Investigation of ultrafast plasmon control in silver block by PEEM

We carried out in situ imaging of ultrafast plasmonic near-field control within silver block through photoemission electron microscope (PEEM) combined with picosecond laser pulses. It is found that the near-field distribution can be confined at the edges of the block, and efficiently localized to different edges depending on the polarization direction of the illuminating laser light. In particular, the localized near-field will switch from the upper edge to the lower one in the block when the polarization angle of the laser is changed from 45 to 135°. Furthermore, we found that, due to the restriction to electron oscillation by the edge of the block, the photoemission yield is greatly enhanced in the edge that is perpendicular to the polarization direction of the laser. In addition, we also discussed the mechanism responsible for brightness difference between the left and upper/down edges in PEEM images under s- and p-polarized ultrafast laser illumination. Our findings pave the way for ultrafast plasmon application in the fields such as optical switches, logic operation and others.