WO2002016975A2

WO2002016975A2 - Lens arrays and methods of making the lens array

Info

Publication number: WO2002016975A2
Application number: PCT/US2001/026244
Authority: WO
Inventors: Roman Carlos Gutierrez; Tony Kai Tang
Original assignee: Siwave, Inc.
Priority date: 2000-08-21
Filing date: 2001-08-21
Publication date: 2002-02-28
Also published as: WO2002016975A3; AU2001288349A1

Abstract

Lens arrays and methods of making the lens arrays are provided. The lens array is made by arranging pre-formed spherical lenses or rod lenses in a substrate using micro-machining techniques. The array of lenses may be polished on one side to form an array of plano-convex lenses.

Description

LENS ARRAYS AND METHODS OF MAKING THE LENS ARRAY

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to lenses, and more particularly to optical lens array fabrication.

Description of the Related Art

Some lens array fabrication processes involve ion milling or reactive ion etching of a glass substrate. The glass substrate is shaped into an array of lenses. Due to imperfect control of an etching profile, the lenses are not made according to desired specifications. Variations from lens to lens can also be a problem.

SUMMARY OF THE INVENTION

Lens arrays and methods of making the lens array are provided in accordance with the present invention. One aspect of the invention relates to arranging pre-formed lenses, such as spherical lenses or rod lenses, in a lens array using micro-machining techniques. The array of lenses may be polished on one side to form an array of planoconvex lenses.

In one embodiment, by using pre-formed lenses, the fabrication method limits or eliminates the amount of lens shaping using ion milling and/or reactive ion etching. Thus, the method eliminates the problems associated with ion milling and reactive ion etching in current lens array fabrication processes.

Optical characteristics of the lens array may be modified by performing additional acts on a planar side of the lens array. In one embodiment, the planar side of the lenses is shaped by using ion milling to reduce aberrations. In another embodiment, a grating or diffractive optical element is deposited on the lenses to compensate for aberrations. In another embodiment, optical coatings, such as an anti-reflection (AR) coating, is applied to the planar side of the lenses to modify at least one optical characteristic. One aspect of the invention relates to a method of making an optical lens array. The method comprises etching at least a first hole and a second hole in a substrate wafer, wherein each hole is sufficiently shaped to fit a sphere without allowing the sphere to pass completely through the hole; placing a first sphere in the first hole and a second sphere in the second hole; and shaping one side of the spheres such that the side is substantially level with a surface of the substrate wafer.

In one embodiment, the shaping comprises polishing. In another embodiment, the shaping comprises lapping. In another embodiment, the shaping comprises lapping and polishing. In one embodiment, the spheres are lapped down and polished before placement in the substrate wafer. In one embodiment, the spheres are lapped down and polished after placement in the substrate wafer.

Another aspect of the invention relates to another method of making an optical lens array. The method comprises etching at least a first hole and a second hole in a substrate wafer, wherein each hole is sufficiently shaped to fit a sphere without allowing the sphere to pass completely through the hole; lapping one side of a first sphere and a second sphere; placing the first sphere in the first hole and the second sphere in the second hole; and lapping the side of the spheres again such that the side is substantially level with a surface of the substrate wafer.

In one embodiment of this aspect of the invention, the method further comprises polishing the side of the spheres. In one embodiment, the first act of lapping comprises a substantial amount of lapping before placing the first sphere in the first hole and the second sphere in the second hole.

Another aspect of the invention relates to another method of making an optical lens array. The method comprises etching at least a first hole and a second hole in a substrate wafer, wherein each hole is sufficiently shaped to fit a spherical lens without allowing the spherical lens to completely pass through the hole; and inserting and attaching a first spherical lens in the first hole and a second spherical lens in the second hole. In this aspect of the invention, the first and second etched holes in the substrate wafer may advantageously position the lenses with a high level of accuracy with respect to each other.

Another aspect of the invention relates to another method of making an optical lens array. The method comprises etching at least a first hole and a second hole in a substrate wafer, wherein each hole is sufficiently shaped to fit a pre-formed lens; and placing a first pre-formed lens in the first hole and a second pre-formed lens in the second hole. In one embodiment, at least one lens comprises a Graded Index Rod lens.

Another aspect of the invention relates to an optical lens array. The optical lens array is made by etching at least a first hole and a second hole in a substrate wafer, wherein each hole is sufficiently shaped to fit a sphere without allowing the sphere to pass completely through the hole. A first sphere is placed in the first hole, and a second sphere is placed in the second hole. One side of the spheres is shaped such that the side is substantially level with a surface of the substrate wafer.

