EXOTIC OPTICAL PROPERTIES OF METAL-DIELECTRIC NANO-STRUCTURES


Book Description

Abstract : Advancement in fabrication technology made it possible to integrated different materials such as metals, dielectrics and semiconductors in a nano-meter scale structure. The capability of making features in the same order or even smaller than wavelength of light, visible and infrared, brought us the opportunity to manipulate light in a capacity which was not possible before. During the last decade, researches introduced several designs to address some of human's dreams, such as making huge object invisible and bringing small particles to human's eye sight. This dissertation presents three different nano-structures with exotic optical properties. The first one is a low loss negative index lens (NIL). The NIL is claimed to have the capability for sub-diffraction imaging, however power dissipation prevented from any realization of the NIL. We developed a method, called plasmon injection scheme, to compensate for power dissipation in the NIL with coherent injection of surface plasmon polariton (SPP). Magneto-optical metamaterial (MOM) is the second nano-structure we introduce in this dissertation. The MOM which is consist of a background magneto-optical (MO) material and metallic inclusions, delivers an order of magnitude enhancement in the Faraday rotation compare to the background MO material. The diagonal elements of the effective permittivity tensor of the MOM could be tuned in such a way to increase the Faraday rotation. This design can potentially reduce the size of non-reciprocal optical devices which work based on the Faraday rotation. The last structure we introduce in this dissertation is a thin-film amorphous Silicon (a-Si) solar cell with a honeycomb silver mesh as the emitter layer. Low efficiency is main disadvantage of thin-film a-Si cells, and the honeycomb mesh increases the efficiency of the cell by enhancing the light absorption in the active layer and reducing the series resistance of the cell. The honeycomb mesh benefits from low cost and scalable nano-bead lithography technique. Our simulations verified a properly designed honeycomb thin-film a-Si solar cell delivers %8 more electric power at the output terminal.




Optical Properties of Nanostructures


Book Description

This book discusses electrons and photons in and through nanostructures by the first-principles quantum mechanical theories and fundamental concepts (a unified coverage of nanostructured electronic and optical components) behind nanoelectronics and optoelectronics, the material basis, physical phenomena, device physics, as well as designs and applications. The combination of viewpoints presented in the book can help foster further research and cross-disciplinary interaction needed to surmount the barriers facing future generations of technology design.




Optical Properties of Nanostructured Metallic Systems


Book Description

The common belief is that light is completely reflected by metals. In reality they also exhibit an amazing property that is not so widely known: under some conditions light flows along a metallic surface as if it were glued to it. Physical phenomena related to these light waves, which are called Surface Plasmon Polaritons (SPP), have given rise to the research field of plasmonics. This thesis explores four interesting topics within plasmonics: extraordinary optical transmission, negative refractive index metamaterials, plasmonic devices for controlling SPPs, and field enhancement phenomena near metal nanoparticles.







Optical Properties of Metal Nanostructures as Probed by Photosenitive Molecules


Book Description

While past research has considered the interaction between metal nanoparticles and photo-sensitive molecules, especially the possibility of initiating nanoscale photopolymerization based on the localized surface plasmons of such particles, this PhD dissertation describes the in-depth characterization and optimization of such interactions that result in nanoscale photopolymerization. The present work demonstrates our ability to use the nanophotopolymerization process to quantitatively map with unprecedented resolution, better than 5 nm, both, the near-field of metallic nanoparticles associated with their localized surface plasmons, and the local electric fields resulting from surface charges density at metal/dielectric interfaces. We will emphasize that a precise characterization of the nanoscale molecular mold of the confined electromagnetic field of metal colloids enabled us to quantify the near-field depth and its enhancement factor. Moreover, a near-field spectrum corresponding to the response of localized surface plasmons of a single metal nanoparticle will be assessed. Additionally, we present nanoscale resolution maps of the spatial distribution of the surface charge density created by the electric field dis-continuity at a non-resonant metal/dielectric interface. Furthermore, this work will prove that the nanoscale photopolymerization approach does not only map the near-field of metal nanoparticles, yet it constitutes, from a more fundamental point of view, a unique opportunity to investigate nanophotochemistry.




