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Observation of twist-induced geometric phases and inhibition of optical tunneling via Aharonov-Bohm effects

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Science Advances  02 Jan 2019:
Vol. 5, no. 1, eaau8135
DOI: 10.1126/sciadv.aau8135
  • Fig. 1 Twisted fiber structures as a platform for realizing synthetic magnetic fields for photons.

    A twisted four-core optical fiber in which the photon tunneling evolution dynamics are analogous to those expected from electrons in the presence of a magnetic field. The constantly rotating local transverse coordinates are depicted at three different planes. The top inset shows a microscope image of the input facet of the four-core fiber used in our experiments. The low-index fluorine-doped core is visible at the center of the fiber. The bottom inset depicts a schematic of a two-dimensional atomic lattice in the presence of a static perpendicular magnetic field (arrows), where a tight-binding formalism can be used to describe the electronic band structure after a Peierls substitution.

  • Fig. 2 Dependence of optical tunneling dynamics on the AB phase.

    Normalized light intensity at the output of core #3 for different values of the AB phase φ (as induced by different twist rates). In all cases, core #1 is excited at the input with CW laser light at λ = 1550 nm. Theoretical results corresponding to the same set of parameters are also provided for comparison. At φ = π/4, the third core always remains dark, indicating AB tunneling suppression.

  • Fig. 3 AB inhibition of tunneling in the presence of optical nonlinearities.

    Output light intensity profiles from a twisted, 24-cm-long, four-core fiber when only core #1 is quasi-linearly excited for (A) φ = 0 (no twist), (B) φ = π/4, and (C) φ ≈ 0.27π. In (A) to (C), the pulses used had a peak power ~500 W at λ = 1064 nm. (D) to (F) show similar results when the input peak power is ~6 kW, and hence, nonlinear Kerr effects are at play. It is evident that the coupling between core #1 and core #3 is completely suppressed in both cases (B and E), regardless of the power levels used, indicating an immunity of the AB tunneling suppression against nonlinear index changes. For higher input powers (D to F), the self-focusing nonlinearity further suppresses light coupling, even among adjacent cores. The numbers in (A) depict the relative arrangement of the four cores in this particular experiment.

  • Fig. 4 AB tunneling suppression for higher-order modes.

    Light intensity distributions at the output of a twisted four-core fiber when the higher-order LP02 mode is excited with CW light at λ = 665 nm. These results are presented for (A) φ = 0 (no twist), (B) φ ≈ 0.11π, and (C) φ = π/4. Although most of the optical power resides in the fundamental LP01 mode in the excited core #1, only the LP02 mode appears in the remaining cores due to its higher coupling coefficient. (C) reveals that AB suppression of light tunneling occurs in a universal fashion, even for higher-order modes. The numbers in (A) depict the arrangement of the cores corresponding to these observations.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/1/eaau8135/DC1

    Section S1. Supermodes of twisted multicore optical fibers

    Section S2. Perturbation analysis of the tunneling inhibition

    Section S3. Coupling of the fundamental mode and higher-order modes

    Section S4. Kerr induced detuning in high powers

    Section S5. Coupling suppression of higher-order modes

    Fig. S1. Twisted N-core fiber.

    Fig. S2. Inhomogeneous couplings among cores.

    Table S1. Multimode behavior of the designed four-core fiber.

  • Supplementary Materials

    This PDF file includes:

    • Section S1. Supermodes of twisted multicore optical fibers
    • Section S2. Perturbation analysis of the tunneling inhibition
    • Section S3. Coupling of the fundamental mode and higher-order modes
    • Section S4. Kerr induced detuning in high powers
    • Section S5. Coupling suppression of higher-order modes
    • Fig. S1. Twisted N-core fiber.
    • Fig. S2. Inhomogeneous couplings among cores.
    • Table S1. Multimode behavior of the designed four-core fiber.

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