U.S. patent application number 09/902002 was filed with the patent office on 2003-01-16 for method and structure for aligning optical elements.
Invention is credited to Bourcier, Roy J., Crook, Russell A., Faber, William G., Forenz, Dominick J..
Application Number | 20030011899 09/902002 |
Document ID | / |
Family ID | 25415165 |
Filed Date | 2003-01-16 |
United States Patent
Application |
20030011899 |
Kind Code |
A1 |
Bourcier, Roy J. ; et
al. |
January 16, 2003 |
METHOD AND STRUCTURE FOR ALIGNING OPTICAL ELEMENTS
Abstract
The present invention relates to a five-degree of freedom
alignment structure 10 for an optical element 28. The alignment
structure 10 is a two piece assembly including a submount 12 and a
support member 18. An optical element 28 is coupled to the mounting
surface 14 of submount 12. The alignment structure 10 is used to
align the optical axis 34 of the optical element 28 with the
optical axes 32 of another optical element 30.
Inventors: |
Bourcier, Roy J.; (Corning,
NY) ; Crook, Russell A.; (Hellertown, PA) ;
Faber, William G.; (Elmira, NY) ; Forenz, Dominick
J.; (Hammondsport, NY) |
Correspondence
Address: |
CORNING INCORPORATED
SP-TI-3-1
CORNING
NY
14831
|
Family ID: |
25415165 |
Appl. No.: |
09/902002 |
Filed: |
July 10, 2001 |
Current U.S.
Class: |
359/813 |
Current CPC
Class: |
Y10T 29/49895 20150115;
G02B 7/1822 20130101; G02B 6/4226 20130101; G02B 7/023 20130101;
G02B 27/62 20130101 |
Class at
Publication: |
359/813 |
International
Class: |
G02B 007/02 |
Claims
What is claimed is:
1. A method for mounting an optical element comprising the steps
of: selecting an optical element; coupling the optical element to a
submount; selecting a support block having at least two
non-coplanar surfaces; coupling said submount to said support block
thereby forming a mounting assembly; selectively manipulating the
position of said submount and said support block to align said
optical element so as to allow said optical element to engage in
optical communication with at least one other optical element; and
fixing the position of said submount and said support block with
respect to the at least one other optical element.
2. The method of claim 1 wherein the step of coupling said submount
to said base includes the steps of: bringing said base and said
submount into close proximity to one another; and dispensing
adhesive between said base and said submount.
3. The method of claim 1 wherein the step of selectively
manipulating comprises the steps of: rotating said submount about a
first axis; translating said submount along in a first plane;
rotating said support block about a second axis wherein said second
axis is not parallel to said first axis; and translating said
support block in a second plane, wherein said second plane is
inclined with respect to said first plane.
4. The method of claim 1 wherein the step of fixing further
comprises the step of irradiating said mounting assembly with light
of the appropriate wavelength and intensity to initiate curing of
the adhesive.
5. An optical element mount made according to the method of claim
1.
6. A mount for an optical element comprising: a support member
having: an anchor surface slidable on a surface; and an alignment
surface disposed at an angle to said anchor surface; and a submount
having: a mounting surface, wherein the optical element is coupled
to said mounting surface; and a bonding surface disposed at an
angle to said mounting surface and coupled said alignment surface
of said support block.
7. The positioner of claim 6 wherein said submount is adhesively
bonded to said support block.
8. The positioner of claim 6 wherein said submount is adhesively
bonded to said support block with a light curable adhesive.
9. A mount for an optical element comprising: a submount having two
parallel surfaces, wherein the optical element is coupled to said
submount; and two support blocks disposed to slidably engage said
two parallel surfaces, wherein said submount is rotatable about an
axis perpendicular to said two parallel surfaces, wherein said
submount may be rotated about two non-parallel axes and translated
in three orthogonal directions, and wherein said submount is
positioned to allow the optical element to engage in optical
communication with at least one other optical element.
10. The mount of claim 9 wherein the positioning of said submount
includes coupling said submount to said two support blocks and
coupling said two support blocks to a substrate.
11. The mount of claim 10 wherein each of said two support blocks
comprises: an anchoring surface; and a mounting surface wherein
said anchoring surface and said mounting surface are adjacent one
another and said mounting surface is coupled to one of said two
parallel surfaces and said anchoring surface is coupled to the
substrate.
