DC Voltage Created Perpendicularly to Nanostructured Metal Films by Surface Plasmon Polariton Excitation at Visible Frequencies.

Plasmonics is a scientific field, encompassing a plethora of novel phenomena related to electron-photon coupling in metal nanostructures and formation of hybrid electromagnetic waves propagating along various metal surfaces, collectively called surface plasmon polaritons (SPPs). SPPs can be excited in a broad band of frequencies from infrared to UV, including visible. SPPs feature extremely strong localized electric fields at selected locations on the boundaries of metal nanostructures, the so-called plasmonic hot spots. These fundamental properties of SPPs currently attract a lot of attention from optoelectronics community. SPPs have a broad range of applications starting from currently mass-produced SPP resonance biosensors for personalized healthcare to the ultrafast circuits for the computers of the future, involving plasmonic components with anticipated bandwidth of several hundred THz. It has been recently proposed and theoretically demonstrated by Durach and collaborators, that propagating optical SPPs create direct current (DC) in metal nanostructures which could have an immense impact on current nanotechnology. We will describe the new results obtained by Matthew LePain working with Dr. Durach, demonstrating that SPPs in a nanostructured metal film create a rectified DC voltage signal perpendicular to the film, which maps the geometrical profile of the film. We obtained the solutions of Maxwell\u27s equations for a metal film nanostructured by a planar grating, through matching a large number of diffraction waves to a large number of guided waves inside the grating structure, to achieve satisfactory approximation of the exact fields involving infinite expansions. Using the obtained electromagnetic fields of SPPs we calculate the rectified forces exerted upon electrons in the metal at particularly intriguing wavelengths. Using a hydrostatic approximation which we developed for the electrons in the nanostructure we are able to obtain voltages applied perpendicular to the film at normal incidence of external radiation. This work represents an important step toward future integration of plasmonics, electronics and optics