JPS6364076B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor laser device used as an optical signal source for optical communications and optical information processing.

In this type of semiconductor laser device, laser oscillation is performed by applying a current to the semiconductor laser element, but the output characteristics of this laser oscillation are limited by the heat generated from the semiconductor laser element. It is.

In other words, an increase in the temperature of a semiconductor laser element is a factor that reduces the laser oscillation output, and in conventional semiconductor laser devices, in order to suppress the temperature rise of the semiconductor laser element and improve the laser oscillation output, the semiconductor laser element is heated. A heat sink for heat dissipation is bonded to it.

FIG. 1 shows a conventional semiconductor laser device in which a heat sink is bonded to a semiconductor laser element in this way. In the figure, 1 is a semiconductor laser element, and a substrate 1
a, a laser oscillation section 1b formed on one main surface of this substrate 1a, and an electrode (not shown), and the output end surface 1 of the laser oscillation section 1b
The laser oscillation output is obtained from c. 2
1 is a rectangular parallelepiped-shaped heat sink whose one surface is bonded to the back surface of the substrate 1a of the semiconductor laser element 1 by a bonding material 3 made of gold and silicon, and is made of silicon.

To explain the heat dissipation effect of the semiconductor laser device configured in this way, heat generated in the laser oscillation part 1b of the semiconductor laser element 1 is transmitted within the substrate 1a, and is transferred from the back surface of the substrate 1a via the bonding material 3. The heat is transmitted to the heat sink 2 and further radiated from the heat sink 2 to the outside, thereby preventing the temperature of the semiconductor laser element 1 from rising.

However, the laser output characteristic of the semiconductor laser device described above is such that only a low output can be obtained as shown by curve B shown in the graph of FIG. In the figure, the vertical axis shows the laser oscillation output, and the horizontal axis shows the applied current. Furthermore, the curve A that rises from the threshold current It value is the curve when the heat generated in the semiconductor laser element is forcibly removed, and is the laser oscillation output characteristic when the heat dissipation characteristics of the semiconductor laser device are very good. It is an ideal straight line.
Further, curve B shows the laser oscillation output characteristics of the conventional semiconductor laser device. As is clear from FIG. 2, in the conventional semiconductor laser device, even if the applied current is increased to increase the output, a certain current value (here, the current value at point a)
However, there was a drawback that the output could not be improved and the upper limit of the output was extremely low.

The reason why the output of conventional semiconductor laser devices is kept low in this way is that the heat generated from the semiconductor laser element is not sufficiently dissipated. Since the substrate 1a is interposed between the oscillation section 1b and the heat sink 2 for heat dissipation, the heat transfer distance becomes long, and the heat transfer portion that transfers the heat of the laser oscillation section 1b to the heat sink 2 is only the back surface of the substrate 1a. Therefore, this is thought to be due to the fact that the heat transfer area is small compared to the amount of heat generated.

On the other hand, as a means to shorten the heat transfer distance and improve heat dissipation characteristics, the surface of the semiconductor laser element 1 on the side of the laser oscillation section 1b is bonded to the heat sink 2, and the laser oscillation section 1b, which is the heat generating section, is connected to the heat sink 3 for heat dissipation. One possible method is to bring them closer together, but in this case, the output end surface 1c of the laser oscillation section 1b is joined in a state where it is almost in contact with the heat sink 2, so the bonding material 3 protruding from the joint surface during the above joining may shield the output end surface 1c. The disadvantage was that the laser oscillation output was prevented from harming the laser oscillation output.

This invention was made in view of the above-mentioned drawbacks, and the heat generated by the semiconductor laser element is efficiently transferred to the heat sink by providing the heat sink with a bonded part that is bonded to at least two surfaces of the substrate constituting the semiconductor laser device. In this way, the output of the semiconductor laser device is improved.

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4. In the figures, reference numeral 4 shows that a predetermined portion of the upper surface of a heat sink 2 made of silicon is etched to a predetermined depth by reactive ion etching. It is a part to be joined consisting of a concave part formed by a recess, and has a bottom surface 4a and three vertical side surfaces 4b, 4c, and 4d connected to the bottom surface 4a. A bonding material 3 made of gold and silicon is applied to 4c and 4d to remove the bottom surface of the substrate 1a of the semiconductor laser device similar to the conventional device and the side surface 3 on the side of the output end surface 1c of the laser oscillation section.
The side surfaces are joined, and the semiconductor laser element 1 is fixed to the heat sink 2 so that the output end face 1c of the laser oscillation part 1b is located on the side opening surface of the part 4 to be joined. Further, since the bonded portion 4 and the semiconductor laser element 1 are bonded only through the substrate 1a, an electrical short circuit with the heat sink 2 is prevented.

