Note: Descriptions are shown in the official language in which they were submitted.
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INTEGRATION OF ARRAY OF NON-ROD SHAPED OPTICAL ELEMENTS
WITH ARRAY OF FIBERS IN A STRUCTURE AND ASSOCIATED
METHODS
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention is directed to integrating an array of non-rod shaped
optical
array with an array of fibers positioned in a structure and associated
methods. The arrays
may be arranged along one or more dimensions.
Description of Related Art
Numerous recent applications, such as optical switching, require precise
positioning of fibers in an array. Such precise positioning is typically
achieved using V-
grooves in a substrate which can be accurately formed and in which the fibers
are then
placed to align them both vertically and horizontally with respect to one
another.
Typically, when using optical elements in conjunction with fibers in V-
grooves, these
optical elements are in the form of a rod, such as a Gradient Index (GRIN)
lens. The use
of such a lens allows V-grooves to also be employed to align these lenses with
the fibers.
While GRIN lenses offer good performance, the individual insertion required to
align each GRIN lens with a respective fiber is tedious and impractical on a
large scale,
especially as the industry moves toward two-dimensional arrays. While a two-
dimensional bundle of optical elements other than rod-shaped elements have
been used
in conjunction with a two dimensional bundle of fibers for imaging
applications, in
which all ofthe fibers and optical elements are forming a single image, the
alignment and
positioning of the fibers is not nearly as demanding as that of the optical
interconnection
applications. Further, since all of the fibers are forming the same image; the
fibers are
arranged in a bundle as close together as possible, and would not be placed in
the
structure used for the accurate positioning of the fibers for optical
interconnection
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applications.
Thus, while the provision of one and two-dimensional array of fibers
accurately
arranged in structures has been realized, non-rod optical elements integrated
therewith
have not. Such non-rod elements are typically thinner, cheaper and an entire
array of
these elements may be of unitary construction for simultaneous alignment.
SUMMARY OF THE INVENTION
The present invention is therefore directed to integrating an array of non-rod
shaped optical elements with an array of fibers positioned in structures and
associated
methods which substantially overcomes one or more of the problems due to the
limitations and disadvantages of the related art.
These and other objects of the present invention will become more readily
apparent from the detailed description given hereinafter. However, it should
be
understood that the detailed description and specific examples, while
indicating the
preferred embodiments of the invention, are given by way of illustration only,
since
various changes and modifications within the spirit and scope of the invention
will
become apparent to those skilled in the art from this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects, aspects and advantages will be described with
reference to the drawings, in which:
Fig. lA is a perspective elevational view of a one-dimensional array of non-
rod
optical elements;
Fig. 1B is a perspective elevational view of a back side of one-dimensional
array
of non-rod optical elements shown in Fig. lA;
Fig. 1 C is a perspective elevational view of a one-dimensional array of
fibers
positioned in V-grooves;
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Fig. 1D is an exploded perspective elevational view of the array of Fig. 1C;
Fig. lE is aperspective elevational view ofthe integrated one-dimensional
arrays
ofFigs. lA and lC;
Fig. 2A is a perspective elevational view of a one-dimensional array of non-
rod
optical elements;
Fig. 2B is a perspective elevational view of a spacer;
Fig. 2C is a perspective elevational view of a one-dimensional array of fibers
positioned in V-grooves;
Fig. 2D is an exploded perspective elevational view of the array of Fig. 2C;
Fig. 2E is a perspective elevational view of the integrated one-dimensional
arrays
of Figs. 2A and 2C with the spacer of Fig. 2B;
Fig. 3A is a perspective elevational view of a one-dimensional array of non-
rod
optical elements;
