  We report experiments on propagation of scalar and vector optical beams
through random phase screens mimicking turbulence and show that the intensity
profile of the beam containing a C-point polarization singularity shows
maximally robust behavior. This observation is explained in terms of the
polarization and orbital angular momentum (OAM) diversity in the beam. The $l =
0$ and $l = 1$ OAM states whose vector combination leads to the C-point
singularity are seen to produce complementary speckle intensity patterns with
significant negative correlation on propagation through a random phase screen.
This unique property of C-point singularity makes it superior to other
inhomogeneous polarization states as demonstrated in our experiments. The
results provide an important generic guideline for designing beams that can
maintain optimally robust beam intensity profile on passing through random
phase fluctuations and are expected to have a number of applications.
