Spatiotemporal imaging of the longitudinal and transverse components of the few-cycle surface plasmon polaritons near-field in nano-femto scale by time-resolved photoemission electron microscopy

We perform the spatiotemporal imaging of the few-cycle surface plasmon polaritons (SPP) in Nano-Femto scale using two different excitation schemes that include the incident light vertical to and along the long axis of the trench milled in a silver film for launching SPP by oblique incidence interferometric time-resolved photoemission electron microscopy (ITR-PEEM). The intuitively dynamic propagation of the transverse and longitudinal components evolution of the identical SPP field in the same probe region was captured using a few-cycle (sub-10 fs) pulses under the ITR-PEEM experimental scheme of the incident light along the long axis of the trench. The feasibility of the spatiotemporal imaging of the longitudinal and transverse components of the SPP near-field is confirmed using the complex dielectric function of silver and FDTD simulation. Meanwhile, benefitting from distinguishable interference patterns of the transverse and longitudinal components of the identical SPP field, we found the photoemission intensity of the interference patterns related to the longitudinal component is far lower than that of the transverse one and, we discussed the difference of photoemission intensity by considering the reflection coefficient of s- and p-polarized pulses, the vector direction between light and SPP, as well as intrinsic field intensity of transverse and longitudinal components of SPP. Based on this the ratio between transverse and longitudinal electric field components is measured for the first time using ITR-PEEM. Our results lay the foundation for a further application of the few-cycle SPP field and provide a potential solution for the experimental mapping of a three-dimensional space–time field of SPP.