Electromagnetic mode conversion in photonic crystal multimode waveguides
First Claim
1. A method for converting electromagnetic (EM) energy between guided modes of a photonic crystal waveguide having a waveguide axis, the method comprising:
- providing the photonic crystal waveguide with a mode coupling segment comprising at least one bend in the waveguide axis, wherein during operation the mode coupling segment converts EM energy in a first guided mode to a second guided mode over a first range of frequencies;
providing EM energy in the first range of frequencies in the first guided mode of the photonic crystal waveguide; and
allowing the EM energy in the first guided mode to encounter the mode coupling segment to convert at least some of the EM energy in the first guided mode to EM energy in the second guided mode.
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Abstract
A method for converting electromagnetic (EM) energy between guided modes of a photonic crystal waveguide having a waveguide axis, the method including: (i) providing the photonic crystal waveguide with a mode coupling segment comprising at least one bend in the waveguide axis, wherein during operation the mode coupling segment converts EM. energy in a first guided mode to a second guided mode; (ii) providing EM energy in the first guided mode of the photonic crystal waveguide; and (iii) allowing the EM energy in the first guided mode to encounter the mode coupling segment to convert at least some of the EM energy in the first guided mode to EM energy in the second guided mode.
298 Citations
50 Claims
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1. A method for converting electromagnetic (EM) energy between guided modes of a photonic crystal waveguide having a waveguide axis, the method comprising:
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providing the photonic crystal waveguide with a mode coupling segment comprising at least one bend in the waveguide axis, wherein during operation the mode coupling segment converts EM energy in a first guided mode to a second guided mode over a first range of frequencies;
providing EM energy in the first range of frequencies in the first guided mode of the photonic crystal waveguide; and
allowing the EM energy in the first guided mode to encounter the mode coupling segment to convert at least some of the EM energy in the first guided mode to EM energy in the second guided mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45)
wherein during operation the second mode coupling segment converts EM energy in the second guided mode to a third guided mode over the first range of frequencies, and wherein the method further comprises allowing the EM energy in the second guided mode to encounter the second mode coupling segment to convert at least some of the EM energy in the second guided mode to EM energy in the third guided mode. -
26. The method of claim 25, further comprising coupling at least some of the EM energy in the third guided mode out of the photonic crystal waveguide.
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27. The method of claim 25, wherein the first and third guided modes are substantially similar.
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28. The method of claim 1, wherein the bend in the mode coupling segment has a radius R and a bend angle θ
- sufficient to convert the EM energy in the first guided mode to the EM energy in the second guided mode.
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29. The method of claim 28, wherein the radius R of the bend in the mode coupling segment is substantially constant.
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30. The method of claim 29, wherein the bend radius R is within an order of magnitude of the absolute value of 2π
- (Δ
β
12)−
1, where Δ
β
12 is the difference in wavevector between the first guided mode and the second guided mode at a frequency in the first frequency range.
- (Δ
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31. The method of claim 28, wherein the mode coupling segment comprises only the one bend.
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32. The method of claim 1, wherein the photonic crystal waveguide comprises a dielectric core region extending along the waveguide axis, and a first set of at least three dielectric layers surrounding the core about the waveguide axis, the difference in refractive index between successive layers in the first set changing sign with each subsequent layer in the first set, wherein the first set of layers guides EM radiation in the first range of frequencies to propagate along the waveguide axis.
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33. The method of claim 32, wherein the photonic crystal waveguide further comprises at least one additional dielectric layer positioned between the core and the first set of layers, wherein the thickness of the additional dielectric layer differs from that of each of any three consecutive layers in the first set of layers by more than 10%.
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34. The method of claim 1, further comprising coupling at least some of the EM energy in the second guided mode out of the photonic crystal waveguide into a polarization sensitive device.
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35. The method of claim 1, wherein the EM energy provided to the photonic crystal waveguide has a wavelength in the range of about 1.2 microns to 1.7 microns.
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36. The method of claim 1, wherein the photonic crystal waveguide is a photonic crystal fiber.
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37. The method of claim 36, wherein the photonic crystal fiber is a Bragg fiber.
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38. The method of claim 1, further comprising coupling at least some of the EM energy in the second guided mode out of the photonic crystal waveguide.
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39. The method of claim 1, wherein the mode coupling segment provides a conversion efficiency of the EM energy in the first guided mode to the EM energy in the second guided mode of greater than 10%.
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40. The method of claim 1, wherein the mode coupling segment provides a conversion efficiency of the EM energy in the first guided mode to the EM energy in the second guided mode of greater than 25%.
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41. The method of claim 1, wherein the mode coupling segment provides a conversion efficiency of the EM energy in the first guided mode to the EM energy in the second guided mode of greater than 50%.
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42. The method of claim 1, wherein the radius R of the bend in the mode coupling segment varies along the waveguide axis.
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43. The method of claim 1, wherein the absolute value of the difference in wavevector Δ
- β
12 between the first guided mode and the second guided mode of the EM energy at a frequency in the first frequency range is smaller than the absolute value of the difference in wavevector Δ
β
ln between any other pair of the guided modes at that frequency.
- β
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44. The method of claim 1, wherein the photonic crystal waveguide has a uniform cross-section with respect to the waveguide axis.
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45. The method of claim 1, wherein the EM energy provided to the photonic crystal waveguide has a wavelength in the range of about 0.7 microns to 0.9 microns.
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46. A method for converting electromagnetic (EM) energy between guided modes of a photonic crystal fiber having a waveguide axis, the method comprising:
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providing the photonic crystal fiber with a mode coupling segment comprising at least one bend in the waveguide axis, wherein during operation the mode coupling segment converts EM energy in a first guided mode to a second guided mode over a first range of frequencies;
providing EM energy in the first range of frequencies in the first guided mode of the photonic crystal fiber; and
allowing the EM energy in the first guided mode to encounter the mode coupling segment to convert at least some of the EM energy in the first guided mode to EM energy in the second guided mode. - View Dependent Claims (47, 48, 49, 50)
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Specification