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Investigation Of Band Gap And Photonic Device Based On Defect Photonic Crystal

Posted on:2017-02-23Degree:MasterType:Thesis
Country:ChinaCandidate:Q B FanFull Text:PDF
GTID:2308330488975387Subject:Electronics and Communications Engineering
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Photonic crystals (PCs) are artificial micro- and nano-structures that distributed periodically by different dielectric constant material. PCs can not only exhibit novel physical phenomena such as negative refraction, self-collimating phenomena and slow light, but also be designed to achieve optical fiber, wavelength division multiplexer (WDM), optical switches, mode converters, power splitters, lasers and other photonic devices. In this thesis, some unique properties of the defect and band of the PCs are thoroughly investigated and their applications to photonic devices are explored.First of all, plane wave expansion (PWE) method has systematically studied the complete photonic band gap (PBG) of copper-coin-shaped triangular lattice PC. The results demonstrate that the copper-coin-shaped scatterers are a combination of two types of PCs (air hole type and dielectric rod type) which in favor of obtain a wider complete PBG width. The width of the complete PBG has certain stability to deviation of doped material and the air hole radius caused by the preparation process. By grouping optimization of parameters, we obtain the widest complete PBG 0.1361(△ωa/2πc) with △ω/ωmid=33.55% at ε=22.75, R=0.483um, d=0.195um, φ=90°and G=1.3.Then the conditions of the quality factor ratio and phase are studied, in which the three-port PC filters need to be met. We have studied the several methods of improving the quality factor and designed two high-performance PC filters.Based on the previous studies, we have designed a novel multi-channel drop filters that consists of four linear gradient microcavities and heterophotonic crystal reflector by using two-dimensional square lattice photonic crystal of dielectric rods in air. The working mechanism of the heterophotonic crystal filter was analyzed by using PWE and two-dimensional finite difference time domain (2D-FDTD) method. Furthermore, we have explored the influence of the distance to drop efficiency which between the reference plane of the microcavity and the hetero-interface. The results show that the reflector is able to achieve 100% reflection and can improve the drop efficiency of the three-port channel drop filter greatly. Each channel of the designed filter has the ability to drop the light wave effectively which the channel space is 10nm, the rates of normalized transmission are all over 90%, and the full-width at half-maximum(FWHM) of the transmission spectrums are all below 0.54 nm. So the filter can achieve the high quality factor. The presented filter shows a compact size with 15.15 μm×13.91 μm and a high efficiency, and has potential application values to integrated optics circuits.We have also investigated the polarization-independent PC waveguides. A line-defect waveguide in a triangular lattice PC made of air holes in dielectric is demonstrated to support transverse magnetic (TM) as well as transverse electric (TE) guided modes simultaneously. A group of suitable geometric parameters were found to make the guided bands overlapped by means of Genetic Algorithm. The optimized waveguide realizes a polarization-independent single-mode transmission and wide operating bandwidth which reaches 0.012 (△ωa/2πc). Moreover, the guided modes are shown to exhibit a wide-bandwidth slow light and an extremely low group velocity dispersion in most frequency range.
Keywords/Search Tags:photonic crystal, photonic band gap, photonic crystal filter, hetero-photonic crystal, polarization-independent waveguide
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