Optical Metamaterials : Design

Artificially engineered metamaterials have emerged with properties and functionalities previously unattainable in natural materials. The scientific breakthroughs made in this new class of electromagnetic materials are closely linked with progress in developing physics-driven design, novel fabrication and characterization methods. The intricate behavior of these novel metamaterials is interesting from both fundamental and practical point of view. New frontiers are being explored as intrinsic limitations challenge the scaling of microwave metamaterial designs to optical frequencies. These materials promise an entire new generation of miniaturized passive and active optical elements. In this study, I demonstrate an on-fiber integrated " fishnet " metamaterial modulator for telecommunication applications. This metamaterial shows remarkable coupling to fiber guided modes (3.5dB) and a photoswitchable tuning range of more than 1.8dB. The design offers extremely small footprint (~10 wavelengths) and complete elimination of bulk optical components to realize low-cost, potential high-speed optical switching and modulation. Unique characterization techniques need to be developed as conventional optical microscopy runs out of steam to resolve the fine features of optical metamaterials. To address this challenge, I have investigated cathodoluminescence imaging and spectroscopy technique. This scanning electron beam based technique allows optical image acquisition and spectroscopy with high spectral and spatial resolution. Monochromatic photon maps (spectral bandwidth ~5nm) show strong variation of localized plasmon modes on length scales as small as 25nm. Numerical simulations performed to model the eigenmodes excited by electron beam show strong agreement with experiments. I also demonstrate progress made in " superlensing " , a phenomenon associated with plasmonic metamaterials, leading to subdiffraction resolution with optical imaging. Fabricating a smooth silver superlens (0.6nm root mean square roughness) with 15nm thickness, I demonstrate 30nm imaging resolution or 1/12 th of the illumination wavelength (near-ultraviolet), far below the diffraction-limit. Moreover, I have extended subdiffraction imaging to far-field at infrared wavelengths. Utilizing a two-dimensional iii array of silver nanorods that provides near-field enhancement, I numerically show that subwavelength features can be resolved in far-field in the form of Moiré features. Development of this unique far-field superlensing phenomenon at infrared wavelengths is of significant importance to chemical and biomedical imaging. iv In memory of Dada and Jee v ACKNOWLEDGEMENTS I have been fortunate to be surrounded by many loving people and it is my great pleasure to thank them for their love, support, blessings and encouragement. First of all, I would like to express my sincere gratitude towards my advisor Prof. Nicholas …