JP4535698B2 - Two-wavelength semiconductor laser device - Google Patents

Description

  The present invention relates to a two-wavelength semiconductor laser device, and more particularly to a two-wavelength semiconductor laser device in which a short circuit between terminals due to a solder flow or the like is prevented when a semiconductor laser element is mounted on a heat sink by soldering and mounting efficiency is improved. .

  Currently, compact discs (CD), recordable compact discs (CD-R), minidiscs (MD), higher-density digital video discs (DVDs), etc. are known as optical recording media. In order to reproduce at least a DVD and a CD / CD-R in the medium pickup, a light source needs an oscillation wavelength 650 nm laser for DVD and a 780 nm laser for CD. Furthermore, in order to realize simplification and miniaturization of the optical pickup, a two-wavelength laser device that can emit both wavelengths of 650 nm and 780 nm from one package is effective.

  Several types of two-wavelength semiconductor laser devices have already been developed. One specific example of the two-wavelength semiconductor laser device will be described with reference to FIG. 5 in order to understand the present invention. 5A is a front view of a conventional two-wavelength semiconductor laser device, and FIG. 5B is a perspective view.

  In the two-wavelength semiconductor laser device 50, for example, an AlGaInP-based first semiconductor laser element LD1 having an emission wavelength of 650 nm and an AlGaAs-based second semiconductor laser element LD2 having an emission wavelength of 780 nm are mutually formed on the same n-type GaAs substrate 11. A laser chip LDC integrated in a separated state is provided.

  The specific microstructures of the AlGaInP-based first semiconductor laser element LD1 and the AlGaAs-based second semiconductor laser element LD2 are well known before the application of the present application (see Patent Documents 1 and 2 below). Only the parts necessary for understanding the invention will be described.

  That is, in the AlGaInP-based first semiconductor laser element LD1 of the laser chip LDC, a single quantum well (SQW) structure or an n-type AlGaInP semiconductor layer 12 and a p-type AlGaInP semiconductor layer 13 are formed on the n-type GaAs substrate 11. A first junction layer 14 including a multiple quantum well (MQW) structure is formed, and a first light emitting unit 15 is formed in a part of the first junction layer. Similarly, in the AlGaAs-based second semiconductor laser element LD2, a second structure having the same configuration as that of the first bonding layer 14 is provided between the n-type AlGaAs semiconductor layer 16 and the p-type AlGaAs semiconductor layer 17 on the n-type GaAs substrate 11. A bonding layer 18 is formed, and a second light emitting unit 19 is formed in a part of the second bonding layer 18.

  The n-side common electrode 20 is formed on the back surface of the n-type GaAs substrate 11 of the laser chip LDC, the first p-side electrode 21 is formed on the top surface of the first semiconductor laser element LD1, and the top surface of the second semiconductor laser element LD2. Are each provided with a second p-side electrode 22.

  In the two-wavelength semiconductor laser device 50 having such a configuration, an AlGaInP-based first semiconductor laser element LD1 is formed by passing a current between the first p-side electrode 21 and the n-side common electrode 20, and the second p-side electrode. The AlGaAs-based second semiconductor laser element LD2 can be driven independently by passing a current between 22 and the n-side common electrode 20, and the wavelength of 650 nm can be driven by driving the first semiconductor laser element LD1. A laser beam having a wavelength of 780 nm can be extracted by driving the second semiconductor laser element LD2 with the laser beam.

  On the other hand, the semiconductor laser element requires a heat sink or cooling means for stabilizing the emission wavelength and increasing the output. In the above laser chip LDC, the first semiconductor laser element LD1 and the second semiconductor laser are used. In order to improve the heat dissipation of the element LD2, a so-called junction down structure is adopted in which the first bonding layer 14 and the second bonding layer 18 are fixed close to the heat sink 23. These two semiconductor laser elements LD1 and LD2 In order to drive the LD 2 independently, a patterned first electrode 24 and second electrode 25 serving as current paths are formed on the laser chip LDC fixing surface of the heat sink 23.

