Some Studies On Negative Refraction And Designed Surface Plasmon In Periodic Structure

Photonic crystals (PhCs) are a novel class of composite periodic materials, which provide a new means to control and manipulate light and electromagnetic waves. In the past decade, PhCs have become a new fast-developing research field due to their unique properties and many important potential applications. In this thesis, we study two physical phenomena resulting from the special dispersion characteristic in PhCs: the negative refraction and the designed surface plasmon. Moreover, we also apply the physical mechanism after these new phenomena to design some novel devices.In Chapter 1, following the history of PhCs research on the dispersion characteristic, we introduce two important concepts involved in the thesis: negative refractions and designed surface plasmons. Due to the different dispersion relation, the negative refraction PhC is classified to the PhC with effective negative refractive index and the PhC with all-angle negative refraction.Since the surface termination and direction of PhCs have great effect on the transmission at the PhCs-dielectric interface, the PhC with the effective negative refractive index can not be directly treated as the negative index material. We discuss the optical property of the PhC with the effective negative refractive index in Chapter 2 and 3, and estimate the effectiveness of this kind of PhCs.In Chapter 2, by investigating the transfer function of imaging system, we analyze the influence of the surface termination to the imaging quality. The band structure of the surface mode in the PhC are calculated and used to explain the influence. It shows that an appropriate surface termination is important to improve the image quality.In Chapter 3, a comprehensive analysis of the coupling coefficients between plane waves in conventional dielectric media and Bloch waves in photonic crystals with effective negative refractions is performed by the layer-KKR method. Employing the infinite layers refraction operator, semi-infinite size photonic crystals are considered. Some special coupling properties are discussed.In Chapter 4, a layer-KKR method is exploited to study the subwavelength imaging through a slab of rods-in-air photonic crystal with all-angle negative refraction. Both the intensity and phase spectra of transmission are investigated. Through a studyof the phase spectrum of transmission, we discuss the physical mechanism of the sub-wavelength imaging.Due to the optical property of PhC with the effective negative refractive index, which is discussed in Chapter 2 and 3, we found the open-cavity designed by Notomi is not valid for PhC with the effective negative refractive index. Therefore, in Chapter 5, we propose a novel and reliable open-cavity, and discuss the influences of the surface termination on the quality factor of the cavity.In Chapter 6, we propose that the negative refraction can be achieved in the designed surface plasmon structure. Using the rigid full-vectorial three-dimensional finite-difference time-domain method, we also numerically demonstrate the sub-wavelength imaging of a point dipole source by using a slab of such a structure.In Chapter 7, by analogy between the designed surface plasmon in the perfect conductor and the surface plasmon in the real metal, we discuss the extraordinary transmission through a metallic film with a periodic array of subwavelength holes. The band structure for the metal film is calculated, and it shows that two different resonances contribute to the enhanced transmission. We also give the explanation for the shape-effect on the enhanced transmission.In Chapter 8, a perfect electric conduct surface with one-dimensional periodic rectangle holes is proposed as a surface-plasmon-like waveguide, where designed surface plasmon modes with very low group velocity are confined in a subwavelength region.In Chapter 9, we conclude the thesis with some remarks, and suggest some topics that deserve further consideration in the future.