  We have experimentally generated higher order optical vortices and scattered
them through a ground glass plate that results in speckle formation. Intensity
autocorrelation measurements of speckles show that their size decreases with
increase in the order of the vortex. It implies increase in angular diameter of
the vortices with their order. The characterization of vortices in terms of
their annular bright ring also helps us to understand these observations. The
results may find applications in stellar intensity interferometry and thermal
ghost imaging.
