Deterministic modal control of second-harmonic generations in a plasmonic two-wire transmission-line

A plasmonic two-wire transmission-line supports two modes, one with surface plamon fields strongly confined in the gap, the other loosely guided by the wire perimeters. Using the modal asymmetry provided by the loosely guided mode, we demonstrate a new way to allow second-harmonic generation (SHG). Moreover, we demonstrate both experimentally and theoretically the ability to deterministically control the SHG modes.