硅纳米柱阵列的连续谱中束缚态研究及传感应用

Due to low loss and unique magnetic resonance, dielectric nanoparticles with high refractive index have recently been paid more attention. The Bloch bound states have been found in arrays of dielectric spheres, but the bound states in the arrays of silicon nano-cylinders have not been reported yet, and the low quality factor of the magnetic resonance mode currently used in the sensor leads to its lower sensitivity than that of surface plasmon sensors. This project intends to investigate the bound states in the continuum in arrays of silicon nano-cylinders by the theoretical analysis and experiments, and the application of bound states in sensing. We start from the energy band structure of arrays of the silicon nano-cylinders, and then analyze its reflection spectra and electromagnetic field distributions, finally the bound states will be found and confirmed. The effects of the magnetic resonance of the single cylinder and structural parameters on the frequency and quality factors of bound states are discussed. Samples with different areas will be fabricated, and then then reflectance spectra at different angles were measured, we investigate the relationship between the quality factor of the bound states, the sensitivity of the sensor, and the size of the sample. We will analyze the effects of the refractive index of the liquid covering silicon nano-cylinders on two types (symmetry protection and topological protection) of the bound states, compare the sensitivity of two types of sensors, and obtain the advantages and disadvantages of the two types of sensors. The research work of this project is of original innovation and will play an important role in the research and application of bound states in the continuum in dielectric nanoparticles with high refractive index.

由于低损耗和独有的磁共振，高折射率介质纳米颗粒最近获得了广泛关注。已经在一维介质球阵列的连续谱中发现布洛赫束缚态，但是二维硅纳米柱阵列的连续谱中束缚态尚未见到报道，并且目前用于传感器的磁共振模式的品质因子较低，导致其灵敏度低于表面等离子体传感器。本项目拟通过理论与实验相结合的方法研究硅纳米柱阵列的连续谱中束缚态及传感应用。从硅纳米柱阵列的能带结构出发，并分析其反射谱和电磁场分布，寻找并确认连续谱中的束缚态。研究单个硅纳米柱磁共振和结构参数对束缚态频率和品质因子的影响。制作不同面积的样品，测量各个角度的反射谱，研究束缚态品质因子、传感器灵敏度与样品面积大小的关系。分析覆盖硅纳米柱的液体折射率改变对两类（对称性保护和拓扑保护）束缚态的影响，比较两类传感器的灵敏度，得到两类传感器的优缺点。本项目的研究工作具有原始创新性，将对高折射率介质纳米颗粒的连续谱中束缚态的研究和相关应用起重要的推动作用。

由于低损耗和独有的磁共振，高折射率介质纳米颗粒最近获得了广泛关注。在本项目中，我们对硅纳米柱阵列的光学性质进行了细致的分析和研究。首先，分析了硅纳米柱的电磁共振现象，观测了单个纳米柱的散射谱，纳米柱阵列的反射谱和电磁场分布，发现硅纳米柱中米氏共振的波长依赖于纳米柱的直径，对纳米柱之间的间距和观察角不敏感。对于SOI衬底上的硅纳米柱阵列，氧化硅层作为法布里-珀罗腔，可以有效地调整硅纳米柱的后向散射，在共振条件下，后向散射得到了极大的增强。对于硅衬底上的硅纳米柱阵列，利用硅纳米柱中的米氏共振吸收来产生反射互补色。通过增加纳米柱的高度，提高结构色的饱和度。有趣的是，生动的蓝色是由梯形纳米柱对长波长的光的吸收而得到的。更重要的是，在所有可见波长的吸收确保了黑色的产生，这对于混色是非常重要的。对于这两种结构，我们均成功地实验实现了色彩鲜艳的图片，并获得了深亚波长的分辨率。其次，研究了硅纳米线的共振模式。发现硅纳米单线的高阶磁共振或者硅纳米双线的间隙耦合模式可以极大的增强近场，提高共振模式的品质因子，有助于光的选择性增强和限制，从而实现定向纳米激射。硅纳米线宽度决定了光谱共振特性和共振模的散射行为。由于硅纳米线对之间的耦合作用，电磁场的增强强烈依赖于纳米线对的间隙。通过合理选择纳米线的尺寸，找到了硅纳米线中高品质因子的共振模式，实现泵浦光场和发射光场的选择性增强，从而得到特定波长的方向性激射。上述有关硅纳米柱阵列的研究将为纳米彩色印刷、微显示器、信息加密、纳米激光器等提供技术储备。