Amplitude and phase control in distributed optical structures

• US 20030039444A1
• Filed: 08/27/2002
• Published: 02/27/2003
• Est. Priority Date: 08/27/2001
• Status: Active Grant

• Current Assignee: OL Security LLC (Intellectual Ventures LLC)
• Original Assignee: Lightsmyth Incorporated
• Inventors: Greiner, Christoph M., Mossberg, Thomas W.
• Granted Patent: US 6,678,429 B2
• Time in Patent Office: Days
• US Class Current: 385/37
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G02B 6/124 Geodesic lenses or integrated gratings
• CPC Class Codes: G02B 6/29326 Diffractive elements having focusing properties, e.g. curved gratings Rowland circle spectrometers G01J3/20
• CPC Class Codes: G02B 6/29328 Diffractive elements operating in reflection
• CPC Class Codes: G03H 1/0248 Volume holograms
• CPC Class Codes: G03H 1/28 superimposed holograms only
• CPC Class Codes: G03H 2223/16 Optical waveguide, e.g. optical fibre, rod
• CPC Class Codes: G03H 2240/13 Amplitude and phase complex modulation

Abstract

An optical element is provided with one or more sets of diffractive elements. Individual diffractive element transfer functions collectively yield corresponding overall transfer functions between corresponding entrance and exit ports. Diffractive elements are defined by contours that include diffracting region(s) altered to diffract, reflect, and/or scatter incident optical fields (altered index, surface, etc). Element transfer functions are determined by: fraction of contour filled by diffracting region(s) (partial-fill grayscale); and/or the spatial profile of the diffracting region(s) (profile-based grayscale). Optical elements may be configured: as planar or channel waveguides, with curvilinear diffracting segments; to support three-dimensional propagation with surface areal diffracting segments; as a diffraction grating, with grating groove segments. These devices may have one or more ports, and may provide one or more spatial/spectral transfer functions between the ports with spatially overlapping sets of diffractive elements.

Claims

1. An optical apparatus, comprising:

an optical element provided with at least one set of at least two diffractive elements,

each diffractive element to diffract a corresponding diffracted component of an incident optical field with a corresponding diffractive element transfer function so that each set of the at least one diffractive element set collectively provides a corresponding overall set transfer function between a corresponding entrance optical port and a corresponding exit optical port,

each diffractive element being spatially defined by a corresponding diffractive element contour and comprising at least one diffracting region thereof, the diffracting regions having at least one altered optical property so as to enable diffraction of a portion of the incident optical field therefrom,

at least one of;

i) the corresponding overall set transfer function; and

ii) at least one corresponding diffractive element transfer function, being determined at least in part by at least one of;

a) a less-than-unity fill factor for the corresponding contour;

b) a non-uniform distribution of multiple diffracting regions of the corresponding contour;

c) variation of a spatial profile of the optical property the at least one diffracting region of the corresponding contour;

d) variation of a spatial profile of the optical property among multiple diffracting regions of the corresponding contour; and

e) variation of the spatial profile of the optical property of the at least one diffracting region among elements in the at least one diffractive element set.

2. The apparatus of claim 1,

the optical element being a waveguide, the waveguide substantially confining in at least one transverse dimension optical fields propagating therein,

each of the diffractive element contours being a curvilinear contour, each of the diffracting regions being a curvilinear diffracting segment thereof.

3. The apparatus of claim 2, the waveguide being provided with at least two optical ports.

4. The apparatus of claim 2, the optical element being a planar waveguide, the planar waveguide substantially confining in one transverse dimension optical fields propagating in two dimensions therein.

5. The apparatus of claim 2, the optical element being a channel waveguide, the channel waveguide substantially confining in two transverse dimensions optical fields propagating in one dimension therein.

6. The apparatus of claim 2, the waveguide comprising a core and lower-index cladding for substantially confining optical fields propagating therein.

7. The apparatus of claim 6, the diffracting segments comprising grooves in the core, the grooves being filled with cladding.

8. The apparatus of claim 6, the diffracting segments comprising ridges of the core protruding into the cladding.

9. The apparatus of claim 2, an index differential between the waveguide and a surrounding volume serving to substantially confine optical fields propagating therein.

10. The apparatus of claim 9, the diffracting segments comprising grooves in the waveguide.

11. The apparatus of claim 9, the diffracting segments comprising ridges protruding from the waveguide.

12. The apparatus of claim 2, the diffracting segments being provided lithographically.

13. The apparatus of claim 2, the diffracting segments being provided by spatially-selective optically-induced optical densification of the waveguide.

