采用微流注射法在光纤端面制备单层胶体微球薄膜

提出了一种在光纤端面制备单层胶体晶体薄膜的新方法——微流注射法,利用针尖微量注射胶体微球溶液,该方法可以在气/液界面直接形成大面积六角密排的周期纳米球阵列,面积达到平方厘米级别,再利用二维胶体单层膜的可转移性,将薄膜转移至到光纤端面衬底上,形成单层胶体微球有序薄膜.采用扫描电子显微镜和光谱分析仪对样品形貌、结构以及光学特性进行了表征和分析.电子显微镜图像表明,光纤端面的胶体晶体为六角密排阵列结构.透射光谱表明,该结构具有光子晶体的带隙特征,带隙的中心波长约为700和850 nm,与分析软件FDTD Solutions仿真结果相吻合.结合溅射沉积方法,得到了银纳米球壳阵列结构,检验了其局域表面等离子体共振效应(LSPR).对比讨论了溶液浓度、弯月面的形成及注射速度等因素对微流组装胶体微球薄膜质量的影响.     

X-两环结构的光学特性研究

提出了一种X-两环的金属周期性阵列结构,该结构由两个同心圆环包围中心X型构成.利用时域有限差分算法研究了该结构的光学特性.计算表明,当光入射到金属表面时,能够在结构中产生法诺共振现象,并在不同的位置下产生共振谷.同时,共振谷的出现又明显依赖于结构的相对参数(X的臂长、内外环的距离、内外环宽度、周期、环数、X所呈的角度),从而可以通过调节结构的相对参数来实现对结构的共振强度及共振谷位置的调控.另外,进一步分析了在不同环境折射率条件下该结构共振谷的变化规律,可以得出该结构也对周围的环境折射率有着较高的敏感度,最高可达1300 nm/RIU.结果表明,该结构在环境折射率传感器及某些光子器件的应用方面有着潜在的价值.     

Different optical properties in different periodic slot cavity geometrical morphologies

In this paper,optical properties of two-dimensional periodic annular slot cavity arrays in hexagonal close-packing on a silica substrate are theoretically characterized by finite difference time domain(FDTD) simulation method.By simulating reflectance spectra,electric field distribution,and charge distribution,we confirm that multiple cylindrical surface plasmon resonances can be excited in annular inclined slot cavities by linearly polarized light,in which the four reflectance dips are attributed to Fabry–Perot cavity resonances in the coaxial cavity.A coaxial waveguide mode TE11 will exist in these annular cavities,and the wavelengths of these reflectance dips are effectively tailored by changing the geometrical pattern of slot cavity and the dielectric materials filled in the cavities.These resonant wavelengths are localized in annular cavities with large electric field enhancement and dissipate gradually due to metal loss.The formation of an absorption peak can be explained from the aspect of phase matching conditions.We observed that the proposed structure can be tuned over the broad spectral range of 600–4000 nm by changing the outer and inner radii of the annular gaps,gap surface topography.Meanwhile,different lengths of the cavity may cause the shift of resonance dips.Also,we study the field enhancement at different vertical locations of the slit.In addition,dielectric materials filling in the annular gaps will result in a shift of the resonance wavelengths,which make the annular cavities good candidates for refractive index sensors.The refractive index sensitivity of annular cavities can also be tuned by the geometry size and the media around the cavity.Annular cavities with novel applications can be implied as surface enhanced Raman spectra substrates,refractive index sensors,nano-lasers,and optical trappers.