基于纳米集成光路芯片的窄线宽局域表面等离子体共振传感和光谱探测的机理研究

With features of ultra-compact footprint, label-free detection and high sensitivity, waveguide integrated localized surface plasmon resonance(LSPR) sensors have boundless prospects in developing portable biomedical molecular detection facilities. However, due to intrinsic metal absorption and radiative scattering losses, linewidths of LSPR spectra are usually a few tens to hundreds of nanometers, which hinders further improvements of sensor sensitivities. In this project, a novel molecular detection technology based on ultra-compact integrated plasmonic circuit combining metal nanostructures and silicon nitride photonic integrated circuit is proposed. Light propagating in the waveguide is proposed to efficiently excite and couple the LSPR mode of the nanostructure integrated on the surface of the waveguide through evanescent field coupling. The whispering gallery mode(WGM) of microdisk resonators will be adopted to squeeze the linewidth of the LSPR spectrum. The waveguide integrated nanostructure chain configuration will be investigated to enhance the Raman scattering. On-chip detection of surface enhanced Raman scattering spectrum signal therefore will be achieved. A narrow-linewidth on-chip LSPR probe will be developed to perform specific detection of C-reactive protein. Our study will reveal the mechanism of mode coupling between light propagating in the WGM micro-resonator and LSPR mode of the nanostructure. Besides, we will clarify the mechanisms of mode coupling between Raman scattering and waveguide mode and enhancement effects of nanostructure chain on Raman scattering. And also, we will make it clear about the experimental condition which affects the stability of the sensors. This project is expected to improve the sensitivity of the on-chip LSPR biomolecular probe and promote the development of integrated sensors with chemical resolvability.

波导集成型局域表面等离子体共振（LSPR，Localized Surface Plasmon Resonance）传感器具有小型化、无标记、高灵敏度等特点，在开发便携式生物医学分子检测设备方面具有广泛前景。然而受金属吸收和辐射散射损耗影响，LSPR光谱线宽通常达百纳米，限制了传感器灵敏度。本项目提出结合纳米结构和集成光路的分子检测技术。利用回音壁模式光学微腔压窄LSPR光谱线宽；利用纳米结构阵列增强拉曼散射信号，实现表面增强拉曼散射光谱信号的平面耦合的激发和检测；开发窄线宽片上LSPR探针对C反应蛋白的特异性检测技术。本项目将阐明回音壁模式光学微腔中的传播光与片上集成的纳米结构LSPR模式的耦合机理，揭示拉曼散射光与纳米结构阵列-波导结构的相互作用机制，明确影响片上LSPR生物分子检测器稳定性主要因素。本项目将提高LSPR生物分子检测器灵敏度，推动集成化、具有化学分辨力的分子检测器的发展。

光谱技术是分析生物化学分子信息的“黄金工具”，在生物分子和化学成分定性、定量检测方面应用广泛。但是传统的光谱检测系统有诸多局限性，例如设备复杂、器件昂贵、系统对外界环境干扰敏感等。片上光谱检测技术近年来成为研究热点。相比自由空间光学系统，硅基集成光路具有集成度高、能耗低、造价低等优点，并且其 CMOS 相兼容的制作工艺保证了集成光路与片上集成的通信系统、信号处理系统具有良好的集成性及互联性。因此，硅基集成光路在开发小型化生物化学分子检测仪器中极具前景。本项目研究了硅基光子器件的特性及其在生化检测方面的应用。项目组设计并优化了狭缝波导和狭缝光纤等器件结构，用以提高波导的光场增强特性，从而提高片上生物化学分子检测的灵敏度，检测二氧化氮分子的灵敏度为2.71nm/ppm,检测下限为0.5ppm。优化了硅基光波导器件的制作工艺，完成了狭缝宽度为80nm的硅基垂直狭缝波导器件的制作，以及亚波长光栅耦合器的制作,光栅耦合器的1dB带宽为30nm，峰值耦合效率为25%。设计并优化了硅基波导集成的窄带反射器件,带宽为 1.5nm，反射率为 96%, 该器件可应用于液相折射率检测。项目组设计并优化了多模硅基波导器件，并研究其多参量传感特性，实现了对二氧化氮分子和温度的同时测量，灵敏度分别为0.02nm/ppm和0.106nm/K。探索了表面等离子共振传感器件表面生物功能化的方法，分别用抗体片段和抗原片段修饰了SPR生物传感器，并比较了这两种传感器的特异性检测性能。经半抗体片段表面修饰后，抗原修饰探针的灵敏度和检测限分别为0.9771nm/(μg/mL)和0.1μg/mL。本项目的完成将推动高灵敏度、具有化学分辨力的、片上集成的分子探测器的发展。