Theoretical Study On Artificial Electromagnetic Media And Optical Micro - Manipulation

The propagation of electromagnetic waves in the medium satisfies the Maxwell’s equations, and permittivity and permeability are the two important optical parameters for the medium. The spatial profiles of the two optical parameters determine the prop-agation and properties of the electromagnetic field. The concept of negative refraction is proposed by Veselago, and he discussed many novel optical properties of negative medium. For the limitation of the media existed in the nature, people pay attention to the negative medium until Pendry’s researches, and then the concept of the metamate-rial is generated. Lots of artificial structures are designed to realize negative permittiv-ity and permeability from microwave to the visible light frequencies. Transformation optics has become a theoretical method to design many electromagnetic devices with novel electromagnetic properties. And many devices are designed after the combina-tion of transformation optics and metamaterials, the famous application among them is cloaking.One aspect of the interaction between the medium and electromagnetic wave is how to control the propagation of the fields, as mentioned above, and the other aspect is op-tical manipulation for micro particles. Optical manipulation has become a substantial field that has a major impact on a variety of disciplines ranging from the microscopic to atomic scales, after the invention of the lasers. Optical tweezers, pioneered by Ashkin, based on the equilibrium of gradient force and scattering force to trap micro particles, are widely used in the fields of biology and medicine. And many types of incident laser beams are used to optimize the applications of optical tweezers. Optical binding, pro-posed after Ashkin’s pioneered works for optical tweezers, is the interaction between the incident laser beams and the many body system. The significant optical force is generated between particles based on the multiple scattering and used to bind many particles to form a specific structure. Optical pulling force, which is a part of scatter-ing force and pulls the particle towards the source of light, arising from interference between multipoles, is founded in the recent years. So far, optical trapping, optical binding and optical pulling are the three methods to be used in the optical manipula-tions. The thesis represents several works for metamaterial and optical manipulations, and be organized in the following.In chapter one, we present the background introduction, which is made up three parts:artificial material and its applications; transformation optics; optical manipula-tions.Theoretical method, Mie multiple scattering theory, used in the thesis is presented in the chapter two. Multiple scattering theory is used to solve scattering problems of infinite cylinders for two dimensions and spheres for three dimensions. Only three di-mensional multiple scattering theory is introduced in this chapter. Based on the method of multiple scattering theory, many physical quantities can be obtained, for instance, the scattering cross section, optical force and band structure calculations.Two electromagnetic devices are designed based on artificial materials in chapter three and chapter four. The first one is the super focusing antenna, which is designed based on the method of transformation optics. The second one is a simple design of two dimensional electromagnetic absorber for TM mode. Multiple scattering theory is used to calculate the electromagnetic properties of the absorber. We use multiple layer structure to design the absorber, and effective medium theory is used.Optical manipulations of one dimensional Airy beam is introduced in chapter five. Angular representation of the Airy beam is used to calculated the expansion coefficients of vector spherical wave functions. Then we used the multiple scattering theory to obtain the optical force of the micro sphere illuminating by one dimensional Airy beam. We discussed, at last, the optical manipulations of the Airy beam. Optical pulling force for very large sized sphere is discussed in the chapter six. Mie scattering theory for very large sized sphere and genetic algorithm are used in this chapter.We give the conclusions of the thesis in the last part.