Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films

We experimentally demonstrate efficient third harmonic generation from an indium tin oxide nanofilm (lambda/42 thick) on a glass substrate for a pump wavelength of 1.4 mu m. A conversion efficiency of 3.3 x 10(-6) is achieved by exploiting the field enhancement properties of the epsilon-near-zero mode with an enhancement factor of 200. This nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies. (c) 2015 AIP Publishing LLC.