PS微球阵列的制备与表面增强拉曼散射研究

为了研究不同直径PS微球(表面溅射Ag膜)基底的表面增强拉曼散射(SERS)效应,制造了一个新的表面增强拉曼散射(SERS)基底。通过在n型(100)单晶硅片上采用旋涂的方法,得到不同直径的呈六角形有序排列的单层PS微球阵列,然后在PS微球阵列表面磁控溅射一层约30nm的Ag膜。利用拉曼光谱仪以罗丹明R6G为探针进行了SERS光谱测定,分析比较了不同直径PS微球阵列的表面增强拉曼散射效应,结果表明,溅射有Ag膜的PS微球基底在不同直径下均有不同程度的SERS效应。随着微球直径的增加,PS微球阵列的起伏程度不断加强(粗糙度不断增加),SERS信号逐渐增强,当球直径达到600nm时,峰的增强信号达到最大,进而获得了一个最优化的SERS基底。同时发现在基底上获得了高信噪比的R6G的SERS光谱,与苯环相关的一系列C=C双键伸缩振动特征谱以及与苯环相关的面内、面外变形振动特征谱均获得了明显增强。这种单一的大区域的拉曼散射基底,呈现出高低相间起伏分布的微观形貌,不同PS微球之间的空隙和深度有很明显的不同,能够显著改善表面Ag膜颗粒的大小和分布,进而提高了PS微球基底的SERS活性。该基底所具有的特殊阵列结构使其在利用SERS探究化学和生物等领域的单分子结构有很大的应用潜力。     

中空Ag纳米球壳的制备及性能表征

 以改性聚苯乙烯微球为模板,采用化学镀法在聚苯乙烯微球表面包覆一层银,在四氢呋喃溶液中将聚苯乙烯微球溶解,得到中空Ag纳米球壳。采用扫描电镜、透射电镜和X射线衍射仪对样品进行了表征及分析,并用紫外可见分光光度计研究了粒子的光学性质。实验结果表明：运用此法成功地制备出中空Ag纳米球壳的内径为250 nm,壁厚约为15 nm,并且成功地使纳米粒子的紫外吸收光谱由600 nm红移至900 nm左右,实现了在可见光至近红外光区调节Ag纳米结构的吸收峰。     

Effect of Au/Ni/4H–SiC Schottky junction thermal stability on performance of alpha particle detection

Au/Ni/n-type 4H–SiC Schottky alpha particle detectors are fabricated and annealed at temperatures between 400℃ and 700℃ to investigate the effects of thermal stability of the Schottky contact on the structural and electrical properties of the detectors. At the annealing temperature of 500?C, the two nickel silicides(i.e., Ni_(31)Si_(12) and Ni_2Si) are formed at the interface and result in the formation of an inhomogeneous Schottky barrier. By increasing the annealing temperature,the Ni_(31)Si_(12) transforms into the more stable Ni_2Si. The structural evolution of the Schottky contact directly affects the electrical properties and alpha particle energy resolutions of the detectors. A better energy resolution of 2.60% is obtained for 5.48-MeV alpha particles with the detector after being annealed at 600℃. As a result, the Au/Ni/n-type 4 H–SiC Schottky detector shows a good performance after thermal treatment at temperatures up to 700℃.     

Design of an all-dielectric long-wave infrared wide-angle metalens

Optical metasurfaces are two-dimensional arrays of nano-scatterers that modify optical wavefronts at subwavelength spatial resolution. They achieve the effect of focusing through phase control under a subwavelength scale, and are called metalenses. They are poised to revolutionize optics by enabling complex low-cost systems. However, there are severe monochromatic aberrations in the metasurfaces. In this paper, the coma of the long-wave infrared optical system is eliminated through a single-layer metasurface. By changing the phase function, this metalens has a numerical aperture of 0.89, a focal length of 150 μm and a field of view of 120° (0.4@60 line pairs/mm) that enables diffraction-limited monochromatic imaging along the focal plane at a wavelength of 10.6 μm. The designed metasurface maintains a favorable value of the modulation transfer function at different angles. This equipment can be widely used in imaging and industrial processing.     

伽马辐照对掺镱光纤材料特性影响的研究

掺镱光纤是高功率激光器的核心材料,但在高能射线辐照后其应用性能会显著下降,因此有必要对掺镱光纤材料在辐照环境下的性能变化进行深入研究。采用改进型化学气相沉积法结合稀土螯合物掺杂制备了系列光纤预制棒及光纤,测试了光纤在不同剂量下射线辐照前后的高功率输出性能,以及光纤预制棒辐照前后的吸收光谱及镱离子荧光寿命。结果表明:小剂量辐照后掺镱光纤的高功率输出显著下降,通过预制棒吸收光谱可看出主要是因为伽马辐照后使掺镱光纤材料中Al的相关缺陷浓度增多,在可见光区域吸收损耗增加。Ce离子的掺杂通过缓减辐致铝氧空位中心(Al-OHC)色心缺陷的增加,减少Yb离子荧光寿命的下降,可在一定程度上抑制高功率掺镱光纤的辐致暗化。     