Another aspect of the invention relates to an optical lens array. The optical lens array is made by etching at least a first hole and a second hole in a substrate wafer, wherein each hole is sufficiently shaped to fit a spherical lens without allowing the spherical lens to pass completely through the hole. A first spherical lens is inserted and attached in the first hole and a second spherical lens is inserted and attached in the second hole.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1A illustrates a cross-section of one embodiment of a substrate wafer.

Figure IB illustrates a cross-section of another embodiment of a substrate wafer.

Figure 2A illustrates glass or silicon spheres placed into the holes of the substrate wafer in Figure 1 A.

Figure 2B illustrates spheres placed into the holes of the substrate wafer in Figure IB.

Figure 3A illustrates the substrate wafer of Figure 2A with spheres that are lapped and/or polished on one side until each sphere is substantially level with a surface of the wafer.

Figure 3B illustrates the substrate wafer of Figure 2B with spheres that are lapped and/or polished on one side until the spheres are substantially level with a surface of the wafer.

Figure 3C illustrates the substrate wafer of Figure 1A with Graded Index Rod Lenses placed in the holes of the wafer substrate.

Figure 4 illustrates a lens array of Figure 3 A with a side of the lenses shaped to a desired shape.

Figure 5 illustrates a lens array with a grating or a diffractive optical element on a surface of the lenses in Figure 3 A. Figure 6 illustrates a lens array with a coating deposited on a surface of the lenses in Figure 3 A.

Figure 7 illustrates a second wafer that is glued, bonded, or otherwise attached to the lens array wafer in Figures 3 A, 4 or 6.

DETAILED DESCRIPTION

Figure 1A illustrates a cross-section of one embodiment of a substrate wafer

100. In Figure 1A, a plurality of holes 102A-102C (referred to herein individually or collectively as 'hole 102') are etched into the substrate wafer 100. In one embodiment, the substrate wafer 100 comprises silicon. In another embodiment, the substrate wafer 100 comprises glass. In one embodiment, the substrate wafer 100 is 600-micron thick. Figure 1A illustrates three holes 102A-102C, but in other embodiments, any number of holes may be etched in the substrate wafer 100. Each hole 102 is suitably sized for a spherical lens, such as a lens 200A in Figure 2A, to be placed in the hole 102, but not pass completely through the hole 102.

The size of each hole 102 may affect the optical characteristics of each lens. Thus, it is important that each hole 102 is formed with an appropriate size to achieve any desired characteristics. In one embodiment, the holes 102A-102C have straight sidewalls, as shown in Figure 1 A. Figure IB illustrates a cross-section of another embodiment of a substrate wafer 110. The substrate wafer 110 in Figure IB has etched holes 104A-104C (referred to herein individually or collectively as 'hole 104') with sloped sidewalls 106A-106C, 108A-108C. In one embodiment, the holes 104A-104C with sloped sidewalls are created using a wet chemical etch, which creates an inverted pyramid-shaped hole. Figure IB illustrates three holes 104A-104C, but in other embodiments, any number of holes may be etched in the substrate wafer 110.

In one embodiment, the holes 102A-102C in Figure 1A and/or the holes 104A-

104C in Figure IB are rounded or shaped in such a way as to provide discrete support points for a spherical lens, such as a spherical lens 200 in Figure 2A. In one configuration, three or more contact points provide support or 'fix' the location of a spherical lens 200.

Figure 2A illustrates spheres 200A-200C (referred to herein individually or collectively as 'sphere 200') placed into the holes 102A-102C of the substrate wafer 100 in Figure 1A. In one embodiment, the spheres 200A-200C comprise glass. In another embodiment, the spheres 200A-200C comprise silicon. In one embodiment, the spheres 200A-200C are coated with an anti-reflection coating. In one embodiment, the spheres 200A-200C are arranged using micro-machining techniques.

