  While adaptive optical systems are able to remove moderate wavefront
distortions in scintillated optical beams, phase singularities that appear in
strongly scintillated beams can severely degrade the performance of such an
adaptive optical system. Therefore, the detection of these phase singularities
is an important aspect of strong scintillation adaptive optics. We investigate
the detection of phase singularities with the aid of a Shack-Hartmann wavefront
sensor and show that, in spite of some systematical deficiencies inherent to
the Shack-Hartmann wavefront sensor, it can be used for the reliable detection
of phase singularities, irrespective of their morphologies. We provide full
analytical results, together with numerical simulations of the detection
process.
