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Spiral Transformation for High-Resolution and Efficient Sorting of Optical Vortex Modes

Research output: Contribution to journalArticle

Original languageEnglish
Article number193904
Number of pages6
JournalPhysical Review Letters
Issue number19
Early online date11 May 2018
DateAccepted/In press - 24 Jan 2018
DateE-pub ahead of print - 11 May 2018
DatePublished (current) - May 2018


Mode sorting is an essential function for optical multiplexing systems that exploit the orthogonality of the orbital angular momentum mode space. The familiar log-polar optical transformation provides a simple yet efficient approach whose resolution is, however, restricted by a considerable overlap between adjacent modes resulting from the limited excursion of the phase along a complete circle around the optical vortex axis. We propose and experimentally verify a new optical transformation that maps spirals (instead of concentric circles) to parallel lines. As the phase excursion along a spiral in the wave front of an optical vortex is theoretically unlimited, this new optical transformation can separate orbital angular momentum modes with superior resolution while maintaining unity efficiency.

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