Fig. 1: Schematic illustrations of the emission dipoles and their polar diagrams.

The 3D arrows indicate the emission dipoles and the dumbbells indicate the polar diagrams: the measurable field intensity as a function of the angle of analyzer on the observation planes (grey plane). The wavy lines depict the oscillating electric field (red) and magnetic field (blue) polarized along the dipole axis. a A single electric dipole is oriented parallel to the observation plane. The dipole’s in-plane orientation angle can be determined from one polar diagram. b A single electric dipole with out-of-plane orientation. The projections of the dipole on two different observation planes render two polar diagrams, from which the three-dimensional (3D) dipole orientation can be determined. c Two dipoles with electric (red arrow) and magnetic (blue arrow) dipolar natures are oriented out-of-plane while they are coupled with an arbitrary fixed angle with respect to each other. Each dipole renders a distinct polar diagram (blue dumbbell — magnetic polar diagram/red dumbbell — electric polar diagram) on the same observation plane, from which the 3D orientation of the coupled dipoles can be determined.