Photodefinition of optical devices

• US 20010031122A1
• Filed: 12/01/2000
• Published: 10/18/2001
• Est. Priority Date: 12/02/1999
• Status: Active Grant

• Current Assignee: Gemfire Corp. (Medtronic Plc)
• Original Assignee: Gemfire Corp. (Medtronic Plc)
• Inventors: Thoms, Travis P.S., Kowalczyk, Tony C., Bischel, William K., Field, Simon J., Lackritz, Hilary S., Lee, Yeong-Cheng
• Granted Patent: US 6,724,968 B2
• Time in Patent Office: Days
• US Class Current: 385/131
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: G02B 2006/12147 Coupler
• CPC Class Codes: G02B 2006/12176 Etching
• CPC Class Codes: G02B 6/02033 Core or cladding made from organic material, e.g. polymeric material G02B1/04 takes precedence
• CPC Class Codes: G02B 6/12002 Three-dimensional structures
• CPC Class Codes: G02B 6/12019 characterised by the optical interconnection to or from the AWG devices, e.g. integration or coupling with lasers or photodiodes coupling integrated waveguide to fibre G02B6/30, to optoelectronic element G02B6/42; monolithic integration of integrated waveguides with other optical elements G02B6/12004
• CPC Class Codes: G02B 6/12021 Comprising cascaded AWG devices; AWG multipass configuration; Plural AWG devices integrated on a single chip
• CPC Class Codes: G02B 6/12033 characterised by means for configuring the device, e.g. moveable element for wavelength tuning switching G02B6/35; thermo-optic devices G02F1/0147
• CPC Class Codes: G02B 6/124 Geodesic lenses or integrated gratings
• CPC Class Codes: G02B 6/13 Integrated optical circuits characterised by the manufacturing method
• CPC Class Codes: G02B 6/138 by using polymerisation
• CPC Class Codes: G02B 6/42 Coupling light guides with opto-electronic elements
• CPC Class Codes: Y10T 428/31504 Composite [nonstructural laminate]

Abstract

An optical structure is fabricated by forming an active layer including a photodefinable material on a substrate or on another underlying layer, forming an upper layer above the active layer, and then patterning the active layer by selective application of radiation through the upper layer. The upper layer is substantially transparent to radiation of the type required to activate the photodefinable material in the active layer.

Claims

1. A radiation-definable material comprising a first layer, a second layer above said first layer, and a third layer above said second layer,

wherein said first, second and third layers each comprise polymers containing unactivated first photosensitive molecules which activate polymerization in response to incident optical energy of a first wavelength,

and wherein said polymer in said second layer further contains a greater concentration by volume of unactivated second photosensitive molecules than does said first and third layers, said second photosensitive molecules activating polymerization in response to incident optical energy of a second wavelength,

said first photosensitive molecules being less susceptible to activating polymerization in response to incident optical energy of said second wavelength than are said second photosensitive molecules, and said second photosensitive molecules being less susceptible to activating polymerization in response to incident optical energy of said first wavelength than are said first photosensitive molecules.

2. A material according to

claim 1

, wherein polymerization activated by said second photosensitive molecules in said second layer causes an index of refraction change in said second layer.

3. A material according to

claim 1

, wherein said first and third layers comprise cladding layers and said second layer comprises a core layer.

4. A material according to

claim 1

, wherein said first, second and third layers all have the same index of refraction.

5. A material according to

claim 1

, wherein said material further comprises a fourth layer below said first layer.

6. A material according to

claim 5

, wherein said first layer has an index of refraction which is greater than that of said third and that of said fourth layer, and wherein said second layer has an index of refraction which matches said third layer.

7. A material according to

claim 1

, wherein said third layer is transparent to radiation of said first type.

8. A material according to

claim 1

, wherein said polymer in said second layer is partially crosslinked.

9. A material according to

claim 1

, comprising one layer which comprises a polymer containing a greater concentration by volume of unactivated third photosensitive molecules than does another layer of said material, said third photosensitive molecules activating polymerization in response to incident optical energy of a third wavelength,

said third photosensitive molecules being less susceptible to activating polymerization in response to incident optical energy of said first wavelength than are said first photosensitive molecules, and less susceptible to activating polymerization in response to incident optical energy of said second wavelength than are said second photosensitive molecules.

