Spiral bandwidth of four-wave mixing in Rb vapour

R. F. Offer, D. Stulga, E. Riis, S. Franke-Arnold, A. S. Arnold

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Laguerre-Gauss beams, and more generally the orbital angular momentum of light (OAM) provide valuable research tools for optical manipulation, processing, imaging and communication. High-efficiency frequency conversion of OAM is possible via four-wave mixing in rubidium vapour. Conservation of the OAM in the two pump beams determines the total OAM shared by the generated light fields at 420nm and 5.2um - but not its distribution between them. Here we experimentally investigate the spiral bandwidth of the generated light modes as a function of pump OAM. A small pump OAM is transferred almost completely to the 420nm beam. Increasing the total pump OAM broadens the OAM spectrum of the generated light, indicating OAM entanglement between the generated light fields. This clears the path to high-efficiency OAM entanglement between widely disparate wavelengths.
Original languageEnglish
Article number84
Number of pages8
JournalCommunications Physics
Publication statusPublished - 21 Nov 2018


  • orbital angular momentum of light (OAM)
  • Laguerre-Gauss beams
  • four-wave mixing
  • spiral bandwidth
  • optical manipulation

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