Abstract
We describe a method for effectively distinguishing the radiation endowed with optical angular momentum, also known as optical vortex, from ordinary light. We show that by detecting the inversion of the transverse intrinsic curvature sign (ITICS) an optical vortex can be locally recognized. The method is effective under conditions of huge importance for the exploitation of optical vortices, such as the far field of the source and access to a small fraction of the wavefront only. The validity of the method has been verified with table-top experiments with visible light, and the results show that a measurement performed over a transverse distance smaller than 4% of the beam diameter distinguishes a vortex from a Gaussian beam with a significance of 93.4%. New perspectives are considered for the characterization of vortices, with potential impact on the detection of extra-terrestrial radiation as well as on broadcast communication techniques.
Highlights
Radiation carrying orbital angular momentum (OAM, or vortex) is a form of exotic radiation discovered at the end of the twentieth century as described by Allen et al [1]
We describe a method for effectively distinguishing the radiation endowed with optical angular momentum, known as optical vortex, from ordinary light
We show that by detecting the inversion of the transverse intrinsic curvature sign (ITICS) an optical vortex can be locally recognized
Summary
Radiation carrying orbital angular momentum (OAM, or vortex) is a form of exotic radiation discovered at the end of the twentieth century as described by Allen et al [1]. Several methods have been proposed in the past to measure vortex properties in the laboratory by using interference, diffraction [15,16,17,18,19,20] and refraction [21,22,23] These techniques are generally intended to provide topological and phase properties by accessing a substantial portion of the vortex field around the phase singularity. Since the intrinsic curvature is a local differential property of the wavefront, this approach can really be strictly local, being related to the topological properties of the helicoidal surface To our knowledge this is the first experimentally proven method to recognize a vortex in a strictly local manner which is of utmost importance for working at large distances from the source, a definite need in many cases of interest. We exploit the measurement of the ITICS to distinguish vortex radiation from ordinary light without any need to access the entire wavefront
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
