Research ArticlePHYSICS

Emission of circularly polarized light by a linear dipole

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Science Advances  28 Jun 2019:
Vol. 5, no. 6, eaav7588
DOI: 10.1126/sciadv.aav7588
  • Fig. 1 The spin angular momentum density of a linear dipole in k space and in real space.

    (A) Transverse and (B) longitudinal spin density components (s˜t and s˜k) of the VAS of a linear dipole moment oriented along the x axis. The dotted black circles mark the transition from the propagating to the evanescent part of the VAS, and the red and blue arrows indicate the local orientation of the corresponding spin density components. Both spin density components are normalized to the same value. (C) Real-space spin density distribution s in the near field of a linear dipole (dipole moment orientation along the x axis indicated by the green vector). The spin density is plotted as cones for five planes of observation marked in gray. The red and blue colors highlight counterclockwise and clockwise distributions of the spin density, respectively.

  • Fig. 2 Experimental demonstration of spin-polarized light emitted by a linearly polarized dipole.

    (A) Sketch of the experimental scheme. (B) Experimentally measured distributions of the far-field intensity I, left- and right-handed circularly polarized intensities I and I+, and the longitudinal far-field spin density srI+I (the handedness of the circular polarization is indicated by the red and blue arrows). All quantities are normalized to the maximum value of I. (C) Theoretically calculated distributions of I, I, I+, and sr.

  • Fig. 3 Numerically calculated spin-polarized coupling of a linearly polarized dipole to crossing waveguides.

    The geometry of the investigated system is depicted in the top-right inset, with the waveguide crossing in gray, the orientation of the electric dipole moment as green arrow, the propagation direction in each waveguide arm as black arrow, and the circular polarization states as gray arrows. The radial component of the spin density sr is shown for an x-y cross section. The corresponding electric field intensity w is shown as bottom-right inset. Both distributions are normalized to the same value.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/6/eaav7588/DC1

    Supplement 1: Real-space spin distribution.

    Supplement 2: Angular spectrum of a dipole.

    Supplement 3: Additional finite difference time-domain simulations.

    Fig. S1. Geometrical origin of the longitudinal spin in k space.

    Fig. S2. Numerically calculated spin-polarized waveguide coupling of linearly polarized dipoles with different dipole moment orientations.

    Reference (40)

  • Supplementary Materials

    This PDF file includes:

    • Supplement 1: Real-space spin distribution.
    • Supplement 2: Angular spectrum of a dipole.
    • Supplement 3: Additional finite difference time-domain simulations.
    • Fig. S1. Geometrical origin of the longitudinal spin in k space.
    • Fig. S2. Numerically calculated spin-polarized waveguide coupling of linearly polarized dipoles with different dipole moment orientations.
    • Reference (40)

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