U.S. patent application number 11/888139 was filed with the patent office on 2007-11-22 for modular diode laser assembly.
This patent application is currently assigned to nLight Photonics Corporation. Invention is credited to Aaron L. Hodges, Scott R. Karlsen, Robert J. Martinsen, Derek E. Schulte, Yu Yan.
Application Number | 20070268946 11/888139 |
Document ID | / |
Family ID | 38053470 |
Filed Date | 2007-11-22 |
United States Patent
Application |
20070268946 |
Kind Code |
A1 |
Schulte; Derek E. ; et
al. |
November 22, 2007 |
Modular diode laser assembly
Abstract
An extremely versatile diode laser assembly is provided, the
assembly comprised of a plurality of diode laser subassemblies
mounted to a stepped cooling block. The stepped cooling block
allows the fabrication of a close packed and compact assembly in
which individual diode laser subassembly output beams do not
interfere with one another.
Inventors: |
Schulte; Derek E.;
(Portland, OR) ; Yan; Yu; (Vancouver, WA) ;
Martinsen; Robert J.; (West Linn, OR) ; Hodges; Aaron
L.; (Hillsboro, OR) ; Karlsen; Scott R.;
(Battle Ground, WA) |
Correspondence
Address: |
Patent Law Office of David G. Beck
P. O. Box 1146
Mill Valley
CA
94942
US
|
Assignee: |
nLight Photonics
Corporation
Vancouver
WA
|
Family ID: |
38053470 |
Appl. No.: |
11/888139 |
Filed: |
July 31, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11378570 |
Mar 17, 2006 |
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11888139 |
Jul 31, 2007 |
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11313068 |
Dec 20, 2005 |
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11378570 |
Mar 17, 2006 |
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60739185 |
Nov 22, 2005 |
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Current U.S.
Class: |
372/36 |
Current CPC
Class: |
H01S 5/02253 20210101;
H01S 5/02469 20130101; H01S 5/02345 20210101; H01S 5/405 20130101;
H01L 2224/48091 20130101; H01S 5/4043 20130101; H01S 5/02326
20210101; H01L 2224/49175 20130101; H01L 2224/48091 20130101; H01L
2924/00014 20130101 |
Class at
Publication: |
372/036 |
International
Class: |
H01S 3/042 20060101
H01S003/042 |
Claims
1. A diode laser assembly comprising: a cooling block comprised of
a plurality of stepped mounting surfaces of increasing height
relative to a plane corresponding to a lowermost portion of a
cooling block bottom surface; a plurality of diode laser
subassemblies, wherein each of said diode laser subassemblies is
comprised of: a mounting block, wherein said mounting block does
not include integral coolant passages; a diode laser submount
mounted to said mounting block, wherein said diode laser submount
is comprised of an electrically conductive material; and a diode
laser mounted to said diode laser submount, wherein said diode
laser is a multi-emitter diode laser; and means for mounting said
plurality of diode laser subassemblies onto said plurality of
stepped mounting surfaces of said cooling block, wherein each
output beam from said plurality of diode laser subassemblies is
displaced relative to an adjacent output beam.
2. The diode laser assembly of claim 1, wherein said electrically
conductive material is selected from the group consisting of copper
and copper tungsten.
3. The diode laser assembly of claim 1, wherein each of said diode
laser subassemblies further comprises a first beam conditioning
lens mounted to said mounting block, wherein an output beam from
said diode laser passes through said first beam conditioning
lens.
4. The diode laser assembly of claim 3, wherein each of said first
beam conditioning lenses comprises a cylindrical lens.
5. The diode laser assembly of claim 3, wherein each of said diode
laser subassemblies further comprises a second beam conditioning
lens mounted to said mounting block, wherein a second output beam
from a different diode laser subassembly of said plurality of diode
laser subassemblies passes through said second beam conditioning
lens.
6. The diode laser assembly of claim 3, wherein said output beam
from said diode laser passes through a second beam conditioning
lens mounted to the mounting block of an adjacent diode laser
subassembly.
7. The diode laser assembly of claim 1, wherein said mounting means
further comprises a plurality of clamping members attached to said
plurality of mounting surfaces of said cooling block, wherein said
plurality of clamping members corresponds to said plurality of
diode laser subassemblies.