14. The apparatus of claim 2, the diffracting segments being provided by spatially-selective mechanically-induced optical densification of the waveguide.

15. The apparatus of claim 2, the diffracting segments being provided by spatially-selective doping of the waveguide.

16. The apparatus of claim 2, the diffracting segments being provided holographically.

17. The apparatus of claim 2, at least one corresponding diffractive element transfer function being determined at least in part by at least one of the less-than-unity fill factor for the corresponding contour and the non-uniform distribution of multiple diffracting segments of the corresponding contour.

18. The apparatus of claim 17, the at least one diffracting segment of at least one corresponding contour comprising a plurality of curvilinear diffracting segments.

19. The apparatus of claim 18, the curvilinear diffracting segments of at least one corresponding contour being of substantially the same length and substantially uniformly spaced along the corresponding contour.

20. The apparatus of claim 18, the curvilinear diffracting segments of at least one corresponding contour being of substantially irregularly varying lengths and substantially irregularly spaced along the corresponding contour.

21. The apparatus of claim 18, the curvilinear diffracting segments of at least one corresponding contour being of varying lengths so that a local fill factor for the corresponding contour filled varies along the length of the contour.

22. The apparatus of claim 17, the at least one diffracting segment of the corresponding contours being collectively arranged so that substantially any portion of an optical field propagating from the entrance optical port encounters a substantially similar number of diffracting segments among the diffractive element set, thereby resulting in a substantially spatially uniform corresponding overall set transfer function between the corresponding entrance optical port and the corresponding exit optical port.

23. The apparatus of claim 17, the waveguide being provided with a second diffractive element set of at least two diffractive elements, the second diffractive element set being at least partially spatially overlapped with a first diffractive element set,

each element of the second diffractive element set to diffract a corresponding diffracted component of the incident optical field with a corresponding diffractive element transfer function so that the second diffractive element set collectively provides a second overall set transfer function between a second entrance optical port and a second exit optical port,

each element of the second diffractive element set being spatially defined by a corresponding diffractive element curvilinear contour and comprising at least one diffracting segment thereof, the diffracting segments having an altered optical property so as to enable diffraction of a portion of the incident optical field therefrom,

the corresponding diffractive element transfer function of at least one element of the second diffractive element set being determined at least in part by at least one of a less-than-unity fill factor for the corresponding contour and a non-uniform distribution of multiple diffracting segments of the corresponding contour,

the at least one diffracting segment of at least one element of at least one of the first and second diffractive element sets comprising a plurality of curvilinear diffracting segments.

24. The apparatus of claim 23, corresponding pluralities of diffracting segments of intersecting contours being arranged along the intersecting contours so that the diffracting segments do not substantially intersect.

25. The apparatus of claim 23, the waveguide being provided with at least three optical ports.

26. The apparatus of claim 2, at least one corresponding diffractive element transfer function being determined at least in part by the thickness and the effective index of the at least one diffracting segment.

27. The apparatus of claim 26, at least one of the thickness and the effective index of the at least one diffracting segment varying along the corresponding contour.

28. The apparatus of claim 2, the corresponding overall set transfer function being determined at least in part by the relative positions of the corresponding diffractive element contours.

29. The apparatus of claim 2, at least one corresponding element transfer function being determined at least in part by at least one of:

variation of the spatial profile of the optical property along the at least one diffracting segment of the corresponding contour, and variation of the spatial profile of the optical property among multiple diffracting segments of the corresponding contour.

30. The apparatus of claim 2, at least one corresponding overall set transfer function being determined at least in part by variation of the spatial profile of the optical property of the diffracting segments among the elements of the corresponding diffractive element set.

31. The apparatus of claim 1, the optical element enabling propagation of optical fields in three dimensions therein,

each of the diffractive element contours being a surface contour, each of the diffracting regions being a diffracting surface areal segment.

32. The apparatus of claim 31, the optical element being provided with at least two optical ports.

33. The apparatus of claim 31, the diffractive elements being provided holographically.

34. The apparatus of claim 31, at least one corresponding diffractive element transfer function being determined at least in part by at least one of the less-than-unity fill factor for the corresponding contour and the non-uniform distribution of multiple diffracting surface areal segments of the corresponding contour.

35. The apparatus of claim 34, the at least one diffracting surface areal segment of at least one corresponding contour comprising a plurality of diffracting surface areal segments.

