Research On Light Waveguides And Devices With Negative Refractive Index Material

Negative refractive index (NRI) material was firstly proposed by Veselago in 1968. The electric field (E), the magnetic field (H) and the wave vector (k) of an electromagnetic wave propagating in NRI material obey the left-handed rule, meanwhile k and Poyntin vector S are antiparallel. So NRI material is also called "left-handed material", "backward-wave material" or "negative-phase velocity material" As NRI material does not exist in the nature, people almost have no interest in it at the beginning. Until recently, scientists have fabricated the first NRI material in microwave region and proved its rationality theoretically and experimentally, NRI material attracts a great deal of attention due to its novel electromagnetic properties. NRI material can be used to realize highly directive antenna, focus of microwave, perfect lens and cloak.Based on NRI material waveguides, the works presented in the disertation include resonant cavity, photonic crystals and new devices with NRI material, the main research activities are detailed as follows:1. By use of modified Marcatili's method, the propagation wave properties of a rectangular waveguide with new semiconductor negative index material (SNIM) is studied. Based on SNIM and nonmagnetic anisotropic positive refractive index material, a new rectangular resonant cavity is proposed. The resonant cavity including two subcases of real and imaginary propagation constants of positive refractive index material is discussed, and the corresponding resonant equations are solved.2. Three photonic crystals (PCs) with anisotropic NRI materials are systematically studied, including the combination of semiconductor NRI material and air, nonmagnetic positive and negative refractive index materials and single-negative materials. The conditions imposed on the materials and structures to realize a photonic band gap (PBG) are analysed, and then the PBG is compared with zero-n, zero-Φeff and Bragg gaps by numerical results. At last, linear and nonlinear defect layers are introduced into PCs constructed by anisotropic single negative materials. The different properties of tunneling modes and bistability are discussed. 3. A compact polarization splitter based on a directional coupler with NRI material is studied. Its operation is by setting the coupling length of TM polarization be half that of TE polarization, and two polarization can be effectively separated. In order to analyse the factor that have impact on the size of polarization splitter, the thickness of NRI material and waveguide material, distance between two waveguides and the lenth of polarization splitter are calculated respectively by graphing method when birefractive index of the waveguide material is different.4. Based on the principle of Mach-Zehnder Interferometer, a very compact intensity modulator is proposed. Two 3 dB directional couplers with NRI material are used to replace conventional Y junctions or directional couplers. Combining the supermode theory with coupled mode theory, the operating principle and characteristics of the intensity modulator are analyzed. At last, the attenuation property of the intensity modulator caused by the lossy NRI material is analyzed.