Enhanced photoelectron emission from dark plasmon mode in gold nanoring

Abstract

By the advantage of light concentration in nanoscale and strong light absorption, LSPRs have presented benefits for ultrafast electron pulse generation, promoting high spatio-temporal electron microscopy and spectroscopy. However, previous studies generally pay more attention to the bright mode of LSPRs; the dark mode, which corresponds to longer dephasing time and less radiative decay that is potential to deliver a leap forward in plasmon-enhanced photoemission, is still neglected. Here, we report on the investigation of quadrupole plasmon mode (dark mode) induced photoemission electron from a gold nanoring with photoemission electron microscopy. The result shows that the photoemission electron yield is around 11,200 for the dark mode supported by nanoring under s-polarized light irradiation, which is higher than the one under p-polarized light irradiation (around 8600). The higher photoemission electron yield is attributed to stronger absorption of the s-pol light excited mode. In addition, the result shows that the dephasing time of s polarization excitation mode is longer than that of p polarization excitation. The experiment results are well reproduced by FDTD simulation. Our investigation may lay the foundation for dark plasmon mode enhanced photoemission and offers an additional benefit for the progress of plasmon-based femtosecond on-chip electronics, high spatial-temporal electron microscopy and spectroscopy.