| Photomixing over nano/micro scale plasmonic structures is a novel concept for generating narrow band radiation, specifically in the terahertz (THz) range. The plasmonic structures can serve as antennas for absorbing incoming photons and conversely emit radiation of a lower frequency if it is generated from mixing. In this experiment, antenna structures are excited by two tuned laser diodes to output THz radiation. Various designs for these antennas are have been considered, with presented results focusing on 2 dimensional arrays of elliptical antennas fabricated from Ag using electron-beam lithography and lift-off. The plasmonic antenna arrays exhibit polarization dependent absorption when excited by visible light in agreement with results from simulations. The effect of varying antenna size on absorption will be discussed, as well as results from photomixing experiments. The effects of absorption and transmission on the arrays have also been simulated 2 dimensionally using COMSOL and MEEP. Array structures were excited by individual and multiple sources in the visible and near-IR range. The effects of varying antenna size, position, and incoming frequencies are examined and compared to some experimental results. Photomixing was observed in a multitude of simulations, and was particularly strong in arrays of shorter antennas with longer antennas placed at intervals of the desired output wavelength. Experimental tests on such an array of 780 nm and 2 microm length antennas showed polarization dependent behavior in the IR regime. |
