Fig. 2: Topological polarization singularities.
a, b Simulated electric energy density profile (a) and polarization angle (b) of the maser eigenmode, with cut planes in three directions. The cavity has a side length of 14.1 mm and a hole radius of 2.5 mm. c Corresponding magnetic energy density, confined within the holes filled with the gain medium. d Experimentally measured reflection spectrum of two orthogonal electric probes at the tangential (Et) and radial direction (Er), revealing the presence of the maser mode with a Q factor of 5130. The use of two probes allows the extraction of the direction of polarization state. e, f Experimentally measured electric field intensity (e) and corresponding polarization angle (f) distribution on a plane parallel to one of the cube’s surfaces. A non-trivial polarization winding of charge 1 is observed around the intensity singularity.