12. The mount of claim 11 wherein said anchoring surface of each of
said two support blocks is bonded to said substrate and said
mounting surface of each of said two support blocks is bonded to
one of said two parallel surfaces.
13. The mount of claim 11 wherein said two support blocks are made
of glass.
14. An optical device comprising: a substrate, said substrate
including a planar surface; a support member including: an anchor
surface coupled to said planar surface, wherein before said anchor
surface in coupled to said planar surface said support member is
slidable and rotatable upon said planar surface; and an alignment
surface, wherein said alignment surface is inclined with respect to
said anchor surface; and an optical element having an optical axis,
said optical element coupled to said alignment surface, wherein
before said optical element is coupled to said alignment surface
said optical element is slidable and rotatable upon said alignment
surface; wherein prior to coupling said optical element to said
support member and coupling said anchor surface to said planar
surface the optical axis of the optical element is positionable in
five degrees of freedom.
15. A method for aligning the optical axes of two optical elements
comprising the steps of: providing a first optical element having a
first optical axis; providing a second optical element having a
second optical axis; providing a substrate, said substrate
including a planar surface; providing a support member, said
support member slidable and rotatable upon said planar surface,
wherein said support member includes an alignment surface; coupling
the first optical element to said alignment surface, wherein said
first optical element is slidable along said alignment surface,
wherein said first optical element is rotatable about an axis
perpendicular to said alignment surface; aligning the first optical
axis with the second optical axis; and fixing the position said
first optical axis with respect to said second optical axis;
wherein said step of aligning includes the steps of sliding said
support member on said planar surface and rotating said support
member about an axis perpendicular to said planar surface; wherein
said step of aligning further includes the steps of sliding the
first optical element on said alignment surface and rotating the
first optical element about an axis perpendicular to said alignment
surface.
16. The method of claim 15 further including the steps of:
providing a submount; and coupling the first optical element to
said submount; wherein the step of coupling the first optical
element to said alignment surface includes coupling said submount
to said alignment surface.
17. The method of claim 16, wherein the step of coupling said
submount to said planar surface includes placing adhesive between
said submount and said planar surface; wherein the step of coupling
the first optical element to said alignment surface includes the
placing adhesive between the first optical element and said
alignment surface; wherein the step of fixing the position said
first optical axis with respect to said second optical axis
includes optically initiating the curing of the adhesive.
18. The method of claim 17 wherein the step of coupling the first
optical element to said alignment surface includes placing and
adhesive between said submount to said alignment surface; and
wherein the step of fixing the position said first optical axis
with respect to said second optical axis includes optically
initiating the curing of the adhesive.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to aligning optical
elements, and particularly to a bonded alignment structure for
optical elements.
[0003] 2. Technical Background
[0004] In the assembly of optical devices it is often desirable to
use free space optics to allow two optical elements to engage in
optical communication with one another. Each optical element may be
thought of as having an optical axis. In order for the optical
elements to engage in efficient optical communication with one
another the optical elements must be optically aligned with one
another. Typically optical alignment consists of aligning the
optical axes of two or more optical elements so that an optical
signal following a desired optical path through the optical
elements possesses certain characteristics. Optical alignment
requires rotating and translating the optical elements in 3-space
to bring their respective optical axes in to a predetermined degree
of alignment. For example, placing a lens in the path of a laser
beam so that the lens performs an optical operation, such as
collimating or focusing, on the laser beam.
[0005] Alignment and structural attachment of miniature photonic
optical elements, including lenses, mirrors and fibers, has proven
difficult. Many optical elements have optical tolerances that are
sufficiently large enough to allow passive alignment of the optical
components. The optical tolerances of many optical elements,
however, are too small to allow passive alignment. The assembly of
these optical elements into optical devices requires active
alignment. Active alignment may be defined as placing at least two
optical elements in optical communication with one another and
repositioning at least one of the optical elements until some
characteristic of the optical signal has a predetermined value.
Typically, active alignment is accomplished by moving one of the
optical elements relative to the other optical elements while
measuring the intensity of the optical signal received by one of
the optical elements.