Linear and Nonlinear Optical Properties of High Refractive Index Dielectric Nanostructures


Book Description

Nano-photonic structures offer a highly interesting platform to enhance light-matter interaction on a nanometer scale. Recently, high-index dielectric structures have gained increasing attention as possible low-loss alternatives to plasmonic nano-antennas made from noble metals. Furthermore, since non-linear effects offer many unique functionalities like the coherent up-conversion of photons, including the generation of harmonics, many efforts are being made to exploit such phenomena in nano-photonics. In this thesis, an analysis is presented on nonlinear optical effects in individual dielectric structures, specifically in silicon nanowires (SiNWs). Nanowires develop strong optical resonances in the visible and infrared spectral range. In this context, strong enhancement of the optical near-field together with a large surface to volume ratio support the appearance of nonlinear effects. We show that, compared to bulk Si, a two orders of magnitude increase in second harmonic generation (SHG) is feasible and furthermore unravel different polarization and size-dependent contributions at the origin of the SHG. Numerical simulations are carried out to reaffirm these experimental findings for which a numerical technique is presented to describe nonlinear effects on the basis of the Green Dyadic Method (GDM). In the last part of the thesis, the GDM is used together with evolutionary optimization (EO) algorithms to tailor and optimize optical properties of photonic nano-structures. We eventually fabricate samples, based on EO design, and successfully verify the predictions of the optimization algorithm. It turns out that EO is an extremely versatile tool and has a tremendous potential for many kinds of further applications in nano-optics.




Semiconductor and Metal Nanocrystals


Book Description

The vast technological potential of nanocrystalline materials, as well as current intense interest in the physics and chemistry of nanoscale phenomena, has led to explosive growth in research on semiconductor nanocrystals, also known as nanocrystal quantum dots, and metal nanoparticles. Semiconductor and Metal Nanocrystals addresses current topics impacting the field including synthesis and assembly of nanocrystals, theory and spectroscopy of interband and intraband optical transitions, single-nanocrystal optical and tunneling spectroscopies, electrical transport in nanocrystal assemblies, and physical and engineering aspects of nanocrystal-based devices. Written by experts who have contributed pioneering research, this reference comprises key advances in the field of semiconductor nanocrystal quantum dots and metal nanoparticles over the past several years. Focusing specifically on nanocrystals generated through chemical techniques, Semiconductor and Metal Nanocrystals Merges investigative frontiers in physics, chemistry, and engineering Documents advances in nanocrystal synthesis and assembly Explores the theory of electronic excitations in nanoscale particles Presents comprehensive information on optical spectroscopy of interband and intraband optical transitions Reviews data on single-nanocrystal optical and tunneling spectroscopies Weighs controversies related to carrier relaxation dynamics in ultrasmall nanoparticles Discusses charge carrier transport in nanocrystal assemblies Provides examples of lasing and photovoltaic nanocrystal-based devices Semiconductor and Metal Nanocrystals is a must read for scientists, engineers, and upper-level undergraduate and graduate students interested in the physics and chemistry of nanoscale semiconductor and metal particles, as well as general nanoscale science.







Optical Properties of Semiconductor Nanocrystals


Book Description

Examines the optical properties of low-dimensional semiconductor structures, a hot research area - for graduate students and researchers.




Optical Properties of Semiconductor Nanostructures


Book Description

Optical methods for investigating semiconductors and the theoretical description of optical processes have always been an important part of semiconductor physics. Only the emphasis placed on different materials changes with time. Here, a large number of papers are devoted to quantum dots, presenting the theory, spectroscopic investigation and methods of producing such structures. Another major part of the book reflects the growing interest in diluted semiconductors and II-IV nanosystems in general. There are also discussions of the fascinating field of photonic crystals. `Classical' low dimensional systems, such as GsAs/GaAlAs quantum wells and heterostructures, still make up a significant part of the results presented, and they also serve as model systems for new phenomena. New materials are being sought, and new experimental techniques are coming on stream, in particular the combination of different spectroscopic modalities.