Investigation of nanophotonic devices based on transformation optics : Transforming reflective optical devices

Abstract: Transformation optics (TO), which provides an elegant way of molding the flow of light to one's wishes, has become one of the most popular photonics research areas during the last few years. Owing to stringent material parameters of transformation media, TO is in general not favourable for designing practical applications. The recent proposal of carpet cloak, a device that optically hides an anomaly on an otherwise at reflective surface, simplifies material requirements due to the relaxed boundary condition on the cloak's reflective border, thus providing the prospect of realization at optical wavelength. In light of this approach, this thesis introduces a general procedure for transforming reflective optical devices, including in particular focal mirrors and diraction gratings. The curved or zigzagged surfaces of such devices are attened through a smooth coordinate mapping which makes convenient use of the loose boundary conditions on the reflective surface. The resulting devices are transformation media without extreme material parameters. For two-dimensional structures, it is even possible to attain an approximate dielectric-only implementation when considering only transverse-electric or transverse-magnetic incidence. The flattened reflective devices are finally adapted to operate in a transmission mode, creating focal lenses and transmissive diffraction gratings. It is illustrated through full-wave simulation that the performance of these transformation optical devices - under the right circumstances also for the dielectric only implementations - surpasses their traditional equivalents.