Light beams with fractional orbital angular momentum and their vortex structure

Abstract

Light emerging from a spiral phase plate with a non-integer phase step has a complicated vortex structure and is unstable on propagation. We generate light carrying fractional orbital angular momentum (OAM) not with a phase step but by a synthesis of Laguerre-Gaussian modes. By limiting the number of different Gouy phases in the superposition we produce a light beam which is well characterised in terms of its propagation. We believe that their structural stability makes these beams ideal for quantum information processes utilising fractional OAM states. 3427-3435 (1990). http: //link.aps.org/abstract/PRA/v41/p3427. 17. J. Courtial, "Self-imaging beams and the Guoy [sic] effect," Opt. Commun.

Quantum digital spiral imaging

“…17 For vortex beams, the design of the diffractive component is the modulo 2p addition of a simple blazed grating with an azimuthal 2p'w phase ramp, yielding the characteristic ,-pronged fork dislocation on the beam axis. This design is readily adapted to non-integer M, giving an additional radial discontinuity to the pattern, 30 and the orientation of this radial discontinuity coincides with the edge discontinuity of the resultant non-integer vortex. However, as can be seen in Equation (7), the non-local spiral spectrum measured experimentally is the mode weight, namely, jC ',{' A ' j 2 , which is independent of the rotation of edge discontinuity.…”

Sorting and detecting orbital angular momentum states by using a Dove prism embedded Mach–Zehnder interferometer and amplitude gratings

“…Theoretically, the OAM quantum number could be any value ranging from −∞ to +∞. This property prospects the potential application of the OAM in the information field [2][3][4][5][6][7][8][9][10][11][12][13]. In recent years several groups built information transmission systems based on OAM [8][9][10][11][12][13].…”

Super pulses of orbital angular momentum in fractional-order spiroid vortex beams

“…Then it became clear why a fractional-order vortex beam can bear a fractional orbital angular momentum (OAM) [3,4]. In connection with it a special attention was focused on the vortex spectral content for controlling values of OAM [5][6][7] and for shaping a wished form of focal traps for manipulations of microparticles or for light communication systems [8,9].The propagation properties of vector halforder vortex-beams in free space and crystals were presented in the papers [10,11]. Moreover it was revealed [12] that a circular fiber array can serve as a medium for propagation of halfinteger order super modes without their decay into integer-order beans (as it was predicted in [2]) while all other integer order ones are a superposition of half-integer-order vortexmodes.…”