Semiconductor Laser

1. Field of the Invention

The present invention relates to an improvement in a semiconductor laser.

More particularly, the present invention concerns an improved structure of the semiconductor laser mount for obtaining accurate position and direction of the laser with respect to the mount.

2. Prior Art

As is well known, semiconductor lasers require a good heat radiation and dissipation, since a current of a high density flows in it when oscillating. Accordingly, in order to assure the good heat dissipation, the semiconductor laser chip is usually mounted on a copper heat sink or mount. As shown in FIG. 1, it has been known that a sub-mount 2 of copper or silicon is inserted between the semiconductor laser chip 4 and a main mount 1 of copper. Solder layers 3 and 31 are used for bonding the semiconductor laser chip 4 on the sub-mount 2 and the sub-mount 2 on the main mount 1, respectively.

In the semiconductor laser device, such sub-mount 2 is usually shaped in a rectangular parallelopiped, since such shape is suitable for making with an accurate size and shape. The accuracy of the shape of the sub-mount is advantageous in good bonding necessary for good heat dissipation and in accurate positioning necessary for avoiding undesirable masking of oscillated light. The bonding of the laser chip on the sub-mount is advantageous in that the testing of the semiconductor laser chip 4 can be made for the chip bonded on the sub-mount 2.

The sub-mount 2 with the semiconductor laser chip 4 thereon is then bonded on the copper heat sink or main mount 1, and the bonding requires a high accuracy in position and direction. Since no particular means is devised for attaining a high accuracy of the position and direction in the conventional structure of FIG. 1, it has been very difficult to attain a high accuracy of position and direction in bonding between the sub-mount and the main mount.

In summary, the conventional configuration of FIG. 1 has not fulfilled the requirements of bonding of the sub-mount 2 with semiconductor laser chip 4 thereon with very highly accurate positional and directional relation with ease and high manufacturing yield.

The present invention adopted novel structure of the heat sink or mount of the semoconductor laser, and can improve accuracy of bonding of the sub-mount on the main mount in positional and directional relation of the bonding, and thereby can improve manufacturing yield of the semiconductor lasers.

FIG. 1 is an elevation view of the conventional semiconductor laser.

FIG. 2(a) is an elevation view of an example of semiconductor laser embodying the present invention.

FIG. 2(b) is a perspective view of the example of FIG. 2(a).

FIG. 3(a) is an elevation view of another example of semiconductor laser embodying the present invention.

FIG. 3(b) is a perspective view of the example of FIG. 3(a).

The present invention is elucidated in detail with reference to FIGS. 2(a), 2(b), 3(a) and 3(b) which show preferred embodiments in accordance with the present invention.

The embodiments of the present invention comprises a first engaging means on the upper face of the main mount and a second engaging means on the bottom of sub-mount, so that the sub-mount is easily guided to a desired accurate position with an accurate direction. The engaging means comprise at least an abutting wall and a slide-guide. By utilizing the engaging means, the sub-mount can be mounted accurately on a designed position and direction without need of particular skill. Furthermore, by means of the engaging means, the sub-mount can be easily slide-guided on the right position of the main mount, so that an accurate mounting work can be made easily. And still furthermore, by means of the above-mentioned structure, the bonding area between the main mount and the sub-mount increases, thereby increasing stability of bonding and thermal conductivity at the bonding.

