Joshi Bhuwan P, Wei Qi-Huo
Liquid Crystal Institute, Kent State University, Kent, OH 44242, USA.
Opt Express. 2008 Jul 7;16(14):10315-22. doi: 10.1364/oe.16.010315.
We propose a new design of optical nanoantennas and numerically study their optical properties. The nanoantennas are composed of two cylindrical metal nanorods stacked vertically with a circular dielectric disk spacer. Simulation results show that when the dielectric disk is less than 5nm in thickness, such nanoantennas exhibit two types of resonances: one corresponding to antenna resonance, the other corresponding to cavity resonances. The antenna resonance generates a peak in scattering spectra, while the cavity resonances lead to multiple dips in the scattering spectra. The cavity resonant frequency can be tuned by varying the size of the dielectric disk. The local field enhancement inside the cavity is maximized when the diameter of the dielectric disk is roughly half that of the rod and when the cavity and antenna resonant frequencies coincide with each other. This new nanoantenna promises applications in single molecule surface enhanced Raman spectroscopy (SERS) owing to its high local field enhancements and large scale manufacturability.
我们提出了一种新型光学纳米天线设计，并对其光学性质进行了数值研究。该纳米天线由两个垂直堆叠的圆柱形金属纳米棒和一个圆形介电盘间隔层组成。模拟结果表明，当介电盘厚度小于5nm时，此类纳米天线呈现出两种共振：一种对应天线共振，另一种对应腔共振。天线共振在散射光谱中产生一个峰值，而腔共振则导致散射光谱中出现多个凹陷。通过改变介电盘的尺寸可以调节腔共振频率。当介电盘的直径约为纳米棒直径的一半且腔共振频率与天线共振频率相互重合时，腔内的局部场增强达到最大值。由于这种新型纳米天线具有高局部场增强和大规模可制造性，有望应用于单分子表面增强拉曼光谱（SERS）。
