Modeling Chiral Sculptured Thin Films as Platforms for Surface-Plasmonic-Polaritonic Optical Sensing

Abstract

Biomimetic nanoengineered metamaterials called chiral sculptured thin films (CSTFs) are attractive platforms for optical sensing because their porosity, morphology and optical properties can be tailored to order. Furthermore, their ability to support more than one surface-plasmon-polariton (SPP) wave at a planar interface with a metal offers functionality beyond that associated with conventional SPP-based sensors. An empirical model was constructed to describe SPP-wave propagation guided by the planar interface of a CSTF -infiltrated with a fluid which supposedly contains analytes to be detected -and a metal. The inverse Bruggeman homogenization formalism was first used to determine the nanoscale model parameters of the CSTF. These parameters then served as inputs to the forward Bruggeman homogenization formalism to determine the reference relative permittivity dyadic of the infiltrated CSTF. By solving the coresponding boundary-value problem for a modified Kretschmann configuration, the characteristics of the multiple SPP modes at the planar interface were investigated as functions of the refractive index of the fluid infiltrating the CSTF and the rise angle of the CSTF. The SPP sensitivities thereby revealed bode well for the implementation of fluid-infiltrated CSTFs as SPP-based optical sensors.

Supershape Nanoparticle Plasmons

“…Also, for excitation of surface plasmon-polaritons at planar interface of a metal thin film and a dielectric medium, the different configurations such as Otto, Kretschmann and Sarid have been designed [23,24]. In recent years, the surface multiplasmonics has been introduced using a homogeneous metal thin film and a nonhomogeneous dielectric sculptured thin film so that it can be used in sensors for simultaneous detection of more than one chemical species [25][26][27].…”

Nanoengineered thin films of copper for the optical monitoring of urine – a comparative study of the helical and columnar nanostructures

“…These can essentially be engineered to generate certain electromagnetic properties based on the geometry, which consequently can lead to design such nanostructures for various application purposes, based on the achieved properties. [2][3][4][5] Among these, one of the prudent applications would be in the area of optical sensing [6,7] -particularly the device that exploits the phenomenon of surface plasmonic resonance (SPR).…”

“…As such, STFs may be used for optical sensing applications exploiting the phenomenon of SPR wherein the condition of resonance remains greatly dependent on the constitutive properties of the STF. [1,6,7] This is mainly because of the reason that the phenomenon of SPR is achieved due to the interface of the two partnering mediums.…”

Exhibition of circular Bragg phenomenon by hyperbolic, dielectric, structurally chiral materials

“…6,7 A nanoscopic-to-continuum model based on the Bruggeman homogenization formalism has also been developed. 8 The optical signature of an SCM is a circular-polarization-sensitive stopband. The center wavelength and the width of this stopband depend on the direction of the wavevector of an incident circularly polarized plane wave.…”

“…Furthermore, the nominal thickness of each metal layer must be a small fraction of the nominal thickness of each dielectric layer, 23 and all layers must be electrically thin. 27,28 Equation (1) would still apply, although the use of the nanoscopic-to-continuum model 8 developed for chiral sculptured thin films may be perilous if the metal volume fraction is not sufficiently small. 29 Anyhow, either one or two of Reðε a Þ, Reðε b Þ, and Reðε c Þ could be negative, with the remainder being positive.…”