Figure 2B illustrates spheres 200A-200C placed into the holes 104A-104C of the substrate wafer 110 in Figure IB. In one embodiment, the spheres 200A-200C in

Figure 2B comprise glass. In another embodiment, the spheres 200A-200C in Figure

2B comprise silicon. In one embodiment, the spheres 200A-200C in Figure 2B are coated with an anti-reflection coating. hi one embodiment, the spheres 200A-200C in Figures 2A and 2B are lapped and/or polished before the spheres 200A-200C are placed in the holes 102A-102C, 104A-104C in Figures 2A and 2B, respectively. In one embodiment, the spheres 200A- 200C in Figures 2A and 2B are lapped a substantial amount before the spheres 200A- 200C are placed in the holes 102A-102C, 104A-104C in Figures 2A and 2B, respectively, such that the spheres 200A-200C are substantially even with a surface of the substrate, as shown in Figure 3 A. hi one embodiment, the spheres 200A-200C in Figures 2A and 2B are glued in place with an epoxy 202, 204, 206, 208, 210, 212. In one embodiment, the epoxy 202, 204, 206, 208, 210, 212 is preferably hard and with low out-gassing such that the epoxy 202, 204, 206, 208, 210, 212 does not ruin a polishing process. In another embodiment, instead of or in addition to epoxy, the spheres 200A-200C are held in place with a mechanical component or held in place with some other suitable type of support, such as positive or negative air pressure.

Once the epoxy 202, 204, 206, 208, 210, 212 is set or the spheres 200A-200C are held in place in some other manner, the wafers 100, 110 and the spheres 200A-200C may be lapped, polished or both lapped and polished. In one embodiment, the spheres 200A-200C are lapped and/or polished by mounting the wafer in a special mount that attaches to a standard lapping machine, a polishing machine or a lapping and polishing machine. In one embodiment, the spheres 200A-200C are lapped until one side of each sphere is substantially level with a surface 304, 306 of the wafer 310, 312, as shown in Figures 3 A and 3B.

Figure 3 A illustrates the substrate wafer of Figure 2A with spheres 300A-300C that are lapped and/or polished on one side 311A-311C until the spheres 300A-300C are substantially level with a surface 304 of the wafer 310. Figure 3B illustrates the substrate wafer of Figure 2B with spheres 302A-302C that are lapped and/or polished on one side 313A-313C until the spheres 302A-302C are substantially level with a surface 306 of the wafer 312. In one embodiment, after lapping, each wafer 310, 312 may be cleaned with a liquid, such as water, and polished until the spheres 300A-300C, 302A-302C and the wafer 310, 312 are level and comprise a desired surface finish. In one embodiment, one side of each sphere 200 is lapped before the sphere 200 is placed in a hole in a substrate 100, 110 (Figure 2A or 2B) and then lapped again such that the side of each sphere is substantially level with the substrate surface 304, 306, as shown in Figures 3A and 3B. Each sphere 200 may then be polished.

In another embodiment, the spheres 200A-200C in Figure 2A or 2B are not lapped or polished. In this embodiment, the holes 102A-102C, 104A-104C are precisely etched in the substrate wafer 100, 110 to advantageously position the spherical lenses 200A-200C with a high level of accuracy with respect to each other.

Figure 3C illustrates the substrate wafer 100 of Figure 1 A with Graded Index Rod Lenses 320A-320C placed in the holes 102A-102C of the wafer substrate 100. In one embodiment, the lenses 320A-320C are glued into the holes 102A-102C. Figure 3C demonstrates that lenses with other shapes, such as the Graded Index Rod Lens 320A-320C, instead of spheres 200A-200C (Figures 2A and 2B), may be inserted and glued into the holes 102A-102C, 104A-104C of the wafer substrates 100, 110 in Figures 1 A and IB.

Lens Modifications

The lens arrays 310, 312 in Figures 3 A and 3B are prepared for one or more lens modifications, hi one embodiment, the planar sides or surfaces 311A-311C, 313A- 313C of the lenses 300A-300C, 302A-302C are modified using reactive ion etching and a layer of photoresist. In one embodiment, a layer of photoresist is deposited using gray-scale photolithography. The layer of photoresist may vary in thickness. Due to a difference in etch rate of the lens material and the photoresist, a pattern in the photoresist is transferred to a lens 300, 302. Ion milling or reactive ion etching may shape sides 311A-311C, 313A-313C of the lenses 300A-300C, 302A-302C to a desired shape. In other embodiments, other methods may be used individually or in combination to shape the lenses, such as diamond turning, laser-assisted etching, laser ablation and/or focused ion beam.

