167 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
Coherent-perfect-absorber and laser for bound states in a continuum
It is shown that two fundamentally different phenomena, the bound states in
continuum and the spectral singularity (or time-reversed spectral singularity),
can occur simultaneously. This can be achieved, in particular, in a rectangular
core dielectric waveguide with embedded active (or absorbing) layer. In such a
system a two-dimensional bound state in a continuum is created in the plane of
a waveguide cross section and it is emitted or absorbed along the waveguide
core. The idea can be used for experimental implementation of a laser or a
coherent-perfect-absorber for photonic bound state that resides in a continuous
spectrum
Waveguides with Absorbing Boundaries: Nonlinearity Controlled by an Exceptional Point and Solitons
We reveal the existence of continuous families of guided single-mode solitons
in planar waveguides with weakly nonlinear active core and absorbing
boundaries. Stable propagation of TE and TM-polarized solitons is accompanied
by attenuation of all other modes, i.e. the waveguide features properties of
conservative and dissipative systems. If the linear spectrum of the waveguide
possesses exceptional points, which occurs in the case of TM-polarization, an
originally focusing (defocusing) material nonlinearity may become effectively
defocusing (focusing). This occurs due to the geometric phase of the carried
eigenmode when the surface impedance encircles the exceptional point. In its
turn the change of the effective nonlinearity ensures the existence of dark
(bright) solitons in spite of focusing (defocusing) Kerr nonlinearity of the
core. The existence of an exceptional point can also result in anomalous
enhancement of the effective nonlinearity. In terms of practical applications
the nonlinearity of the reported waveguide can be manipulated by controlling
the properties of the absorbing cladding.Comment: Published versio
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