424 research outputs found
Modes and exceptional points in waveguides with impedance boundary conditions
A planar waveguide with impedance boundary, composed of non-perfect metallic
plates, and with passive or active dielectric filling is considered. We show
the possibility of selective mode guiding and amplification when homogeneous
pump is added to the dielectric, and analyze differences in TE and TM mode
propagation. Such a non-conservative system is also shown to feature
exceptional points, for specific and experimentally tunable parameters, which
are described for a particular case of transparent dielectric.Comment: Optics Letters (2016
Defect modes of a Bose-Einstein condensate in an optical lattice with a localized impurity
We study defect modes of a Bose-Einstein condensate in an optical lattice
with a localized defect within the framework of the one-dimensional
Gross-Pitaevskii equation. It is shown that for a significant range of
parameters the defect modes can be accurately described by an expansion over
Wannier functions, whose envelope is governed by the coupled nonlinear
Schr\"{o}dinger equation with a delta-impurity. The stability of the defect
modes is verified by direct numerical simulations of the underlying
Gross-Pitaevskii equation with a periodic plus defect potentials. We also
discuss possibilities of driving defect modes through the lattice and suggest
ideas for their experimental generation.Comment: 14 pages, 9 Figures, 1 Tabl
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