  An efficient electro-optical modulation has been demonstrated here by using
an edge plasmon mode specific for the hybrid plasmonic waveguide. Our approach
addresses a major obstacle of the integrated microwave photonics caused by the
polarization constraints of both active and passive components. In addition to
sub-wavelength confinement, typical for surface plasmon polaritons, the edge
plasmon modes enable exact matching of the polarization requirements for
silicon based input/output grating couplers, waveguides and electro-optical
modulators. A concept of the hybrid waveguide, implemented in a sandwich-like
structure, implies a coupling of propagating plasmon modes with a waveguide
mode. The vertically arranged sandwich includes a thin layer of
epsilon-near-zero material (indium tin oxide) providing an efficient modulation
at small length scales. Employed edge plasmons possess a mixed polarization
state and can be excited with horizontally polarized waveguide modes. It allows
the resulting modulator to work directly with efficient grating couplers and
avoid using bulky and lossy polarization converters. A 3D optical model based
on Maxwell equations combined with drift-diffusion semiconductor equations is
developed. Numerically heavy computations involving the optimization of
materials and geometry have been performed. Effective modes, stationary state
field distribution, an extinction coefficient, optical losses and charge
transport properties are computed and analyzed. In addition to the polarization
matching, the advantages of the proposed model include the compact planar
geometry of the silicon waveguide, reduced active electric resistance R and a
relatively simple design, attractive for experimental realization.
