JP2538450Y2 - Semiconductor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a semiconductor laser device that emits a plurality of laser beams.

(B) Conventional technology A so-called multi-beam output type semiconductor laser device that emits a plurality of laser beams has been developed by the present applicant and the like. For example, IEICE Technical Report Vol.86, No.323, pp.75-79. page,
(1987). Such a semiconductor laser beam chip for emitting a plurality of laser beams is usually assembled with a laser beam emitting portion separated upward with respect to a heat sink, as shown in FIG.

By assembling the emission part from which the laser beam is emitted to the heat sink in this way, it is possible to control the emission operation of the laser beam independently, because the electrodes of each emission part are provided separately. Becomes

However, in such a structure, since there is a distance corresponding to the thickness of the semiconductor substrate from the emission part to the heat sink,
The heat generated from the emission unit cannot be efficiently guided to the heat sink, and as a result, there is a disadvantage that not only the temperature rise in the emission unit but also the adjacent emission unit is affected by heat. In particular, in a semiconductor laser beam chip capable of selectively emitting three laser beams, the central emission part is affected by heat of the emission parts on both sides, so that the temperature rise is more remarkable than the other emission parts. .

(C) Problems to be Solved by the Invention The present invention relates to a semiconductor laser device that emits a plurality of laser beams independently from a plurality of emission units as described above.
The temperature rise of the light emitting portion is remarkable, and the output fluctuation and the shortening of the life caused by the temperature rise are not solved.

(D) Means for Solving the Problems In order to solve the above problems, the semiconductor laser device of the present invention has a GaAs semiconductor substrate, a growth layer formed on the substrate, and individually provided at a plurality of locations on the growth layer. A semiconductor laser beam chip having an emission portion for independently emitting a laser beam, and a heat sink made of Si for fixing the laser beam chip in good thermal conductivity from the semiconductor substrate side, comprising: The pitch is set to about 100 μm and the thickness of the semiconductor substrate is set to about 70 μm or less.
It is characterized by the following.

(E) Action As described above, the semiconductor laser beam chip and the heat sink for holding the laser beam chip from the semiconductor substrate side are provided. By setting the thickness of the semiconductor substrate to about 70 μm or less, each of the plurality of emission sections is individually formed. It is possible to suppress the thermal influence of the heat generation on the other light emitting portions.

(F) Embodiment FIG. 1 shows a main part of the semiconductor laser device of the present invention.
(1) a heat sink made of single crystal Si fixed to the stem of a package (not shown) with good thermal conductivity, (2)
Is a semiconductor laser beam chip similarly fixed to the heat sink (1) with good thermal conductivity. The laser beam chip (2) is composed of a GaAs single crystal semiconductor substrate (3) and an epitaxial growth on the substrate (3). A growth layer (4) on which a semiconductor junction to emit a laser beam is formed; and a separation groove (5) for reaching the growth layer (4) to the substrate (3).
The first to third emission portions (6a), (6b), and (6c), which are divided into three portions by (5) and emit laser beams independently from the growth layer portions indicated by black circles in the figure, respectively. . The first to third emission portions (6a), (6b), and (6c) of the semiconductor laser beam chip (2) independently supply laser beams when supplied with power from individual electrodes (not shown). The semiconductor laser beam chip (2) has a so-called junction-up structure that is protected from the semiconductor substrate (3) side with respect to the heat sink (1).

FIG. 2 is a characteristic diagram showing the dependence of the operating current and the optical output on the temperature at the emission section. It can be seen that the lower the temperature of the emission section, the higher the output laser beam can be obtained with the same operating current. That is, when the operating current is constant when the temperature of the emitting portion changes, the output of the laser beam also changes, and the form of the change causes a decrease in output with respect to a rise in temperature. Therefore, in order to obtain a laser beam having a constant output, the operating current may be increased with increasing temperature. The output of the laser beam emitted in the direction opposite to the required emission direction is monitored by an optical sensor by utilizing the bidirectional emission of the laser beam from the semiconductor laser beam chip with respect to such output fluctuation. Drive by increasing or decreasing the operating current (hereinafter simply APC
Driving) is known. However, the APC drive has its own limitations. Particularly, in a semiconductor laser device capable of emitting three laser beams as described above, the temperature rise of the second emitting portion (6b) is The first on both sides,
As a result of being affected by the heat generated by the third light emitting portions (6a) and (6c), the output is the highest, and the output of the second light emitting portion (6b) is within an allowable range, for example, a required characteristic of a rewritable optical disk. It is difficult to control the output fluctuation to 1% or less only by APC drive.

FIG. 3 shows the relationship between the thickness of the semiconductor substrate (3) and the temperature rise for the central second emission part (6b). Curve (a) shows an output of 20 mW only at the second emission part (6b)
The curve (b) shows the continuous operation of the second emission part (6b) and the adjacent first and third emission parts (6a), (6c) output 20
This is when pulse driving is performed at mW. The pitch of the laser beam at this time is 100 μm. Thus, the thickness of the semiconductor substrate (3) is closely related to the temperature rise. APC
In the driving, the output fluctuation of the second emitting section (6b) is controlled by the above-described 1
The inventors of the present invention have found that the temperature rise due to the heat from the other emission portions (6a) and (6c) should be about 6.6 ° C. or less in order to make the emission percentage or less. Therefore, curve (b)
Semiconductor substrate (3) in which the temperature difference between the curve and curve (a) is about 6.6 ° C.
Is about 70 μm. This value is about 50 μm thin because the thickness of the conventional semiconductor substrate (3) is about 120 μm. That is, by setting the thickness of the semiconductor substrate (3) to be about 70 μm or less, which is thinner than the conventional one, even if the central emission part (6b) is used, the other emission parts (6a) and (6c)
Can be suppressed to a temperature range that can be compensated for in a circuit.

(G) Effect of the Invention As is clear from the above description, the semiconductor laser device of the present invention is fixed to the Si heat sink from the GaAs semiconductor substrate side with good thermal conductivity, the laser beam pitch is set to about 100 μm, and the thickness of the semiconductor substrate is set. Is about 70 μm or less, and the temperature rise due to thermal influence from other emission sections is about 6.6 ° C. or less, so that the output fluctuation width due to the temperature rise can be reduced and the life can be extended. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a main part of the semiconductor laser device of the present invention,
FIG. 2 is a characteristic diagram showing the dependence of the operating current and the optical output on the temperature at the emission portion, and FIG. 3 is a characteristic diagram showing the relationship between the thickness of the semiconductor substrate and the temperature rise. (1) ... heat sink, (2) ... semiconductor laser beam chip, (3) ... semiconductor substrate, (4) ... growth layer,
(6a) to (6c) ... first to third emission units.

Claims (1)

(57) [Scope of request for utility model registration] 1. A semiconductor laser beam chip comprising: a GaAs semiconductor substrate; a growth layer formed on the substrate; and emission sections individually provided at a plurality of locations of the growth layer and independently emitting laser beams. A heat sink made of Si for fixing the laser beam chip from the semiconductor substrate side in good thermal conductivity, and the pitch of the laser beam is set to about 100 μm.
m, the thickness of the semiconductor substrate is about 70 μm or less, and the temperature rise due to the influence of heat from the other emission section is about 6.6 ° C. or less.