8. The diode laser assembly of claim 7, wherein each clamping
member of said plurality of clamping members compresses a portion
of each diode laser submount against a portion of each mounting
block of each corresponding diode laser subassembly of said
plurality of diode laser subassemblies and compresses said portion
of each mounting block against a portion of each corresponding
stepped mounting surface of said cooling block.
9. The diode laser assembly of claim 8, wherein each clamping
member of said plurality of clamping members compresses at least
one electrical interconnect against at least one electrical contact
pad on said portion of each diode laser submount.
10. The diode laser assembly of claim 7, further comprising a
plurality of bolts corresponding to said plurality of clamping
members, wherein said plurality of bolts are attached to said
plurality of stepped mounting surfaces of said cooling block.
11. The diode laser assembly of claim 7, wherein at least two of
said plurality of clamping members corresponds to each of said
plurality of diode laser subassemblies.
12. The diode laser assembly of claim 1, wherein said mounting
means further comprises at least one attachment bolt per diode
laser subassembly.
13. The diode laser assembly of claim 1, further comprising a
cooling source coupled to said cooling block.
14. The diode laser assembly of claim 13, wherein said cooling
source is integrated within said cooling block.
15. The diode laser assembly of claim 1, wherein each of said diode
laser submounts further comprises a first electrical contact pad on
a first portion of said diode laser submount and a second
electrical contact pad on a second portion of said diode laser
submount.
16. The diode laser assembly of claim 1, wherein said cooling block
bottom surface is inclined.
17. The diode laser assembly of claim 16, wherein a separation
distance corresponding to the distance between each of said
plurality of stepped mounting surfaces of said cooling block and
said inclined cooling block bottom surface is the same for each of
said plurality of stepped mounting surfaces.
18. A diode laser assembly comprising: a cooling block comprised of
a plurality of stepped mounting surfaces of increasing height
relative to a plane corresponding to a lowermost portion of a
cooling block bottom surface; a plurality of diode laser
subassemblies, wherein each of said diode laser subassemblies is
comprised of: a mounting block, wherein said mounting block does
not include integral coolant passages; a diode laser submount
mounted to said mounting block, wherein said diode laser submount
is comprised of an electrically conductive material; a diode laser
mounted to said diode laser submount, wherein said diode laser is a
multi-emitter diode laser; a first beam conditioning lens mounted
to said mounting block, wherein an output beam from said diode
laser passes through said first beam conditioning lens; and a
second beam conditioning lens mounted to said mounting block,
wherein a second output beam from a different diode laser
subassembly of said plurality of diode laser subassemblies passes
through said second beam conditioning lens; and means for mounting
said plurality of diode laser subassemblies onto said plurality of
stepped mounting surfaces of said cooling block, wherein each
output beam from said plurality of diode laser subassemblies is
displaced relative to an adjacent output beam
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional application of U.S. patent
Ser. No. 11/378,570, filed Mar. 17, 2006, which is a
continuation-in-part of U.S. patent Ser. No. 11/313,068, filed Dec.
20, 2005, which claims the benefit of U.S. Provisional Patent
Application Ser. No. 60/739,185, filed Nov. 22, 2005, the
disclosure of which is incorporated herein by reference for any and
all purposes.
FIELD OF THE INVENTION
[0002] The present invention relates generally to semiconductor
lasers and, more particularly, to a laser assembly that permits the
output from multiple diode lasers to be effectively and efficiently
combined.
BACKGROUND OF THE INVENTION
[0003] High power diode lasers have been widely used in industrial,
graphics, medical and defense applications. The beam divergence and
the relatively low output power of such lasers has, however,
limited their usefulness.
[0004] The output beam of a diode laser is asymmetric due to the
beam having a higher angular divergence in the direction
perpendicular to the diode junction of the emitter (i.e., the fast
axis of the emitter) than in the direction parallel to the diode
junction (i.e., the slow axis of the emitter). As a result of the
differences in beam divergence, the cross section of the output
beam of a diode laser has an elliptical shape, typically requiring
the use of a cylindrical lens or other optics to alter the
divergence characteristics and shape the output beam for its
intended use. Although beam optics can be used on individual diode
lasers, in the past the use of such optics has made it difficult to
combine multiple diode laser beams into a single beam of sufficient
output power to suit many applications.
