通过表面等离激元远程激发局域表面等离激元的去相位时间的控制

Control of Dephasing Time of Localized Surface Plasmons Remotely Excited by Surface Plasmons

摘要: 近年来，传播表面等离激元(Surface Plasmon Polaritons, SPP)激发的局域表面等离激元(Localized Surface Plasma, LSP)，由位于金属膜上的纳米颗粒支持，由于其非凡的性能，例如在光催化剂和传感领域具有潜在的应用，受到了越来越多的关注。然而，对该系统的研究，特别是对近场光谱和传感性能的进一步优化所必需的时间响应的研究仍然十分迫切。在本文中，我们研究了在SPP的远程激发下，能够产生LSP的金纳米球的局域近场光学响应。可以发现随着半径的增大，SPP激发的LSP近场强度也会增大，并且在半径为70 nm时近场强度发生了突变，这是由于此时的LSP和SPP的耦合作用更强导致的。此外，发现SPP激发的LSP的去相时间比激光场直接激发的情况要长，增幅近两倍(从3.8 fs延长至7.81 fs)并且随着金纳米球半径的增加而延长(从6.67 fs延长至7.57 fs)。本文的研究结果可用于定向调制局域表面等离激元的近场强度，为延长共振场的去相位时间提供了新的途径。

Abstract: In recent years, localized surface plasmons (LSPs) excited by propagating surface plasmon polaritons (SPPs), supported by nanoparticles located on metal films, have received increasing attention due to their extraordinary properties, such as potential applications in the fields of photocatalysis and sensing. However, the study of the system, especially the time response required for further optimization of near-field spectroscopy and sensing performance, is still very urgent. In this paper, we study the localized near-field optical response of gold nanospheres capable of generating LSP under the remote excitation of SPP. It can be found that as the radius increases, the LSP near-field intensity excited by SPP also increases, and the near-field intensity changes abruptly when the radius is 70 nm, which is due to the stronger coupling between LSP and SPP at this time. In addition, it is found that the dephasing time of LSP excited by SPP is longer than that excited by laser field directly, and the increase is nearly twice (from 3.8 fs to 7.81 fs) and increases with the increase of the radius of gold nanospheres (from 6.67 fs to 7.57 fs). The results of paper can be used to modulate the near-field intensity of localized surface plasmons, which provides a new way to extend the dephasing time of the resonance field.