Nature Mater. 11, 208–212 (2012)

Credit: © 2012 NPG

Electronic elements such as resistors, inductors and capacitors are commonly used as building blocks to control and manipulate radiofrequency signals in electronic circuits. Nader Engheta and co-workers previously proposed that optical nanostructures, if properly designed and judiciously arranged, could behave as analogous nanoscale circuit elements for use at optical frequencies. The researchers have now experimentally verified their predictions by using arrays of nanorods to build a two-dimensional optical nanocircuit that operates at mid-infrared wavelengths. The researchers designed and fabricated arrays of Si3N4 nanorods and then quantitatively evaluated the equivalent impedance of these nanostructures in the mid-infrared regime. Using Fourier transform infrared spectroscopy, they showed that the nanostructures can indeed function as two-dimensional optical circuit elements. In addition, the connections between the nanocircuit elements, in particular whether they function in a series or parallel arrangement, can be controlled through the polarization of the optical control signals. The researchers say that introducing optical nonlinearity into such optical circuits could provide a platform for mixing multiplexing optical signals with different incidence angles and polarizations.