JPH07147463A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain a beam having the cross-section of desired circular shape or approximate to a circle by a method wherein the radiation of beam of each semiconductor laser element is formed in the same direction in parallel with each other, and the angle of element arrangement and the shape of compound beam cross-section are specified. CONSTITUTION:The beam radiation of semiconductor laser elements 11 and 12 is brought into the same direction in parallel, and the angle of normal line of the semiconductor laser elements 11 and 12 is formed in element arrangement of 180/m (deg). The shape of cross section of the compound beam formed by compounding all beams is made at about 2n symmetric by rotation (n=2, 3...). Also, the beam in the direction of the same major axis is formed by the semiconductor laser elements 11 and 12, and the element number for each angle of beam is formed in the same number. At this point, the elements 11 and 12 are adhered on a copper heat sink 2 having a gold-plated chip stand having the angle of 90 deg.. Accordingly, the cross section of beam can be brought close to a circle which can be handled more easily than stacking or arranging in lateral direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser,
In particular, the present invention relates to a semiconductor laser used for a laser radar system, a robot eye, etc., by obtaining a high-power beam with a plurality of semiconductor laser elements.

[0002]

2. Description of the Related Art In recent years, a radar system has been studied which uses a semiconductor laser to measure the distance between cars and keeps the car-to-car distance constant or gives an alarm when the car ahead is too close. There is. In such a system, it is necessary to detect an object about 100 m ahead, and as a semiconductor laser, a pulsed optical output of 40 to 80 W is required. However, at present, the commercially available one-chip semiconductor laser can obtain only a maximum of about 30 W.
Therefore, in order to obtain a large output, it is supplied as a stack type laser in which one-chip lasers are vertically stacked (FIG. 9) or an array type laser in which they are arranged side by side.

Further, in the above system, an optical lens is used to focus the laser light beam in a range having a desired spread angle. However, the cross-sectional shape of the laser beam of one chip is originally an ellipse that is long in the direction perpendicular to the surface of the light emitting layer due to the diffraction effect of light, and the shape is a stack of the elliptical shapes. The laser beam has a beam shape that spreads more vertically.

[0004]

In designing and manufacturing a lens, it is desirable to use a circular cross-sectional beam as the cross-sectional shape of the beam of the semiconductor laser, which is easy to handle.
In the beam shape of the stack type laser as described above, there is a problem that an optical lens used for forming a beam having a desired spread is very difficult to design and manufacture. JP 55
-132091 proposes a method of making the beam shape closer to a circular shape by an array type laser in which the laser emitting layers are arranged side by side (Fig. 10), but the beam divergence angle in the vertical direction is 2-3 times that in the horizontal direction. Therefore, it is not possible to achieve a circular shape by simply arranging them side by side, and it is difficult to correct the spread difference with an optical lens. As the beam cross-sectional shape, a circular shape is desirable because it is optically easy to handle. Therefore, it is an object of the present invention to provide a semiconductor laser for obtaining a desired circular or near circular cross-section beam.

[0005]

In order to solve the above-mentioned problems, the structure of the present invention has a beam cross section of a substantially elliptical shape,
In a semiconductor laser using a plurality of semiconductor laser elements having a light emitting layer in which the major axis of the substantially elliptical shape is a normal direction perpendicular to the laser light emitting layer surface, the beam emission directions of the respective semiconductor laser elements are the same direction and parallel, The semiconductor laser device has an element arrangement in which the angle formed by the normal line is 180 / n (deg), and the combined beam cross-sectional shape obtained by combining all the beams is approximately 2n rotational symmetry (n = 2,3, ...). It has become. Further, the structure of the related invention is characterized in that a plurality of semiconductor laser elements form a beam in the same major axis direction, and the number of elements for each beam at each of the angles is the same.

Another feature of the present invention is that the positive m
The semiconductor laser element is arranged on each side surface of a prism (m = 3, 4, ...) Or on each inner surface of a regular m square hole, and the combined beam cross-sectional shape is symmetrical about 2m times.