10. A material according to

claim 9

, wherein said one layer is said second layer.

11. A material according to

claim 9

, comprising a fourth layer between said second and third layers,

wherein said one layer is said fourth layer.

12. A material according to

claim 1

, wherein said first layer comprises a mechanical support for said second and third layers.

13. A material according to

claim 12

, wherein said mechanical support is flexible.

14. A material according to

claim 1

, provided as a roll.

15. A radiation-definable material comprising a first layer, a second layer above said first layer, and a third layer above said second layer,

wherein at least said second and third layers have the same index of refraction,

and wherein said second layer is more susceptible than either said first or third layer to index of refraction changes in response to incident radiation of a first type.

16. A material according to

claim 15

, wherein said first, second and third layers all have the same index of refraction.

17. A material according to

claim 15

, wherein said second layer comprises a polymer which contains a greater concentration by volume of unactivated photosensitive molecules of a first type than does said third layer, said first type of photosensitive molecule activating polymerization in response to radiation of said first type.

18. A material according to

claim 17

, wherein said polymer in said second layer is partially crosslinked.

19. A material according to

claim 17

, wherein said polymer in said second layer further contains unactivated photosensitive molecules of a second type, said second type of photosensitive molecules being less susceptible to activating polymerization in response to radiation of said first type than are said first type of photosensitive molecules, said second type of photosensitive molecule activating polymerization in response to radiation of a second type.

20. A material according to

claim 15

, wherein said first layer comprises a mechanical support for said second and third layers.

21. A material according to

claim 20

, wherein said mechanical support is flexible.

22. A material according to

claim 15

, provided as a roll.

23. A method for forming an optical material, comprising the steps of:

forming a first layer of optical material above a support layer; and

subsequently forming a second layer of optical material above said first layer,

wherein said first layer is more susceptible than both said support layer and said second layer to index of refraction changes in response to incident radiation of a first type.

24. A method according to

claim 23

, further comprising the step of forming a third layer of optical material between said support layer and said first layer, said first layer being more susceptible than said third layer to index of refraction changes in response to incident radiation of said first type.

25. A method according to

claim 23

, wherein said first and second layers both have the same index of refraction.

26. A method according to

claim 25

, further comprising the steps of forming a third layer of optical material between said support layer and said first layer and forming a fourth layer of optical material between said support layer and said third layer,

wherein said third layer has an index of refraction that is higher than that of said first layer and that of said fourth layer.

27. A method according to

claim 23

, wherein said second layer is transparent to radiation of said first type.

28. A method according to

claim 23

, wherein said support layer is transparent to radiation of said first type.

29. A method according to

claim 23

, wherein said step of forming a first layer comprises the step of forming a polymer which contains a greater concentration by volume of unactivated photosensitive molecules of a first type than does said second layer, said first type of photosensitive molecule activating polymerization in response to radiation of said first type.

30. A method according to

claim 29

, wherein said step of forming a second layer comprises the step of avoiding inclusion of molecules of said first type in said second layer.

31. A method according to

claim 29

, wherein said step of forming a polymer which contains a greater concentration by volume of unactivated photosensitive molecules of a first type than does said second layer, comprises the steps of:

forming a polymer which contains unactivated photosensitive molecules of said first type; and

only partially activating said molecules of said first type.

32. A method according to

claim 31

, wherein said step of forming a second layer comprises the step of:

forming a polymer which contains unactivated photosensitive molecules of said first type; and

fully activating the molecules of said first type in said second layer.

33. A method according to

claim 29

, wherein said step of forming a first layer further comprises the step of including in said polymer in said second layer unactivated photosensitive molecules of a second type, said second type of photosensitive molecules being less susceptible to activating polymerization in response to radiation of said first type than are said first type of photosensitive molecules, said second type of photosensitive molecule activating polymerization in response to radiation of a second type.

