【作者】 张猛；

【导师】 张林；

【作者基本信息】 天津大学 ， 光电子与光子学技术， 2018， 硕士

【摘要】 光栅耦合器是光子学领域的重要器件,本论文基于光栅耦合器研究了应用于模分复用光通信和光镊领域的集成功能器件。现今,数据中心和长距离传输系统的数据传输量正在指数增长,传输的数据容量逐渐达到单模光纤的传输极限。利用少模光纤中的高阶模式传输信息可以解决数据网和通信网日益增加的数据传输需求问题,但是利用模分复用方法实现这种大容量数据传输需要具有模式转换功能的光耦合器件。本论文提出了可实现模式转换功能的光栅耦合器,这类耦合器具有耦合效率高、加工工艺简单等优点。当光波导中输入TE基模时,光经过光栅耦合器可以激发少模光纤中的LP₀₁、LP_11a、LP_11b和LP_21b模式,利用光栅耦合器激发上述各种模式的耦合效率均可超过50%。此外,本论文还从带宽、耦合效率和对加工误差的容忍度这三个方面分析了光栅耦合器的性能。目前,可实现微粒的光学操控和束缚的集成波导结构引起了广泛的关注。对于尺寸比较大的结构,本论文提出了用二维光场分布估算光力的方法,并验证了其准确性;用粒子群算法优化结构参数,设计了可用于光学束缚的光栅耦合器。该光栅耦合器可以辐射出具有60°发散角的光束,光场产生的光力可以将尺寸大于6μm的微粒束缚在光栅表面区域。最后,本论文提出了可以和光栅耦合器联用的狭缝等离子波导光镊结构,该波导型光镊结构具有易于加工和可级联的优势。本论文对结构中的光场分布和光力分布进行了分析,结果表明半径为300 nm的微粒可以受到百皮牛的光力,这足以稳定地束缚微粒;对微粒的状态进行了动态分析,并计算了微粒运动的轨迹,最终确认了微粒被波导狭缝捕获的可能性。结果表明将微流体水速控制在一定范围内,可以有效地将微粒捕获在狭缝区域。更多还原

【Abstract】 Grating coupler is a key device in integrated photonics.Here,we investigate integrated functional devices based on grating couplers for various applications.Recently,data traffic in long-haul telecom systems and data centers is growing exponentially and will reach the capacity limit of single mode fibers（SMFs）.The significantly increased requirement for telecom and datacom system capacity calls for mode division multiplexing,in which it is essential to combining light coupling between transceivers and fibers with mode conversion functions.We show that this can be done with a high efficiency.The proposed devices are very compact,with no extra fabrication efforts required.It is shown that the LP₀₁,LP_11a,LP_11b and LP_21b modes in a few-mode optical fiber can be excited directly from the proposed grating couplers,when the TE mode is used.The overall coupling efficiency,including mode conversion efficiency,can be 50%.We also analyze the performance of the grating couplers in terms of bandwidth,efficiency and tolerance to device fabrication errors.Optical manipulation and trapping of particles using integrated optical waveguides have been attractive.We present a method of estimating optical force using two-dimensional optical field distribution for large size structures waveguide,and verify its accuracy.We demonstrate an optical tweezer using a grating coupler that can radiate light with a divergence angle of 60°.The structure of the grating couplers are optimized by Particle Swarm Optimization.The analysis on field and the optical force distribution shows that particles of>6μm in size can be trapped to the grating coupler.Finally,we show an optical tweezer using surface plasmon polaritons of metal,which can be used together with grating couplers.This device is fabrication-friendly and cascadable.We study its field and force distributions.The force on particles with a radius of 300 nm can be sub-nN,high enough to trap particles stably.Also,we show an in-depth analysis of the trapping dynamics to the potential well and the trajectory of particles.We conclude that this novel structure can be successfully used for optical trapping and manipulation of nanoparticles by controlling water velocity.更多还原