Electro‐Optic Metasurfaces Based on Barium Titanate Nanoparticle Films

Abstract

Metal‐oxides are promising candidates to substitute silicon in intra‐chip optical interconnects, as they exhibit great electric field tuning capabilities. The development of crystal ion slicing of thin films from bulk crystals and the advances over epitaxial growth have allowed the integration of metal‐oxides on a single chip. In terms of performance, they possess strong electro‐optic response over broad bandwidths across near‐infrared. However, lattice and thermal expansion coefficient mismatch limits the compatibility with available substrates and other materials, while physical hardness makes high quality nanostructures difficult to implement. Here, a novel concept of electro‐optic (EO) switching is introduced: an adjacent BaTiO3 nanoparticle film to a plasmonic metasurface provides reflection changes up to 0.15% under 4 V of control signal for modulation frequencies up to 20 MHz, in the near‐infrared. The nanoparticle films show EO coefficients (37.04 ± 25.6 pm V−1) comparable to lithium niobate crystals, are deposited uniformly over large scale and on any type of substrate, while retain optical nonlinear properties (e.g. second‐harmonic generation). Photonic nanostructures such as metasurfaces incorporated with nanoparticle films can harness the multifunctional properties of metal‐oxides such as BaTiO3 to form a new family of switchable nano‐devices across the entire visible to near‐infrared part of the spectrum.