[0006] The active alignment process may be complicated by the fact
that the structural assembly must allow the optical elements to be
both aligned and fixed in place without inducing unacceptable
shifts in location of the optical element. Active positioning is
comparatively expensive and is often difficult to implement due to
the limited space inside photonic packages. Captive positioning is
desirable, but designs often require a high degree of mechanical
complexity and have relatively large tolerances.
[0007] There is a need for a relatively simple captive alignment
structure capable of obtaining the tight tolerances necessary for
optical alignment while minimizing the shift in location of the
optical components during attachment.
SUMMARY OF THE INVENTION
[0008] The present invention is directed towards methods and
structures for mounting optical components that require active
alignment.
[0009] One embodiment of the present invention is a method for
mounting an optical element using five (5) Cartesian degrees of
freedom. The method for mounting an optical element includes the
step of selecting an optical element to be mounted for optical
communication with another optical element. The method also
includes the step of coupling the optical element to a submount.
The method further includes forming a mounting assembly by
selecting a support block having at least two non-coplanar surfaces
and coupling the support block to the submount. The optical element
is then positioned for optical communication with another optical
element by selectively manipulating the position of the submount
and the support block to align the optical element with at least
one other optical element. The relative position of the submount
and the support block with respect to the other optical element are
then fixed.
[0010] In another embodiment, the present invention includes a
mount for an optical element. The mount includes a support member
having an anchor surface slidable on a substrate and a alignment
surface at an angle to the anchor surface. The mount further
includes a submount having a bonding surface and a mounting
surface. The bonding surface and the mounting surface are at an
angle to one another. The bonding surface is coupled to the
alignment surface of the support block and the optical element is
coupled to the mounting surface of the submount.
[0011] In another embodiment, the present invention includes a
mount for an optical element. The mount includes a submount and two
support blocks. The submount has two parallel surfaces and the two
support blocks are placed to slidably engage the two parallel
surfaces. The optical element is coupled to the submount. The
submount and two support blocks are arranged so that the submount
is rotatable about an axis perpendicular to the two parallel
surfaces and is translatable in a plane parallel to the two
parallel surfaces. The optical element is positioned to engage in
optical communication with at least one other optical element by
selectively rotating the submount about two non-parallel axes and
translating the submount in three orthogonal directions.
[0012] One advantage of the present invention is that it provides a
mount for an optical element adjustable in five (5) degrees of
Cartesian freedom.
[0013] Another advantage of the present invention is that the
adhesive bonds may be thoroughly cured without thermal
distortion.
[0014] Another advantage of the present invention is that it has a
relatively low vertical profile which is important in the packaging
of active opto-electronic devices.
[0015] Additional features and advantages of the invention will be
set forth in the detailed description which follows, and in part
will be readily apparent to those skilled in the art from that
description or recognized by practicing the invention as described
herein, including the detailed description which follows, the
claims, as well as the appended drawings.
[0016] It is to be understood that both the foregoing general
description and the following detailed description are merely
exemplary of the invention, and are intended to provide an overview
or framework for understanding the nature and character of the
invention as it is claimed. The accompanying drawings are included
to provide a further understanding of the invention, and are
incorporated in and constitute a part of this specification. The
drawings illustrate various embodiments of the invention, and
together with the description serve to explain the principles and
operation of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a perspective view of an alignment structure in
which the present invention is embodied;
[0018] FIG. 1A is a top plan view of the alignment structure shown
in FIG. 1;
[0019] FIG. 1B is a side elevation view of the alignment structure
shown in FIG. 1;
[0020] FIG. 1C is a front elevation view of the alignment structure
shown in FIG. 1;
[0021] FIG. 2 is a side elevation view of the support member shown
in FIG. 1;
[0022] FIG. 3 is a side elevation view of an alternative embodiment
of the support member shown in FIG. 1;
[0023] FIG. 4 is a side elevation view of an alternative embodiment
of the support member shown in FIG. 1;
[0024] FIG. 5 is a side elevation view of an alternative embodiment
of the submount shown in FIG. 1;
[0025] FIG. 6 is a side elevation view of an alternative embodiment
of the submount shown in FIG. 1;
[0026] FIG. 7 is a side elevation view of an alternative embodiment
of the submount shown in FIG. 1;
[0027] FIG. 8 is a side elevation view of an alternative embodiment
of the submount shown in FIG. 1;
[0028] FIG. 9 is a side elevation view of an alternative embodiment
of the submount shown in FIG. 1;
[0029] FIG. 10 is a side elevation view of an alternative
embodiment of the submount shown in FIG. 1;
[0030] FIG. 11 is a perspective view of an alternative embodiment
of the alignment structure of the present invention;
[0031] FIG. 12 is a front elevation view of the alignment structure
shown in FIG. 11;
[0032] FIG. 13 is a side elevation view of the alignment structure
shown in FIG. 11; and
[0033] FIG. 14 is a top plan view of the alignment structure shown
in FIG. 11.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] Reference will now be made in detail to the present
preferred embodiments of the invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers will be used throughout the drawings to
refer to the same or like parts. An exemplary embodiment of the
alignment structure of the present invention is shown in FIG. 1,
and is designated generally throughout by reference numeral 10.