[0005] One method of combining the output beams from multiple
lasers is disclosed in U.S. Pat. No. 4,828,357. As shown, the
output from each laser is directed using multiple mirrors in order
to form a bundle of parallel beams or to cause the beams to
converge into a relatively narrow region. The patent discloses that
if greater power is required than can be generated by a single beam
bundle, multiple bundles of parallel beams can be combined to form
a beam bundle of even greater power. The patent does not
specifically disclose the use of laser diodes nor does the patent
disclose altering the beam shape of the individual laser beams
prior to directing the beams into the beam bundle.
[0006] U.S. Pat. No. 6,075,912 discloses an alternate technique for
combining the output beams from multiple lasers into a single beam.
In the disclosed system the output beam of each laser impinges on a
discrete facet of a multi-faceted beam deflector. By properly
positioning each laser relative to the facets of the beam
deflector, all of the output beams are deflected into an optical
fiber. The patent discloses interposing an optical system between
each laser source and the corresponding beam deflector facet in
order to properly image the output beam onto the deflector facet.
The patent also discloses interposing an output optical system
between the beam deflector and the optical fiber, the output
optical system imaging the deflected output beams as a focused
group of beam images into the core of the input face of the optical
fiber.
[0007] U.S. Pat. No. 4,716,568 discloses a laser array assembly
formed from a plurality of linear diode laser array subassemblies
stacked one above the other, each of the subassemblies electrically
connected to the adjacent subassembly. Each linear diode laser
array subassembly is made up of a plurality of individual laser
emitters mounted in thermal communication with a conductive plate.
Although the patent discloses several ways of stacking the
subassemblies in order to form the desired 2-D laser array, the
patent does not disclose any optical systems for use in combining
the output beams of the individual emitters and/or
subassemblies.
[0008] U.S. Pat. No. 5,887,096 discloses an optical system that is
used to guide the output beams from a rectilinear diode laser array
to form a substantially uniform radiation field or pattern. In one
disclosed embodiment, the optical system utilizes a plurality of
reflectors where each reflector corresponds to an individual diode
laser. In a preferred embodiment, the centers of the irradiated
surface areas of the individual reflectors are situated in a
straight line with the distance between a reflector and the
corresponding diode laser exit facet being the same for each diode
laser/reflector pair.
[0009] U.S. Pat. No. 6,240,116 discloses a diode laser array
designed to achieve high beam quality and brightness. In one
embodiment, the array includes a pair of diode arrays in which the
emitting surface planes of the two arrays are displaced from one
another in a direction parallel to the one of the optical axes
defined by the arrays. The optical axes of the two arrays are
offset from each other in a direction perpendicular to one of the
optical axes. Lenses are used to reduce the divergence of the
output beams. In at least one embodiment, reflectors are used to
reduce or eliminate the dead spaces between adjacent collimated
beams.
[0010] Although a variety of diode laser arrays and beam combining
systems have been designed, what is needed in the art is a
versatile diode laser assembly which can be easily tailored to
specific application needs. The present invention provides such a
diode laser assembly.
SUMMARY OF THE INVENTION
[0011] The present invention provides a diode laser assembly
comprised of a plurality of diode laser subassemblies mounted to a
stepped cooling block. Each diode laser subassembly of the diode
laser assembly includes a mounting block which, during diode laser
subassembly mounting, is coupled to the corresponding mounting
surface of the stepped cooling block. Although the diode laser
subassemblies are coupled to the cooling block, liquid coolant does
not flow through the subassembly mounting blocks, rather the
mounting blocks are merely in thermal contact with the cooling
block.
[0012] Mounted to a surface of each subassembly mounting block is a
diode laser submount. The diode laser submount is preferably
fabricated from an electrically conductive material. Mounted to a
surface of the diode laser submount is the diode laser, preferably
a multi-emitter diode laser. In at least one embodiment the diode
laser submount includes a pair of contact pads that are
electrically coupled to the diode laser, thus providing a means of
supplying power to the individual lasers.
