光纤耦合光波导相控阵光束优化方法研究

发布时间：2018-07-14 07:48

【摘要】：光波导光学相控阵器件具有驱动电压低、功耗小、响应速度快(ns量级)等特点,是未来光学相控阵的重要发展方向之一。由于光波导阵列器件制作工艺的限制,导致阵列器件存在一定的缺陷(例如各阵列单元波导芯层的厚度不一致、折射率不均匀性等)。光束经光波导阵列传输后,出射波束主瓣偏离理论计算位置,副瓣强度较高,对远场扫描探测影响大。现有的光学元器件和信息处理系统越来越倾向于集成化和微小化发展,实现光波导阵列与光纤集成封装,不仅有效提高激光功率利用效率,同时也将减小系统体积,提高系统稳定性。然而,对光纤耦合光波导相控的理论研究还鲜有报道。本论文的主要工作是系统研究光纤光束与光波导阵列耦合特性,探索光波导相控阵输出光束质量改善方法,实现高精度和低副瓣光束扫描,为光波导相控阵的性能改善提供理论和实验指导。考虑实际系统中激光光束通过单模光纤耦合到光波导阵列端面,而单模光纤基模电场分布为零阶贝塞尔函数,入射光场可用高斯分布表示。本文在传统平面波光学相控阵波束分析理论研究基础上,依据平板波导理论和波导耦合理论,在平行光束和高斯光束入射下,分析研究了光波导器件中光功率及远场分布随波导长度变化的关系。仿真分析了高斯光束下光纤与波导阵列端面间距不同时15层光波导阵列远场分布。实验验证了不同间距对远场分布的影响,当间距达到一定距离时,其远场分布与平行光入射下的远场分布一致。实验研究表明,由于波导阵列加工工艺产生的器件存在缺陷,直接依据均匀的波导阵列加电方案,实际光束偏转角度不仅误差大且偏转范围小。针对这一问题,基于模式搜索法开展出射光束优化,得到高衍射效率和低归一化精度误差的加电电压。仿真结果表明,对波导阵列加载优化后的电压,衍射效率明显提高,归一化精度误差得到改善。对波导阵列加载优化电压后的实验结果表明,对于1064nm脉冲激光,可实现光束扫描范围20?,扫描角度误差小于5.2mrad,远场主瓣半峰值宽度(FWHM)为2.02?,主副瓣比最高可达15dB;但对于980nm连续激光,虽然可以实现20?的光束扫描范围,但远场FWHM为4?,这与实验中使用的半导体激光器性能参数有关。
[Abstract]:Optical waveguide optical phased array devices have the characteristics of low driving voltage, low power consumption and fast response speed (ns). It is one of the important development directions of optical phased array in the future. Due to the limitation of fabrication technology of optical waveguide array devices, there are some defects in array devices (such as the thickness of waveguide core layer is inconsistent, the refractive index is not uniform, etc.). After the beam is propagated through the optical waveguide array, the main lobe of the outgoing beam deviates from the calculated position, and the sidelobe strength is high, which has a great influence on the far-field scanning detection. The existing optical components and information processing systems are becoming more and more integrated and miniaturized. The integrated packaging of optical waveguide arrays and optical fibers will not only improve the efficiency of laser power utilization, but also reduce the volume of the system. Improve system stability. However, there are few reports on the theory of fiber-coupled optical waveguide phase-control. The main work of this thesis is to study the coupling characteristics of optical fiber beam and waveguide array, to explore the method of improving the output beam quality of optical waveguide phased array, and to realize high precision and low sidelobe beam scanning. It provides theoretical and experimental guidance for improving the performance of optical waveguide phased array. In the practical system, the laser beam is coupled to the end surface of the waveguide array through a single mode fiber, while the fundamental mode electric field distribution of the single mode fiber is a zero-order Bessel function, and the incident light field can be represented by the Gao Si distribution. In this paper, based on the traditional theory of plane wave optical phased array beam analysis, and based on the theory of planar waveguide and waveguide coupling, under the incident of parallel beam and Gao Si beam, The relationship between optical power and far-field distribution with waveguide length in optical waveguide devices is analyzed. The far-field distribution of 15-layer optical waveguide array with different distance between fiber and waveguide array under Gao Si beam is simulated and analyzed. The effect of different distances on the far field distribution is verified by experiments. When the distance reaches a certain distance, the far field distribution is consistent with the far field distribution under the incident of parallel light. The experimental results show that due to the defects of the devices produced by the waveguide array fabrication process, the deflection angle of the actual beam is not only large but also the deflection range is small according to the uniform power supply scheme of the waveguide array. Aiming at this problem, the output beam optimization is carried out based on the mode search method, and the charging voltage with high diffraction efficiency and low normalized precision error is obtained. The simulation results show that the diffraction efficiency is improved obviously and the normalized precision error is improved for the optimized voltage of the waveguide array. The experimental results after loading the optimized voltage for waveguide array show that for 1064nm pulse laser, the beam scanning range is 20g, the scanning angle error is less than 5.2mrad, the half peak width of far lobe is 2.02g, and the ratio of principal to sidelobe is up to 15db, but for 980nm continuous laser, Although can achieve 20? But the far-field FWHM is 4 渭 m, which is related to the performance parameters of the semiconductor laser used in the experiment.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN252

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