[0035] As embodied herein and depicted in FIG. 1, the alignment
structure 10 is a five-degree of freedom mount for an optical
element 28. The alignment structure 10 is a two piece assembly
including a submount 12 and a support member 18. An optical element
28 is coupled to the mounting surface 14 of submount 12. The
alignment structure 10 is used to align the optical axis 34 of the
optical element 28 with the optical axes 32 of another optical
element 30. The optical element 30 may be adjustable in position or
fixed in position, for the purposes of this illustrative example of
a two piece alignment structure 10 embodiment of the present
invention set forth herein, the position of the optical element 30
will be assumed to be fixed in space relative to the optical
element 28 mounted to the alignment structure 10. It will be
apparent to those skilled in the art that the following detailed
description of an embodiment of the alignment structure 10 of the
present invention is also applicable when the position and
orientation of the optical element 30 is adjustable. Both of the
optical elements 28, 30 are shown as generic three-dimensional
rectangular structures for illustrative purposes in FIG. 1. The
optical elements 28, 30 may, however, have any geometric shape. The
optical elements 28, 30 may be, for example, lenses, collimators,
optical fibers, a light-emitting device, such as for example a
laser or a diode, or a light receiving device, such as, for example
a photodetector. The preceding list is merely illustrative of a
small number of optical elements and is intended merely to show the
broad scope of applicability of the present invention and should
not be considered a limitation of the invention. The present
invention may be utilized for aligning the various components of
any free space optical system.
[0036] The support member 18 is configured for engagement with a
substrate 24. The support member 18 includes an anchor surface 22.
In one embodiment, for use when the substrate 24 is a planar
surface, the anchor surface 22 is configured to allow the alignment
structure 10 to move in the directions indicated by the arrows 35,
39 shown in FIGS. 1A and 1B and to be rotated in the direction
indicated by the arrow 36.
[0037] Typically, the substrate 24 is a planar surface of an
optical platform, for example, the interior floor of a butterfly
package for a laser.
[0038] The support member 18 has an alignment surface 20 and an
anchor surface 22. Preferably the alignment surface 20 and the
anchor surface 22 are substantially planar surfaces that are
orthogonal to one another. The anchor surface 22 has a flatness and
surface finish that facilitate positioning the alignment structure
10 on the substrate 24 and the coupling of the anchor surface 22 to
the substrate 24. For example, when the support member 18 is made
of glass the anchor surface 22 could be ground to provide a
suitable finish and flatness. The finish and flatness of the anchor
surface 22 depend on the bonding agent used and the detailed design
specification of the alignment structure 10. The surface finish and
the flatness of the anchor surface 22 required for a specific
installation of this embodiment of the present invention may be
readily determined by those skilled in the art. FIGS. 2, 3 and 4
illustrate examples of possible support member geometries. The
submount 12 includes a mounting surface 14 and a bonding surface
16. Preferably the mounting surface 14 and the bonding surface 16
are orthogonal to one another. The submount 12 is coupled to a
support member 18 using a liquid, light curable adhesive. The
adhesive is applied between the alignment surface 20 and the
bonding surface 16. Preferably, the adhesive has a viscosity less
than about 250 centipoise (cps). For example, UV15adhesive,
available from Master Bond Inc. of Hackensack, N.J., has a
viscosity in the range from about 120 cps to about 150 cps. Curing
of the adhesive is not initiated until the optical elements 28, 30
are brought into final alignment with one another. The use of a
light curable adhesive minimizes thermal expansion induced
distortion of the alignment structure and can yield aligned
structures with no more than submicron shifts in the spatial
orientation of the optical element 28 during the curing cycle.