In general, when the laser chip LDC is fixed, the first p-side electrode 21 and the second p-side electrode 22 on the bonding side of the laser chip LDC and the first electrode 24 and the second electrode 25 of the heat sink 23 are assembled together. Is done. At that time, both surfaces of the first p-side electrode 21 and the second p-side electrode 22 below the waveguides that become the light emitting portions 15 and 19 of the laser chip LDC are formed over the entire surface in order to increase the thermal conductivity. Bonding is performed so that the first solder layer 26 or the second solder layer 27 contacts.
JP-A-11-186651 (Claims, paragraphs [0017] to [0023], FIG. 1) JP 2002-329934 A (Claims, FIGS. 1 and 4)

  By the way, in the two-wavelength semiconductor laser device, in order to share an optical member such as a lens, it is desirable that the laser elements are close to each other, and the distance between the elements (light emitting portions) is generally 100 to 120 μm. It is often said. Therefore, in the two-wavelength semiconductor laser device 50 having the conventional structure described above, the distance between the patterned first electrode 24 and second electrode 25 of the heat sink 23 is narrower than the distance between the light emitting units 15 and 19. It will be several tens of μm. As a result, when bonding the semiconductor laser device 50 to the heat sink 23, a short circuit occurs immediately if a positional shift occurs, so a very high chip bond accuracy is required, and as shown in FIG. In some cases, there is a problem that the first solder layer 26 and the second solder layer 27 are melted to form the short-circuit portion 28, and it is difficult to increase the assembly yield.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a two-wavelength semiconductor laser device in which the assembly yield is improved by solving the problems of the conventional two-wavelength semiconductor laser device described above.

The above object of the present invention can be achieved by the following constitution. That is, the invention according to claim 1 of the present application is
In a two-wavelength semiconductor laser device in which two semiconductor laser elements that can be independently driven on a single semiconductor laser chip and can emit laser beams of different wavelengths are formed, and the semiconductor laser chip is mounted on a heat sink,
The semiconductor laser chip has a junction-down structure in which a bonding layer serving as a light emitting portion is fixed close to a heat sink,
Of the two semiconductor laser elements emitting different wavelengths,
A first electrode is provided on the heat sink fixing surface below the semiconductor laser element on the short wavelength side via a solder layer so as to be in contact with the entire surface of one electrode of the semiconductor laser element on the short wavelength side,
The heat sink fixing surface on the lower side of the semiconductor laser device on the long wavelength side is partially in contact with the portion other than the lower portion of the waveguide that becomes the light emitting portion of one electrode of the semiconductor laser device on the long wavelength side. A second electrode is provided through a solder layer.

  In the invention according to claim 2 of the present application, in the two-wavelength semiconductor laser device, an area of the semiconductor laser element on the short wavelength side on the heat sink is larger than an area occupied by the semiconductor laser element on the long wavelength side. It is characterized by.

  The invention according to claim 3 of the present application is characterized in that, in the two-wavelength semiconductor laser device, a light detection element is further formed on the heat sink.

  The present invention has the following excellent effects by having the above-described configuration. That is, according to the two-wavelength semiconductor laser device according to claim 1 of the present application, the light-emitting portion of one electrode of the semiconductor laser element on the long wavelength side is formed on the heat sink fixing surface below the semiconductor laser element on the long wavelength side Since the second electrode is provided through the solder layer so as to be in partial contact with the portion other than the lower portion of the waveguide, it is provided on the heat sink fixing surface below the semiconductor laser element on the short wavelength side. Since it is possible to increase the distance between the first electrode and the solder layer, the tolerance of misalignment when the semiconductor laser element is bonded to the heat sink is increased. The opportunity for the two solder layers to melt together to form a short-circuit portion can be greatly reduced, and the assembly yield of the two-wavelength semiconductor laser device can be greatly improved as compared with the conventional one. Uninaru.

  Further, according to the two-wavelength semiconductor laser device according to claim 2 of the present application, the semiconductor laser element on the short wavelength side has lower emission efficiency than the semiconductor laser element on the long wavelength side, and thus generates a large amount of heat. Since the heat radiation efficiency is improved, the frequency stability of the laser light is improved.

  Furthermore, according to the two-wavelength semiconductor laser device according to claim 3 of the present application, it is not necessary to separately provide a photodetector such as a monitoring photodiode, so that a miniaturized two-wavelength semiconductor laser device can be obtained. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the same reference numerals are given to the same components as those of the conventional example shown in FIGS. 5 and 6 and detailed description thereof will be omitted. To do. However, the embodiment shown below exemplifies a two-wavelength semiconductor laser device for embodying the technical idea of the present invention, and the present invention is intended to be specified as the two-wavelength semiconductor laser device of this embodiment. However, the present invention is equally applicable to those included in the technical scope described in the claims.

  1A and 1B are diagrams illustrating a two-wavelength semiconductor laser device having wavelengths of 650 nm and 780 nm according to a first embodiment, in which FIG. 1A is a front view and FIG. 1B is a perspective view.