The invention is hereinafter elucidated with reference to the accompanying drawings, wherein FIG. 2(a) and FIG. 2(b) show a first example, and FIG. 2(a) is a front elevation view, wherein direction of output laser light is perpendicular to the surface of the paper. A main part 1 of the heat sink or mount is made of a material of good thermal conductivity, for instance, copper. A linear protrusion or ridge protrusion 12 extending to the front end of the main mount 1 and a flat abutting wall 13 which is disposed perpendicular to the ridge protrusion 12 are provided on a principal face or upper surface 11 of the main mount 1. The ridge protrusion 12 and the abutting wall 13 constitute a first engaging means. A semiconductor laser chip 4, for instance, a GaAs-GaAsAl laser chip is bonded on the upper face of a sub-mount 2 made of a material of good thermal conductivity, for instance, silicon. And the sub-mount 2 has a linear groove 21 of an inverted V shaped section on its bottom face to be bonded on the principal face 11 of the main mount 1. A rear end face 22 of the sub-mount 2 forms a flat abutting face to be bonded on the abutting wall 13. The linear groove 21 and the abutting face 22 form a second engaging means. In assembling, the semiconductor laser chip 4 is bonded by means of a solder 3 of, for instance an In-solder on the upper face of the sub-mount 2 by utilizing a known microscope for assembling; and thereafter the sub-mount 2 is bonded on the upper face of the main-mount 1 by means of another solder 31 of, for instance an In-solder of a lower melting temperature than that of the solder 3. When mounting the sub-mount 2 on the main mount 1, a suitable jig (not shown) having the same thickness as the thickness t.sub.1 of the main mount is used, in a manner that the sub-mount 2 is slid from the upper face of the jig to the upper face 11 of the main mount 1, engaging the groove 21 on the ridge protrusion 12 and sliding the sub-mount 2 along the ridge protrusion as a sliding guide, and the sub-mount 2 is slid until the rear end face 22 of the sub-mount abuts the abutting wall 13 of the main mount 1. The solder layer 31 has been preliminarily formed on the upper surface 11 of the main mount 1. After the sub-mount 2 is disposed to the right position on the main mount 1, the assemblage is heated to solder them each other by melting the solder layer 31. The ridge protrusion 12 serves as a sliding guide.

FIG. 3(a) and FIG. 3(b) show a second example and FIG. 3(a) is a front elevation view, wherein direction of output laser light is perpendicular to the surface of the paper. A main part 1 of the heat sink or mount is made of a material of good thermal conductivity, for example, copper. A square recess 19, which is defined by side walls 12' and 12' extending to the front end of the main mount 1 and by abutting wall 13' perpendicular to the side walls 12' and 12', is formed on the upper face 11 of the main mount 1. The side walls 12' and 12' and the abutting wall 13' constitute a first engaging means. A semiconductor laser chip 4, for instance, a GaAs-GaAlAs laser chip is bonded on the upper face of a sub-mount 2 made of a material of good thermal conductivity, for instance, silicon. And the sub-mount 2 has a flat or straight side walls 21' and 21' and a flat or straight rear end face or abutting face 22. The side walls 12' and 12' as well as 21' and 21' together form a sliding means. The rear end face 22 of the sub-mount 2 form a flat abutting face to be bonded on the abutting wall 13'. The flat side walls 21' and 21' and the rear end face 22 form a second engaging means. In assembling, the semiconductor laser chip 4 is bonded by means of a solder 3 of, for instance an In-solder on the copper face of the sub-mount 2 by utilizing a known microscope for assembling; and thereafter the sub-mount 2 is bonded on the upper face of the main mount 1 by means of another solder 31 of, for instance an In-solder of a lower melting temperature than that of the solder 3. When mounting the sub-mount 2 on the main mount 1, a suitable jig (not shown) having the same thickness as the thickness t.sub.2 of the main mount 1 at the recess part 19 is used, in a manner that the sub-mount 2 is slid from the upper face of the jig to the face of the recess part 19 of the main mount 1, engaging the side walls 21' and 21' to the side walls 12' and 12' and sliding the sub-mount 2 along the slide guide formed by the side walls 12',12',21' and 21', and the sub-mount 2 is slid until the rear end face 22 of the sub-mount 2 abuts the abutting wall 13' of the main mount 1. The solder layer 31 has been preliminarily formed on the abutting face 13', the side walls 12' and 12' and the upper surface of the recess part 19 of main mount 1. After the sub-mount 2 is disposed to the right position on the main mount 1, the assemblage is heated to solder them each other by melting the solder layer 31. As is observed from FIG. 3(a) and FIG. 3(b), side walls 12', 12', 21' and 21', the abutting wall 13' and the rear end face 22 form engaging means, and at the same time increases bonding area. Therefore, the accuracy of bonding of the sub-mount 2 on the main mount 1 is much improved and simultaneously the bonding area increases much, thereby increasing bonding force and heat radiation.