[0039] Before curing the adhesive between the submount 12 and the
support member 18 vertical position (Z direction) of the submount
12 is easily adjusted by sliding the submount 12 up and down on the
alignment surface 20 of the support member 18. Thus the alignment
structure 10 provides three translational degrees of freedom for
aligning the optical elements 28, 30.
[0040] Furthermore, the support member 18 may be rotated on the
substrate 24 about an axis perpendicular to the substrate 24 ,
thereby allowing lateral angular alignment of the optical element
28. Additionally, the submount 12 may be rotated about an axis
perpendicular to the Z-axis. Therefore, the alignment structure 10
possesses five degrees of freedom for aligning the optical element
28.
[0041] A light curable adhesive having a viscosity less than about
250 centipoise (cps), for example, UV15 adhesive, available from
Master Bond Inc. of Hackensack, N.J. is placed between the
substrate 24 and the anchor surface 22 of the support member 18.
The light curable adhesive may be placed between the substrate 24
and the anchor surface 22 of the support member 18 either before or
after the alignment process is begun. Final adjustments to the
alignment structure 10 are made and the alignment structure 10 is
fixed in place by irradiating it with of the appropriate wavelength
and intensity until the adhesive between the substrate 24 and the
anchor surface 22 and the adhesive between the bonding surface 16
and the alignment surface 20 is cured. Preferably both the support
member 18 and the submount 12 are made from a material that is
transparent to the required light.
[0042] As depicted in FIG. 1, FIG. 1A, FIG. 1B and FIG. 1C both the
submount 12 and the support member 18 are L-shaped members,
however, the submount 12 and the support block may be of any shape
having two surfaces inclined with respect to one another. In the
preferred embodiment of the submount 12 of the alignment structure
10 of the present invention has two orthogonal planar surfaces.
Similarly, the support block may be of any shape having two
surfaces inclined with respect to one another. In a preferred
embodiment, the support member 18 of the alignment structure 10 of
the present invention has two orthogonal planar surfaces. The
orthogonal surfaces of the submount 12 and the support member 18
allows the optical element 28 to be aligned with another optical
element 30 so that movement of the support member 18 on the
substrate 24 does not effect the vertical alignment of the optical
element 28 with the stationary optical element 30. Similarly,
vertical (Z direction) or longitudinal (X direction) movement of
the submount 12 with respect to the support member 18 by sliding
the bonding surface 20 along the alignment surface 20 does not
effect the lateral (Y direction) alignment of the optical element
28 with respect to the stationary optical element 30.In accordance
with the invention, the present invention for an optical alignment
structure includes a submount 12, examples of which are illustrated
in FIG. 5 through FIG. 10.
[0043] As embodied herein and depicted in FIG. 5, the submount 12
is an L-shaped member including a mounting surface 14 and a bonding
surface 16. The mounting surface 14 may be a planar surface, a
curved surface, a grooved surface or any other type of surface that
an optical element may be attached to. A planar surface is
particularly suitable for the mounting of optical elements having a
flat surface; examples of which are prismatic lenses and certain
types of thin film filters.
[0044] The bonding surface 16 is preferably a substantially planar
surface. The surface roughness of the bonding surface is such to
facilitate the adhesive coupling of the submount to a support
member 18. The bonding surface preferably has an area in the range
from about 1 square millimeter to about 25 square millimeters. The
mounting surface 14 and the bonding surface 16 are at some angle to
one another, preferably the mounting surface 14 and the bonding
surface 16 are perpendicular to one another.
