Measuring optical vortices in a speckle pattern using a multi-pinhole interferometer

We show that it is possible to find and characterise optical vortices in a speckle pattern using a multi-pinhole interferometer. This measurement does not require an interferometric setup, providing great experimental ease. In addition, a multi-pinhole interferometer can be made arbitrarily large and can therefore be adjusted to the expected speckle size. We present experimental results confirming our understanding.