Figure 4 illustrates a lens array 400 with the sides 311A-311C of the lenses 300A-300C in Figure 3A shaped to a desired shape, such as by depositing a layer of photoresist and reactive ion etching. The shape of the lens 402A-402C can be used to reduce aberrations and/or modify the properties of the lenses 402A-402C in the array 400. In one embodiment, the lenses 402A-402C have a plano-convex shape.

In another lens modification, a grating is formed on one side 304, 306 of the lens array 310, 312 (Figure 3 A or 3B). A 'grating' is an optical element in which a substantially periodic variation in index of refraction with very fine periodicity (close to the wavelength of the light) uses interferometric effects of light to change the shape of the wavefront as light passes through the grating. The grating may be formed directly on the polished surfaces 311A-311C, 313A-313C of the lenses 300A-300C, 302A-302C or on a film that is deposited on the surfaces 311 A-311 C, 313 A-313C.

In another lens modification, a diffractive optical element is formed on a side 304, 306 of the lens array 310, 312 (Figure 3A or 3B). A 'diffractive optical element' is a version of a grating in which the variation in index of refraction is not periodic. A nonperiodic index of refraction allows more flexibility in the changes that can be made to the shape of the wavefront. The diffractive optical element may be formed directly on the polished surfaces 311A-311C, 313A-313C of the lenses 300A- 300C, 302A-302C or on a film that is deposited on the surfaces 311A-311C, 313A- 313C.

Figure 5 illustrates a lens array 500 where a grating or a diffractive optical element 502A-502C is formed on the surfaces 311 A-311 C of the lenses 300A-300C in Figure 3A. The grating or diffractive optical element 502A-502C can be used to reduce aberrations and/or to modify the properties of the different lenses 504A-504C in the array 500.

In another lens modification, a coating is deposited on one side 304, 306 of the lens array 310, 312 in Figure 3A or 3B. Figure 6 illustrates a lens array 600 with a coating 602A-602C deposited on the surfaces 311A-311C of the lenses 300A-300C in Figure 3A. In one embodiment, the coating 602A-602C comprises an AR coating. In other embodiments, the coating 602A-602C comprises other types of coating. In one embodiment, the coating 602A-602C allows a particular wavelength of light to pass through the lenses 604A-604C, as used in WDM applications.

In another lens modification, a wafer 700 with holes 702A-702C is glued, bonded, or otherwise attached to the lens array wafer 310, 400 or 600 in Figures 3 A, 4 or 6, as shown in Figure 7. In one embodiment, the wafer 700 is a fiber array comprising a plurality of fibers 704A-704C in the holes 702A-702C. In one embodiment, the lenses 300A-300C, 402A-402C or 604A_r604C are aligned with a plurality of fibers 704A-704C in the fiber array 700. Some exemplifying embodiments of fiber arrays are described in co-assigned patent applications entitled "High Density Fiber Terminator/Connector" (Attorney Docket No. M-9920) and "Angled Fiber Termination And Methods of Making the Same" (Attorney Docket No. M-11564), which are both hereby incorporated by reference in their entireties.

In one embodiment, the wafer 700 in Figure 7 is used as a spacer to provide a well-controlled distance between the array of lenses 300A-300C, 402A-402C or 604A- 604C and a fiber array 700. In one embodiment, one or more features are etched into a surface of the lens array wafer 310, 400 or 600 in Figure 7 that is facing the fiber array 700. The features may comprise slots, grooves or holes. The fiber array 700 may have corresponding features on a surface facing the lens array 310, 400 or 600 that fit into the slots, grooves or holes of the lens array 310, 400 or 600. In other embodiments, the fiber array 700 has etched features, such as slots, grooves or holes, and the lens array 310, 400 or 600 has corresponding features that fit into the slots, grooves or holes of the fiber array 700. The etched features, such as slots, grooves or holes, and the corresponding features that fit into the etched features may be used to precisely align the lenses 300A-300C or 604A-604C of the lens array 310, 400 or 600 with the fibers 704A-704C of the fiber array 700.

In some embodiments, the lenses described herein are not lapped or polished at all.

The above-described embodiments of the present invention are merely meant to be illustrative and not limiting. Various changes and modifications may be made without departing from the invention in its broader aspects. The appended claims encompass such changes and modifications within the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A method of making an optical lens array, the method comprising: etching at least a first hole and a second hole in a substrate wafer, wherein each hole is sufficiently shaped to fit a sphere without allowing the sphere to pass completely through the hole; placing a first sphere in the first hole and a second sphere in the second hole; and shaping one side of the spheres such that the side is substantially level with a surface of the substrate wafer.