Fig. 3B is a perspective elevational view of a one-dimensional array of fibers
1 S positioned in V-grooves;
Fig. 3C is an exploded perspective elevational view of the array of Fig. 3B;
Fig. 3D is aperspective elevational view ofthe integrated one-dimensional
arrays
of Figs. 3A and 3B;
Fig. 4A is a perspective elevational view of a one-dimensional array of non-
rod
optical elements;
Fig. 4B is a perspective elevational view of a one-dimensional array of fibers
positioned in V-grooves;
Fig. 4C is an exploded perspective elevational view of the array of Fig. 4B;
Fig. 4D is a perspective elevational view of the integrated one-dimensional
arrays
of Figs. 4A and 4B;
Fig. 4E is a cross-section of the interface shown in Fig. 4D;
Fig. 4F is a cross-section of an alternative interface for fibers with angled
endfaces;
Fig. 4G is a cross-section of a two-dimensional configuration of Fig. 4F;
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Fig. 4H is a cross-section of another alternative interface for fibers with
angled
endfaces;
Fig. SA is a perspective elevational view of a two-dimensional array of non-
rod
optical elements;
Fig. SB is a perspective elevational view of a two-dimensional array of fibers
positioned in V-grooves;
Fig. SC is an exploded perspective elevational view of the array of Fig. SB;
Fig. SD is a perspective elevational view of the integrated two-dimensional
arrays
of Figs. SA and SB;
Fig. 6A is a perspective elevational view of two one-dimensional arrays of non-
rod optical elements;
Fig. 6B is a perspective elevational view of a two-dimensional array of fibers
positioned in V-grooves;
Fig. 6C is an exploded perspective elevational view of the array of Fig. 6B;
Fig. 6D is a perspective elevational view of the integrated arrays of Figs. 6A
and
6B;
Fig. 7A is a perspective elevational view of a two-dimensional array of non-
rod
optical elements;
Fig. 7B is a perspective elevational view of two one-dimensional arrays of
fibers
positioned in V-grooves;
Fig. 7C is an exploded perspective elevational view of the arrays of Fig. 7B;
Fig. 7D is a perspective elevational view of the integrated arrays of Figs. 7A
and
7B;
Fig. 8A is a perspective elevational view of a two-dimensional array of non-
rod
optical elements;
Fig. 8B is a perspective elevational view of two-dimensional array of holes in
a
substrate;
Fig. 8C is a perspective elevational view of the fibers arranged in a two-
dimensional array;
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Fig. 8D is a perspective elevational view of the integrated arrays of Figs. 8A-
8C;
Fig. 9A is a cross-section of an alternative to using v-grooves in accordance
with
the present invention; and
Fig. 9B is a cross-section of another embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be described in detail through preferred
embodiments
with reference to accompanying drawings. However, the present invention is not
limited
to the following embodiments but may be implemented in various types. The
preferred
embodiments are only provided to make the disclosure of the invention complete
and
make one having an ordinary skill in the art know the scope of the invention.
The
thicknesses of various layers and regions are emphasized for clarity in
accompanying
drawings.
Figures lA-1D illustrate the simplest configuration of the present invention.
Figure lA is a one-dimensional array 100 ofnon-rod optical elements 104 formed
on a
1 S substrate 102. This array 100 is unitary. This array 100 may be formed on
a wafer level,
e.g., photolithographicaly, and then diced to formed a desired one-dimensional
array.
The optical elements may be of refractive elements, diffractive elements or
hybrids
thereof. The elements 104 of the array 100 do not have to be the same. The
elements 104
may perform any desired optical function or combinations thereof, such as
collimating,
focusing, homogenizing, etc. The elements 104 are spaced in accordance with
the fiber
spacing in a one-dimensional array 108 of fibers 106 shown in Figures 1C and
1D.
As can be seen in Figures 1 B and 1 C, the one-dimensional array 108 of fibers
106
includes an array of upper V-grooves 110 in an upper substrate 112 and an
array of lower
V-grooves 114 in a lower substrate 116. The fibers 106 are placed in
respective V-
grooves 110, 114 which are aligned with one another. The substrates 112, 116
are then
adhered to one another in a conventional manner.
