus aberration due to OL and reconstruct the exact phase distribution of the object wavefront, we use a physical mean to compensate the quadratic phase term due to OL and then the physical characteristics of the optical components can be measured quantitively. The proposed scheme is that an offset lens is inserted after OL, the OL and offset lens are separated such that their foci are common and together (confocal), to physically compensate for the quadratic phase term due to OL, thus the recorded holograms which were captured by CCD will not contain the defocus aberration no longer. Meanwhile, through the analysis of the optical operator, it can be shown that the inverted and magnified object wavefront, which has passed through the OL and compensation lens configuration, will not carry and contain the quadratic phase term anymore. We exploit the Mach-Zehnder interferometry to implement the in-line and off-axis DHM optical setups, and the arbitrary phase-step digital holography (APSDH) to suppress the blur, i.e. zero-order and twin-image terms. For the off-axis configuration, we use Chen et al. method which is the second reconstruction plane added to spatially filter the unwanted terms, and then numerically reconstruct the object wavefront at the original plane. For demonstrating the effect of the phase compensation, the optical experiments without and with phase compensation (modified) DHM scheme are conducted, and verified that the modified scheme can satisfactorily compensate for the defocus aberration due to OL. After using the numerical algorithms to eliminate those blur, obviously the reconstructed magnitude- and phase-contrast images do present no defocus aberration and blur. Moreover, optical characteristics and reconstruction results which were obtained from in-line and off-axis modified DHM are briefly reviewed and discussed. Furthermore, we also demonstrate how to implement off-axis setups, without cutting (destruction) the whole piece LLA (lenticular lens array), to measure the pitch of a 62 LPI (lenticular per inch) LLA, and the error is about 3.17% when compared the nominal value. The suggested scheme can be applied to DHM, phase object measurement, and optical metrology.