13 research outputs found
Gap solitons with null-scattering
We study excitation of gap solitons under the conditions of coherent perfect
absorption (CPA). Our system consists of a symmetric periodic structure with
alternating Kerr nonlinear and linear layers, illuminated from both the ends.
We show near-total transfer of incident light energy into the gap solitons
resulting in null-scattering. We also report on the nonlinear super-scattering
(SS) states. Both the CPA and the SS states are shown to be characterized by
typical field distributions. Both the exact and the approximate results (based
on nonlinear characteristic matrix method) are presented, which show good
agreement
Cavity controlled spectral singularity
We study theoretically a PT-symmetric saturable balanced gain-loss system in
a ring cavity configuration. The saturable gain and loss are modeled by
two-level medium with or without population inversion. We show that the
specifics of the spectral singularity can be fully controlled by the cavity and
the atomic detuning parameters. The theory is based on the mean-field
approximation as in standard theory of optical bistability. Further, in the
linear regime we demonstrate the regularization of the singularity in detuned
systems, while larger input power levels are shown to be adequate to limit the
infinite growth in absence of detunin
Nonlinearity Induced Critical Coupling
We study a critically coupled system (Opt. Lett., \textbf{32}, 1483 (2007))
with a Kerr-nonlinear spacer layer. Nonlinearity is shown to inhibit
null-scattering in a critically coupled system at low powers. However, a system
detuned from critical coupling can exhibit near-complete suppression of
scattering by means of nonlinearity-induced changes in refractive index. Our
studies reveal clearly an important aspect of critical coupling as a delicate
balance in both the amplitude and the phase relations, while a nonlinear
resonance in dispersive bistability concerns only the phase
Optimization of second-harmonic generation from touching plasmonic wires
We employ transformation optics to optimize the generic nonlinear wave
interaction of second-harmonic generation from a pair of touching metallic
wires. We demonstrate a 10 orders of magnitude increase in the second-harmonic
scattering cross-section by increasing the background permittivity and a 5
orders of magnitude increase in efficiency with respect to a single wire. These
results have clear implications for the design of nanostructured metallic
frequency-conversion devices. Finally, we exploit our analytic solution of a
non-trivial nanophotonic geometry as a platform for performing a critical
comparison of the strengths, weaknesses and validity of other prevailing
theoretical approaches previously employed for nonlinear wave interactions at
the nanoscale