金纳米石门结构参数对消相位时间影响的研究

Study on the Influence of Gold Dolmen Structure Parameters on Dephasing Time

摘要: 耦合等离激元纳米结构的光学性质及消相位时间在基础研究和应用研究中受到了极大的关注。本文利用FDTD仿真模拟研究了金纳米石门结构中等离激元模式耦合对消相位时间影响的研究。研究结果表明，石门结构两模式的消相位时间依赖于结构尺寸的变化，通过调节结构参数(改变耦合强度)，影响模式的能量劈裂，可以同时对一个结构中两种杂化模式的消相位时间进行调控。利用准正则(QNM)模型获得了金纳米石门结构热点处等离激元成键模式和反键模式的消相位时间分别是4.5 fs和5.6 fs。进一步研究发现，当单棒长度L1逐渐变长时，成键模式的消相位时间逐渐增大(从4.5 fs增加到7 fs)；而反键模式的消相位时间呈现相反的趋势，逐渐从5.6 fs减小到3.9 fs。当单棒与二聚体棒结构之间的间隙g逐渐减小(耦合强度增加)时，成键模式的消相位时间逐渐增大(从4.3 fs增加到5.3 fs)，反键模式的消相位时间逐渐减小(从5.7 fs减小到5.1 fs)。这项工作加深了人们对等离激元模式耦合的消相位时间影响的理解。

Abstract: The optical properties and dephasing time of coupled plasmon nanostructures have received great attention in basic and applied research. In this paper, FDTD simulation is used to study the influence of plasmon mode coupling on the dephasing time of gold dolmen structure. The results show that the dephasing time of the two modes of dolmen structure depends on the change of structure size, and the energy splitting of the mode can be adjusted by adjusting the structural parameters (changing the coupling strength) to affect the energy splitting of the mode, and the dephasing time of the two hybrid modes in a structure can be regulated at the same time. The quasi-normal (QNM) model was used to obtain the dephasing time of plasmon bonding mode and antibonding mode at the hot spot of the gold dolmen structure at 4.5 fs and 5.6 fs, respectively. Further studies show that when the length of the L1 gradually increases, the dephasing time of the bonding mode increases gradually (from 4.5 fs to 7 fs). However, the dephasing time of the antibonding mode shows an opposite trend, gradually decreasing from 5.6 fs to 3.9 fs. When the gap g decreases (the coupling strength increases), the dephasing time in bonding mode increases gradually (from 4.3 fs to 5.3 fs), and the dephasing time in antibonding mode decreases gradually (from 5.7 fs to 5.1 fs). This work has deepened the understanding of the dephasing time effects of plasmon mode coupling.