The topological charge (TC) inversion of optical vortex is demonstrated along the beam propagation direction by using plasmonic geometric metasurfaces with the initial wave fronts designed from the principle of caustic surface. The detailed TC inversion evolution process is observed together with the transmutation point where the vortex vanishes. The orbital angular momentum (OAM) mode distributions during the TC inversion process are studied to show the dynamic redistributions of OAM mode density between the central area and the surrounding area of the beam with the total OAM conserved. Furthermore, the TC inversion of self‐accelerating vortex beam along the parabolic trajectory is presented. The realization of controlling TC inversion of optical vortex along arbitrary beam trajectory paves the way for many applications with more complex functionalities in optical trapping and manipulation, optical sensing, quantum information and computation, and data communication.
The free‐space optical vortex transmutation is realized by using geometric plasmonic metasurfaces with the designed noncanonical vortex phase profiles possessing discrete rotational symmetries of finite order. Based on the introduced continuous‐to‐discrete rotational symmetry breaking in metasurfaces, the vortex transmutation phenomena are observed behind the metasurfaces from the near‐field to far‐field diffraction in free space. The near‐field optical beam profile represents the input vortex, while in the far field the input vortex is diffracted into the central output vortex with topological charge determined by the transmutation rule and the symmetrically distributed off‐axis vortices with unity topological charge bifurcating from the input vortex, with the total orbital angular momentum conserved. The demonstrated free‐space optical vortex transformation will promise many potential applications related to optical communication, particle manipulation, and quantum information processing.
more » « less- NSF-PAR ID:
- 10457763
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Optical Materials
- Volume:
- 7
- Issue:
- 22
- ISSN:
- 2195-1071
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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