Using Spatial Orbitals

Elisa De Ranieri

Sheng Feng, Prem Kumar

Directly contradictory arguments coexist regarding the conservation rule of orbital angular momentum in spontaneous parametric down-conversion. We analytically show how this rule is decided by spatial symmetry. We discover that the down-converted photon pairs can carry non-negligible extrinsic orbital angular momentum in the degrees of relative-movement freedom due to spatial symmetry breaking, leading to nonconservation of total orbital angular momentum in type-II down-conversion. Also, we demonstrate that the traditional technique does not measure the extrinsic orbital angular momentum.

Wei Gao, Sandan Wang, Jinpeng Yuan +3 more

Optical vortex orbital angular momentum modes, namely the twists number of the light does in one wavelength, play a critical role in quantum-information coding, super-resolution imaging, and high-precision optical measurement. Here, we present the identification of the orbital angular momentum modes based on spatial self-phase modulation in rubidium atomic vapor. The refractive index of atomic medium is spatially modulated by the focused vortex laser beam, and the resulted nonlinear phase shift of beam directly related to the orbital angular momentum modes. The output diffraction pattern carries clearly distinguishable tails, whose number and rotation direction correspond to the magnitude and sign of the input beam orbital angular momentum, respectively. Furthermore, the visualization degree of orbital angular momentums identification is adjusted on-demand in the terms of incident power and frequency detuning. These results show that the spatial self-phase modulation of atomic vapor can provide a feasible and effective way to rapidly readout the orbital angular momentum modes of vortex beam.

A. Sh. Makhmudov, Z. M. Khakimov, A. A. Levin +2 more

Magnus T. L. Hsu, Warwick P. Bowen, Ping Koy Lam

The transverse spatial attributes of an optical beam can be decomposed into the position, momentum, and orbital angular momentum observables. The position and momentum of a beam are directly related to the quadrature amplitudes, while the orbital angular momentum is related to the polarization (spin) variables. In this paper, we study the quantum properties of these spatial variables, using a representation in the Stokes-operator basis. We propose a spatial detection scheme to measure all three spatial variables and, consequently, propose a scheme for the generation of spatial Stokes-operator squeezing and entanglement.