Zhang Haixi, Ho Ho-Pui
Department of Electronic Engineering, Center for Advanced Research in Photonics, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR 852, China.
Opt Express. 2009 Nov 9;17(23):21159-68. doi: 10.1364/OE.17.021159.
A novel surface-enhanced Raman scattering (SERS) excitation source based on focusing of surface plasmons around the center hole of a metal disk for cascaded enhancement is put forward and studied theoretically. The device offers intense SERS excitation with quasi-uniformity and horizontal polarization over a comparatively large hole through the combination of electromagnetic field focusing and hole plasmon resonance. As revealed by finite-difference time-domain (FDTD) method, the intensity spectra and the characteristics of the near field for the wavelength range of 650-1000nm exhibit a number of enhancement modes. Electric field intensity of the optimal mode enhances the SERS signal inside the hole by over four orders. An analytical model was also developed to gain precise interpretation on FDTD results. Our model also reveals the possibility of achieving eight orders of enhancement by optimizing the scale of the disk. In addition to generation of highly optimized hot spots, the large active hole also offers potential applications in fluorescence enhancement and nonlinear spectroscopy.
提出了一种基于金属圆盘中心孔周围表面等离子体激元聚焦以实现级联增强的新型表面增强拉曼散射（SERS）激发源，并进行了理论研究。该装置通过电磁场聚焦和孔等离子体激元共振的结合，在相对较大的孔上提供具有准均匀性和水平极化的强SERS激发。有限时域差分（FDTD）方法表明，650 - 1000nm波长范围内的强度光谱和近场特性呈现出多种增强模式。最优模式的电场强度将孔内的SERS信号增强了四个多数量级。还建立了一个分析模型以对FDTD结果进行精确解释。我们的模型还揭示了通过优化圆盘尺寸实现八倍增强的可能性。除了产生高度优化的热点外，大的有源孔在荧光增强和非线性光谱学中也具有潜在应用。
