Figure 2
Incidence and refraction wavevectors and phase gradient 
in sphere of equifrequency surface.
(a) Incidence wavevector (red) and phase gradient 
(green) are shown in sphere of equifrequency surface. (b) Refraction wavevector (blue) and phase gradient 
(green) are shown in sphere of equifrequency surface. In both (a,b) the topological magnetic monopole is located at the center of sphere of equifrequency surface. The Berry curvatures are directed along radial vectors with polar angles determined by incidence and refraction angles θi and θt.
