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The Research on Optical Properties of Photonic Lattice in Defect States

Author: HeDongMei
Tutor: YangLiSen
School: Inner Mongolia Normal
Course: Optics
Keywords: photonic lattice defect state photorefractive crystal the method of cross phase mesh-defect
CLC: O734
Type: Master's thesis
Year: 2010
Downloads: 29
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Abstract

The application of optical fiber has inaugurated a new ear in information transformation which uses photons. The research on optical semiconductor, the materials for controlling the movement of photon, has become the precondition for the development of photonic device. E.Yablonovitch has pointed out the conception of photonic crystal in 1987, the behaviour of photons which propagates in the periodically distributed dielectric constant has draw researchers’ great attention. This kind of material is called photonic crystal or photonic lattices, but there are photonic band-gap in completed photonic lattices. In application, only the photonic lattices with defect have the ability of controlling the movement of photon. The fabrication and research of lattices with defect are a important task for the implementation of the all integrated photonic devices.Currently, institutions from both domestic and abroad have been doing theoretical research on the structure of photonic lattices in defect state, but the experimental research is limited. The reason is that the fabrication of lattices with defect is difficult to achieve. The method of light-induced has paved a brand new way for fabrication of photonic lattices with defect.In this thesis, two new methods of forming photorefractive photonic lattices with various structures of line-defect in iron-doped lithium niobate (LiNbO3:Fe) crystals are used, including the method of cross-phase and the method of slice-beam, then the ability of controlling photons are researched in detail. The main works are as follows:1. By cross-phase method, we have manufactured the different structures of two-dimensional (2D) photorefractive photonic lattice with line-defect, the width of which is measured by micron-scale in LiNbO3:Fe crystals. There are two advantages of the method , one is that its optical path is easy to set up, another is the line-defect is not only very sharp but also nondiffracted. The influences of the width, the direction and the number of lattices between two defects has been researched. The position of the defect mode changed in band-gap with angle of the probe light have been observed. The width of defect mode has been measured and been calculated by theoretical depending on the conditions of our experiment and the two results coincided well. According to the Kukhtarev equations in steady-state and the theory of two-beam coupling, we carry on the numerical simulation to light intensity and refractive index distribution of photonic lattice with line-defect.2. Using the method of slice-beam which is shaped by cylindrical lenses, we fabricated successfully the 2D photorefractive photonic lattice with single-line-defect, the width of which is 40μm , in LiNbO3:Fe crystals. The influences of irradiation time, the ratio of light intensity, the holes pitch of mask and the frequency of probe light on optical properties of photon lattice in defect states are analysed and discussed. Accordingly, we have found the optimum condition of experiment. Through theoretical calculation, a single-line-defect photonic crystal lattice was numerically simulated.3. We point out the method of fabricated to 2D photonic lattice with mesh-defect in photorefractive materials for the first time. And the 2D photonic lattice with mesh-defect is fabricated in LiNbO3:Fe crystals successfully. At the same time, the phenomenon of localize light-wave and the phenomenon of superposition light to enhance are found in the mesh-defect. In order to get the best results, the influence of experimental conditions about fabricated defects are analyzed in experimental and theoretical. According to theoretical calculations the light intensity distribution of photonic lattice with mesh-defect are simulated, the result of experiment correspond with the one in theory. Thus the feasibility of the method are confirmed, which plays a positive role in the invention of the integrated optical path and light computer.

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