2. The method of Claim 1, wherein shaping one side of the spheres comprises polishing.

3. The method of Claim 1, wherein shaping one side of the spheres comprises lapping.

4. The method of Claim 1, wherein shaping one side of the spheres comprises lapping and polishing.

5. The method of Claim 1, wherein shaping one side of the spheres occurs before placing a first sphere in the first hole and a second sphere in the second hole.

6. The method of Claim 1, wherein shaping one side of the spheres occurs after placing a first sphere in the first hole and a second sphere in the second hole.

7. The method of Claim 1 , wherein the substrate wafer comprises silicon.

8. The method of Claim 1, wherein the substrate wafer comprises glass.

9. The method of Claim 1 , wherein the spheres comprises silicon.

10. The method of Claim 1 , wherein the spheres comprises glass.

11. The method of Claim 1, further comprising using gray-scale photolithography to deposit a layer of photoresist on the side of each sphere that is substantially level with a surface of the substrate wafer.

12. The method of Claim 1, further comprising using ion milling to shape the side of the spheres that is substantially level with a surface of the substrate wafer to a desired shape.

13. The method of Claim 1, further comprising using reactive ion etching to shape the side of the spheres that is substantially level with a surface of the substrate wafer to a desired shape.

14. The method of Claim 1, further comprising using diamond turning to shape the side of the spheres that is substantially level with a surface of the subsfrate wafer to a desired shape.

15. The method of Claim 1, further comprising using laser-assisted etching to shape the side of the spheres that is substantially level with a surface of the substrate wafer to a desired shape.

16. The method of Claim 1, further comprising using laser ablation to shape the side of the spheres that is substantially level with a surface of the subsfrate wafer to a desired shape.

17. The method of Claim 1, further comprising using a focused ion beam to shape the side of the spheres that is substantially level with a surface of the substrate wafer to a desired shape.

18. The method of Claim 1, further comprising forming a grating on the side of the spheres that is substantially level with a surface of the substrate wafer to a desired shape.

19. The method of Claim 1, further comprising forming a diffractive optical element on the side of the spheres that is substantially level with a surface of the substrate wafer to a desired shape.

20. The method of Claim 1, further comprising applying a coating to an outer surface of the spheres to modify at least one optical characteristic of the spheres.

21. The method of Claim 1, further comprising applying an anti-reflection coating to an outer surface of the spheres.

22. The method of Claim 1, wherein placing the first and second spheres in the first and second holes comprise using at least one micro-machining technique.

23. A method of making an optical lens array, the method comprising: etching at least a first hole and a second hole in a subsfrate wafer, wherein each hole is sufficiently shaped to fit a sphere without allowing the sphere to pass completely through the hole; lapping one side of a first sphere and a second sphere; placing the first sphere in the first hole and the second sphere in the second hole; and lapping the side of the spheres again such that the side of the spheres are substantially level with a surface of the substrate wafer.

24. The method of Claim 23, further comprising polishing the side of the spheres.

25. A method of making an optical lens array, the method comprises: etching at least a first hole and a second hole in a substrate wafer, wherein each hole is sufficiently shaped to fit a spherical lens without allowing the spherical lens to pass completely through the hole; and inserting and attaching a first spherical lens in the first hole and a second spherical lens in the second hole.

26. A method of making an optical lens array, the method comprises: etching at least a first hole and a second hole in a subsfrate wafer, wherein each hole is sufficiently shaped to fit a pre-formed lens; and placing a first pre-formed lens in the first hole and a second pre-formed lens in the second hole.

27. The method of Claim 26, wherein at least one pre-formed lens comprises a Graded Index Rod Lenses.

28. The method of Claim 26, further comprising gluing at least one preformed lens in a hole.

29. An optical lens array, the optical lens array made by: etching at least a first hole and a second hole in a substrate wafer, wherein each hole is sufficiently shaped to fit a sphere without allowing the sphere to pass completely through the hole; placing a first sphere in the first hole and a second sphere in the second hole; and shaping one side of the spheres such that the side is substantially level with a surface of the substrate wafer.

30. An optical lens array, the optical lens array made by: etching at least a first hole and a second hole in a substrate wafer, wherein each hole is sufficiently shaped to fit a spherical lens without allowing the spherical lens to pass completely through the hole; and inserting and attaching a first spherical lens in the first hole and a second spherical lens in the second hole.