【作者】 刘颖；

【导师】 周忠祥；

【作者基本信息】 哈尔滨工业大学 ， 光学， 2010， 硕士

【摘要】 随着全光网的发展,光开关成为光网络通信技术的核心器件。全息光开关利用激光的全息技术和晶体的光折变效应,将光栅全息图写入晶体内部,通过衍射控制实现开关功能。电控全息光开关是基于二次电光效应从而实现对光栅开关状态的电场控制,这种方法制作的光开关由于具有高的衍射效率和快的响应速度已成为光开关实现的新的替代方案。顺电相钽铌酸钾锂(KLTN)晶体在相变温度附近电光效应显著,鉴于其优越的性能,对顺电相下KLTN晶体性能及其光开关器件的研究将促进全光网络以及光信息处理的发展。采用提拉法生长室温下具有顺电相结构的KLTN晶体,通过掺杂提高顺电相晶体的空间电荷场,从而提高晶体的光折变性能。利用二波耦合技术和顺电相全息晶体的二次电光效应,在掺锰钽铌酸钾锂晶体(Mn:KLTN)内部写入体相位Bragg光栅,讨论不同外加电压下体相位栅的衍射效率随各参数间变化关系。在不同入射光波长532nm、632.8nm下分别测得了光栅的写入擦除曲线,讨论了光栅记录角度、温度等参数对衍射效率的影响。实验还观察了较大外加电压下光栅的衍射现象。通过参数优化,实现最佳衍射条件。通过在顺电相电控全息晶体Mn:KLTN的内部写入两重Bragg光栅,实现了对632.8nm和532nm两波长信号光的电控衍射。根据此电控衍射的工作原理,给出两种光开关制作方案,实现了对两种波长信号光的合束、分束及同时读取,并对衍射信号光的均匀性进行了分析。结果表明,这种利用多重写入技术制作的光开关可同时实现1×2及2×1光开关功能,具有成本低、响应快、性能稳定的优点,适用于多种光学互连网络。搭建小角度记录光路,在顺电相全息晶体Mn:KLTN的内部写入光栅,得到具有Raman-Nath衍射的高阶衍射光栅,实现了对光束的电控高阶分束。通过实验获得了不同波长光垂直入射以及斜入射时高阶衍射现象,讨论了垂直入射和斜入射两不同入射方式时零级衍射的相似性,分析了斜入射情况下高阶衍射能量分布情况。通过记录角度的改变,得到高阶衍射时一阶衍射效率的变化情况,说明了高阶衍射对记录角度的敏感性。通过变化不同波长及其入射角入射时的高阶衍射现象比较,说明高阶衍射没有波长选择、角度选择功能。更多还原

【Abstract】 With the development of AON (All Optical Network), optical switch becomes a core component in optical network communication. Based on holographic techniques by Laser and photorefractive effect in a paraelectric electroholographic crystal, phase gratings was written in to achieve the on-off function. Based on quadratic electro-optic effect, electroholographic switch worked at on-off states by the controlled of external electric field, it has been considered as a promising switch for the combining advantages of high diffraction efficiency and fast electro-optic response time. Paraelectric potassium lithium tantalate niobate (KLTN) crystal has the largest quadratic electro-optic coefficient compared with other crystals, and prominent electro-optic effect near the phase transition temperature. Photorefractive effect was enhanced under external electric field. Due to its excellent properties of KLTN crystal, study on its properties and applications of switch made by paraelectric KLTN crystal would advance the development of all optical network and optical information processing.The Czochralski method was used to grow paraelectric KLTN crystals which phase transition temperature were near room temperature. The space-charge field of paraelectric KLTN crystal was enhanced with several dopant types, so that the photorefractive effect of the crystal was also enhanced. Processing techniques was improved to gained a high quality crystal plate. Two wave mixing setup was designed and built, recording and reading process of Bragg gratings were realized. Based on two wave coupling theory and quadratic electro-optic effect in a paraelectric electroholographic crystal, volume phase Bragg gratings was written in manganese doped potassium lithium tantalate niobate (Mn:KLTN). Diffraction efficiency versus various parameters was discussed at different external voltage. Diffraction efficiency versus read-in time curve and grating erasing curve were given at both 632.8nm and 532nm incident lights. The impact of diffraction efficiency by changing record angle and temperature were also discussed. The abnormal phenomenon of grating diffraction curve was discovered with a high external voltage. The best diffraction qualification was carried out when the related parameters were optimized.Two Bragg gratings were written in a thick paraelectric electroholographic crystal Mn:KLTN, and then both 632.8nm and 532nm signal were diffracted at the same time under electric field controlling. Based on the mechanism of this electro-controlled diffraction, two kinds of switches were designed to accomplish the beam splitting, combining and reading together. Uniformity of the diffractive signal light was also analyzed. The results indicated that the switch made by multiple writing techniques was very suitable to various optical connecting networks, because of its advantages of multifunction, fast response, low cost and low intensity to environment disturbance.Two wave mixing setup was built where the angle of the two recording beams was really tiny. Two-dimensional grating was written in a thin paraelectric electroholographic crystal Mn:KLTN, the Raman-Nath grating was obtained and the high-order diffraction appeared, beam incidence was separated into multi-beam by the controlled of external electric field. At both 632.8nm and 532nm incident lights, the high-order diffraction phenomenon were gained in the way that vertical incidence and oblique incidence contained. Then in the two incident way, the zero-order diffraction was discussed and intercompared. Energy distribution of high-order diffraction was analyzed in the way of oblique incidence. Diffraction efficiency of first order versus incident angle was measured and the conclusion was given. By changing the incident angle and wavelength, the high-order diffraction phenomenon were gained and intercompared. It was proved that Raman-Nath diffraction was insensitivity to the incident angle and wavelength.更多还原