基于同心金属圆环光栅太赫兹波导管端面耦合的小型化传感器的研究

The exploration of integrated and miniaturized photonic devices by incorporation of metallic and semiconductor micro and nanostructures onto the end facets of optical fibers is currently a hot research topic. However, the creation of metallic micro and nanostructures onto the facets of THz waveguide tubes to form miniaturized refractive index sensors has not been reported so far. This research program aims at to combine concentric metallic ring grating onto the THz waveguide tube to experimentally realize a polarization independent, high sensitivity, high Signal-to-Noise, high stability miniaturized refractive index sensor in THz wavelength band, and to investigate its application in biologic sensing further.The sensing function of this miniaturized device is realized by sending THz wave as a probe to the concentric metallic ring grating and by collecting the response signal in the back-reflection through the THz waveguide tube. A pronounced peak due to the Rayleigh anomaly of the metallic ring grating in the reflection spectrum is used as sensing signal, whose center wavelength is sensitive to the change in the environmental refractive index outside of the THz waveguide tube. The performances of this sensor are promised by the its unique design: (1) The rotational symmetry with respect to the THz waveguide tube axis of the concentric metallic ring grating making the sensor response independent of the polarization of the probe THz wave; (2) The Rayleigh anomaly reflection peak of the concentric metallic ring grating shows high sensitivity to the change of the environmental refractive index; (3) The value of the Signal-to-Noise can be optimized by adapting the right value of the duty cycle of the concentric metallic ring grating; (4) The signal of this sensor can be stabilized by choosing the right parameters of the THz waveguide tube.The sensor can be fabricated in the following steps: Firstly, photo lithography is employed to fabricate the master of concentric SU8 ring gratings with varying values of duty cycle on silicon wafers, and then the master of concentric SU8 ring gratings is metallized by evaporating gold on them to form the concentric metallic ring gratings. Secondly, the wafers are cut into small pieces according to the area of the metallic ring gratings. Thirdly, the small pieces are glue onto the facets of the THz waveguide tube with the metallic ring grating face up as the sensing surface.

将金属或者半导体微纳光子结构制备在波导端面上，实现微纳光子结构与波导的无缝结合是目前国际上开发新型集成化和小型化光子器件的一个研究热点。而在THz波导管端面制备金属微纳结构，开发THz波段小型化的折射率传感器件的相关研究尚未见报道。本项目旨在将同心金属圆环光栅与THz波导管相结合，实验上实现THz波段偏振无关的高灵敏度、高信噪比、高稳定性的小型化折射率传感器件，并进而开发其在生物检测方面的应用。器件的独特结构设计确保了器件的各项性能的实现：（1）采用轴对称的同心金属圆环光栅与圆形THz波导管相结合，实现器件的偏振无关性；（2）利用同心金属圆环光栅的Rayleigh反常反射峰作为检测信号，实现器件的高灵敏度响应；（3）通过优化同心金属圆环光栅的占空比，实现Rayleigh反常反射峰信号信噪比的提高；（4）通过波导管的优化设计，提高同心金属圆环光栅与THz波导管结合后的信号稳定性。

传感技术（信息获取技术）同通信技术（信息的传输）、计算机技术（信息的处理）一起被称为信息技术的三大支柱。传感技术的发展水平是衡量一个国家信息化程度的重要标志。获取信息靠各类物理量、化学量或生物量的传感器，传感器件是传感技术的体现。传感器的功能与品质决定了传感系统获取信息的质和量。高性能、小型化、新型传感器件的研发是目前传感研究领域的两个重要研究方向。.本项目以开发新型、小型化太赫兹以及可见光波段的传感器件为研究目标。主要研究内容分为以下两个部分：（1）开发THz 波段小型化的折射率传感器件；（2）开发可见光波段及通信波段的新型光纤拉曼以及振动传感器件。.重要结果：（1）太赫兹波段基于法-珀效应的瑞利反常反射峰的边带压低的实现。在金属光栅与基底之间添加一个介质层后，瑞利反常信号的边带被显著地压低，信噪比显著提高。通过实验和理论上的深入研究，阐明了其边带压低的机理。相关研究成果作为邀请论文发表在国际知名期刊Journal of Optics上，杂志编辑给予本文高度评价，被该期刊评选为2014年度6篇高质量学术论文之一，以LabTalk方式在杂志期刊主页加以报道。（2）太赫兹波导管输入输出耦合器的设计及加工。采用黄铜材料完成了太赫兹波导管输入输出耦合器的设计和加工。（3）”光纤拉曼雷达”的设计、制备和表征。提出了光纤耦合拉曼雷达的概念。提出将光纤端面上的表面拉曼增强基底设计从二维平面结构拓展到三维立体结构，从而为反射式光纤拉曼传感方案与性能优异的不透光表面拉曼增强基底提供更大的相容空间，解决了不透光的优异表面拉曼增强基底与为反射式光纤拉曼传感方案难以兼容这一问题，开启了新型光纤拉曼传感器件新的研究思路。在实验上采用双光子3D光刻系统、金属热蒸镀以及激光脉冲烧蚀技术完成了器件的制备。拉曼光谱实验表明，该光纤耦合拉曼雷达传感器件对于结晶紫溶液的检测，其浓度值可以低达10-6 摩尔每升。该项研究成果以内封面形式发表在国际著名期刊Advanced Optical Materials上。（4）提出并在实验上实现了一种新型光纤麦克风声音传感器件。采用具有窄带高反特性（对1550 nm的光波高反）的光栅波导薄膜作为振动敏感元件，实现对声音的感知。采用双光子3D光刻技术完成了器件的制备；搭建了光纤麦克风测试系统。实验观测表明，器件在400 Hz到2000 Hz 对正弦波信号有着良好的响应