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The one-dimensional array 100 and the one-dimensional array 108 are aligned
and
adhered to form the integrated optics-fiber structure 118 as shown in Figure
1D. The
alignment may be performed actively, with light traveling through the
elements, or
passively. While passive alignment features may be provided on the one-
dimensional
array 100 of optical elements 104, since the V-grooves 110, 114 are typically
formed by
dicing a substrate containing longer V-grooves, such alignment features are
not readily
formed thereon. However, since the V-grooves 110, 114 can be so precisely
formed, for
example by anisotropic etching on a semiconductor substrate, such as a silicon
substrate,
the V-grooves 110, 114 themselves may be used as the passive alignment
features for
aligning the optics 104 and the fibers 106. Thus, the alignment features on
the one-
dimensional array 100 will be for passively aligning, either visually or
mechanically, with
the corresponding V-grooves 110, 114 of the one-dimensional array 108.
The visual alignment features may include optical fiducial marks, while the
mechanical mating features may include protrusions 103 shown in Figure 1 B on
a surface
of the array 100 facing the fiber array, such that these protrusions 103 fit
into the empty
space in the v-groove 110 above and/or below the fiber. When the optical
elements are
lithographically formed, it is advantageous to create the alignment features
lithographically as well. The lithographic creation ofthe alignment features
may be with
the same mask used for creation of the optical elements, or with another mask.
The configuration shown in Figures 2A-2E is similar to that ofFigures lA-lE,
as
indicated by the use of the same reference numerals for the same elements.
Therefore,
additional description ofthese elements will be eliminated. As shown in
Figures 2B and
2E, the present configuration includes a spacer 201, e.g., a transparent
spacer or a hollow
spacer providing empty space in a region in which light is to travel between
the optics
and the fiber. When using a hollow spacer, the desired beam size to be
realized in a
shorter distance, since the light to or from the fiber will converge or
diverge faster in free
space than in a medium.
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The configuration shown in Figures 3A-3E is similar to that of Figures 2A-2E,
as
indicated by the use of the same reference numerals for the same elements.
Therefore,
additional description of these elements will not be reiterated. As shown in
Figures 3A
and 3E, the one-dimensional array 300 in addition to the previous optical
elements 104,
includes optical elements 304 which are used exclusively for alignment. By
providing
alignment features 306 on a surface where an optical element should be,
passive
alignment of the one-dimensional array 300 may be realized by aligning the
alignment
marks 306 on the periphery of the array 300 with a corresponding fiber 106.
The
corresponding channel will not be used in the end application. Such passive
alignment
is particularly useful when the positioning structure for the fibers 106 does
not include
V-grooves or other features which may be used for alignment on the end face of
the
structure, for example, when precisely formed holes in which the fibers 106
are inserted
are used to precisely position the fibers.
The configuration in Figures 4A-4D illustrate how the optics and fiber may be
integrated when the endfaces of the fibers are at an angle. Angled endfaces
help reduce
back reflections, and the losses associated therewith.
As shown in Figure 4A, the one-dimensional array 400 includes a substrate 402
having non-rod optical elements 404 therein. These optical elements 404 are
refractive
elements, they are no longer circular as in the other examples, but now are
elliptical to
match the shape of the fiber endfaces. Further, the optical elements 404 are
preferably
diffractive elements which compensate for the shape of the light output by the
angled
fiber.
As can be seen in Figures 4B and 4C, the one-dimensional array 408 of fibers
406
having angled endfaces 407 includes an array of upper V-grooves 410 in an
upper
substrate 412 and an array of lower V-grooves 414 in a lower substrate 416. As
before,
the fibers 406 are placed in respective V-grooves 410, 414 which are aligned
with one
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another and the substrates 412, 416 are then adhered to one another in a
conventional
manner. However, the substrates 412, 416 also have angled endfaces 413, 417 in
accordance with the angle of the fiber endfaces 407.
The one-dimensional array 400 and the one-dimensional array 408 are aligned
and
S adhered to form an integrated optics-fiber structure 418. The alignment may
be
performed as discussed above. Since the one-dimensional array 400 of the
elliptical
optical elements 404 is still formed from a flat wafer, an endface 419 of the
integrated
optics-fiber structure 418 is still angled in accordance with the angle of the
fiber endface
407.
A better view of the interface between the optics block and the angled fiber
is seen
in Fig. 4E. Since the beam coming out ofthe angled fiber endface is
elliptical, the optical
elements 404 are anamorphic to collimate the beam. However, since the optics
block is
tilted, the beam is still tilted. Further, mounting the optics block at an
angle is more
difficult than straight.