  The two-wavelength semiconductor laser device 10 has a junction-down structure in which a junction portion serving as a light emitting portion is fixed close to the heat sink 23 as a semiconductor laser chip LDC. Here, the semiconductor laser on the left side when viewed from the front of FIG. The first semiconductor laser element LD1 whose element emits laser light having a wavelength of 650 nm for DVD and the second semiconductor laser element LD2 whose right semiconductor laser element emits light having a wavelength of 780 nm for CD / CD-R is used. The separation groove is provided between the two semiconductor laser elements. Here, the interval between the light emitting portions 15 and 19 of both semiconductor laser elements is approximately 110 μm.

  A first electrode 24 and a second electrode 25 made of patterned Ti—Pt—Au are formed on the surface of the heat sink 23. In the first embodiment, on the surface of the first p-side electrode 21 immediately below the light emitting portion (waveguide) 15 of the first semiconductor laser element LD1, the first solder layer (for example, , Au-Sn) 26 is in contact with the entire surface, and the heat generated in the first semiconductor laser element LD1 is efficiently transmitted to the heat sink 23 via the first p-side electrode 21, the first solder layer 26, and the first electrode 24. It is heated and dissipated.

  On the other hand, the solder layer and the electrode are not provided immediately below the light emitting portion 19 of the second semiconductor laser element LD2 that emits a laser beam of 780 nm, and the second solder layer is provided only in a portion away from the light emitting portion 19. (For example, Au—Sn) 27 and the second electrode 25 are provided. Then, since the second semiconductor laser element LD2 has a long wavelength of emitted laser light, the light emission efficiency and temperature characteristics are very excellent compared to the first semiconductor laser element LD1 that emits laser light of 650 nm. Even if there is no solder layer or electrode in the lower part 30 of the second light emitting part, there is almost no influence.

  FIG. 2 shows a state where the first and second solder layers 26 and 27 are melted and flowed in the semiconductor laser device 10 of the first embodiment. As can be clearly understood by comparing FIG. 2 and the description of FIG. 6 showing the state in which the solder of the conventional example flows, the two-wavelength semiconductor laser device 10 of the first embodiment is different from the two-wavelength semiconductor laser device 50 of the conventional example. In comparison, since the distance between the solder layers 26 and 27 is long, the possibility of a short circuit due to the solder flow as in the conventional example is extremely small, and the first and second solder layers 26 and Since not only the distance 27 but also the distance between the first electrode 24 and the second electrode 25 is longer than that of the conventional example, the displacement due to the bonding of the laser chip LDC to the surface of the heat sink 23 is prevented. Since the tolerance is increased, the assembly yield is improved.

  As shown in FIG. 3, the second embodiment is formed in the same manner as in the first embodiment except that Si is used as the heat sink material and the photodiode 31 is formed on the surface of the heat sink 23 for monitoring the laser output. A two-wavelength semiconductor laser device 10 ′ was obtained.

  With such a configuration, the patterns of the first electrode 24 and the second electrode 25 become thin in the portion where the photodiode 31 is formed, but the conventional example when bonding the laser chip LDC onto the heat sink is used. The problems that were present could be solved effectively as in the case of Example 1.

  As Example 3, as shown in FIG. 4, the width of the first semiconductor laser element LD1 that emits a laser beam having a wavelength of 650 nm on the left side when viewed from the front, that is, the area occupied by the first semiconductor laser element LD1, The area occupied by the second semiconductor laser element LD2 that emits light having a wavelength of 780 nm on the right side is made larger, the separation groove is provided on the second semiconductor laser element LD2 side than the middle between the two semiconductor laser elements, and other configurations A two-wavelength semiconductor laser device 10 ″ was prepared in the same manner as in Example 1.

  With such a configuration, between the first solder layer 26 formed on the surface of the first p-side electrode 21 of the first semiconductor laser element LD1 and the first electrode 24 provided on the surface of the heat sink 23. Therefore, the heat radiation effect on the first semiconductor laser element LD1 side with respect to the two-wavelength semiconductor laser device 10 according to Example 1 was improved, and the frequency stability of the laser beam was improved.

  On the other hand, the contact area between the second p-side electrode 22 of the second semiconductor laser element LD2 and the second solder layer 27 formed on a part of the surface, and the contact between the second solder layer 27 and the second electrode 25 Since the contact area between them decreased, it was predicted that the heat dissipation efficiency would decrease, but the wavelength stability of the second semiconductor laser element LD2 hardly changed. This is because the wavelength of the laser beam emitted from the second semiconductor laser element LD2 is long, and therefore the second semiconductor laser element LD2 has better light emission efficiency than the first semiconductor laser element LD1, and therefore the influence of heat generation is small. This is expected.

  Also in the third embodiment, the problems of the conventional example when bonding the laser chip LDC onto the heat sink can be effectively solved as in the first embodiment.

