Semiconductor laser device

Details Semiconductor laser device Semiconductor laser device

2001-11-27

2004-01-27

Davie, James (Department: 2828)

Coherent light generators

Particular beam control device

Optical output stabilization

C372S109000

Reexamination Certificate

active

06683897

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor laser device to be employed as a light source or the like of an optical pickup device for reading the data of, for example, CD-ROM (compact disc read only memory), DVD (digital versatile disc) or the like.
As a semiconductor laser device of this kind, there is the one shown in
FIG. 8A
(Japanese Patent Laid-Open Publication No. HEI 6-5990). This semiconductor laser device is the semiconductor laser device of a hologram laser system. As shown in the exploded perspective view of
FIG. 8B
, in this semiconductor laser device
100
, a heat sink
102
is formed integrally with a base
101
, and a semiconductor laser element
105
is mounted on a side surface of this heat sink
102
via a submount
104
for heat radiation. A light-receiving element
107
for signal detection use is mounted on the upper surface of the heat sink
102
. A plurality of leads
108
are each fixed to the base
101
while being electrically insulated by hermetic seals
109
. Pads (not shown) of the semiconductor laser element
105
and the light-receiving element
107
are connected by wire bonding (not shown) to inner leads
108
a
, which are the portions that belong to the leads
108
and protrude on the heat sink side of the base
101
. Then, the heat sink
102
, the semiconductor laser element
105
, the light-receiving element
107
and the inner leads
108
a
, which are located on the base
101
, are covered with a cap
110
, and a hologram element
112
is fitted in an opening window
110
a
opened in a position that belongs to this cap
110
and is facing the semiconductor laser element
105
.
FIG. 9A
is a perspective view showing a prior art semiconductor laser device (Japanese Patent Laid-Open Publication No. HEI 6-5990), while
FIG. 9B
is an exploded perspective view of this semiconductor laser device. For the semiconductor laser device shown in
FIGS. 9A and 9B
, the portions that have the same functions as those of the semiconductor laser device shown in
FIG. 8
are denoted by the same reference numerals, and no detailed description is provided for the portions. The semiconductor laser device
120
of
FIGS. 9A and 9B
differs from the semiconductor laser device
100
shown in
FIGS. 8A and 8B
only in that the base and the cap have different shapes. In this semiconductor laser device
120
, the base
101
and the cap
110
are roughly elliptic in shape, where two opposed bow-shaped portions are removed from a circular shape, and this device has a width smaller than that of the semiconductor laser device
100
of FIG.
8
. If this semiconductor laser device
120
is mounted with the widthwise direction thereof directed in the direction of thickness of the optical pickup device, then an optical pickup device that has a small thickness can be provided.
The semiconductor laser device shown in
FIGS. 10A
,
10
B and
11
(refer to Japanese Patent Laid-Open Publication No. HEI 10-256649) differs from the semiconductor laser device
100
shown in
FIGS. 8A and 8B
in the structure of connecting wiring leads to the base. In
FIGS. 10A and 10B
, the portions that have the same functions as those of the semiconductor laser device of
FIGS. 8A and 8B
are denoted by the same reference numerals. As shown in
FIG. 10B
, this semiconductor laser device
125
has resin lead blocks
127
and
127
in which leads
108
are partially implanted. The resin lead blocks
127
and
127
are fixed by ultrasonic welding onto both sides of a base
101
on which the semiconductor laser element
105
and the light-receiving element
107
are mounted, forming a stem
128
. Then, a cap
110
is fixed to this stem
128
so as to cover the semiconductor laser element
105
, and a hologram element
112
is arranged in an opening window
110
a
provided on the upper surface of this cap
11
, forming a semiconductor laser device
125
.
This semiconductor laser device
125
is not required to insulate and fix a plurality of leads
108
to the base
101
each via the hermetic seals
109
, dissimilarly to the semiconductor laser device
100
shown in
FIGS. 8A and 8B
, and therefore, the semiconductor laser device
125
can easily be assembled.
In each of the semiconductor laser devices
100
,
120
and
125
shown in
FIGS. 8A through 11
, the cap
110
is provided with a flange portion
110
b
, and this flange portion
110
b
is resistance-welded to the end surface of the base
101
, fixing the cap
110
to the base
101
. The end surface of the base
101
to which the flange portion
101
b
is welded has a mounting reference surface
101
a
for mounting each of these semiconductor laser devices
100
,
120
and
125
on the mounting portion of the optical pickup device in a portion other than the portion to which the flange portion
110
b
of the cap is welded.
FIG. 12
is a view showing an optical pickup device that employs the semiconductor laser device
120
shown in FIG.
9
. It is to be noted that optical pickup devices that employ the semiconductor laser devices
110
and
125
shown in
FIGS. 8 and 10
also have the same construction as that of the semiconductor laser device of FIG.
12
.
In this optical pickup device, the semiconductor laser device
120
mounted on a mounting plate
132
, a collimator lens
133
, a mirror
134
and an object lens
136
mounted on an actuator (not shown) are assembled with an assembly plate
131
. The semiconductor laser device
120
is mounted on the mounting plate
132
with the mounting reference surface
101
a
fit close to the mounting surface
132
a
of the mounting plate
132
.
The above-mentioned optical pickup device operates as follows. Laser light emitted from the semiconductor laser device
120
is split into three beams by a diffraction grating provided in the hologram element
112
, and these three beams are reflected on the mirror
134
and condensed onto an optical disk
138
by means of the object lens
136
. Return light from the optical disk
138
passes through a path identical to that of the emitted beam and returns to the semiconductor laser device
120
. The return light that has returned to the semiconductor laser device
120
is diffracted by the hologram pattern of the hologram element
112
and made incident on the light-receiving segment of the light-receiving element
107
of the semiconductor laser device
120
.
When mounting the semiconductor laser device
120
on the mounting portion of the optical pickup device, the semiconductor laser device
120
is turned for adjusting the mounting position so that the three beams are appropriately condensed onto three pit lines
138
a
, i.e., the tracks on the optical disk
138
, and thereafter fixed to this mounting plate
132
.
However, the aforementioned prior art semiconductor laser devices
110
,
120
and
125
have a problem that the devices tend to become loose when turned for adjusting the mounting position on the mounting plate
132
. In more detail, when turning the semiconductor laser devices
110
,
120
and
125
, the mounting reference surface
101
a
is turned while being fit close to the mounting surface
132
a
of the mounting plate
132
. However, the mounting reference surface
101
a
, which is the surface other than the welded portion of the end surface of the base
101
to which the flange portion
110
b
of the cap
110
is welded, has a very small area. Therefore, the area of contact of this reference surface
101
a
with the mounting surface
132
a
is very small. Therefore, when the semiconductor laser devices
110
,
120
and
125
are turned, the direction of the semiconductor laser devices
110
,
120
and
125
with respect to the mounting plate
132
becomes disadvantageously unstable and loose. As a result, there is the problem that the mounting accuracy of the semiconductor laser devices
110
,
120
and
125
with respect to the optical pickup device is poor.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide a semiconductor laser device capable of being easily accur

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