[0013] In at least one preferred embodiment of the invention,
either a single clamping member or a pair of clamping members
compresses the diode laser submount against the mounting block, and
the mounting block against the mounting surface of the cooling
block. The clamping members preferably hold electrical
interconnects against electrical contact pads located on the diode
laser submount. In an alternate embodiment of the invention, at
least one threaded means (e.g., bolt, all-thread and nut assembly,
etc.) attaches each diode laser subassembly to the corresponding
cooling block mounting surface. In yet another alternate embodiment
of the invention, solder or other bonding material attaches each
diode laser subassembly to the corresponding cooling block mounting
surface.
[0014] In at least one preferred embodiment of the invention, a
beam conditioning lens is attached, for example by bonding, to each
diode laser subassembly mounting block such that the output beam(s)
of the diode laser passes through the lens. In one embodiment the
beam conditioning lens is a cylindrical lens. Preferably a second
beam conditioning lens is also attached, for example by bonding, to
each diode laser subassembly mounting block such that the output
beam(s) of the diode laser from a different diode laser subassembly
passes through the lens. The different diode laser subassembly can
be an adjacent subassembly. Alternately one or more diode laser
subassemblies can be located between the second beam conditioning
lens and the subassembly containing the diode laser that produces
the output beam that passes through the second beam conditioning
lens.
[0015] In at least one embodiment of the invention, a cooling
source is coupled to the cooling block. The cooling source can be
coupled to the cooling block or integrated within the cooling
block, for example using cooling liquid channels. The cooling block
can have a flat bottom surface, thus creating different separation
distances between each mounting surface of the stepped cooling
block and the cooling block bottom surface. Alternately the cooling
block can have an inclined bottom surface, thus causing the
separation distances between each mounting surface of the stepped
cooling block and the cooling block bottom surface to be the
same.
[0016] A further understanding of the nature and advantages of the
present invention may be realized by reference to the remaining
portions of the specification and the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a perspective view of the primary components of a
diode laser subassembly in accordance with the invention;
[0018] FIG. 2 is a perspective view of the assembled diode laser
subassembly of FIG. 1, minus the second conditioning lens;
[0019] FIG. 3 is a perspective view of the assembled diode laser
subassembly of FIG. 1, including the second conditioning lens
associated with another (not shown) diode laser subassembly;
[0020] FIG. 4 illustrates the relationship between the second
conditioning lens and a specific diode laser subassembly;
[0021] FIG. 5 illustrates the relationship between the second
conditioning lens and a specific diode laser subassembly different
from that shown in FIG. 4;
[0022] FIG. 6 is an illustration of a diode laser subassembly
similar to that shown in FIGS. 1-3, utilizing a three-stripe diode
laser rather than a single stripe diode laser;
[0023] FIG. 7 is an illustration of a cooling block for use with a
diode laser subassembly such as those shown in FIGS. 1-6;
[0024] FIG. 8 is an illustration of an embodiment in which multiple
diode laser subassemblies are clamped to a stepped cooling block
using two clamping members per subassembly;
[0025] FIG. 9 is an illustration of an embodiment in which multiple
diode laser subassemblies are clamped to a stepped cooling block
using a single clamping member per subassembly;
[0026] FIG. 10 is an illustration of an embodiment in which
multiple diode laser subassemblies are attached to a stepped
cooling block using a single attachment bolt per subassembly;
[0027] FIG. 11 is an illustration of an embodiment in which
multiple diode laser subassemblies are attached to a stepped
cooling block using a single attachment bolt per subassembly, the
attachment bolt passing through both the subassembly submount and
mounting block;
[0028] FIG. 12 is a cross-sectional view of a cooling
block/mounting block that illustrates an alternate subassembly
mounting arrangement;
[0029] FIG. 13 illustrates an alternate cooling block with an
inclined cooling plane;
[0030] FIG. 14 is an illustration of an embodiment similar to that
shown in FIG. 10, except for the inclusion of two rows of diode
laser subassemblies; and
[0031] FIG. 15 illustrates portions of a diode laser subassembly
that utilizes an electrically conductive submount.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
[0032] The present invention provides the system designer with the
means to tailor a diode laser assembly to the specific needs of a
particular application. In order to provide this versatility, the
system utilizes a diode laser subassembly that can be mounted in a
variety of configurations.
