We record time-resolved nonlinear photoemission electron microscopy (tr-PEEM) images of propagating surface plasmons (PSPs) launched from a lithographically patterned rectangular trench on a flat gold surface. Our tr-PEEM scheme involves a pair of identical, spatially separated, and interferometrically-locked femtosecond laser pulses. Power dependent PEEM images provide experimental evidence for a sequential coherent nonlinear photoemission process, in which one laser source creates a PSP polarization state through a linear interaction, and the second subsequently probes the prepared state via two photon photoemission. The recorded time-resolved movies of a PSP allow us to directly measure various properties of the surface-bound wave packet, including its carrier wavelength (785 nm) and group velocity (0.95c). In addition, tr-PEEM in concert with finite-difference time domain simulations together allow us to set a lower limit of 75 µm for the decay length of the PSP on a 100 nm thick gold film.
Revised: July 29, 2015 |
Published: May 13, 2015
Citation
Gong Y., A.G. Joly, D. Hu, P.Z. El-Khoury, and W.P. Hess. 2015.Ultrafast Imaging of Surface Plasmons Propagating on a Gold Surface.Nano Letters 15, no. 5:3472-3478.PNNL-SA-108438.doi:10.1021/acs.nanolett.5b00803