Self-Assembled Silver-Germanium Nanolayer Metamaterial with the Enhanced Nonlinear Response
Plasmonic metamaterials and metasurfaces are important for many linear
and nonlinear photonic applications. Here, the possibility to control a nanostructured
layer spontaneously formed near an interface of a thin silver film is
shown, where the interplay between a grain boundary structure and surface
segregation of germanium atoms leads to encapsulation of the grains and,
as the result, formation of a composite metamaterial near the film surface.
This Ag/Ge composite exhibits strong localized surface plasmon resonances
at Ge-encapsulated silver grains, leading to extraordinary second harmonic
generation for both transverse magnetic and transverse electric polarized
fundamental light with up to two orders of magnitude enhancement compared
to thin Ag films without Ge atoms. Segregation phenomena open the
possibility for fabrication of a new class of composite materials and gives
additional degree of freedom in designing optical properties of nanostructured
metamaterials.