1 S An alternative embodiment is shown in Fig. 4F. Here, the lens array block
420
is kept straight, while support elements 422, 424 are provided on either side
of the
support structure for the fiber 406, e.g., the v-groove block 408. These
support elements
422, 424, serve as a mount for the optics block 400. This configuration is
advantageous
for two-dimensional arrays, as shown in Fig. 4G, where two fibers 406 forming
a two
dimensional array, with additional fibers being in the plane of the page above
and below
the representative fibers . The intermediate support structure between the
upper and
lower fibers is indicated at 426. This configuration eliminates adhesive in
the optical
path, but does require more parts. Further, the use of an anamorphic lens on
the flat
surface now removes tilt from the beam. While the angle here is exaggerated
for
illustration, the angle of the endface of the fiber is typically about 8
°-12 ° perpendicular
to the optical axis of the fiber.
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Another configuration is shown in Fig. 4G, in which the optics block 430 has
one
surface thereof sloped to match the angle of the fiber endface, while another
surface
thereof is orthogonal to the fiber axis. Thus, the surfaces of the optics
block 430 are not
parallel. However, since the angle of the fiber endface is relatively small,
the difference
in distance traveled by the beam does not significantly affect the output.
This
configuration corrects for the tilt as well. If optical elements are only
formed on the
straight surface, the angle on the other surface may be formed by polishing
that surface
after formation of the elements.
A configuration for two-dimensional arrays is shown in Figures SA-SD. Figure
SA is a two-dimensional array 500 ofnon-rod optical elements 504 formed on a
substrate
502. This array 500 may be formed on a wafer level and then diced to formed a
desired
two-dimensional array which contains at least two rows and at least two
columns of
optical elements. This array 500 in unitary. The array 500 may be of
refractive elements,
diffractive elements or hybrids thereof. The elements 504 of the array 500 do
not have
to be the same. The elements 504 are spaced in accordance with the fiber
spacing in a
two-dimensional array 508 of fibers 506 shown in Figures SB and SC.
As can be seen in Figures SB and SC, the two-dimensional array 508 of fibers
506
includes an upper V-groove 510 in an upper substrate 512 and a lower V-groove
514 in
a lower substrate 516. The two-dimensional array 508 also includes an upper
middle V-
groove 520 and a lower middle V-groove 522, both of which are in a middle
substrate
524. An upper row of fibers 506 are placed in respective V-grooves 510, 520,
and a
lower row of fibers 506 are placed in respective V-grooves 514, 522. All of
these V-
grooves 510, 514, 520, 522 are aligned with one another and the substrates
512, 516, 524
are then adhered to one another in a conventional manner. Obviously, numerous
middle
substrates could be provided to accommodate any desired number of rows of
fibers.
The two-dimensional array 500 and the two-dimensional array 508 are aligned
and
adhered to form the integrated optics-fiber structure 518 as shown in Figure
SD. The
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alignment may be performed as discussed above.
However, alignment of two-dimensional arrays is more difficult than alignment
of one-dimensional arrays. Therefore, it is advantageous to deconstruct at
least one of
two into a plurality of one-dimensional arrays. As used herein,
"deconstructed"is to
mean each array, typically a one-dimensional array, of the deconstructed array
may be
aligned independently from each other.
As shown in Figures 6A-6D, instead of providing a two-dimensional array 500,
a deconstructed two-dimensional array 600 having two one-dimensional arrays
100 of
optical elements 104 is provided. The structure ofthe fiber array 508 is
similar to that of
Figures SB-SC, as indicated by the use of the same reference numerals for the
same
elements, and has not been reiterated.
Now when aligning the two-dimensional arrays 600, 508 to form the integrated
optics-fiber structure 618 shown in Figure 6D, any deviation in the thickness
of the
middle substrate 524 from a desired thickness may be compensated. Further, the
use of
the deconstructed two-dimensional array 600 is particularly advantageous when
the fibers
in different rows are to be offset from one another.
