  In this paper, we present a method to retrieve tensor polarizabilities of
general bi-anisotropic particles from their far-field responses to plane-wave
illuminations. The necessary number of probing excitations and the directions
where the scattered fields need to be calculated or measured have been found.
When implemented numerically, the method does not require any spherical
harmonic expansion nor direct calculation of dipole moments, but only
calculations of co- and cross-polarized scattering cross sections for a number
of plane-wave excitations. With this simple approach, the polarizabilities can
be found also from experimentally measured cross sections. The method is
exemplified considering two bi-anisotropic particles, a reciprocal omega
particle and a non-reciprocal particle containing a ferrite inclusion coupled
to metal strips.