  In the present invention, an insulating material having excellent heat conduction such as AlN, SiN, Si, and diamond can be used as the heat sink. Even when a conductive material is used, an insulating film can be formed on the surface, and an electrode can be patterned thereon for use.

  Although the package of the two-wavelength semiconductor laser device is not specifically illustrated, various packages such as a well-known metal can package and a resin frame package can be used.

1A and 1B are diagrams showing the structure of a two-wavelength semiconductor laser device according to a first embodiment of the present invention, in which FIG. 1A is a front view and FIG. 1B is a perspective view. It is a figure which shows the state when the solder by Example 1 of this invention flows. It is a figure which shows the 2 wavelength semiconductor laser apparatus of Example 2 of this invention. It is a figure which shows the 2 wavelength semiconductor laser apparatus of Example 3 of this invention. It is a figure which shows the 2 wavelength semiconductor laser apparatus by a prior art example, FIG. 5 (a) is a front view, FIG.5 (b) is a perspective view. It is a figure which shows the state when the solder by a prior art example flows.

Explanation of symbols

LD1 First semiconductor laser element LD2 Second semiconductor laser element LDC Laser chip 10, 10 ', 10 "Two-wavelength semiconductor laser device 11 n-type GaAs substrate 12 n-type AlGaInP semiconductor layer 13 p-type AlGaInP semiconductor layer 14 first bonding layer 15 First light-emitting portion 16 n-type AlGaAs semiconductor layer 17 p-type AlGaAs semiconductor layer 18 second bonding layer 19 second light-emitting portion 20 n-side common electrode 21 first p-side electrode 22 second p-side electrode 23 heat sink 24 first electrode 25 second Electrode 26 First solder layer 27 Second solder layer 50 Conventional two-wavelength semiconductor laser device

Claims (3)

In a two-wavelength semiconductor laser device in which two semiconductor laser elements that can be independently driven on a single semiconductor laser chip and can emit laser beams of different wavelengths are formed, and the semiconductor laser chip is mounted on a heat sink,
The semiconductor laser chip has a junction-down structure in which a bonding layer serving as a light emitting portion is fixed close to a heat sink,
Of the two semiconductor laser elements emitting different wavelengths,
A first electrode is provided on the heat sink fixing surface below the semiconductor laser element on the short wavelength side via a solder layer so as to be in contact with the entire surface of one electrode of the semiconductor laser element on the short wavelength side,
The heat sink fixing surface on the lower side of the semiconductor laser device on the long wavelength side is partially in contact with the portion other than the lower portion of the waveguide serving as the light emitting portion of one electrode of the semiconductor laser device on the long wavelength side. A two-wavelength semiconductor laser device, wherein a second electrode is provided via a solder layer. In a two-wavelength semiconductor laser device in which two semiconductor laser elements that can be independently driven on a single semiconductor laser chip and can emit laser beams of different wavelengths are formed, and the semiconductor laser chip is mounted on a heat sink,
The semiconductor laser chip has a junction-down structure in which a bonding layer serving as a light emitting portion is fixed close to a heat sink,
Of the two semiconductor laser elements emitting different wavelengths,
A first electrode is provided on a heat sink fixing surface below the semiconductor laser element on the short wavelength side via a solder layer so as to be in contact with the entire surface of one electrode of the semiconductor laser element on the short wavelength side,
The heat sink fixing surface on the lower side of the semiconductor laser device on the long wavelength side is partially in contact with the portion other than the lower portion of the waveguide that becomes the light emitting portion of one electrode of the semiconductor laser device on the long wavelength side. A second electrode is provided via the solder layer;
2. The two-wavelength semiconductor laser device according to claim 1, wherein an area occupied by the semiconductor laser element on the short wavelength side is larger than an area occupied by the semiconductor laser element on the long wavelength side. In a two-wavelength semiconductor laser device in which two semiconductor laser elements that can be independently driven on a single semiconductor laser chip and can emit laser beams of different wavelengths are formed, and the semiconductor laser chip is mounted on a heat sink,
The semiconductor laser chip has a junction-down structure in which a bonding layer serving as a light emitting portion is fixed close to a heat sink,
Of the two semiconductor laser elements emitting different wavelengths,
A first electrode is provided on the heat sink fixing surface below the semiconductor laser element on the short wavelength side via a solder layer so as to be in contact with the entire surface of one electrode of the semiconductor laser element on the short wavelength side,
The heat sink fixing surface on the lower side of the semiconductor laser device on the long wavelength side is partially in contact with the portion other than the lower portion of the waveguide serving as the light emitting portion of one electrode of the semiconductor laser device on the long wavelength side. A second electrode is provided via the solder layer;
A two-wavelength semiconductor laser device, wherein a light detection element is further formed on the heat sink.

Images