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A Circular Nanoslit as a Spin-to-Orbital Angular Momentum Converter

A Circular Nanoslit as a Spin-to-Orbital Angular Momentum Converter

Scientific talk I gave at Physics@FOM Veldhoven 2012.

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Philip Chimento

January 23, 2012
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Transcript

  1. A Circular Nanoslit as a Spin-to-Orbital Angular Momentum Converter Philip

    Chimento Gert ‘t Hooft Eric Eliel
  2. Suspicious behavior in subwavelength slits

  3. Chimento, Kuzmin, Bosman, et al. (2011). Opt. Expr. 19 (24),

    24219. Slit in a metal film
  4. Chimento, Kuzmin, Bosman, et al. (2011). Opt. Expr. 19 (24),

    24219. Slit in a metal film Subwavelength in one direction “Infinite” in the other
  5. Chimento, Kuzmin, Bosman, et al. (2011). Opt. Expr. 19 (24),

    24219. Almost ideal metal TM TE Slit width in λ
  6. Chimento, Kuzmin, Bosman, et al. (2011). Opt. Expr. 19 (24),

    24219. Real metal TM TE Slit width in λ
  7. Chimento, Kuzmin, Bosman, et al. (2011). Opt. Expr. 19 (24),

    24219. Real metal If designed carefully, there is a point where the slit is a quarter-wave plate Analyzer rotation Input state Measured output
  8. Photo credit: Dandelion And Burdock, Flickr We roll the slit

    up into a circle
  9. Space-variant λ/4 plate

  10. Space-variant λ/4 plate TM TM TE TE

  11. Space-variant λ/4 plate Input: circular polarization σ+ state

  12. Space-variant λ/4 plate Output: ?

  13. Transmitted polarization state Schematic

  14. Transmitted intensity Experiment

  15. Transmitted polarization state Left-handed elliptical Right-handed elliptical Ellipticity <10% Experiment

  16. Photo credit: Cayusa, Flickr Where did the spin angular momentum

    disappear to?
  17. Cylindrical symmetry means no angular momentum is transferred to the

    plate Photo credit: pixaio, sxc.hu
  18. Fascinating! What does the far field look like?

  19. Far field Angle Angle Intensity (arb. units)

  20. Far field Angle Angle Intensity (arb. units) No hole in

    the middle!
  21. Far field Component with the same handedness as the input

    (σ+) Component with opposite handedness to the input (σ−)
  22. Phase of central spot Component with the same handedness as

    the input (σ+) Component with opposite handedness to the input (σ−)
  23. A proper calculation mode con- verter ￿ѫ +,￿ = ￿

    ￿ѫ+ ,￿ = ￿ ￿ѫ −,￿ = ￿
  24. A proper calculation mode con- verter ￿+TQJO￿ = −￿ I

    ￿+PSCJU￿ = ￿ I ￿+TQJO￿ = +￿ I ￿+PSCJU￿ =  ￿ѫ +,￿ = ￿ ￿ѫ+ ,￿ = ￿ ￿ѫ −,￿ = ￿
  25. A proper calculation mode con- verter ￿+TQJO￿ = −￿ I

    ￿+PSCJU￿ = ￿ I ￿+TQJO￿ = +￿ I ￿+PSCJU￿ =  Total angular momentum remains the same! ￿ѫ +,￿ = ￿ ￿ѫ+ ,￿ = ￿ ￿ѫ −,￿ = ￿
  26. We found, constructed, and understood a novel spin-to-orbit angular momentum

    coupling device.
  27. None
  28. None
  29. Orbital angular momentum ⟨Jspin ⟩ = 0 ⟨Jorbit ⟩ =

    ̵ h