In the semiconductor laser device formed in this manner, the back surface and three side surfaces of the semiconductor laser element 1 are joined to the heat sink 2, and the laser oscillation part 1b of the semiconductor laser element 1, which is a heat generating part, is bonded to the heat sink 2.
Since the heat sink 2 is bonded close to the semiconductor laser device, the heat transfer area and heat transfer distance are improved compared to conventional semiconductor laser devices. Furthermore, when the laser oscillation output characteristics of such a semiconductor laser device were investigated in the same manner as the conventional device, the characteristics of curve C in FIG. 2 were obtained.
Curve B is the laser oscillation output characteristic of the conventional device.
An improvement in the laser oscillation output is seen compared to the above, and the effect of improving the heat transfer area and heat transfer distance of the semiconductor laser device of the present invention contributes to the improvement in the laser oscillation output characteristics.

In addition, in the above embodiment, the three side surfaces 4b, 4c, and 4d that are continuous with the bottom surface 4a of the part to be joined 4 are connected to the bottom surface 4a.
However, as shown in FIG. 5, these three side surfaces 4b, 4c, and 4d have their upper portions tapered to make the upper opening wider than the bottom surface 4a. It has the same effect even if
By doing so, there is an effect that the insertion operation when the semiconductor laser element 1 is inserted into the part to be joined 4 consisting of the recessed part and joined is facilitated.

Further, FIGS. 6 and 7 show still another embodiment, in which an auxiliary recess 5 is formed by connecting to the welded part 4 consisting of a recess, and a groove is further formed around the bottom surface 5a of the welded part 4. 6 facilitates the bonding work between the semiconductor laser element 1 and the heat sink 2. That is, by providing the auxiliary recess 5 and the groove 6, the semiconductor laser element 1 is inserted into the bonded portion 4 formed on the heat sink 2, as shown in FIG. After performing a temporary bonding preparation work, all that is left to do is to heat the bottom surface of the heat sink 3 at a constant temperature, and the molten bonding material 3 will flow around the groove 6 and the gap between the semiconductor laser element 1 and the part to be bonded 4. The bonding is performed in a complicated manner. On the other hand, the surplus bonding material 3 is stored in the groove 6, and the laser oscillating part 1b
It does not adhere to the surface and does not have any adverse effects.

In each of the embodiments shown in FIGS. 3 to 7 above, four surfaces of the semiconductor laser device 1, that is, the back surface and three side surfaces, are bonded to the heat sink 2, but the bonding of the semiconductor laser device 1 is Depending on the circumstances, the heat transfer area and heat transfer distance can be improved compared to conventional devices even if there are only two surfaces, the back surface and one side surface, and therefore the laser oscillation output characteristics can be improved. be.

As described above, according to the present invention, in a semiconductor laser device in which a semiconductor laser element is bonded to a heat sink, a bonding material that is heated and melted is inserted into the heat sink through a concave portion and a groove having a side opening surface, and is connected to the concave portion and is heated and melted. Since the semiconductor laser element is bonded to the heat sink on at least two sides, the bonding area between the semiconductor laser element and the heat sink is increased, and the heat transfer distance between the heat generating part of the semiconductor laser element and the heat sink is increased. is shortened, the temperature rise of the semiconductor laser element can be suppressed, the output of the semiconductor laser device can be improved, and the semiconductor laser element can be easily bonded to the heat sink.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a conventional semiconductor laser device, FIG. 2 is a graph showing the laser oscillation output characteristics of the semiconductor laser device, FIGS. 3 and 4 are perspective views showing an embodiment of the present invention, and FIG. The figure is a perspective view showing another embodiment of the invention, and FIGS. 6 and 7 are perspective views showing still other embodiments of the invention. In the figure, 1 is a semiconductor laser element, 1a is a substrate, 1b is a laser oscillation part, 1c is an output end face, 2 is a heat sink, 3 is a bonding material, 4 is a recess, and 5 is an auxiliary recess. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A heat sink having a recess consisting of a bottom surface, three side surfaces connected to the bottom surface, and a side opening surface, and an auxiliary recess connected to the recess through a groove into which a heat-melted bonding material is placed; A semiconductor laser device comprising a semiconductor laser element bonded to at least two surfaces of the recess of the heat sink using the bonding material so that the output end face of the laser oscillation section is located on the side opening surface of the recess. 2. The semiconductor laser device according to claim 1, wherein the upper opening surface of the recess is formed wider than the bottom surface of the recess.