[0045] In another alternative embodiment, as embodied herein and as
shown in FIG. 6, the submount 12 is a L-shaped member having a
mounting surface 14 and a bonding surface 16. Preferably the
mounting surface 14 and the bonding surface 16 are orthogonal to
one another. The mounting surface 14 includes a groove 15. The
groove 15 is configured for engagement with an optical element, for
example a glass ferrule attached to an optical waveguide fiber
device. Typically the optical axis of the optical element, for
example an optical waveguide fiber in a glass ferrule, coupled to
the submount is parallel to the groove 15. Preferably, the groove
15 is parallel to the bonding surface 16. The groove 15 may be of
any cross section for engagement with an optical element. Examples
of groove shapes used in the mounting of optical elements include
V-grooves, U-grooves, and arcuate grooves.
[0046] In another alternative embodiment, as shown in FIG. 7, the
submount 12 has a polygonal cross section having a mounting surface
14 and a bonding surface 16a. The mounting surface 14 may be a
planar surface, a curved surface, a grooved surface or any other
type of surface that an optical element may be attached to. A
planar surface is particularly suitable for the mounting of optical
elements having a flat surface. The mounting surface 14 is inclined
with respect to the bonding surface 16a. The bonding surface 16a is
preferably a planar surface adapted for adhesive bonding to the
alignment surface 20 of the support member 18. Preferably, the
mounting surface 14 and the bonding surface 16a are perpendicular
to one another.
[0047] In another alternative embodiment, as shown in FIG. 8, the
submount 12 has a polygonal cross section having a mounting surface
14 and a bonding surface 16a, wherein the mounting surface defines
a groove 15. The groove 15 is configured for engagement with the
optical element 28. The optical element 28 may include an alignment
structure (not shown) that engages the groove 15 or the optical
element 28 may itself engage that groove 15, such as, for example
when the optical element 28 is a cylindrical ferrule for.
Preferably, the groove 15 is located such that when the optical
element 28 engages the groove 15 the optical axis of the optical
element is parallel to the bonding surface 16a. The groove 15 may
be of any cross section for engagement with an optical element.
Examples of groove shapes used in the mounting of optical elements
include V-grooves, U-grooves, and arcuate grooves.
[0048] In another alternative embodiment, as embodied herein and as
shown in FIG. 9, the submount 12 is a U-shaped member having a
mounting surface 14 and two bonding surfaces 16a, 16b. Preferably
the two bonding surfaces 16a, 16b are parallel planar surfaces. The
mounting surface 14 may be a planar surface, a curved surface, a
grooved surface or any other type of surface that an optical
element may be attached to. A planar surface is particularly
suitable for the mounting of optical elements having a flat
surface; examples of which are prismatic lenses and certain types
of thin film filters. The mounting surface 14 is inclined with
respect to the two bonding surfaces 16a, 16b.
[0049] In another alternative embodiment, as embodied herein and
shown in FIG. 10, the submount 12 is a U-shaped member having a
mounting surface 14, and two bonding surfaces 16a, 16b. Preferably
the two bonding surfaces 16a, 16b are parallel planar surfaces. The
mounting surface 14 includes a groove 15. The groove 15 is
preferably parallel to the two bonding surfaces 16a, 16b. The
groove 15 may be of any cross section for engagement with an
optical element. Examples of groove shapes used in the mounting of
optical elements include V-grooves, U-grooves, and arcuate
grooves.
[0050] The submount 12 may be made by machining and redrawing a
glass shape in order to obtain components of a desirable size. Thus
easily machined glass shapes may be reduced in cross sectional
dimension to allow their use in small optical packages. It may be
necessary to grind or polish either the mounting surface 14 or the
bonding surface 16 or both to achieve the desired flatness or
surface finish for these two surfaces.
[0051] Additionally, both or either of the submount 12 and the
support member 18 may be made from porous Vycor.RTM. material,
available from Corning Incorporated of Corning, N.Y. Using porous
Vycor.RTM. material for either or both the submount 12 and the
support member 18 allows the alignment structure 10 to function as
a getter when used inside a laser package.
[0052] In an alternative embodiment, the optical element 28 may be
directly coupled to the alignment surface 20. In this alternative
embodiment, the optical element 28 includes a surface corresponding
to the bonding surface 16 of the submount 12. Such a surface maybe,
for example, the frame of a lens element. Thus the submount 12 is
functionally replaced by the surface of the optical element 28.
[0053] As embodied herein and depicted in FIG. 11, the alignment
structure 40 is a three piece assembly including a submount 42 and
two support blocks 44, 46 used to position an optical element 28.
