  A general strategy for the realization of electric and magnetic quasi-trapped
modes located at the same spectral position is presented. This strategy's
application makes it possible to design metasurfaces allowing switching between
the electric and magnetic quasi-trapped modes by changing the polarization of
the incident light wave. The developed strategy is based on two stages: the
application of the dipole approximation for determining the conditions required
for the implementation of trapped modes and the creation of the energy channels
for their excitation by introducing a weak bianisotropy in nanoparticles. Since
excitation of trapped modes results in a concentration of electric and magnetic
energies in the metasurface plane, the polarization switching provides
possibilities to change and control the localization and distribution of
optical energy at the sub-wavelength scale. We demonstrate a practical method
for spectral tuning of quasi-trapped modes in metasurfaces composed of
nanoparticles with a pre-selected shape. As an example, the optical properties
of a metasurface composed of silicon triangular prisms are analyzed and
discussed.
