Design and optical characterization of anisotropic plasmonic metamaterials at visible and infrared wavelengths

• Main Author: Vasilantonakis, Nikolaos
• Other Authors: Zayats, Anatoly ; Wurtz, Gregory Alexandre
• Published: King's College London (University of London) 2016
• Subjects: 530
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.679787

The eld of plasmonics studies the interaction of light and free electrons in metals, giving rise to excitation of surface waves, on a metallodielectric interface. One branch of plasmonics is the design of metamaterials in visible and infrared spectral range which are articial structures designed to manipulate the propagation of light in a way not possible with conventional materials. This thesis is categorized in 3 main parts. The rst part examines the effects of waveguided modes in Au nanorod metamaterial waveguides. It shows, both theoretically and experimentally, that these materials can be designed to control the sign and magnitude of modal group velocity depending on the geometry and polarization chosen exhibiting high eective refractive indices (up to 10) and have an unusual cut-o from the high-frequency side, providing deep-subwavelength (0/6 { 0/8 waveguide thickness) single-mode guiding. This allows slow light to exist in such waveguides in a controllable environment which is a critical factor for nonlinear and active nanophotonic devices, quantum information processing, buering and optical data storage components. The second part discusses, analytically and numerically, strategies for biosensing and nonlinearity enhancement with hyperbolic nanorod metamaterials. It shows how the sensitivity of unbound, leaky as well as waveguided modes can be enhanced based on geometrical considerations. Additionally, refractive index variation of the host medium produces 2 orders of magni- tude higher sensitivity compared to nanorod or superstrate refractive index changes. In certain congurations, both TE and TM-modes of the metamaterial transducer have comparable sensitivities opening up opportunities for polarization multiplexing in sensing experiments. The gure of merit of the aforementioned structure is one order of magnitude higher than surface plasmon polariton and localized surface plasmon sensors making it ideal for sensitive-dependant applications such as chemo- and biosensors and nonlinear photonic devices. The third part investigates Strontium Ruthenate thin lms as a new material for near-IR plasmonic applications. It is demonstrated that their plasmonic behavior can be optimized by their deposition conditions leading to a selective and tunable plasma frequency in 324 - 392 nm range and epsilon-near-zero wavelength in 1.11 { 1.47 m range. Applications of these lms range from heat-generating nanostructures in the near-IR spectral range, to metamaterial-based ideal absorbers and epsilon-near-zero components, where the interplay between real and imaginary parts of the permittivity in a given spectral range is needed for optimizing the spectral performance.