The following description may be better understood by also
referring to FIGS. 12, 13, and 14, which are, respectively, a front
elevation view, a side elevation view and a top plan view of the
alignment structure 40 illustrated in FIG. 11. The optical element
28 to be positioned by the alignment structure 40 is coupled to the
mounting surface 48 of the submount 42. The coupling of the optical
element 28 to the mounting surface 48 may be accomplished by a
number of methods known to those skilled in the art including, for
example, adhesive bonding, mechanical connection, using fasteners,
using glass frits, soldering and welding.
[0054] The submount 42 is located between the two support blocks
44, 46. The submount 42 includes a mounting surface 48 and two
bonding surfaces 50, 52. Preferably, the two bonding surfaces 50,
52 are parallel to one another and orthogonal to the mounting
surface 48. In this embodiment the submount 42 is made from glass
although it is envisioned that the submount 42 may be made from any
one of a number of materials, including metals, plastics and
ceramics, depending upon the design requirements of the alignment
structure 40. The selection of the shape and material for the
submount is a mere design choice easily made by those skilled in
the art.
[0055] The embodiments of the submount 12 shown in FIGS. 7, 8, 9,
and 10 may also find use as the submount 42 in the alignment
structure 40. When used as a submount 42 the submounts 12 shown in
FIGS. 7, 8, 9, and 10 also include a second bonding surface 16b.
The second bonding surface 16b corresponds to the bonding surface
52 of FIG. 11. The second bonding surface 16b is substantially
parallel to the bonding surface 16a.
[0056] Preferably, the support blocks 44, 46 or the submount 42
should be optically transparent. Alternatively the support blocks
44, 46 and the submount 42 may all be optically transparent. The
optical transparency of the either the support blocks 44, 46 or the
submount 42 to light allows the submount 42 be coupled to the
support blocks 44, 46 by an optically initiated epoxy adhesive
bond. The use of an light curable adhesive in this embodiment of
the present invention allows the submount 42 to move with respect
to the support blocks 44, 46 because in its uncured state the light
curable adhesive is a liquid that allows the respective alignment
surfaces and bonding surfaces to slide engage one another without
binding while still maintaining enough cohesive force to keep the
submount 42 coupled to the support blocks 44, 46.
[0057] Each of the support blocks 44, 46 includes an anchor surface
54, 56 and an alignment surface 58, 60. The alignment surfaces 58,
60 are substantially planar surfaces and preferably are orthogonal
to the surface 24. Preferably the support blocks 44, 46 are
positioned so that the alignment surfaces 58, 60 are substantially
parallel with one another. The submount 42 is held in place between
the alignment surfaces by an light curable adhesive preferably
having a viscosity less than about 250 centipoise (cps), for
example, UV15 adhesive, available from Master Bond Inc. of
Hackensack, N.J. UV15 adhesive has a viscosity in the range from
about 120 cps to about 150 cps.
[0058] Before the adhesive is cured by irradiating it with light of
the appropriate wavelength and intensity, such as, for example
ultraviolet light, the orientation of the optical element 28 may be
adjusted to bring it into optical alignment with the stationary
optical element 30. The orientation of the optical element 28 is
adjusted by sliding the submount 42 in the X and Z directions and
rotating the submount between the two alignment surfaces 58, 60.
When the mounting surface 48 is orthogonal to the two bonding
surfaces 50, 52 rotation of the submount 42 rotates the optical
element 28 about an axis parallel to the Y-axis.
[0059] Preferably the surface 24 is a substantially planar surface
allowing the alignment structure 40 to be moved about on it without
changing the distance in the Z direction between the mounting
surface 48 and the optical element (not shown) that the optical
element 28 is to be aligned with. The anchor surfaces 54, 56 are
configured to allow the support blocks to slide over the surface
24.
[0060] While the support blocks 44, 46 are shown as U-shaped
members, the support blocks may also be rectangular blocks,
L-shaped members or any other shape having a surface slidable on
the surface 24 and positionable so as to allow the mounting surface
48 to vary in distance from the surface 24 and be variably inclined
with respect to the surface 24.
