Fine-tune the spectrum of indium-tin-oxide nanorod arrays in the visible range

All-optical modulation of light using metallic nanostructures can potentially enable processing of information with speed in the terahertz range. This is because the optical nonlinearity of metals dictated by the electron-phonon coupling is intrinsically fast. Nobel metals have achieved great success to this end due to their superior plasmonic properties in the visible. However, each type of noble metals only works in a specific wavelength range and therefore broadband spectral response covering the wide visible spectrum can be a challenge. Here we introduce indium-tin-oxide nanorod arrays (ITO-NRAs) which exhibit broadband response covering the visible spectrum. We show that the static spectral response of ITO-NRAs does not depend on the incident polarization and is insensitive to whether the lattice is a square or a rectangle. We further demonstrate that the transmission spectrum can be slightly shifted by changing the sample temperature, as well as adjusting the doping concentration which can be achieved by annealing the sample in oxygen rich environments. When pumped by an optical pulse with photon energy above the bandgap, the transmission can be modified in the entire visible range. These preliminary results show that ITONRAs offer unique opportunities for all-optical modulation in optical frequencies.