36. The apparatus of claim 35, the diffracting surface areal segments of at least one corresponding surface contour being of substantially the same area and substantially uniformly arranged over the corresponding surface contour.

37. The apparatus of claim 35, the diffracting surface areal segments of at least one diffractive element being of substantially irregularly varying areas and substantially irregularly arranged over the corresponding surface contour.

38. The apparatus of claim 35, the diffracting surface areal segments of at least one corresponding surface contour being of varying areas so that a local fill factor for the corresponding surface contour varies across the contour.

39. The apparatus of claim 34, the at least one diffracting surface areal segment of the corresponding surface contour being collectively arranged so that substantially any portion of an optical field propagating from the entrance optical port encounters a substantially similar number of diffracting surface areal segments among the diffractive element set, thereby resulting in a substantially spatially uniform corresponding overall set transfer function between the corresponding entrance optical port and the corresponding exit optical port.

40. The apparatus of claim 34, the optical element being provided with a second diffractive element set of at least two diffractive elements, the second diffractive element set being at least partially spatially overlapped with the first diffractive element set,

each element of the second diffractive element set to diffract a corresponding diffracted component of the incident optical field with a corresponding diffractive element transfer function so that the second diffractive element set collectively provides a second overall set transfer function between a second entrance optical port and a second exit optical port.

each element of the second diffractive element set being spatially defined by a corresponding diffractive element surface contour and comprising at least one diffracting surface areal segment thereof, the diffracting surface areal segments having an altered optical property so as to enable diffraction of a portion of the incident optical field therefrom,

the corresponding diffractive element transfer function of at least one element of the second diffractive element set being determined at least in part by at least one of a less-than-unity fill factor for the corresponding contour and a non-uniform distribution of multiple diffracting surface areal segments of the corresponding contour,

the at least one diffracting surface areal segment of at least one element of at least one of the first and second diffractive element sets comprising a plurality of diffracting surface areal segments.

41. The apparatus of claim 40, corresponding pluralities of diffracting surface areal segments of intersecting surface contours being arranged on the intersecting surface contours so that the diffracting surface areal segments do not substantially intersect.

42. The apparatus of claim 40, the optical element being provided with at least three optical ports.

43. The apparatus of claim 31, at least one corresponding diffractive element transfer function being determined at least in part by the thickness and the effective index of the at least one diffracting surface areal segment.

44. The apparatus of claim 43, at least one of the thickness and the effective index on the at least one diffracting segment varying across the corresponding contour.

45. The apparatus of claim 31, the corresponding overall set transfer function being determined at least in part by the relative positions of the corresponding diffractive element contours.

46. The apparatus of claim 31, at least one corresponding element transfer function being determined at least in part by at least one of:

variation of the spatial profile of the optical property along the at least one diffracting segment across the corresponding contour, and variation of the spatial profile of the optical property among multiple diffracting surface areal segments of the corresponding contour.

47. The apparatus of claim 31, at least one corresponding overall set transfer function being determined at least in part by variation of the spatial profile of the optical property of the diffracting segments among the elements of the corresponding diffractive element set.

48. The apparatus of claim 1, the optical element being a diffraction grating, each of the diffractive element contours being a curvilinear contour, each of the diffracting regions being a curvilinear diffracting segment thereof.

49. The apparatus of claim 48, the diffraction grating being provided with at least two optical ports.

50. The apparatus of claim 48, the diffraction grating being a reflection grating.

51. The apparatus of claim 48, the diffraction grating being a transmission grating.

52. The apparatus of claim 48, the diffraction grating being a volume grating.

53. The apparatus of claim 52, the diffracting segments comprising segments having a refractive index higher than the average refractive index of the volume grating.

54. The apparatus of claim 52, the diffracting segments comprising segments having a refractive index lower than the average refractive index of the volume grating.

55. The apparatus of claim 52, the diffracting segments being provided by spatially-selective optically-induced optical densification of the volume grating.

56. The apparatus of claim 52, the diffracting segments being provided by spatially-selective mechanically-induced optical densification of the volume grating.

57. The apparatus of claim 52, the diffracting segments being provided by spatially-selective doping of the volume grating.

58. The apparatus of claim 52, the diffracting segments being provided holographically.

59. The apparatus of claim 52, at least one corresponding diffractive element transfer function being determined at least in part by the thickness and the effective index of the corresponding diffracting segment.

