Semiconductor device and optical pickup device

Details Semiconductor device and optical pickup device Semiconductor device and optical pickup device

2000-11-22

2004-10-26

Wong, Don (Department: 2828)

Coherent light generators

Particular active media

Semiconductor

C372S043010, C372S044010, C372S045013

Reexamination Certificate

active

06810057

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor device and an optical pickup device used for optical information processing, optical measurement, optical communication and the like.
BACKGROUND OF THE INVENTION
A conventionally known semiconductor device integrated with two light sources has either a hybrid integration in which a red semiconductor laser element and an infrared semiconductor laser element are arranged independently inside an optical-pickup or a monolithic integration in which a red semiconductor laser structure and an infrared semiconductor laser structure are integrated on the same substrate.
These two examples of integration will be described below.
First, a conventional semiconductor device with a monolithic integration of two light sources will be described schematically by referring to FIG.
14
.
As shown in
FIG. 14
, in this semiconductor device
1
, on top of a photodiode IC
2
, a semiconductor laser element
3
emitting a laser beam L
11
having a wavelength of about 650 nm, for example, used for DVD, a semiconductor laser element
4
emitting a laser beam L
12
having a wavelength of about 780 nm, for example, used for CD, a photodetector
5
having a plurality of sensor elements
5
a
to
5
d
and a micro-prism
6
functioning as a reflecting mirror are integrated. Furthermore, on the upper side of the micro-prism
6
, a hologram plate
7
is disposed for dividing a light beam returning from an optical recording medium (not shown) such as an optical disc into the zero-order light, the + first-order light, and the − first-order light and allowing them to enter the sensor elements
5
a
to
5
d
(See JP11 (1999)-149652A). In addition, as for the semiconductor laser elements
3
,
4
, those formed on the same LOP
8
are known (Nikkei Electronics, the Jun. 28, 1999 Issue, pages 29 to 30).
Next, a conventional semiconductor device with a hybrid integration of two light sources will be described schematically by referring to FIG.
15
.
As shown in
FIG. 15
, in this semiconductor device
9
, on top of a substrate
10
, a semiconductor laser element
11
emitting a laser beam L
13
having a wavelength of about 650 nm, for example, used for DVD, a semiconductor laser element
12
emitting a laser beam L
14
having a wavelength of about 780 nm, for example, used for CD, a plurality of photodetectors
13
,
14
and a micro-prism
15
functioning as a reflecting mirror are integrated. Moreover, on the upper side of the micro-prism
15
, an optical element (not shown) is disposed for allowing light beams L
13
′, L
14
′ returning from an optical recording medium (not shown) such as an optical disc to enter the photodetector
13
,
14
(See JP9 (1997)-120568A, JP10(1998)-64107A, JP11 (1999)-39693A, JP11 (1999)-161993A). In addition, the semiconductor laser elements
11
,
12
are mounted respectively on the substrate
10
via mounts
17
,
18
.
However, the conventional configurations described above had the following problems.
First, with regard to the conventional semiconductor device with a monolithic integration of two light sources, the semiconductor laser element
3
and the semiconductor laser element
4
are arranged next to each other in such a manner that the emitting end faces of the lasers are facing the same direction. Therefore, it was difficult to reduce the interval between the emission points of the semiconductor laser element
3
and the semiconductor laser element
4
to 100 &mgr;m or less. As a result, the red laser and the infrared laser respectively emitted from the two semiconductor laser elements
3
,
4
were affected differently from the optical element, so that one of the semiconductor laser elements suffered from deterioration of its operating characteristics. In particular, when the semiconductor laser element
3
and the semiconductor laser element
4
are arranged close to each other and one of the two semiconductor laser elements
3
,
4
is operated with a high power of 30 mW or higher, heat generated in one of the semiconductor laser elements affects the other semiconductor laser element, which causes the characteristics of the semiconductor laser elements to deteriorate.
Furthermore, with regard to the conventional semiconductor device with a hybrid integration of two light sources, the micro-prism
15
is arranged between the semiconductor laser element
11
and the semiconductor laser element
12
. Therefore, when the location of the micro-prism
15
is shifted from. the predetermined position, the optical paths of the laser beams L
13
, L
14
emitted from the semiconductor laser elements
11
,
12
respectively are shifted. As a result, according to this amount of shifting, an apparent interval between the emission points of the semiconductor laser element
11
and the semiconductor laser element
12
(hereinafter, reference to “interval of emission points” includes “apparent interval of emission points”) varied, which made it difficult to reduce the interval of the emission points.
Moreover, the conventional semiconductor device described above is configured such that the semiconductor laser elements are mounted via a mount such as the LOP
8
, so that the interval of the emission points varied according to the uneven thickness of the mount, which made it difficult to reduce the interval of the emission points.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the conventional problems described above by providing a semiconductor device and an optical pickup device, which are capable of reducing an interval of emission points between a plurality of semiconductor laser elements and also capable of preventing heat generated when a semiconductor laser element is operated with a high power from affecting other semiconductor elements.
To achieve the above object, a configuration of a semiconductor device of the present invention includes a substrate, a protrusion having a plurality of side faces formed on the substrate by processing the substrate, and a plurality of semiconductor laser elements disposed on the substrate, wherein the plurality of semiconductor laser elements is arranged such that each end face thereof is opposed to a different side face of the protrusion. According to the configuration of this semiconductor device, the protrusion having a plurality of side faces is formed on the substrate, so that a micro-prism is no longer necessary. Furthermore, the plurality of semiconductor laser elements can be arranged on a straight line, so that an interval of emission points between the plurality of semiconductor laser elements can be reduced. In addition, since the plurality of semiconductor laser elements is arranged such that each end face thereof is opposed to a different side face of the protrusion, heat generated when a semiconductor laser element is operated with a high power can be prevented from affecting other semiconductor elements. As a result, it is possible to prevent the characteristics of the semiconductor laser elements from deteriorating.
Furthermore, in the configuration of the semiconductor device of the present invention, it is preferable that the protrusion is formed into a truncated pyramidal shape, and that a photodetector is disposed on a top face of the protrusion. According to this preferred configuration, the photodetector can be positioned in one place, so that the semiconductor device can be miniaturized.
Moreover, in the configuration of the semiconductor device of the present invention, it is preferable that the semiconductor device further includes a plurality of small protrusions formed on the substrate by processing the substrate, and that a semiconductor laser element is mounted on each of the small protrusions. According to this preferred configuration, particularly when the semiconductor laser elements are mounted p-side down, it is possible to prevent a part of the laser beams emitted from the end faces of the semiconductor laser elements from being blocked by the surface of the substrate.
Furthermore,

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