Transmission Characteristics Of Light In The Surface Waveguide And Multimode Waveguide Of Photonic Crystal

Although the concept of integrated optics has been presented for40years, the photonic integration is far from the expectation due to the large differences in principles, materials, and fabrications of conventional photonics devices used in integration, especially the large sizes of components and low degree of integration. Photonic crystals (PCs), which are artificially fabricated periodic structure, have gained worldwide attention due to the ability to control the light-wave in size of wavelength. The photonics devices based on the photonic crystal waveguides have a expensively promising application in photonic integration circuits (PICs) because of the high transmission efficiency and small feature size. This thesis starts with the external and inner of PCs slab, and then investigating the properties of the propagating field in the surface waveguides and total internal reflection multimode waveguides by using surface modes and total internal reflection effect.The light transmitting and coupling characteristics of surface-mode-waveguides (SMWs) based on PCs with a triangular lattice of air holes are investigated and simulated. We demonstrate that surface waves can be efficiently propagated and served as a new kind of high efficiency single-SMW-based filter with broad bandwidth in the outer space of PCs. We also explore the highly efficient coupling of hetero-SMWs constructed by cascading different truncated surfaces. The coupling efficiency is insensitive to the interface position.The properties of the propagating field in multimode PCs waveguides exhibiting no photonic band gaps with triangular lattices are investigated. By utilizing effective refractive index method, these structures are equaled as three layer planar dielectric waveguides. And the multimode interference effect is numerically analyzed and simulated based on self-imaging principle. The results show that the field can be guided with high efficiency and resemble index-guided modes due to the combination of total internal reflection and distribution Bragg reflection. High transmission region shifts toward the shorter wavelength region, the bandwidth and transmissivity are increased with the increase of filling ratio, which provides a theoretical reference for selecting an appropriate filling ratio in practical applications.The current power splitters (PSs) based on symmetric interference in photonic crystal (PC) multimode waveguides are restricted to one input port. Multiple-input multiple-output (MIMO) PSs are difficult to be realized by symmetric interference. On the other hand, it is difficult to identify and manipulate reproduced multiple-fold images for asymmetric interference due to the complex of interference, which introduces MIMO PSs based on PC slab have not been presented. In this paper, the properties of two-fold images, based on asymmetric interference in PC slab multimode waveguide with an air holes array are investigated. With these image properties, a new kind of2x2ultracompact PSs is studied and designed. Arbitrary splitting ratio can be achieved by modifying the effective refractive indices of one pair of air holes in the multimode region. As an example, a3dB ultracompact2×2power splitter with a size of16×8μm2, with output efficiency as high as97%is presented with finite-difference time-domain simulations. The method can be extended for the design of MxN PSs and have potential application for photonic integrated circuits applications.