摘要
Surface plasmon polaritons (SPPs) and their low-frequency counterpart spoof SPPs have attracted intensive interests in sciences [1,2], due to their unprecedented capabilities to confine electromagnetic (EM) fields at deep-subwavelength scale, leading to many applications such as super-resolution imaging [3], plasmonic lasers [4], surfaced-enhanced Raman effect [5], plasmonic waveguides [6,7] or circuits [8], etc. In practice, scatterings of SPPs to propagating waves (PWs) are inevitable as SPPs encounter discontinuities (say, interfaces between two different plasmonic systems). Such scatterings can lead to undesired radiation losses which should be avoided, especially in those applications employing SPPs as information carriers (say, plasmonic waveguides and nano-circuits [6–8]). Meanwhile, SPP-PW scatterings can also be utilized to achieve certain desired functionalities. For example, one can purposely place a set of carefully designed scatters on a plasmonic surface to scatter SPPs, generating fascinating effects such as holograms, focusing, or even directional radiations [9,10]. However, theoretical understandings on the inherent physics governing SPP-PW scatterings are far from satisfactory. Without a simple picture on such processes, people usually have to rely on full-wave simulations to optimize the devices to either suppress or utilize the SPP-PW scatterings. Although several theoretical approaches were proposed to study the SPP transmission/ reflection behaviors at certain plasmonic interfaces [11,12], the SPP-PW scatterings are usually overlooked. Moreover, since PWs have infinite channels to transport in free space, it is difficult to derive an analytical formula to describe such SPP-PW processes.
基金
financially supported by National Key Research and Development Program of China(2017YFA0303500 and2017YFA0700201)
National Natural Science Foundation of China(11734007,11874118,11674068,91850101,11704240,and11474057)
Shanghai Science and Technology Committee(16ZR1445200,16JC1403100,18ZR1403400,17ZR1409500 and18QA1401800)
Shanghai East Scholar Plan and Fudan UniversityCIOMP Joint Fund