60. The apparatus of claim 48, the diffraction grating being a surface grating.

61. The apparatus of claim 60, at least one corresponding diffractive element transfer function being determined at least in part by a groove depth of the corresponding diffracting segment.

62. The apparatus of claim 60, at least one corresponding diffractive element transfer function being determined at least in part by a groove shape of the corresponding diffracting segment.

63. The apparatus of claim 60, the diffracting segments being provided holographically.

64. The apparatus of claim 60, the diffracting segments being provided lithographically.

65. The apparatus of claim 60, the diffracting segments being provided by ruling the surface grating.

66. The apparatus of claim 48, at least one corresponding diffractive element transfer function being determined at least in part by at least one of the less-than-unity fill factor for the corresponding contour and the non-uniform distribution of multiple diffracting segments of the corresponding contour.

67. The apparatus of claim 66, the at least one diffracting segment of at least one corresponding contour comprising a plurality of curvilinear diffracting segments.

68. The apparatus of claim 67, the curvilinear diffracting segments of at least one corresponding contour being of substantially the same length and substantially uniformly spaced along the corresponding contour.

69. The apparatus of claim 67, the curvilinear diffracting segments of at least one corresponding contour being of substantially irregularly varying lengths and substantially irregularly spaced along the corresponding contour.

70. The apparatus of claim 67, the curvilinear diffracting segments of at least one corresponding contour being of varying lengths so that a local fill factor for the corresponding contour filled varies along the length of the contour.

71. The apparatus of claim 66, the at least one diffracting segment of the corresponding contour being collectively arranged so that substantially any portion of an optical field propagating from the entrance optical port encounters a substantially similar number of diffracting segments among the diffractive element set, thereby resulting in a substantially spatially uniform corresponding overall set transfer function between the corresponding entrance optical port and the corresponding exit optical port.

72. The apparatus of claim 66, the diffraction grating being provided with a second diffractive element set of at least two diffractive elements, the second diffractive element set being at least partially spatially overlapped a first diffractive element set,

each element of the second diffractive element set to diffract a corresponding diffracted component of the incident optical field with a corresponding diffractive element transfer function so that the second diffractive element set collectively provides a second overall set transfer function between a second entrance optical port and a second exit optical port.

each element of the second diffractive element set being spatially defined by a corresponding diffractive element curvilinear contour and comprising at least one diffracting segment thereof, the diffracting segments having an altered optical property so as to enable diffraction of a portion of the incident optical field therefrom,

the corresponding diffractive element transfer function of at least one element of the second diffractive element set being determined at least in part by at least one of a less-than-unity fill factor for the corresponding contour and a non-uniform distribution of multiple diffracting segments of the corresponding contour,

the at least one diffracting segment of at least one element of at least one of the first and second diffractive element sets comprising a plurality of curvilinear diffracting segments.

73. The apparatus of claim 72, corresponding pluralities of diffracting segments of intersecting contours being arranged along the intersecting contours so that the diffracting segments do not substantially intersect.

74. The apparatus of claim 72, the diffraction grating being provided with at least three optical ports.

75. The apparatus of claim 48, the corresponding overall set transfer function being determined at least in part by the relative positions of the corresponding diffractive element contours.

76. The apparatus of claim 48, at least one corresponding element transfer function being determined at least in part by at least one of:

variation of the spatial profile of the optical property along the at least one diffracting segment of the corresponding contour, and variation of the spatial profile of the optical property among multiple diffracting segments of the corresponding contour.

77. The apparatus of claim 48, at least one corresponding overall set transfer function being determined at least in part by variation of the spatial profile of the optical property of the diffracting segments among the elements of the corresponding diffractive element set.

78. An optical apparatus, comprising:

a waveguide provided with a plurality diffractive elements, the waveguide substantially confining in at least one transverse dimension optical fields propagating therein,

each diffractive element to diffract a corresponding diffracted component of an incident optical field with a corresponding diffractive element transfer function so that the diffractive elements collectively provide an overall transfer function between an entrance optical port and an exit optical port,

each diffractive element being spatially defined by a corresponding curvilinear diffractive element contour and comprising at least one diffracting segment thereof, the diffracting segments having an altered optical property so as to enable diffraction of a portion of the incident optical field therefrom,

at least one of;

i) the overall transfer function; and

ii) at least one corresponding diffractive element transfer function, being determined at least in part by at least one of;

a) a less-than-unity fill factor for the corresponding contour;

b) a non-uniform distribution of multiple diffracting regions of the corresponding contour;

c) variation of a spatial profile of the optical property along the at least one diffracting region along the corresponding contour;

d) variation of a spatial profile of the optical property among multiple diffracting regions of the corresponding contour; and

e) variation of the spatial profile of the optical property of the at least one diffracting region among the diffractive elements.

