Square versus hexagonal lattices effects on the optical and dielectric properties of plasmonic Ag-LiNbO3 composite Articles uri icon

publication date

  • December 2024

start page

  • 416482-1

end page

  • 416482-7

volume

  • 695

International Standard Serial Number (ISSN)

  • 0921-4526

Electronic International Standard Serial Number (EISSN)

  • 1873-2135

abstract

  • We investigate the effect on the optical and transport properties of square and hexagonal lattice arrangements of silver nanoparticles (NPs) in uniaxial LiNbO3 as optically active layer within a multilayer configuration. This multilayer is constituted by Indium Tin Oxide (ITO), the polymer PMMA and a substrate of SiO2. The effective dielectric function of the ensemble of Ag NPs and uniaxial LiNbO3 crystal are treated through the Bruggeman
    approximation. The multilayer absorbance for s- and p-polarization at normal and oblique incidences are determined by means of the Transfer Matrix Method. Changes in the ratio between the diameter of the nanoparticles, 𝐷, and the distance between particles or pitch, 𝑃 , are analyzed. A change in the 𝐷∕𝑃 ratio implies a different filling factor. For small 𝐷∕P ratio, the calculated absorbance for square- and hexagonallattices are equivalent; however, for greater 𝐷∕𝑃 factor, the hexagonal lattice clearly shows higher absorbance values. Moreover, the Brewster angle seems to be sensitive to the Ag NPs size as well as the type of arrangement
    (square or hexagonal). The ac-electrical conductivity of the effective medium layer of the two arrangements in the perpendicular and parallel directions of the Ag NPs plane were analyzed. Our results demonstrate that
    the ac-conductivity is higher for hexagonal lattice than for square case, which means a higher density of Ag
    NPs. In addition, for the perpendicular direction, in the hexagonal-lattice (𝐷∕𝑃 = 0.5), we have found the
    negative epsilon (NE) condition, characteristic of metamaterials.

subjects

  • Physics

keywords

  • absorption; ac–conductivity; ag–square lattice; ag–hexagonal lattice; simulations