Abstract
In this thesis, we investigate the general wave scattering response of an individual scatterer excited by incident waves. Through choosing the suitable conditions, we show that these subwavelength scatterers could have anomalous wave features, analogous to metamaterial counterparts, for example superabsorber, perfect absorber, invisible cloak, zero-forward scattering and superscattering. There are three major studies of interests in this thesis: nano-light harvesting for photocatalysis, design of quantum invisible cloak and physical limitation on general passive scatterers. In the first part, we derive the formulas from exact Mie theory and integrate basic physics: various characteristic cross sections, long wavelength approximation, optical theorem and causality of frequency dispersive relation. We apply this Mie theory to understand the relationship between absorption of light and the photocatalytic activity of TiO2 compared with experimental data. By tuning geometries and simplifying the complicated photochemistry reaction as pure optical problem, we nd that our calculation could agree with experimental results. Although scattering signal is really affected by geometries due to exciting modes and channels as well as function of cavity, we show that in large-sized parameters the absorbed power could maintain the same by tuning thickness up to 0.4 . This non-sensitive absorbed power on the thickness ratio may bring a lot of benefits on saving cost of material. In optimized situation, our theory predicts that one could raise the efficiency of hydrogen generation up to 500%. In the second part, we design a new quantum invisible cloak from different methods. Following the recipe of transformation optics, the solution to design quantum cloaks would need complicated anisotropic and inhomogeneous material parameters and have infinite singular point for effective mass at the inner cloak. In this part, we introduce a new concept of Goos-Hanchen effect, producing total internal reflection happened at the boundary of core-shell cloak. Choosing the proper core parameters, we could eliminate the scattering contributions from s and p waves based on conventional scattering cancellation method. We could not only create a hidden region but also largely compress the total scattering signals. This method could largely reduce the difficult of engineering level because of its simple core-shell isotropic and homogeneous only. In the final part, we develop the phase diagram to recognize the limitation of phase and amplitude of complex scattering coefficient for each harmonic channel. Scattering coefficient not only connects various cross sections but also has an influence on extrinsic characteristic. Through this phase diagram it can completely display possible solutions of Mie theory beyond any design and structures, including minimum or maximum of the power assigned toward different extrinsic states. Choosing any paths or any specific positions in the allowable territory in diagram, the corresponding parameters could be calculated, highlighting the possibility of manipulation of light.