2 research outputs found
On chemiluminescent emission from an infiltrated chiral sculptured thin film
The theory describing the far-field emission from a dipole source embedded
inside a chiral sculptured thin film (CSTF), based on a spectral Green function
formalism, was further developed to allow for infiltration of the void regions
of the CSTF by a fluid. In doing so, the extended Bruggeman homogenization
formalism--which accommodates constituent particles that are small compared to
wavelength but not vanishingly small--was used to estimate the relative
permittivity parameters of the infiltrated CSTF. For a numerical example, we
found that left circularly polarized (LCP) light was preferentially emitted
through one face of the CSTF while right circularly polarized (RCP) light was
preferentially emitted through the opposite face, at wavelengths within the
Bragg regime. The centre wavelength for the preferential emission of LCP/RCP
light was red shifted as the refractive index of the infiltrating fluid
increased from unity, and this red shift was accentuated when the size of the
constituent particles in our homogenization model was increased. Also, the
bandwidth of the preferential LCP/RCP emission regime decreased as the
refractive index of the infiltrating fluid increased from unity
On columnar thin films as platforms for surface-plasmonic-polaritonic optical sensing: higher-order considerations
The ability to tailor the porosity and optical properties of columnar thin
films (CTFs) renders them promising platforms for optical sensing. In
particular, surface-plasmon-polariton (SPP) waves, guided by the planar
interface of an infiltrated CTF and a thin layer of metal, may be harnessed to
detect substances that penetrate the void regions in between the columns of a
CTF. This scenario was investigated theoretically using a higher-order
homogenization technique, based on an extended version of the second-order
strong-permittivity-fluctuation theory, which takes into account the size of
the component particles which make up the infiltrated CTF and the statistical
distribution of these particles. Our numerical studies revealed that as the
size of the component particles increases and as the correlation length that
characterizes their distribution increases: (i) the phase speed of the SPP wave
decreases and the SPP wave's attenuation increases; (ii) the SPP wave's
penetration into the CTF decreases; (iii) the angle of incidence required to
excite the SPP wave in a modified Kretschmann configuration increases; (iv) the
sharpness of the SPP trough in the graph of reflectance versus angle of
incidence increases; and (v) the sensitivity to changes in refractive index of
the infiltrating fluid decreases