Fig. 4: The far field characteristics of the Archimedean VCSELs.

a The polarization states of the laser beam. The divergence angle are marked with dashed lines. b, c The measured self-interference patterns of the laser beams in the forward direction and in the backward direction, respectively. Here, the pump fluence is 21 μJ/cm2. d The numerically calculated phase profile of emission from the Archimedean spiral grating. The white dashed lines represent the angle of 10°.