A magnetic, single-axis crystal is used to modify the polarization state
of light, whereby light passes through pre-determined areas of the
crystal. To change the polarization state of the light, a magnetic field
pulse is applied to the crystal with a magnetic field amplitude, at which
the crystal no longer remains in the single-domain state at the end of
the pulse, but returns to a defined multi-domain state that is determined
by the direction of the applied magnetic field, thus achieving large
usable apertures of the switching element and extremely short change
periods. According to the invention, energy is only required for the
change operation and not for maintaining a specific state.