不同加料方式对共沉淀法制备YAG纳米粉体的影响

用共沉淀法制备了钇铝石榴石(Y3Al5O12)纳米粉体,研究了正滴定、反滴定和一步注入工艺对钇铝石榴石纳米粉体合成过程及最终产物的影响。利用X射线衍射仪、傅立叶红外光谱仪、同步热分析仪、场发射电子显微镜对YAG前驱体及不同温度煅烧后的粉体进行表征。结果表明:通过正滴定、反滴定和一步注入工艺,分别制备出化学组成为10[8.9Al(OH)3+1·1NH4Al·(OH)2CO3]·3[Y2(CO3)3·3H2O]、10[7.3Al(OH)3+2.7NH4Al·(OH)2CO3]·3[Y2(CO3)3.3H2O]、10[Al(OH)3]·3[Y2(CO3)3·3H2O]的前驱体。前驱体经900℃煅烧2 h后,正、反滴定工艺得到的粉体主相为YAG(Y3Al5O12),但有少量的YAP(YAlO3),一步注入工艺则得到纯的YAG相。晶粒尺寸分别为85 nm、70 nm和65 nm,且一步注入工艺获得的粉体粒径分布较窄,分散性良好。     

熔石英光学元件的损伤前驱及其抑制技术北大核心CSCD

基于抛光所引起的熔石英元件表面、亚表面所存在的损伤前驱体分布,研究了不同种类的损伤前驱体所引起的损伤形貌。然后根据不同种类的损伤前驱体分别采用表面活性剂、强氧化性酸、氢氟酸的水溶液对不同的损伤前驱体进行处理。研究结果显示:经过前期预先清洗以后,吸收性杂质所导致的雾状损伤得以消除,亚表面分布的裂纹得以很好地平滑钝化,极大地提升了熔石英光学元件的抗损伤性能,损伤阈值从4.8J/cm2提高到11.0J/cm2,最大提升幅度达到原来的2.3倍。     

介质超透镜自动设计技术及软件研究

由于超透镜在光场相位调控、多功能复合、微纳集成等方面具备传统透镜无法比拟的优势,故其在许多领域具备极大的应用潜力。但是,超透镜的设计需要专业人员具备专业知识及丰富的经验,这使得非专业人员无法快速掌握,为此阻碍了超透镜的规模化制备。通过MATLAB和时域有限差分法(FDTD)的混合编程,研究了不依赖于预设物理模型的超透镜的设计过程,实现了介质超透镜的自动化设计。通过在MATLAB编写的软件界面上输入所需的超透镜参数,后台调用FDTD设计仿真程序来构建纳米结构,可以计算出结构的尺寸与相位和透过率的关系。根据所需的相位分布来构建超透镜,最后对超透镜进行数值模拟仿真及性能评估。所述的设计流程及软件能极大地方便非专业人员进行超透镜的设计。     

SiO_2胶体晶体自组装技术

介绍了垂直沉降法和旋涂法制备SiO2胶体晶体,并对两种方法制备的胶体晶体在宏观形貌、微观结构及光子带隙性质进行了比较。采用改进的Stober法在乙醇介质中合成粒径不同、单分散性较好的SiO2微球,用垂直沉积法和旋涂法制备出有序性较好的密排结构的SiO2胶体晶体。宏观照片表明,用旋涂法制备的SiO2胶体晶体经白光照射出现的光柱呈6次对称,而垂直沉降法制备的胶体晶体表面出现条纹。SEM分析表明,选用不同溶剂在同等旋涂工艺下制备SiO2胶体晶体,用乙醇和乙二醇混合溶液作溶剂制备出的SiO2胶体晶体质量最好。透射光谱表明,垂直沉降法所制备的胶体晶体在(111)方向具有明显的光子带隙性质,而旋涂法制备的胶体晶体则不明显。     

Temperature-responded tunable metalenses based on phase transition materials

Once the metalenses are fabricated, the functions of most metalenses are invariable. The tunability and reconfigurability are useful and cost-saving for metalenses in realistic applications. We demonstrate this tunability here via a novel hybrid metalens with the strategic placement of an ultra-thin VO₂ layer. The hybrid metalens is capable of dynamically modulating the focusing intensity of transmitted light at a wavelength of 1550 nm, and demonstrate a 42.28% focusing efficiency of the incident light and 70.01% modulation efficiency. The hybrid metalens' optothermal simulations show an optothermal conversion process of dynamic focusing, and a maximum laser density of 1.76×10³ W/cm² can be handled at an ambient temperature lower than 330 K. The hybrid metalens proposed in this work, a light-dose sensitive tunable smart metalens that can protect other instruments/systems or materials from being damaged, has its specific applications such as in anti-satellite blinding, bio-imaging, etc.