34. A method according to

claim 23

, wherein said step of forming a second layer comprises the step of forming a polymer which contains unactivated first photosensitive molecules which activate polymerization in response to incident optical energy of a first wavelength,

and wherein said step of forming a first layer comprises the step of forming a polymer which contains additional unactivated ones of said first photosensitive molecules, and which further contains a greater concentration by volume of unactivated second photosensitive molecules than does said second layer, said second photosensitive molecules activating polymerization in response to incident optical energy of a second wavelength,

said first photosensitive molecules being less susceptible to activating polymerization in response to incident optical energy of said second wavelength than are said second photosensitive molecules, and said second photosensitive molecules being less susceptible to activating polymerization in response to incident optical energy of said first wavelength than are said first photosensitive molecules.

35. A method according to

claim 34

, wherein said steps of forming a first layer and forming a second layer collectively further comprise the step of exposing said first and second layers to optical energy of said first wavelength to only partially activate the first photosensitive molecules in said first and second layers.

36. A method according to

claim 34

, wherein said step of forming a first layer further comprises the step of exposing said first layer to optical energy of said first wavelength to only partially activate the first photosensitive molecules in said first layer prior to said step of forming a second layer.

37. A method according to

claim 36

, wherein said step of forming a second layer further comprises the step of exposing said second layer to optical energy of said first wavelength to at least partially activate the first photosensitive molecules in said second layer.

38. A method according to

claim 34

, wherein said polymer formed in said first layer includes third photosensitive molecules which activate polymerization in response to incident optical energy of a third wavelength,

said first and second photosensitive molecules being less susceptible to activating polymerization in response to incident optical energy of said third wavelength than are said third photosensitive molecules,

and wherein said step of forming a first layer further comprises the step of exposing said first layer to optical energy of said third wavelength to at least partially activate the third photosensitive molecules in said first layer.

39. A method according to

claim 38

, wherein said polymer formed in said second layer includes additional ones of said third photosensitive molecules,

and wherein said step of forming a second layer further comprises the step of exposing said second layer to optical energy of said third wavelength to at least partially activate the third photosensitive molecules in said second layer.

40. A method according to

claim 34

, wherein said polymer formed in said step of forming a first layer further contains a greater concentration by volume of unactivated third photosensitive molecules than does said second layer of said material, said third photosensitive molecules activating polymerization in response to incident optical energy of a third wavelength,

said third photosensitive molecules being less susceptible to activating polymerization in response to incident optical energy of said first wavelength than are said first photosensitive molecules, and less susceptible to activating polymerization in response to incident optical energy of said second wavelength than are said second photosensitive molecules.

41. A method according to

claim 34

, further comprising the step of forming a polymer in a third layer between said first and second layers, said polymer in said third layer containing a greater concentration by volume of unactivated third photosensitive molecules than do said first and second layers of said material, said third photosensitive molecules activating polymerization in response to incident optical energy of a third wavelength,

said third photosensitive molecules being less susceptible to activating polymerization in response to incident optical energy of said first wavelength than are said first photosensitive molecules, and less susceptible to activating polymerization in response to incident optical energy of said second wavelength than are said second photosensitive molecules.

42. A method according to

claim 23

, wherein said support layer is flexible.

43. A method according to

claim 23

, further comprising the step of winding said material onto a roll.

44. A method according to

claim 23

, further comprising the step of curing said first layer prior to said step of forming a second layer.

45. A method according to

claim 44

, further comprising the step of curing said second layer.

46. A method according to any of claims 23, 24, 26, 29, 43 and 44, further comprising the step of selectively exposing said first layer through one of said second layer and said support layer to radiation of said first type to form an index of refraction feature in said first layer but not in said second layer or said support layer.

47. A product made according to the process of any of claims 23, 24, 26, 29, 43 and 44.

48. A method for forming an optical material, comprising the steps of:

forming a second polymer layer above a first layer, said second layer including both first and second types of molecules, said first molecules being more susceptible to activating polymerization in response to incident radiation of a first type than incident radiation of a second type, and said second molecules being more susceptible to activating polymerization in response to incident radiation of a second type than incident radiation of a first type;

exposing said second layer to radiation of said first type but not said second type;

forming a third polymer layer above said second layer; and

curing said third layer without precluding further activation of polymerization by said second molecules in said second layer in response to incident radiation of said second type.

49. A method according to

claim 48

, further comprising the steps of:

forming said first layer above a support layer prior to said step of forming a second polymer layer, said first layer comprising a polymer which includes molecules of said first type; and

curing said first layer prior to said step of forming a second polymer layer, said step of curing said first layer comprising the step of exposing said first layer to radiation of said first type.

