Nano Lett.http://doi.org/hxg (2012)

Credit: © 2012 ACS

Surface plasmons are optical resonances that are of broad interest for sensing and photonic applications. However, the localized nature of these resonances on the nanoscale has made their characterization difficult. Aycan Yurtsever and Ahmed Zewail have now demonstrated a powerful new analytical technique that enables the measurement of local optical fields around nanoparticles with high spatial resolution. In their photon-induced near-field electron microscopy technique, nanostructures are illuminated by laser light to excite the strong localized electromagnetic fields around the object. An ultrashort electron pulse at high energy from an electron microscope is simultaneously directed at these nanoparticles, and the electrons are scattered by the intense fields around them. Analysis of the scattering then enables the retrieval of entire two-dimensional maps of the optical field with ultrahigh spatial resolution. This enables efficient study of the optical properties of plasmonic nanoparticles. Further extensions of this technique could promise not only the three-dimensional mapping of optical fields, but also measurements mapping such fields with ultrafast temporal resolution.