[0007]

[Advantageous Effects of the Invention and Effects of the Invention] By arranging the light emitting layer surface of the laser with an angle, the distribution of the beam cross section depending on the light emitting layer has an angle, and each beam cross section is substantially Since the elliptical shape is almost 2-fold symmetrical, the cross-sectional shape of the combined beam is approximately 4-fold symmetrical in the case of 90 ° element arrangement and approximately 6-fold symmetrical in the case of 60 ° element arrangement. With this laser element, the cross-sectional shape of the composite beam can be made multi-rotationally symmetrical. Further, by using the required number of laser elements by slightly shifting the angle, a more rotationally symmetric composite beam can be obtained. Therefore, the beam cross-sectional shape can be approximated to a circular shape that is easy to handle, rather than stacking the beams or simply arranging them side by side. Also, by making the number of laser elements the same for each angle, the distribution of the beam intensity becomes more uniform, and a laser beam that is easy to control can be obtained. Further, it is possible to give a characteristic that the beam intensity has a distribution by making each laser element emit light separately.

[0008]

EXAMPLES The present invention will be described below based on specific examples. FIG. 1 shows two semiconductor laser elements 11 and 12 in the light emission direction of an orthogonal beam laser in which an angle of 90 ° is made to a normal to a light emitting layer surface (v in FIG. 1, usually a direction perpendicular to a semiconductor substrate surface). In a cross-sectional view of a vertical plane, the elements 11 and 12 are bonded by using a brazing material (not shown) on a copper heat sink 2 having a chip base having a 90 ° angle with gold plating on the surface. A gold wire 3 for supplying electric power from the outside to each element is connected to the upper surface of each element as an electrode lead wire, and a copper heat sink 2 constitutes a part of another electrode.

Each semiconductor laser device has a well-known structure, for example, a striped multi-quantum well layer and a p-type electrode are laminated on an n-GaAs substrate having an n-type electrode on the back surface, and its cross section is shown in FIG. With a structure like the laser elements 11 and 12, p
It is common to have a gold wire over the mold electrode. The size of the semiconductor laser device used is approximately 500μ.
Therefore, the size of the copper heat sink is also about 1 to 2 mm. If the chip is large, the copper heat sink that constitutes the chip base will also be large.

In order to form the structure of FIG. 1, the laser device 1 is manufactured by a well-known method for manufacturing a semiconductor laser chip.
After forming 1 and 12, electrodes are formed above and below the element,
A chip base of a copper heat sink 2 as shown in FIG. 1 is plated with gold and then bonded by a vacuum evaporation method with a brazing material (not shown). The inventors used a Sn / Au film as the brazing material. Since the semiconductor laser chips 11 and 12 are arranged obliquely, the brazing material is melted at a temperature of about 400 ° C. and fixed to the heat sink 2 while applying a load to the elements 11 and 12 by the die bonder device. Then, a wire 3 made of gold (Au) is bonded to the upper part of the laser chip by a wire bonding device and put in a package to complete this orthogonal beam laser.

The laser beam emitted from this orthogonal beam laser is a cross section of four-fold symmetry as shown in FIG. 2, in which beams from individual laser elements having beam distributions different from each other by 90 ° overlap each other as the name implies. Beam. In particular, in the overlapping central portions, the strength is doubled with a more circular shape. Strictly speaking, since the optical axes are different near the laser chip, the overlap is deviated, but the difference in the optical axes is on the order of several millimeters at the most, and in the practical beam area several cm or more, The axis difference can be ignored.

(Second Embodiment) Further, as shown in FIG. 3, the angle formed by the normal to the light emitting layer surface of the laser chip is 60 °,
When a beam is formed using three chips, a beam having a six-fold symmetric cross section as shown in FIG. 7 is obtained, and the overlapping portion of the individual beams has a triple intensity, and is closer to a circular shape than the orthogonal laser beams. Beam cross section. Therefore, when it is configured to be more rotationally symmetric, the overlapping portion of the beams approaches a circular shape with higher luminous intensity.

