Negative real parts of the equivalent permittivity, permeability, and refractive index of sculptured-nanorod arrays of silver

Abstract

Thin films comprising parallel nanorods were deposited by directing silver vapor obliquely toward a plane substrate. The direction of the vapor flux was varied in two different ways to sculpture the nanorods in different shapes. The reflection and transmission coefficients of the thin films were measured at three wavelengths in the visible regime for normal-illumination conditions for two linear-polarization states, using walk-off interferometry and polarization interferometry. The authors found that sculpturing significantly affects the signs of the real parts of the equivalent permittivity, permeability, and refractive index of the silver thin films for the two polarization states at different wavelengths. Thus, vapor deposition combined with sculpturing can be useful for large-scale production of materials having different equivalent constitutive parameters with negative real parts.

Bideposited silver nanocolloid arrays with strong plasmon-induced birefringence for SERS application

“…The double negative permittivity and permeability yield a negative index of refraction. The densely packed slanted silver nanorod array has a negative index of refraction for p-polarized light and a positive index of refraction for s-polarized light 20 , which leads to the huge birefringence. A 1.5-period nano-zigzag array (NZA) with a pitch length of 137.3 nm was deposited at the same deposition angle and deposition rate as the NRA.…”

Metal/dielectric/metal sandwich film for broadband reflection reduction

“…The cross-sectional image shows that each nanopillar is actually an Al-SiO 2 -Al sandwich. When the SWF is illuminated from the top, a magnetic reversal effect16 is expected to occur in the SiO 2 spacer between the two Al sections of each nanopillar. The top-surface image shows that the cross-section of each nanopillar is roughly circular with diameter D .…”

“…The SWF can be considered as a material continuum that presents (i) an equivalent refractive index and equivalent relative impedances to normally incident light whose electric field is polarized along the x axis, and (ii) refractive index and equivalent relative impedances when that electric field is polarized along the y axis8. We use the qualifier equivalent to denote the constitution of a homogeneous film with the same reflection and transmission coefficients for normal incidence as that of the SWF under examination1516. Despite the non-uniqueness inherent in their determination (even though we ensured the satisfaction of certain reasonable constraints12), these equivalent parameters help understand and explain the reflection and transmission characteristics for normal-incidence conditions.…”

Design and deposition of a metal-like and admittance-matching metamaterial as an ultra-thin perfect absorber

“…Extraordinary light absorption is expected from an ultra-thin metamaterial. The permittivity and permeability of a metamaterial must be considered separately 15 . The corresponding optical constants of a metamaterial film, admittance ( E ) and refractive index ( N ), can be derived from permittivity ( ɛ ) and permeability ( μ ) using simple relationships , and 16 .…”