High-order topological charges measurement of LG vortex beams with a modified Mach-Zehnder interferometer

We present a new method to measure the high-order topological charges (TCs) of Laguerre-Gaussian (LG) vortex beams by using a modified Mach-Zehnder interferometer. Counting the number of interference bright fringes between the LG beam and its conjugate beam determines integer and half-integer TCs through half of the bright fringe number. The proposed method can measure the order of the integer TC up to 90, which is higher than that achieved by previous methods. This technique opens up new applications for LG vortex beams. (C) 2015 Elsevier GmbH. All rights reserved.