QQ客服 官方微博 反馈留言

题名	飞秒激光在透明介质中制作光学波导器件研究
作者	董明明
学位类别	硕士
答辩日期	2013
授予单位	中国科学院上海光学精密机械研究所
导师	赵全忠
关键词	飞秒激光 光波导 透明介质 集成光学
其他题名	Fabrication of Optical Waveguide Devices in Transparent Dielectrics by Femtosecond Laser
中文摘要	飞秒激光用于制作光学波导器件已经引发了持久不衰的研究热潮，灵活的三 维加工能力、简单方便的加工工序和高封装密度等特点使其相对于其他波导制作方法具有独特的优势。经过十多年的发展，目前利用各种参数的飞秒激光已经在玻璃、晶体、陶瓷和聚合物等透明介质中形成了各种各样的无源、有源和功能波导及波导器件。现有的波导制作可以分为两种不同的类型：利用低能量飞秒激光直接作用下折射率增加的区域作为波导区的I型波导；高能量激光损伤在周围产生应力场，II型波导利用这种压光效应导致的折射率升高区域作为芯层，其典型代表是双线波导。 但以上波导制作方法仍然存在无法克服的缺点。一方面自聚焦和象散引起的聚焦光斑畸变会破坏I型波导截面的对称性，而且激光和材料作用后不可避免地会破坏材料的结构从而改变或损伤材料的光学、电学、力学和热稳定性能，这在波导制备过程中时通常是不愿意被看到的，更重要的是I型波导所依赖的折射率升高机制受材料和激光参数的影响太大，在大部分晶体和部分玻璃材料中会出现加工窗口很窄甚至根本无法形成波导的情况。另一方面，II型双线波导在垂直于损伤线方向的截面折射率分布是阶跃型的，而平行于双线方向的分布是渐变型的，这种不对称的折射率分布会导致偏振相关传输特性，而不平衡的应力导致的双折射效应在光通信领域是不利的。 本研究的目的是提供一种能避免上述缺点的飞秒激光制作波导的方法，该方法同样基于II型折射率改变，但是形成的波导能从根本上避免应力双折射，波导折射率轮廓不受光束畸变的影响，具有对称且可控的波导截面，并保留基底材料固有的物理性质。本研究提出的方法可以作为现有波导制作方法的补充，扩大飞秒激光制作波导的应用前景。本文具体可分为以下两个方面： 1、 提出了一种能避免现有技术诸多缺陷的飞秒激光制作光学波导的方法。使用1kHz低重复频率的飞秒激光在透明介质内部诱导激光成丝损伤结构，利用激光作用时的微爆炸冲击波在辐照区域周围产生梯度应力场。在样品内部沿闭合曲线扫描光斑形成柱形损伤壳层，受到四周挤压的被包围区域由于压光效应导致折射率增大可作为波导芯层，而激光损伤壳层由于密度稀疏化导致折射率被降低可作为波导包层。在沿水平闭合曲线扫描结束后辅以垂直移动形成多个首尾相连的壳层节可形成长尺寸波导。对制作的波导进行了性能测试和分析。形成的波导具有截面可控、芯层性质保留完好、热稳定性高、材料适用性强等优点。 2、 在成功制作出直线波导的基础上制作出了三维波导分束器。在壳层节连接过程中引入微小错位形成空间弯曲波导，制作的波导分束器具有单个输入端、多个输出端和扇出结构的倾斜分束臂，通过改变分束角和弯曲曲率可以配置分束比，另外可以通过调节波导分束器的入射角度实时调节分束比。本方法相对传统飞秒激光制作光波导器件具有特有的优点，将丰富和完善飞秒激光制作微光电子学器件的手段。
英文摘要	Persistent research efforts have been invested in femtosecond laser as a tool to fabricate optical waveguide devices due to its dominant advantages over other waveguide machining methods including its 3D processing flexibility, simple machining procedures and high packaging density. Over a decade of development, various femtosecond lasers have been used to inscribe passive, active and functional waveguides and waveguide devices into transparent dielectrics such as glasses, crystals, ceramics and polymers. So far, two basic fabrication mechanisms have emerged, including type I laser-induced index enhancement with low energy pulses and type II stress-induced index increased neighboring region as core upon high energy pulses, among which the double filaments sandwiched waveguide acts as a typical instance. However, the above waveguide processing approaches contain irreconcilable contradictions. On the one hand, the astigmatic spot of focused laser and self-focusing would produce tear-drop modified structure inside bulk materials, which will destroy the symmetry of waveguide cross-section. Besides the laser modified region inevitably accompanied by structure damage tends to show tailored or degraded optical, electrical, mechanical properties and thermal stability. Moreover, the underlying mechanism, on which type I method relies, is highly depend on materials and laser parameters thus sets a narrow or even closed processing window in most crystals and some glasses. On the other hand, type II double filaments waveguides are characterized by approximate step-index distribution in the direction vertical to writing laser beam while graded-index in the parallel direction, which would lead to polarization dependent guiding phenomenon and is unfavorable to optical communication.. This research aims to provide a waveguide processing approach that avoids the drawbacks mentioned above. It is also based on type II refractive index change but can fundamentally bypass stress-induced birefringence. The cross-section of the waveguide is immune to beam deformation and remains symmetrical and controllable with the core region preserving the physical properties of the substrate. The proposed method may enrich current waveguide fabrication techniques and widen the application prospect of femtosecond laser as a powerful waveguide machining tool. This dissertation covers following research: 1. A new waveguide fabrication approach using femtosecond laser has been proposed that can avoid many drawbacks of current methods. Femtosecond laser pulses with low repetition rate of 1kHz were used to induce destructive filaments inside transparent dielectrics causing gradient stress field upon micro-explosion shockwave. A cylindrical shell was produced by scanning the elongated laser focus along an enclosed routine, giving rise to an encompassed and squeezed central core with enhanced refractive index due to piezo-optical effect, which is surrounded by laser-rarified and index-depressed cladding shell. A long waveguide consists of dozens of sequentially overlapping tubular segments produced by horizontal scanning followed by a minor vertical descent. The performance of the waveguides was investigated and analyzed. The resulted waveguides feature controllable cross-section, intact core region, high thermal stability and strong material adaptability. 2. Three-dimensional waveguide splitters were also demonstrated based on current waveguides mechanism. Spatially curved waveguides can be formed by introducing a minor dislocation of tubes during the connecting process. A waveguide splitter as made comprises a entrance port, multiple exit ports and tilting fan-out splitting arms. The splitting ratio can be configured by changing the splitting angle and bending curvature. Besides it can also be tuned in real time by adjusting the incident angle. Considering its unique merits over traditional approaches, current method enriches and improves the capability of femtosecond laser as a measure of waveguide fabrication.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/16785]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	董明明. 飞秒激光在透明介质中制作光学波导器件研究[D]. 中国科学院上海光学精密机械研究所. 2013.

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。