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Applicant:
Indian Institute of Technology (IIT) Patna 
Author:
P. Kumar and N. K. Nishchal 
Corresponding Authors:
N. K. Nishchal 
DOI #:
https://doi.org/10.1364/JOSAA.36.001447 
Title:
Modified Mach-Zehnder interferometer for determining high-order topological charge of Laguerre-Gaussian vortex beams 
Journal:
Journal of Optical Society of America A 
Year:
2019 
Volume:
36 
Page:
1447-1455 
Keywords:
vortex beams, Interferometer 
Abstract:
This study demonstrates a self-referenced interferometric method to estimate the magnitude and sign of a high-order topological charge (TC) carried by incoming optical vortex beams. The proposed method uses a right-angle prism in a Mach–Zehnder interferometer setup with controlled lateral shift and tilt between the wavefronts of interfering beams. The in-line interference with its conjugate results in a petal-shaped fringe pattern, where the number of petals reveals the magnitude of the TC. When the direction of one of the interfering beams is laterally displaced and rotated to emerge at a small angle for off-axis interference such that the vortices overlap at the output plane, then a fork-like interference pattern with better visibility is obtained, which can be used for estimating the magnitude as well as the sign of the TC. Through numerical simulation and optical experiment, it is shown that the technique is capable of estimating the TC of Laguerre–Gaussian beams even with a nonzero radial index. 
Entered by:
Physics Head on 2020-08-03 
 
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