50. A method according to

claim 49

, wherein said step of forming a third polymer layer comprises the step of including molecules of a third type in said third layer, said third molecules activating polymerization in response to incident radiation of a third type, said first and second molecules each being less susceptible to activating polymerization in response to incident radiation of said third type than are said third molecules,

and wherein said step of curing said third layer comprises the step of exposing said third layer to radiation of said third type.

51. A method according to

claim 49

, wherein said support layer comprises a flexible web.

52. A method according to

claim 49

, further comprising the step of, after said step of curing said third layer, selectively exposing said second layer to radiation of said second type through one of said first and third layers to form an integrated optical index of refraction feature in said second layer.

53. A method according to

claim 52

, further comprising the step of, after said step of selectively exposing said second layer to radiation of said second type, exposing said material generally to radiation of said first type.

54. A method according to

claim 53

, further comprising the steps of, between said step of curing said third layer and said step of selectively exposing said second layer:

winding said material into a roll;

relocating said roll from a first site to a second site; and

inserting said roll into web processing equipment which performs at least said step of selectively exposing said second layer.

55. A product made by the method of any of claims 48, 52 and 54.

56. A method for patterning an optical stack, comprising the steps of:

providing a material comprising a support layer, a first layer above said support layer, and a second layer above said first layer, said first layer being more susceptible than both said support layer and said second layer to index of refraction changes in response to incident radiation of a first type;

inserting said material into selective exposure equipment; and

selectively exposing said first layer to radiation of said first type through one of said support and second layers to form an integrated optical index of refraction feature in said first layer.

57. A method according to

claim 56

, wherein said step of selectively exposing said first layer comprises the step of selectively exposing said first layer through said second layer.

58. A method according to

claim 56

, wherein said index of refraction feature comprises an optical waveguide.

59. A method according to

claim 56

, further comprising the step of, after said step of selectively exposing, exposing said material generally to radiation of said first type.

60. A method according to

claim 56

, wherein said first layer is susceptible to polymerization in response to incident radiation of a second type,

further comprising the step of, after said step of selectively exposing said first layer to radiation of said first type, exposing said material generally to radiation of said second type.

61. A method according to

claim 60

, wherein said step of selectively exposing said first layer to radiation of said first type comprises the step of selectively illuminating said first layer with optical energy of a first wavelength,

and wherein said step of exposing said material generally to radiation of said second type comprises the step of illuminating said materially generally with optical energy of a second wavelength.

62. A method according to

claim 56

, wherein said step of selectively exposing said first layer to radiation of said first type comprises the step of selectively illuminating said first layer with optical energy of a first wavelength.

63. A method according to

claim 56

, wherein said step of selectively exposing said first layer to radiation of said first type comprises the steps of:

forming a selectively etched photolithographic mask on said material above said second layer; and

illuminating said material through said mask.

64. A method according to

claim 56

, wherein said step of selectively exposing said first layer to radiation of said first type comprises the step of illuminating said material through a reticle.

65. A method according to

claim 56

, wherein said step of selectively exposing said first layer to radiation of said first type comprises the step of writing a pattern into said first layer with a laser beam.

66. A method according to

claim 56

, further comprising the step of selectively exposing at least said first layer to form a Bragg grating in at least said first layer.

67. A method according to

claim 56

, wherein said step of inserting said material into selective exposure equipment comprises the step of inserting said material into a single-station processing device.

68. A method according to

claim 56

, wherein said step of inserting said material into selective exposure equipment comprises the steps of:

inserting said material into multi-station processing equipment; and

conveying said material into a selective exposure station of said multistation processing equipment.

69. A method according to

claim 56

, wherein said step of providing a material comprises the step of providing a roll of said material.

70. A method according to

claim 56

, further comprising the step of unwinding said material from a roll prior to said step of selectively exposing.

71. A product made by the method of any of claims 56, 59, 60 and 69.

72. A method for patterning an optical stack, comprising the steps of:

providing a material comprising a flexible support layer, a first layer above said support layer, and a second layer above said first layer, said first layer being more susceptible than either said support layer or said second layer to index of refraction changes in response to incident radiation of a first type, and

selectively exposing said first layer to radiation of said first type through one of said support and second layers.