As shown in Figures 7A-7D, instead of providing a two-dimensional array 508,
a deconstructed two-dimensional array 708 having two one-dimensional arrays of
fibers
706 is provided as shown in Figures 7B and 7C. The structure of the two-
dimensional
array 500 is similar to that of Figure SA, as indicated by the use of the same
reference
numerals for the same elements, and has not been reiterated.
As can be seen in Figures 7B and 7C, the deconstructed two-dimensional array
708 of fibers 706 includes an array of upper V-grooves 710 in an upper
substrate 712 and
an array of lower V-grooves 714 in a lower substrate 716. The deconstructed
two-
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dimensional array 708 also includes an array of upper middle V-grooves 720
formed in
an upper middle substrate 721 and an array of lower middle V-grooves 722
formed in a
lower middle substrate 723. An upper row of fibers 706 are placed in
respective V-
grooves 710, 720, and a lower row of fibers 706 are placed in respective V-
grooves 714,
722. The V-grooves 710, 720 are aligned with one another and the substrates
712 and
721 are then adhered to one another in a conventional manner. Similarly, the V-
grooves
714, 722 are aligned with one another and the substrates 716 and 723 are then
adhered
to one another in a conventional manner. Obviously, numerous middle substrates
could
be provided to accommodate any desired number of rows of fibers.
Now when aligning the two-dimensional arrays 500, 708 to form the integrated
optics-fiber structure 718 shown in Figure 7D, any deviation in the vertical
separation
of the optical elements 504 from a desired separation may be compensated.
The configuration shown in Figures 8A-8D, holes 811 in a substrate 812 are
used
instead of V-grooves to accurately position and house the fibers 106 therein
to form the
integrated optics-fiber structure 818 shown in Figure 8D. Otherwise, the
structure is
similar to that of Figures SA-SD, as indicated by the use of the same
reference numerals
for the same elements, and has not been reiterated. These holes may be drilled
or may be
formed lithographically. Of course, the substrate 813 with holes 811 could be
used with
any of the above configurations. When holes are used, a potential mechanical
mating
feature would be to provide rods extending from the array 500 for insertion
into one of
the holes 811 to facilitate alignment.
Another alternative to v-grooves is shown in Figs. 9A and 9B. As shown
therein,
a polymer film 902 is provided on the optics block 900 having the optical
elements 904
thereon. The polymer film 902 may be a single layer or a plurality of layers.
The polymer
film 902 includes a plurality of holes 903 which align the fibers 906 to the
optics block
900. The holes 903 may be formed lithographically in the polymer layer using
the same
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alignment marks as used in creating the optics on the optics block 900. This
reduces the
requirements on the support structure for the fibers 906, since these fibers
are now
aligned by the holes in the polymer film. The fibers may be tapered to further
facilitate
the alignment in the holes and the loose alignment in the support. Fig. 9B
illustrates
another alternative ofthe configuration in Fig. 9A in which there are two
substrates, 900,
908, each which may have optical elements thereon. The substrates may be
bonded
together. Any of the previous configurations may include the use of a
plurality of
substrates bonded together, and optical elements may be provided on either
side of the
substrate(s).
While all of the example of two-dimensional arrays used fibers with flat
endfaces,
no spacers, and circular optical elements alone, any of the arrays discussed
in connection
with the one-dimensional arrays could be employed in any of the two-
dimensional
configurations. Further, when forming a two-dimensional array, a plurality of
one-
dimensional arrays could be used for both the optical elements and the fibers,
e.g., by
integrating array 600 with array 708. Additionally, while the configurations
show the
fibers in V-grooves or holes, any structure for providing precise positioning
of the fibers
may be used. Anti-reflection coatings may be provided wherever needed.
Finally, either
active and/or passive alignment, either visual and/or mechanical, may be used
with any
of the configurations.
While the present invention is described herein with reference to illustrative
embodiments for particular applications, it should be understood that the
present
invention is not limited thereto. Those having ordinary skill in the art and
access to the
teachings provided herein will recognize additional modifications,
applications, and
embodiments within the scope thereof and additional fields in which the
invention would
be of significant utility without undue experimentation. Thus, the scope of
the invention
should be determined by the appended claims and their legal equivalents,
rather than by
the examples given.
