Broad-Band Near-Infrared Plasmonic Nanoantennas for Higher Harmonic Generation

We propose a broad-band near-infrared trapezoidal plasmonic nanoantenna, analyze it numerically using finite integration and difference time domain techniques, and explain qualitatively its performance via a multidipolar scenario as well as a conformal transformation. The plasmonic nanoantenna reported here Intercepts the incoming light as if it were of cross-sectional area larger than double its actual physical size for a 1500 nm bandwidth expanding from the near-infrared to the visible spectrum. Within this bandwidth, it also confines the incoming light to Its center with more than 1 order of magnitude field enhancement. This wide-band operation is achieved due to the overlapping of the different dipole resonances excited across the nanoantenna. We further demonstrate that the broadband field enhancement leads to efficient third harmonic generation in a simplified wire trapezoidal geometry when a Kerr medium is Introduced, due to the lightning rod effect at the fundamental and the Purcell effect at the Induced third harmonic.