73. A method according to

claim 72

, wherein said step of selectively exposing said first layer comprises the step of selectively exposing said first layer through said second layer.

74. A method according to

claim 72

, comprising the step of forming an index of refraction feature in said first layer in response to said step of selectively exposing said first layer.

75. A method according to

claim 74

, wherein said index of refraction feature comprises an integrated optical index of refraction feature.

76. A method according to

claim 74

, wherein said index of refraction feature comprises an optical waveguide.

77. A method according to

claim 74

, wherein said index of refraction feature comprises an optical redirector.

78. A method according to

claim 74

, wherein said index of refraction feature comprises an optical grating.

79. A method according to

claim 72

, further comprising the step of, after said step of selectively exposing, exposing said material generally to radiation which cures said first layer.

80. A method according to

claim 72

, wherein said step of selectively exposing said first layer to radiation of said first type comprises the step of selectively illuminating said first layer with optical energy of a first wavelength.

81. A method according to

claim 72

, wherein said step of providing a material comprises the step of providing a roll of said material.

82. A method according to

claim 72

, further comprising the step of unwinding said material from a roll prior to said step of selectively exposing.

83. A product made by the method of any of claims 72, 79 and 82.

84. A method for forming an optical material, comprising the steps of:

forming a first layer of optical material above a support layer;

forming a second layer of optical material above said first layer;

forming a third layer of optical material above said second layer;

forming a fourth layer of optical material above said third layer; and

forming a fifth layer of optical material above said fourth layer,

wherein said second layer is more susceptible than any of said other layers to index of refraction changes in response to incident radiation of a second type,

and wherein said fourth layer is more susceptible than any of said other layers to index of refraction changes in response to incident radiation of a fourth type.

85. A method according to

claim 84

, wherein said third layer is more susceptible than any of said other layers to index of refraction changes in response to incident radiation of a third type.

86. A method according to

claim 84

, wherein said third, forth and fifth layers are transparent to radiation of said second type,

and wherein said fifth layer is transparent to radiation of said fourth type.

87. A method according to

claim 84

, wherein said support layer and said first layer are transparent to radiation of both said second and fourth types.

88. A method according to

claim 84

, wherein said step of forming a second layer comprises the step of forming a polymer which contains a greater concentration by volume of unactivated photosensitive molecules of a second type than does any other of said layers, said second type of photosensitive molecule activating polymerization in response to radiation of said second type.

89. A method according to

claim 88

, wherein said step of forming a fourth layer comprises the step of forming a polymer which contains a greater concentration by volume of unactivated photosensitive molecules of a fourth type than does any other of said layers, said fourth type of photosensitive molecule activating polymerization in response to radiation of said fourth type.

90. A method according to

claim 88

, wherein said step of forming a second layer further comprises the step of including in said polymer in said second layer unactivated photosensitive molecules of a further type, said further type of photosensitive molecules being less susceptible to activating polymerization in response to radiation of said second type than are said second type of photosensitive molecules, said further type of photosensitive molecule activating polymerization in response to radiation of a further type.

91. A method according to

claim 84

, wherein said support layer is flexible.

92. A method according to

claim 84

, further comprising the step of curing said first layer prior to said step of forming a second layer.

93. A method according to

claim 92

, further comprising the step of only partially curing said second layer prior to said step of forming a third layer.

94. A method according to

claim 93

, further comprising the step of curing said third layer prior to said step of forming a fourth layer.

95. A product made according to the process of

claim 84

.

96. A method for fabricating a multilayer optical device, comprising the steps of:

providing a material having a first cladding, a first core layer above said first cladding layer, a second cladding layer above said first core layer, a second core layer above said second cladding layer, and a third cladding layer above said second cladding layer;

forming a first index of refraction feature in said first core layer of said material; and

forming a second index of refraction feature in said second core layer of said material.

97. A method according to

claim 96

, wherein said first core layer is more susceptible to index of refraction changes in response to incident radiation of a first type than is any of said second core layer and said first, second and third cladding layers,

and wherein said second core layer is more susceptible to index of refraction changes in response to incident radiation of a second type than is any of said first core layer and said first, second and third cladding layers.

