Research Of Key Technology Of One-way Photonic Crystal Delay Waveguide And Silicon Based Broadband Anti-reflection Films

Devices based on photonic crystal follow photonic band gap guiding mechanisms. They are ideal choices for future compact integrated optical circuit, with many advantages which traditional devices don't have. Therefore, they have attracted a lot of attention of researchers and have been studied intensively and extensively during the past decade. This dissertation study some key technologies of one-way photonic crystal delay waveguide, a new kind of device based on magneto-optical photonic crystal, propose a different strategy of photonic crystal delay structures, performe simulation for the one-way meander-line delay waveguide using Plane Wave Expansion (PWE) method and Finite-Difference Time-Domain (FDTD) method, and analyze the structures and performance of the one-way delay waveguide, thus build a good foundation for further researches on one-way photonic crystal delay waveguide. In addition, this dissertation analyse the reflectivity of silicon based triangular-structural anti-reflaction films, caculate the reflectivity, and conclude that this structure holds a small reflectivity over a relatively large wavelength range.The dissertation is organized as follows:In Introduction, the main theoretic foundations and research background of this thesis are reviewed. First the basic concepts of photonic crystal are introduced. Then the PWE theoretic foundations and the mathematic models for carrying out research and calculation of photonic crystal in frequency domain are introduced. Based on these, the magneto-optical defects in photonic crystals and the one-way edge modes in the magneto-optical photonic crystals are listed and investigated, which are theoretical bases of the designs of one-way meander-line waveguide later.The beginning of the Chapter 2 describes the principles, including the Yee algorithm for Maxwell's equations and the perfectly matched layer absorbing boundary condition. These topics are extremely important in electromagnetic time-domain simulation. After that, an open source FDTD package (MEEP) developed at MIT, is investigated in detail. Then based on this, the package is revised to support the magneto-optical media FDTD simulation, and the revised process is given in detail.In Chapter 3, a different strategy is presented to design delay waveguide based on the one-way waveguide. A row of PEC slabs are introduced to enhance the delay time with a little broadening, which could be negligible in certain frequency range contained in the one-way modes. For the pulse with the central frequency 0.56(2πc/a) and width 0.02(2πc/a), the delay time of the proposed waveguide increases from 40.125(a/c) to 100.95(a/c) by introducing the three PEC slabs with smooth surface, and it was observed that this effect wasn't susceptible to the line defects in the upper cladding of the meander-line waveguide. This virtue can be used to tolerate the fabricated imperfection. Achieving such enhanced delay effect may be important for miniaturization and on-chip integration of the delay devices. The delay effect of the meander-line one-way waveguide with PEC slabs titled 45°is studied in detail. At the end of this chapter it is shown that the slow light modes can be found in the meander-line waveguide, in which the length of the PEC slabs within magneto-optical photonic crystal is 5a.Chapter 4 presents that the proposed unidirectional waveguide is of ultra-small transmission distortion and analyze the origin. By introducing PEC slabs to the unidirectional PCW, the proposed meander-line waveguide has ultra-small distortion and enhanced delay effect with a wide operating bandwidth (i.e. about 1.80% of the center frequency). FDTD simulation is carried out to observe the light propagation in the waveguide with PEC slabs. Compared with a conventional W1 PCW structure, the results show that the proposed structure has advantage not only in the delay time, but also in the GVD. On the other hand, the delay time of the proposed meander-line waveguide can be modulated by altering the length of the PEC slabs. Such delay waveguide may find its application in miniaturization and on-chip integration for broad bandwidth isolation and delay devices.Chapter 5 systematically analyzes the reflection property of the triangular-structural surface of solar cells, including the establishment of theoretical models, the FDTD simulation methods, and the comparison between the experimental results and the simulation results. When the triangle has aspect ratio of 21.63, the surface reflectivitiy at the wavelength range from 320nm to 1100nm is below 5%. At the same time, we compare the available experimental result with the FDTD simulation data, and our simulation data is in agreement with the experimental result.Chapter 6 summarizes the results of this dissertation. Future research topics are proposed.