(Third Embodiment) Further, as shown in FIG. 5 (a), when the semiconductor laser elements are arranged on each side surface of the rectangular parallelepiped, if one semiconductor laser element is provided on each side, it is left and right in FIG. 5 (a). Since the beam from the element has the same cross section of the beam, the intensity of the beam is doubled when they are overlapped, but the beam of the upper element can only obtain the intensity of one element, so the beam intensity distribution is unbalanced. become. Therefore, a uniform strong beam can be obtained by forming the upper element in two stages such as a stack type (stacking type) and making the number of elements in each direction the same. In the case of FIG. 5B, the heat sink is a square hole. In this configuration, the semiconductor laser element cannot be directly bonded as it is, and therefore the heat sink is combined. In this case, since the semiconductor laser elements are arranged closer to each other, there is an advantage that the parallelism of the optical axes is high.

(Fourth Embodiment) When a semiconductor laser device is arranged on the side surface of a regular hexagonal prism heat sink, a beam of approximately six-fold symmetry is obtained (FIG. 6 (a)). In this case, the heat sink of the second embodiment is combined. Since the number of elements increases, the problem of heat treatment occurs. However, if the problem of heat generation can be cleared by the heat generation property of the laser element and the usage environment, the regular polygonal arrangement has a good beam distribution balance. The same applies to the case where the semiconductor laser element is arranged on the inner wall of the regular hexagonal heat sink (FIG. 6 (b)). In this case as well, the laser element is arranged closer to the prismatic heat sink, and the parallelism of the optical axes is reduced. The higher the cost, the more desirable. In either case,
The beam distribution may be changed by stacking the elements on each surface to increase the intensity of the beam or by selecting one of the laser elements to emit light.

Similarly, a semiconductor laser device is arranged on a heat sink having a more polygonal columnar shape and polygonal holes, and a multi-rotationally symmetric laser beam having a more circular shape can be obtained. Further, in that case, the laser elements can be stacked to obtain a stronger beam intensity. Alternatively, the elements may be arranged side by side.

As described above, when the light emitting layer surface normals of the semiconductor laser device are arranged at an angle and the beams from the respective devices are combined, a laser beam having a rotationally symmetrical cross section is obtained, and the semiconductor laser is easy to handle. Can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a plane perpendicular to a beam emission direction of a rectangular beam laser according to a first embodiment.

2 is a beam cross-sectional view of the orthogonal beam laser of FIG.

FIG. 3 is a configuration diagram showing a cross section of a beam laser according to a second embodiment.

4 is a beam cross-sectional view of the beam laser of FIG.

FIG. 5 is a configuration diagram showing a cross section of a beam laser according to a third embodiment.

FIG. 6 is a configuration diagram showing a cross section of a beam laser according to a fourth embodiment.

FIG. 7 is a configuration diagram showing a cross section of a conventional single laser.

8 is a beam cross-sectional view of the laser shown in FIG.

FIG. 9 is a configuration diagram showing a cross section of a conventional stack type laser beam.

FIG. 10 is a configuration diagram showing a cross section of a conventional array type laser beam.

[Description of Reference Signs] 11, 12 Semiconductor Laser Element 2 Copper Heat Sink 3 Gold (Au) Wire 111, 121 Semiconductor Laser Light Emitting Section (Light Emitting Layer) 112, 122 Semiconductor Laser Upper Electrode Layer 113, 123 Semiconductor Laser Lower Electrode layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiki Ueno 1-1, Showa-cho, Kariya city, Aichi Prefecture Nihondenso Co., Ltd.

Claims (3)

[Claims] 1. A semiconductor laser using a plurality of semiconductor laser devices each having a light-emitting layer having a substantially elliptical beam cross section and a major axis of the substantially elliptical shape being in a direction normal to a laser light-emitting layer surface. The beam emission directions of the laser elements are made the same and parallel, and the angle formed by the normal direction of each of the semiconductor laser elements is set to 18
A semiconductor laser having an element arrangement of 0 / n (deg) and a sectional shape of a synthetic beam obtained by synthesizing all beams is approximately 2n rotational symmetry (n = 2, 3, ...). 2. The semiconductor laser according to claim 1, wherein a plurality of semiconductor laser elements form a beam in the same major axis direction, and the number of elements for each beam at each angle is the same. 3. The semiconductor laser device is arranged on each side surface of a regular m prism (m = 3, 4, ...) Or on each inner surface of a regular m square hole, and the sectional shape of the combined beam is symmetrical about 2m times. The semiconductor laser according to claim 1, wherein the semiconductor laser is present.