[0033] FIGS. 1-3 illustrate a diode laser subassembly utilizing a
single emitter diode laser 101. In addition to the diode laser 101,
the primary components associated with the diode laser subassembly
are the subassembly mounting block 103, submount 105, first
conditioning lens 107 and second conditioning lens 109. As
described in detail below, although second conditioning lens 109 is
mounted to subassembly mounting block 103, it is used with the
output beam of a diode laser mounted to another diode laser
subassembly that is not shown in FIGS. 1-3.
[0034] Subassembly mounting block 103 serves several functions.
First, it provides a convenient means for registering the various
components of the diode laser assembly, thereby lowering the
manufacturing costs associated with the overall assembly. Second,
it provides a convenient means for registering the individual diode
laser subassemblies within the cooling block as shown below. Third,
it provides an efficient thermal path between diode laser 101 and
the cooling block shown in later figures. Although subassembly
mounting block 103 does not include coolant passages, thus
simplifying assembly of the diode laser subassemblies to the
stepped cooling block, it is fabricated from a material with a high
coefficient of thermal conductivity (e.g., copper), thus providing
the desired diode laser cooling.
[0035] Diode laser 101 is not attached directly to subassembly
mounting block 103, rather it is mounted to submount 105.
Preferably submount 105 as well as the means used to attach
submount 105 to mounting block 103 are both materials with a high
coefficient of thermal conductivity, thus insuring that the heat
produced by diode laser 101 is efficiently coupled to mounting
block 103. Additionally the coefficient of thermal expansion for
the material selected for submount 105 is matched, to the degree
possible, to diode laser 101 in order to prevent de-bonding or
damage to the laser during operation. In at least one embodiment of
the invention, submount 105 is soldered to mounting block 103 using
indium solder.
[0036] Submount 105 is preferably fabricated from an electrically
conductive material (e.g., copper, copper tungsten, etc.) although
it can also be fabricated from an electrically insulative material
(e.g., aluminum nitride, beryllium oxide, CVD diamond, silicon
carbide, etc.). In the embodiment illustrated in FIGS. 1-3,
submount 105 is fabricated from an electrically insulating ceramic.
The material used to bond diode laser 101 to submount 105 is
selected, at least in part, on the composition of submount 105
and/or the composition of any layers (e.g., contact pads)
interposed between submount 105 and diode laser 101. In the
illustrated embodiment, electrically conductive contact pads
111/113 are deposited or otherwise formed on the top surface of
submount 105. Contact pads 111/113 can be formed, for example, of
gold over nickel plating while a gold-tin bonding material can be
used to bond diode laser 101 to contact pad 113. It will be
appreciated that there are a variety of materials well known in the
industry that are suitable for use as contact pads as well as diode
laser bonding material.
[0037] In a preferred embodiment of the invention, one contact
(e.g., anode) of diode laser 101 is on its bottom surface, thus
allowing one diode contact to be made by bonding the diode laser to
one of the contact pads (e.g., pad 113) using an electrically
conductive material. A wire bond or ribbon bond 115 is then used to
electrically couple the second contact (e.g., cathode) of each
diode laser to the second contact pad 111. It will be appreciated
that the invention is not limited to this contact arrangement. For
example, a pair of wire or ribbon bonds can be used to couple the
diode laser to a pair of contact pads.
[0038] First conditioning lens 107, which in at least one
embodiment is a cylindrical lens, is properly positioned relative
to diode laser 101 using the extended arm portions 117 and 119 of
mounting block 103. Typically lens 107 is located immediately
adjacent to the exit facet of diode laser 101. Once lens 107 is
properly positioned, it is bonded into place. The purpose of
conditioning lens 107 is to reduce the divergence of diode laser
101 in the fast axis, preferably to a value that is the same as or
less than the divergence in the slow axis.
[0039] In order to properly condition the output beam of diode
laser 101, preferably a second conditioning lens 109 is used. It
should be understood that the specific second conditioning lens 109
shown in FIGS. 1-3, although mounted to the top surfaces 121 and
123 of respective arm portions 117 and 119, is not used to
condition the beam from the illustrated diode laser 101. Rather the
illustrated conditioning lens 109 is used to condition the output
beam from an adjacent diode laser subassembly (e.g., beam 401 in
FIG. 4), or the output beam from a diode laser subassembly that is
more than one subassembly removed from the subassembly (e.g., beam
501 in FIG. 5). It will be appreciated that the focal length of
second conditioning lens 109 as well as the height of arm portions
117 and 119 is dependent on which diode laser output beam is
intended to pass through which second conditioning lens (i.e., the
number of diode laser subassemblies separating the second
conditioning lens from the diode laser source).
