Detection of phase singularity using a lateral shear interferometer

We demonstrate use of lateral shear interferometry for the detection of phase singularities in optical fields. Existing interferometric methods of vortex detection entail a separate reference wave front, either plane or spherical, to yield fork or spiral fringes as vortex signatures. The method of vortex detection reported here is a self-referencing technique, as the reference wave front required to form interference fringes is drawn from the test wave front itself. The technique is simple, robust and vibration insensitive. Isolated vortices as well as randomly distributed vortices in a speckle field are detected using this technique. It is shown that detection of optical vortices is possible even with an ordinary glass plate acting as the shear plate.