Continuous amplitude control of second harmonic waves from the metasurfaces through interference paths

Abstract

Nonlinear plasmonic metasurfaces represent a promising platform for generating and controlling the multiple degrees of freedom of harmonic waves at the subwavelength scale. Among various functionalities, the amplitude control of the harmonic waves is usually achieved by varying the fundamental frequency and the pumping power. However, these kinds of methods lack the ability to control the energy distributions of the nonlinear waves at different diffraction orders. Here, we report the continuous intensity control of the harmonic waves from the plasmonic metasurfaces through interference paths. The metasurfaces consist of geometric phase controlled gold meta-atoms with threefold rotational symmetry. By controlling the relative phase of two neighboring metasurface paths, the intensity of the diffracted second harmonic waves can be artificially modulated. Our findings suggest that the conventional interference technique represents a powerful route for controlling the radiation of the nonlinear waves from sub-wavelength meta-atoms and may have great applications in developing ultra-compact nonlinear optical sources.