98. A method according to

claim 97

, wherein said step of forming a first index of refraction feature in said first core layer comprises the step of selectively exposing said material to radiation of said first type,

and wherein said step of forming a second index of refraction feature in said second core layer comprises the step of selectively exposing said material to radiation of said second type.

99. A method according to

claim 96

, wherein said first index of refraction feature comprises a region in said first core layer having an index of refraction which is elevated relative to laterally-adjacent regions of said first core layer, relative to sub-adjacent regions of said first cladding layer, and relative to super-adjacent regions of said second cladding layer.

100. A method according to

claim 96

, further comprising the step of forming a third index of refraction feature in said second cladding layer of said material.

101. A method according to

claim 100

, wherein said first index of refraction feature comprises a first waveguide,

wherein said second index of refraction feature comprises a second waveguide having a second length which is parallel to a corresponding first length of said first waveguide,

and wherein said third index of refraction feature comprises an interaction region between said first length of said first waveguide and said second length of said second waveguide, said interaction region having an index of refraction which is elevated relative to laterally adjacent regions of said second cladding layer.

102. A product made by the process of

claim 96

or

100

.

103. A method for fabricating a multilayer optical device, comprising the steps of:

providing a material having a first cladding, a first core layer above said first cladding layer, a second cladding layer above said first core layer, a second core layer above said second cladding layer, and a third cladding layer above said second cladding layer;

forming a first waveguide in said first core layer of said material; and

forming a second waveguide in said second core layer of said material.

104. A method according to

claim 103

, wherein said material further comprises an intervening layer adjacent to said first core layer,

and wherein said step of forming a first waveguide in said first core layer comprises the step of forming an index of refraction rib in said intervening layer.

105. A method according to

claim 103

, wherein said material further comprises an intervening layer adjacent to said second core layer, and wherein said step of forming a second waveguide in said second core layer comprises the step of forming an index of refraction rib in said intervening layer.

106. A method according to

claim 103

, further comprising the step of forming a coupling region of elevated index of refraction in said second cladding layer of said material.

107. A method according to

claim 103

, wherein said multilayer optical device comprises an optical splitter which spreads in the vertical dimension.

108. A method according to

claim 107

, wherein said optical splitter further spreads in the horizontal dimension.

109. A method according to

claim 103

, wherein said multilayer optical device comprises a WDM add/drop multiplexer/demultiplexer.

110. A method according to

claim 109

, comprising the steps of:

forming a waveguide grating wavelength demultiplexing element in one of said first and second core layers of said material; and

forming a waveguide grating wavelength multiplexing element in the other of said first and second core layers of said material.

111. A method for patterning an optical stack, comprising the steps of:

providing a material comprising a support layer, a first layer above said support layer, and a second layer above said first layer, said first layer being more susceptible than both said support layer and said second layer to index of refraction changes in response to incident radiation of a first type;

selectively exposing said first layer to radiation of said first type through one of said support and second layers to form an integrated optical index of refraction feature in said first layer; and

selectively exposing at least said first layer to form a first Bragg grating in at least said first layer.

112. A method according to

claim 111

, wherein said integrated optical index of refraction feature comprises an integrated optical waveguide.

113. A method according to

claim 112

, wherein said first Bragg grating intersects an optical mode guided by said waveguide.

114. A method according to

claim 111

, wherein said step of selectively exposing at least said first layer to form a first Bragg grating comprises the step of illuminating at least said first layer with first and second interfering plane waves to produce an interference pattern in said first layer.

115. A method according to

claim 111

, wherein said step of selectively exposing at least said first layer to form a first Bragg grating comprises the step of illuminating at least said first layer with an optical beam transmitted through a phase mask to produce a grating pattern in said first layer.

116. A method according to

claim 111

, further comprising the step of selectively exposing at least said first layer to form a second Bragg grating in at least said first layer, said second Bragg grating overlapping said first Bragg grating in said first layer.

117. A method according to

claim 111

, further comprising the step of fabricating a heating electrode on said stack and in sufficient proximity to said first Bragg grating for thermal tunability of said first Bragg grating.

118. A product made by the method of any of claims 111, 113 and 117.