Fig. 2: Spiral phase in real space.
From: Observation of chiral emission enabled by collective guided resonances
a, The amplitudes (Amp) of collective modes in our circular PhC cavity are Bessel functions Jm(r) with quantum numbers m and l in the azimuth and radial directions, respectively (upper panel), and their Hz field distributions are plotted (lower panel). b, As the candidate for lasing oscillation, the field strength (∣E∣) of collective mode (1, 1) is illustrated as a donut pattern. Moreover, the snapshots of magnetic fields Hz at a sequence of time intervals in one oscillation cycle (0, T) show the temporal rotating of the mode that generates a spiral phase from 0 to 2π. c, The polarization-solved distribution of collective mode (1, 1) exhibits two lobes with equal density intensities as a distinct feature of the vortex beam.
