Visualization of the birth of an optical vortex using diffraction from a triangular aperture
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The study and application of optical vortices have gained significant prominence over the last two decades. An interesting challenge remains the determination of the azimuthal index (topological charge) l of an optical vortex beam for a range of applications. We explore the diffraction of such beams from a triangular aperture and observe that the form of the resultant diffraction pattern is dependent upon both the magnitude and sign of the azimuthal index and this is valid for both monochromatic and broadband light fields. For the first time we demonstrate that this behavior is related not only to the azimuthal index but crucially the Gouy phase component of the incident beam. In particular, we explore the far field diffraction pattern for incident fields incident upon a triangular aperture possessing non-integer values of the azimuthal index l. Such fields have a complex vortex structure. We are able to infer the birth of a vortex which occurs at half-integer values of l and explore its evolution by observations of the diffraction pattern. These results demonstrate the extended versatility of a triangular aperture for the study of optical vortices. (c) 2011 Optical Society of America
Mourka , A , Baumgartl , J , Shanor , C , Dholakia , K & Wright , E M 2011 , ' Visualization of the birth of an optical vortex using diffraction from a triangular aperture ' Optics Express , vol 19 , no. 7 , pp. 5760-5771 . DOI: 10.1364/OE.19.005760
© 2011 Optical Society of America. This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-22-1-1077. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.
Funding: EPSRC, UK
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