https://doi.org/10.1140/epjb/e2004-00003-7
Giant enhancement of optical nonlinearity in mixtures of graded particles with dielectric anisotropy
1
Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, P.R. China
2
Department of Physics, Suzhou University, Suzhou 215 006, P.R. China
Corresponding author: a lgaophys@pub.sz.jsinfo.net
Received:
16
August
2003
Published online:
30
January
2004
To investigate the
effective linear dielectric constant 
and third-order
nonlinear susceptibility 
of composite media,
in which graded inclusions with radial dielectric anisotropy
are randomly embedded in a linear isotropic matrix, we develop an
nonlinear anisotropic differential effective dipole
approximation (NADEDA).
Alternatively, based on a first-principles approach, the exact
expressions for and are also derived for the
linear dielectric profiles with small slopes. Then, excellent
agreement between the two methods is numerically demonstrated. As
an application, we further apply the NADEDA to a nonlinear
metal-dielectric composite, in which the metal
particles possess spatially varying radial dielectric anisotropy, in an attempt to study
the nonlinearity enhancement and the figure of merit of the
composite. To this end, it is shown that the presence of gradation
in the radial dielectric constant plays a crucial role in
enhancing the optical nonlinearity as well as the figure of merit.
PACS: 77.22.Ej – Polarization and depolarization / 42.65.-k – Nonlinear optics / 42.79.Ry – Gradient-index (GRIN) devices / 77.84.Lf – Composite materials
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2003
