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

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