Study On Optical Properties And Application Of Micro - Nano Photonic Structures

With the advances in nanotechnology, research on micro/nano photonics has made significant progress and become one of main topics in the fields of optics. Micro/nano photonics is aiming at manipulating the propagation, absorption and emission of light through micro/nano photonic structures, which may fall into three categories, including photonic crystals, plasmonics and metamaterials. Recently, researches on photonic structures with short-range order, plasmonic materials with low loss, and extension of concepts in metamaterials to acoustic waves and surface water waves have attracted great interests. In this thesis, we present the results of our research on these aspects.The thesis consists of five chapters:In the first chapter, we briefly introduce the major aspects of micro/nano photonics and their research progress.In the second chapter, we briefly discuss two theoretical methods used, including finite-difference time-domain and transfer matrix methods.In the third chapter, we study optical properties of a new type of short-range-ordered photonic structures, namely, disordered macroporous structures. We find that these structures can exhibit broadband light scattering enhancement, arising from the existence of short-range order and complexity of local structures. PBG effects resulting from these inherent features in the structures are thoroughly investigated, and their relationship with optical properties of the structures is discussed. Absorption enhancement in disordered macroporous Si structures is also dicussed, which may find applications in photovoltaics.In the fourth chapter, we study theorectically optical properties of graphene on subwavelength dielectric gratings. Band structures and band gap of graphene plasmons (GPs) are investigated. Flat bands above the light line can be observed, suggesting GP modes can be excited directly over broad angles, which can lead to enhancement of optical absorption in graphene. Our results indicate that the introduction of subwavelength dielectric gratings can offer an excellent approach to control the excitation of GPs and enhance optical coupling efficiency in graphene.In the fifth chapter, we study theoretically the propagation of surface water waves over a system with radially graded water depth profile. Under certain conditions, the system exhibits black-hole like attraction and can attract a broad band of water waves into its core. Due to the wave nature, water waves with wavelengths much longer than the size of the system cannot be captured by the system. Our results provide a new mechanism to focus water waves and may have impact on ocean wave energy harvest.