Dual-polarization interferometer using spin-orbit beams

A dual interferometer that can be switched between Fizeau and spiral interferometer configurations is introduced here. The nature of fringes obtained in these two configurations can be used to obtain the phase and phase gradient distributions of the test wavefront. In metrology, this feature helps us to distinguish peaks from valleys in the test surface. By lifting peak-valley degeneracy, surface profiling becomes easy in this dual interferometer. The dual nature is achieved by using spin-orbit beams in the interferometer. In this paper, we demonstrate it by using a lemon in the interferometer. Each of the surface extrema in the test wavefront is seeded with a lemon and, by polarization selection, the dual nature of the interferometer is brought out.