Control of plasmonic field enhancement by mode-mixing

We demonstrate experimentally that nanoscale control of plasmonic field enhancement becomes available by changing the polarization state of light. This is revealed by photoelectron emission from plasmonic nanorods illuminated with linearly and circularly polarized femtosecond laser pulses. Simulations show that the tunability of the field enhancement originates from the mode-mixing property of circularly polarized illumination, meaning simultaneous excitation of multiple plasmon modes of the nanostructures. Performing trajectory calculations of the photoemitted electrons, we prove that the kinetic energy scaling law remains the same irrespective to the polarization state.