利用时域有限差分法分别模拟计算了X型金纳米结构和L型纳米天线以及由这两种结构所组成的金纳米交叉结构的消光光谱和近场分布, 并研究了金纳米交叉结构对周围介质折射率变化的敏感性。研究结果表明, X型金纳米结构在入射光正入射时能激发起偶极共振模式而在斜入射时可以同时激发起偶极和四极共振模式。L型纳米天线的成键和反成键共振模式的产生可以通过改变入射光偏振方向进行控制。此外入射光偏振方向变化时在金纳米交叉结构中都可产生法诺共振效应, 由于激发起法诺共振效应, 金纳米交叉结构的光谱线型更加精细, 传感质量因子可达到12.5, 这些结果可指导金纳米交叉结构作为纳米光子器件用于生物传感方面。

The extinction spectra and distribution of electric near field of the X-shaped gold nanostructure, L-shaped nanoantennas and gold nanocross structure composed of these two kinds of structures were calculated by using the finite-difference time-domain method (FDTD). The sensitivity of gold nanocross structure to the change of refractive index of surrounding medium was studied. The results show that X-shaped gold nanostructures can be excited simultaneously dipole and quadrupole resonance modes at oblique incidence of the incident light and only the dipole resonance mode is excited when the incident light is incident. Generation of bonding and antibonding resonance mode of L-shaped nanoantennas can be controlled by changing the polarization direction of the incident light. In addition, gold nanocross structure most can produce fano resonance effect with polarization of incident light varying. Due to excite the fano resonance effect, the spectral line of gold nanocross structure becomes more stringent and the figure of merit (FOM) can reach 12.5. These results can be used to guide the application of gold nanocross structure as a nanophotonic device in the biological sensing.