[0040] Although the diode laser subassembly shown in FIGS. 1-5
utilizes a single emitter, the present invention is equally
applicable to multi-emitter diode lasers. For example, FIG. 6 is an
illustration of a diode laser subassembly utilizing a three-stripe
diode laser 601. Due to the size of diode laser 601, the contact
pads 603/605 on submount 607 are typically of a different size than
those on submount 105 used with the single emitter diode laser.
Additionally the second conditioning lens (i.e., lens 609) is
multi-faceted (i.e., facets 611-613) in order to properly condition
the individual output beams of diode laser 601.
[0041] FIG. 7 is a perspective view of a preferred cooling block
700 for use with the previously described, or alternate, diode
laser subassemblies. As shown, cooling block 700 includes a series
of stepped mounting surfaces 701, thus allowing the output beams
from a plurality of diode laser subassemblies to exit the assembly
unimpeded. The steps also provide a convenient means of registering
the laser subassemblies to the cooling block.
[0042] It will be appreciated that there are numerous techniques
that can be used to mount the diode laser subassemblies to the
cooling block, these techniques using various arrangements of
clamping members, bolts and/or bonding materials (e.g., solder,
adhesive). FIG. 8 illustrates one mounting technique in which pairs
of clamping members 801, preferably bolted to the cooling block,
hold diode laser subassemblies 803-807 in place on cooling block
809. Clamp members 801 serve three purposes. First, they hold the
diode laser subassemblies in place. Second, by firmly pressing the
subassemblies into place, they insure that good thermal contact is
made between subassembly mounting blocks 103 and cooling block 809.
Third, clamp members 801 provide a convenient means of electrically
contacting the two contact pads 111/113 (or 603/605), either
through direct contact or by pressing an electrical contact against
the pads, the electrical interconnect being interposed between the
clamping member and the contact pad on the submount. During use,
preferably either the cooling block is thermally coupled to a
cooling source (e.g., thermoelectric cooler), or the cooling source
is integrated within the cooling block (e.g., integral liquid
coolant conduits within the cooling block that are coupled to a
suitable coolant pump).
[0043] In the embodiment illustrated in FIG. 8, the second
conditioning lens for each subassembly is located on the arm
portions of the adjacent subassembly mounting block. It will be
appreciated that the uppermost subassembly, i.e., subassembly 803,
does not include a second conditioning lens and that the second
conditioning lens for the lowermost subassembly, i.e., subassembly
807, is simply mounted to a stand alone lens carrier 811. Carrier
811 can either be integral to cooling block 809, i.e., machined
from the same material, or it can be an independent carrier that is
mounted to cooling block 809.
[0044] In an alternate embodiment illustrated in FIG. 9, a single
clamping member 901 is used to hold each diode laser subassembly
903-907 in place on cooling block 909. As in the previous
embodiment, in addition to holding the diode laser subassemblies in
place the clamp members help to insure that good thermal contact is
made between subassembly mounting blocks 103 and the cooling block.
Depending upon the size of the clamping members as well as the
location of the subassembly contact pads, the clamping members can
also be used as a means of electrically contacting one or both
contact pads. The clamping members can either make electrical
contact through direct contact or by pressing an electrical contact
against one or both pads, the electrical interconnect being
interposed between the clamping members and the contact pads on the
submounts.
[0045] Although both FIGS. 8 and 9 show the use of clamping members
to hold the subassemblies to the cooling block, as previously noted
there are numerous other techniques that can be used to mount the
subassemblies. For example, the subassemblies can be bonded or
soldered to the cooling block. In an alternate embodiment
illustrated in FIG. 10, each subassembly mounting block 103 of
subassemblies 1001-1005 is attached to cooling block 1007 with a
bolt 1009. For the sake of illustration clarity, FIG. 10 does not
show the second conditioning lens (e.g., lens 109) nor does it show
the stand alone lens carrier (e.g., carrier 811). Although in the
embodiment shown in FIG. 10 the mounting bolts only go through the
mounting blocks of the subassemblies, the bolts could also pass
through the subassembly submounts as well, as illustrated in FIG.
