Unidirectional emission control of second harmonic generation from tailored plasmonic nanostructures

Wavelength conversion using plasmonic nanostructures has been attracting attention as a novel nonlinear optical effect occurred in nano-sized regions. In general, the second order nonlinear polarization does not occur in the isotropic metal, while the breaking symmetry on the metal surface is considered to permit the SHG (second harmonic generation). The radiation control of the SHG signal is essential in order to apply plasmonic nanostructures as wave conversion devices. However, its radiation control has been difficult because the second order nonlinear polarization on the metal surface is sensitive to the surface roughness. In this study, we demonstrated the control of the SHG radiation pattern and phase by the unique idea that the second order nonlinear polarization couples to the dipole plasmon mode.