Coherent light generators – Particular temperature control – Heat sink
Reexamination Certificate
2000-12-20
2002-12-17
Leung, Quyen (Department: 2828)
Coherent light generators
Particular temperature control
Heat sink
C372S034000
Reexamination Certificate
active
06496524
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser diode module.
2. Description of the Related Art
A conventional laser diode module has a structure as shown in
FIGS. 8
to
10
, for example.
In the laser diode module
1
shown in
FIGS. 8
to
10
, a thermo electrical cooler (TEC)
3
, a base
4
, a heatsink
5
, a laser diode (LD) chip
6
and an optical fiber
7
are housed in a package
2
.
The TEC
3
is placed on a bottom plate
2
a
of the package
2
, and the base
4
is fixed on a substantially central portion of an upper mounting surface
3
a
of the TEC for mounting thereon optical components such as the LD chip
6
. As shown in the figures, the LD chip
6
is fixed on the base
4
with the heatsink
5
interposed therebetween, and the optical fiber
7
is also fixed on the base with two fixing members
8
interposed therebetween. The optical fiber
7
is a lensed optical fiber having a lensed portion
7
a
formed as optical coupling means at one end thereof facing the LD chip
6
, and a ferrule
7
b
is attached to a portion of the fiber corresponding in position to the fixing members
8
. The other end portion of the optical fiber
7
is extended to the outside of the module through an outlet portion
2
c
formed in a peripheral wall
2
b
of the package
2
.
The laser diode module
1
has a temperature sensor (not shown) arranged at a suitable location within the package
2
for detecting the temperature of the mounting surface
3
a
of the TEC
3
. In accordance with the temperature detected by the temperature sensor of the module
1
, the operation of the TEC
3
is controlled externally by control means, not shown.
A cover
2
d
is normally attached to the package
2
from above the peripheral wall
2
b
, as shown in
FIG. 8
; however, in order to show the interior of the package, the cover is omitted from
FIG. 9
, as well as from
FIGS. 2 and 7
explained later.
In the conventional laser diode module
1
, to stabilize temperature dependent optical characteristics of the LD chip
6
against variations in environmental temperature and heat generated by the LD chip
6
during operation thereof, the temperature of the LD chip
6
is controlled to a predetermined temperature by the TEC
3
. Especially, the temperature of the mounting surface
3
a
of the TEC
3
on which the LD chip
6
is mounted is controlled to a predetermined temperature.
As the temperature of the mounting surface
3
a
of the TEC
3
increases during operation due to heat generated by the LD chip
6
, for example, the TEC
3
transfers heat to the lower surface thereof, to thereby keep the temperature of the mounting surface
3
a
at the predetermined temperature. Consequently, there occurs a large temperature difference between the mounting surface
3
a
and lower surface
3
b
of the TEC
3
. Since the TEC
3
itself is thus subject to temperature change during operation, some expansion or contraction takes place inside the parts constituting the TEC
3
. As a result, a change in flatness (hereinafter merely referred to as warp) such as a some warp with a level difference of the micrometer order occurs in the mounting surface
3
a
of the TEC
3
, and warps the base
4
on which the LD chip
6
and optical fiber
7
are mounted, as shown in FIG.
10
.
In
FIG. 10
, the warp of the TEC
3
and of the base
4
is exaggerated for the sake of illustration, and this is the case with
FIGS. 3 and 4A
explained later.
If such a warp is caused, the condition of optical coupling between the LD chip
6
and optical coupling means of the laser diode module
1
deteriorates. Especially, if a warp is caused along the direction of laser beam emission, the efficiency of laser beam coupling with the optical fiber
7
lowers, giving rise to a problem that adequate optical power cannot be output to the optical fiber
7
.
SUMMARY OF THE INVENTION
The present invention was created in view of the above circumstances, and an object thereof is to provide a laser diode module which is capable of suppressing reduction in the efficiency of laser beam coupling with an optical fiber even in the case where a warp is caused in the mounting surface of a thermo electrical cooler on which a laser diode chip is mounted.
To achieve the above object, the present invention provides a laser diode module comprising a laser diode chip, a thermo electrical cooler for controlling temperature of the laser diode chip to a predetermined temperature, a heat sink arranged between the laser diode chip and the thermo electrical cooler for transferring heat from said laser diode chip, and an optical fiber for guiding a laser beam emitted from the laser diode chip to outside via optical coupling means, all of the laser diode chip, the thermo electrical cooler, the heat sink and the optical fiber being housed in a package, wherein the heat sink and the optical coupling means are mounted directly or indirectly on a mounting surface of the thermo electrical cooler, and the laser diode chip and the optical coupling means are located on an identical side of the mounting surface along an emitting direction of the laser beam, with respect to a first center line intersecting perpendicularly with a tangential plane tangent to the mounting surface of the thermo electrical cooler at a center thereof and/or a second center line passing through the center of the mounting surface of the thermo electrical cooler and perpendicular to both the first center line and an axis representative of the emitting direction of the laser beam emitted from the laser diode chip.
To achieve the above object, the present invention also provides a laser diode module comprising a laser diode chip, a thermo electrical cooler for controlling temperature of the laser diode chip to a predetermined temperature, a heat sink arranged between the laser diode chip and the thermo electrical cooler for transfering heat from the laser diode chip, and an optical fiber for guiding a laser beam emitted from the laser diode chip to outside via optical coupling means, all of the laser diode chip, the thermo electrical cooler, the heat sink and the optical fiber being housed in a package, wherein the heat sink and the optical coupling means are mounted directly or indirectly on a mounting surface of the thermo electrical cooler, and the laser diode chip and the optical coupling means are arranged in a manner such that, where an axis representative of an emitting direction of the laser beam emitted from the laser diode chip is projected onto the mounting surface of the thermo electrical cooler with use of a bundle of light rays intersecting perpendicularly with a tangential plane tangent to the mounting surface of the thermo electrical cooler at a location directly under the laser diode chip, thereby obtaining a projected line image, and also where the laser diode chip and the optical coupling means are projected onto the mounting surface with use of the bundle of light rays, thereby obtaining respective projected images, the projected images of the laser diode chip and the optical coupling means are located on the projected line image of the axis and on an identical side of the mounting surface with respect to a middle point of a line segment connecting two points at which the projected line image intersects with a contour line representative of a contour of the mounting surface.
Preferably, the laser diode chip is located closer to the center of the mounting surface of the thermo electrical cooler than the optical coupling means.
Also preferably, the optical coupling means is mounted on the thermo electrical cooler with a base interposed therebetween, and a portion of the base on which the optical coupling means is mounted partly extends beyond the mounting surface.
Further preferably, the optical coupling means is formed at an end of the optical fiber and includes a portion with an end face which is formed like a lens and on which the laser beam emitted from the laser diode chip falls.
According to the present invention, a laser diode module is
Irie Yuichiro
Kasahara Hiroshi
Miyokawa Jun
Shimizu Takeo
Leung Quyen
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
The Furukawa Electric Co. Ltd.
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