11. Alternately, and as illustrated in the cross-sectional view of
FIG. 12, the mounting bolts 1201 can pass through the bottom of the
cooling block 1203 and be screwed directly into the bottom of the
mounting blocks 103.
[0046] As the cooling block (e.g., cooling block 809, 909, 1007) is
comprised of a series of steps onto which the diode laser
subassemblies are mounted, the cooling rate and thus the operating
temperature of the individual laser subassemblies varies depending
upon the distance between the cooling source coupled to the cooling
block and the individual subassemblies. Since the operating
wavelength of a diode laser is temperature dependent, the inventors
have found that the operating temperature variations between
subassemblies that arise due to the stepped cooling block and the
use of a bottom mounted cooling source, alone or in conjunction
with a side mounting cooling source, can be used to match diode
laser subassembly wavelengths. Accordingly in at least one
embodiment of the invention, the output wavelength of each
subassembly is determined based on the subassembly's position
within the cooling block. Then each subassembly is positioned
within the cooling block to provide the closest possible match to
the desired output wavelength of the entire assembly.
[0047] Although the figures described above illustrate at least one
preferred embodiment of the invention, it will be appreciated that
there are numerous minor variations that are clearly envisioned by
the inventors. For example, FIG. 13 illustrates an alternate
embodiment of a cooling block in which the bottom surface 1301 of
the cooling block is inclined. As a result of this configuration,
each mounting surface 1303 is the same distance from the bottom
surface 1301, thus maintaining the same cooling rate for each
mounted diode laser subassembly (not shown) even when thermally
coupling the cooling source to the bottom surface (i.e., surface
1301) of the cooling block.
[0048] In the above figures, the illustrated exemplary
configurations include only a single row of subassemblies. It
should be appreciated, however, that assemblies in accordance with
the invention can include rows of subassemblies that include either
more or less than the five diode laser subassemblies shown in FIGS.
8-11. Additionally, assemblies that contain more than a single row
of diode laser subassemblies can be fabricated using the present
invention. For example, FIG. 14 illustrates an assembly similar to
that shown in FIG. 10 that includes a total of ten diode laser
subassemblies, five per row. It should be appreciated that
multi-row assemblies can use any of the disclosed subassembly
mounting techniques, not just the illustrated technique.
Additionally, the output beam from each row can either be combined
using known optical techniques, or the assembly can be used to
produce two separate output beams.
[0049] As previously noted, the diode laser subassemblies of the
present invention can utilize either electrically insulating or
electrically conducting submounts as well as any of a variety of
different diode laser contacting arrangements. Thus the
submount/contact arrangement shown in FIGS. 1-3 and 6 is only an
exemplary configuration and should not be viewed as a limitation of
the present invention. For example, FIG. 15 illustrates portions of
a diode laser subassembly that utilizes an electrically conductive
submount 1501. In this embodiment diode laser 101 is attached to
submount 1501 with an electrically and thermally conductive solder
or bonding material. As a consequence, one contact to diode laser
101 is made via electrically conductive submount 1501, directly or
via subassembly mounting block 103 and/or the cooling block (not
shown). Of course if electrical contact is made via subassembly
mounting block 103, then an electrically conductive solder or
bonding material must be used to attach submount 1501 to the
subassembly mounting block. Similarly if electrical contact is made
via the cooling block (not shown), then an electrically conductive
solder or bonding material must be used both to attach submount
1501 to the subassembly mounting block and to attach the
subassembly mounting block to the cooling block. The second contact
to the diode laser is made via a contact pad 1503, each diode laser
being connected to contact pad 1503 via a wire bond or ribbon bond
1505.
[0050] As will be understood by those familiar with the art, the
present invention may be embodied in other specific forms without
departing from the spirit or essential characteristics thereof.
Accordingly, the disclosures and descriptions herein are intended
to be illustrative, but not limiting, of the scope of the invention
which is set forth in the following claims.
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