Theoretical Study On Optical Properties Of Several Nanostructures

Maxwell equations are the basic equations of classical electromagnetic theory. We can get the distribution of the electromagnetic field by solving these equations. There two base solutions:analysis method and numerical method. The analysis method can only be used to solve some regular structures, for the complex ones this method will cost long time and usually we cannot give an explicit equation. The numerical method can give a more accurate and faster result. As the development of the computer technology, it has gradually shown its advantage. In this thesis, firstly, we explain the unusual phenomenon of the flower beetle. Secondly, give the optimized tube parameters for different optical materials in tube walls. Thirdly, introduce the electromechanically torsional fibre muscle from helically aligned conductive nanotubes.This thesis consists of four chapters. In Chapter One, we introduce the development of the electromagnetism. Then, we present two solutions:analysis method and numerical method. At last, specifically introduce the latter one.In Chapter Two, we describe four of the numerical methods, such as the Plane-Wave-Method, the Transmission-Matrix-Method, the Scattering-Matrix-Method and the Mie-Scattering-Method. For the periodic structure, we usually use the first three methods, and each method has its advantages and disadvantages. When we study different structures we can chose the appropriate one. The last method is the accurate solutions for the Maxwell equations in the spherical coordinates. The derivation consists of many partial differential equations and non-elementary functions, but for all of us, the results are much more important than the derivation.In Chapter Three, we explain the bright color of the flower beetle. The color originates from microstructures called physical color. At first, we show the transmission electron micrographs for the microstructures of elytra, we give both transverse cross section and longitudinal cross section of the elytra. Then, we present an interesting method that considers a quasiordered structure as a combination of some periodic ones. We use this method to study the beetle. At last, calculate the band structure and the reflection spectra by numerical method.In Chapter Four, we study the liquid sensing capability of tubular optical microtube. The tube with Whispering gallery modes (WGMs) present a high Q factor, and it can act as optical sensors for identifying different liquids. In this chapter, we introduce the structure of the microtube and give the analysis method, but the analysis method can’t give the Q factor quickly, so we use the Mie scattering method. Based on the method, we study systematically the optical resonances and liquid sensing capability of sensitivities. And finally find the optimized tube parameters.In Chapter Five, introduce the electromechanically torsional fibre muscle from helically aligned conductive nanotubes and it obey the conservation of energy. This transition can occur in almost all available environmental media. The produced stress is over100times of the strongest natural skeletal muscle with high reversibility and good stability upon pass of a low current. But the maximum stress appears in a critical helical angle. In this chapter, we show the structure of the carbon nanotubes and the result of the experiment. Based on the Ampere’s Law, we simulation the process and explain the phenomenon.