79. The apparatus of claim 78, at least one corresponding diffractive element transfer function being determined at least in part by at least one of the less-than-unity fill factor for the corresponding contour and the non-uniform distribution of multiple diffracting segments of the corresponding contour.

80. The apparatus of claim 79, the at least one diffracting segment of at least one corresponding contour comprising a plurality of curvilinear diffracting segments.

81. The apparatus of claim 79, the at least one diffracting segment of the corresponding contours being collectively arranged so that substantially any portion of an optical field propagating from the entrance optical port encounters a substantially similar number of diffracting segments among the diffractive elements, thereby resulting in a substantially spatially uniform overall transfer function between the entrance optical port and the exit optical port.

82. The apparatus of claim 78, at least one corresponding diffractive element transfer function being determined at least in part by the thickness and the refractive index of the at least one diffracting segment.

83. The apparatus of claim 78, the overall transfer function being determined at least in part by the relative positions of the corresponding diffractive element contours.

84. The apparatus of claim 78, at least one corresponding element transfer function being determined at least in part by at least one of:

variation of the spatial profile of the optical property along the at least one diffracting segment of the corresponding contour, and variation of the spatial profile of the optical property among multiple diffracting segments of the corresponding contour.

85. The apparatus of claim 78, the overall transfer function being determined at least in part by variation of the spatial profile of the optical property of the diffracting segments among the diffractive elements.

86. An optical apparatus, comprising:

a waveguide provided with first and second diffractive element sets, the waveguide substantially confining in at least one transverse dimension optical fields propagating therein,

the first and second diffractive element sets being at least partially spatially overlapped;

each of the first and second diffractive elements sets including a plurality diffractive elements,

each diffractive element to diffract a corresponding diffracted component of an incident optical field with a corresponding diffractive element transfer function so that the first and second diffractive element sets collectively provide corresponding first and second overall transfer functions between corresponding first and second entrance optical ports and corresponding first and second exit optical ports,

each diffractive element being spatially defined by a corresponding curvilinear diffractive element contour and comprising at least one diffracting segment thereof, the diffracting segments having an altered optical property so as to enable diffraction of a portion of the incident optical field therefrom,

at least one of;

i) the first overall set transfer function;

ii) the second overall set transfer function; and

iii) at least one corresponding diffractive element transfer function, being determined at least in part by at least one of;

a) a less-than-unity fill factor for the corresponding contour;

b) a non-uniform distribution of multiple diffracting regions of the corresponding contour;

c) variation of a spatial profile of the optical property along the at least one diffracting region of the corresponding contour;

d) variation of a spatial profile of the optical property among multiple diffracting segments of the corresponding contour; and

e) variation of the spatial profile of the optical property of the at least one diffracting region among the diffractive elements of at least one of the first and second diffractive element sets.

87. The apparatus of claim 86, at least one corresponding diffractive element transfer function being determined at least in part by at least one of the less-than-unity fill factor for the corresponding contour and the non-uniform distribution of multiple diffracting segments of the corresponding contour.

88. The apparatus of claim 87, the at least one diffracting segment of at least one element of at least one of the first and second diffractive element sets comprising a plurality of curvilinear diffracting segments.

89. The apparatus of claim 87,

the at least one diffracting segment of at least one element of at least one of the first and second diffractive element sets comprising a plurality of curvilinear diffracting segments,

corresponding pluralities of diffracting segments of intersecting contours being arranged along the intersecting contours so that the diffracting segments do not substantially intersect.

90. The apparatus of claim 86, at least one corresponding diffractive element transfer function being determined at least in part by the thickness and the refractive index of the at least one diffracting segment.

91. The apparatus of claim 86, at least one corresponding overall set transfer function being determined at least in part by the relative positions of the corresponding diffractive element contours.

92. The apparatus of claim 86, at least one corresponding element transfer function being determined at least in part by at least one of:

variation of the spatial profile of the optical property along the at least one diffracting segment of the corresponding contour, and variation of the spatial profile of the optical property among multiple diffracting segments of the corresponding contour.

93. The apparatus of claim 86, at least one corresponding overall set transfer function being determined at least in part by variation of the spatial profile of the optical property of the diffracting segments among the elements of the corresponding diffractive element set.