[0061] In an alternate embodiment of the invention, as embodied
herein and as shown in FIG. 15, the present invention includes a
method for aligning optical elements designated generally
throughout by reference numeral 100. The method 100 will be
described with specific reference to the alignment structure 10
embodiment of the present invention shown in FIG. 1 and described
above. Those skilled in the art, however, will appreciate that the
method 100 is readily adaptable for use with the alignment
structure 50 embodiment of the present invention shown in FIGS. 1
and 11 described above and is not limited to the detailed example
provided below.
[0062] The method 100 includes a first step 110 of selecting the
optical element to be aligned. Examples of optical elements
requiring alignment with other optical elements included lenses,
collimators, isolators, lasers, filters, circulators, and the ends
of optical waveguide fibers.
[0063] The method 100 further includes the step 112 of coupling the
optical element to a submount. The submount includes two
non-parallel surfaces, a mounting surface and a bonding surface.
Preferably the bonding surface and the mounting surface are
substantially planar surfaces orthogonal to one another. Preferably
the submount is transparent to light. The optical element is
coupled to the mounting surface. The optical element may be coupled
to the submount using techniques for mounting optical elements that
are known to those skilled in the art. Examples of techniques
employed by those skilled in the art to attach an optical element
to a substrate include adhesive bonding, fusing, mechanical
fastening, soldering and welding. Additionally, the optical element
may be supported by a frame that is attached to the submount.
[0064] The method 100 further includes the step 114 of selecting a
support block having at least two non-parallel surfaces. One of the
two non-parallel surfaces, referred to as the anchor surface, is
configured to be slidable and rotatable on a surface of an optical
platform, for example an interior surface of a butterfly package
for a laser. The other surface is referred to as the alignment
surface and is configured for adhesive bonding to the bonding
surface of the submount. Preferably the alignment surface and the
anchor surface are substantially planar surfaces orthogonal to one
another.
[0065] The method 100 further includes the step 116 of coupling the
submount to the support block. The submount is coupled to the
support block using a small volume of low viscosity adhesive.
Preferably, the adhesive is an ultraviolet curable adhesive having
a viscosity less than about 250 centipoise (cps) is preferable. An
example of an ultraviolet curable adhesive that meets these
requirements is UV15 adhesive, available from Master Bond Inc. of
Hackensack, N.J. UV15 adhesive has a viscosity in the range from
about 120 cps to about 150 cps. The submount is coupled to the
support block by bringing the alignment surface of the support
block and the bonding surface of the submount into close proximity
and dispensing the light adhesive between the surfaces.
Alternatively, the adhesive may be applied to either the bonding
surface or the alignment surface before bringing the two surfaces
into close proximity with one another. The capillary forces exerted
by the adhesive are strong enough to pull the two surfaces close
together (less than 10 micrometers of separation).
[0066] The method 100 further includes the step 118 of selectively
manipulating the position of the submount and the support block.
The optical element is aligned with another optical element so the
two optical elements may engage in optical communication with one
another. The optical elements are aligned with one another by
sliding the anchor surface of the support block about the surface
of the optical platform. This slidability of the support block with
respect to the surface of the optical platform allows translation
of the alignment structure in two directions (X and Y of FIG. 1).
Furthermore, the alignment structure may be rotated about an axis
(Z of FIG. 1) perpendicular to the surface of the optical
platform.
[0067] The submount may be slid on the alignment surface in two
directions (Z and X of FIG. 1) and rotated about an axis (Y of FIG.
1). When the anchor surface and the alignment surface are
orthogonal to one another and the bonding surface and the mounting
surface are orthogonal to one another the alignment structure
possesses five degrees of Cartesian freedom for use in aligning the
optical element.
[0068] The method 100 further includes the step 120 of fixing the
position of the submount with respect to at least one other optical
element. This step 120 is accomplished through irradiating the
optical alignment structure with light of the appropriate
wavelength and intensity to initiate curing of the adhesive.
Because the support block and the submount are transparent to light
the adhesive may be thoroughly cured without exposing the alignment
structure to a distortion inducing thermal treatment.
[0069] It will be apparent to those skilled in the art that various
modifications and variations can be made to the present invention
without departing from the spirit and scope of the invention. Thus,
it is intended that the present invention cover the modifications
and variations of this invention provided they come within the
scope of the appended claims and their equivalents.
* * * * *