JP2002208751A - Method of manufacturing semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shade the return light to exactly control an APC. SOLUTION: A shade member 23 for shading the return light from a front area is disposed in front of a photodetector 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor laser device serving as a light source for optical communication and optical disks, and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 9 is a sectional view showing a conventional semiconductor laser device. In FIG. 9, 1 is a stem, 2, 3, 4
Is a bonding post, 5 is a cap, 6 is glass, 7
Is a photodiode mounting base, 8 is a submount for a photodiode element, 9 is a photodiode, 10 is a block,
11 is a sub-mount for a laser diode element, 12 is a laser diode element, 13 is front light, 14 is rear light, 1
Reference numeral 5 denotes return light due to reflection.

In the above-described semiconductor laser device, the laser diode element 12 usually has two end faces, a front end face and a rear end face, in order to produce an end face by cleavage. Therefore, when driving the laser diode element 12,
Both front light 13 and rear light 14 will be generated.
Since the intensity of the front light 13 and the rear light 14 have a one-to-one linear relationship, the rear light 14 is received by the photodiode 9,
If a monitor current generated by the photodiode 9 is detected and a drive current to the laser diode element 12 is supplied while controlling the monitor current to be always constant,
The intensity of the front light 13 is always constant (Automati
c Power Control: hereinafter referred to as APC control).

[0004]

In the conventional semiconductor laser device, if the front light 13 of the laser diode element 12 is emitted into free space, the return light 15 does not exist, so that the APC control is easily performed. can do. However, the ordinary laser diode element 12 is often used as a structure that is coupled to an optical fiber or an optical disk through an optical system. In this case, there is a reflection from the optical system, the optical fiber and the optical disk, which returns to the laser diode element 12 as return light 15. The return light 15 has two kinds of effects on the laser diode element 12. One is that the return light 15 returns directly to the end face of the laser diode element 12 and changes the oscillation characteristics of the laser diode element 12. One is
It directly enters the photodiode 9 and changes the monitor current. In the latter case, since the monitor current apparently increases, there is a disadvantage that accurate APC control cannot be performed.

In view of the above problems, it is an object of the present invention to provide a semiconductor laser device and a method of manufacturing the same, which enable accurate APC control by blocking return light.

[0006]

According to a first aspect of the present invention, there is provided a method of mounting a light shielding member on a top surface of a laser element via a first solder, and a step of mounting a second light shielding member on a top surface of a mount member. Mounting the laser element via solder, and arranging the light intensity monitoring light receiving element on the rear end face side of the laser element so that the light shielding member is provided between the front end face side of the laser element and the light receiving element. And a step of mounting the light shielding member, wherein the first solder having a higher melting point than the second solder is used.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment (Configuration) FIGS. 1 and 2 show a first embodiment of the present invention. The semiconductor laser device of the present embodiment is used by being coupled to an optical fiber or an optical disk through an optical system, and includes an edge-emitting laser element 21 (laser diode chip) and a rear end face side of the laser element 21 (laser diode chip). A light intensity monitoring light receiving element 22 (photodiode) disposed on the rear side) and a light shielding member 23 for shielding light between the front end face side (front) of the laser element 21 and the light receiving element 22. It is.

The laser element 21 is formed so that its end face is cleaved and emits light toward the front and rear end faces. The back electrode of the laser element 21 is adhered to the upper surface of the heat-dissipating submount 24 (first mounting member) made of copper-tungsten or the like with the solder 35 (second solder) shown in FIGS. ing. The submount 24 is
Via a block 25 (second mounting member), for example, a central portion of a disk-shaped stem 26 is adhered with solder 34 (second solder similar to the solder 35) shown in FIGS. I have. Incidentally, reference numeral 21a in FIG. 2 denotes a light emitting region of the laser element 21.

The light receiving element 22 is provided with the laser element 21.
It is used to detect the rear surface light from the monitor as monitor light and to control its intensity, and has a light receiving region 27 having a predetermined diameter at the center of the surface by covering the surface periphery with a metal film or the like. The back electrode of the light receiving element 22 is adhered to the upper surface of the heat dissipating submount 28 by solder or the like (not shown).
The submount 28 is adhered to an electrode (not shown) at the center of the stem 26 via a plate-like mount 29 and connected to the APC control circuit SC. The APC control circuit SC includes a current detecting means Sc1 for detecting a monitor current value from the light receiving element 22, and the laser element so that the monitor current is always constant based on a detection result of the current detecting means Sc1. And a drive control means Sc2 for controlling a drive current to the power supply 21. The drive control means Sc2 is connected to a drive circuit DC for driving the laser element 21.

The light shielding member 23 is provided, for example, in FIGS.
And a metal plate 23a of copper-tungsten or the like similar to that of the submount 24 for heat radiation, and metal thin films 23b, 23b of titanium-gold formed on both upper and lower surfaces of the metal plate 23a.
And is bonded to the upper surface electrode of the laser element 21 with the solder 33 (first solder) shown in FIGS. 3, 4, and 5, and the post of the stem 26 is bonded via the bonding wire 31. 32. The melting point of the solder 33 is set to a higher temperature than the solders 34 and 35. Further, the width of the light shielding member 23 is formed to be larger than the diameter of the light receiving area of the light receiving element 22, specifically, larger than the width of the laser element 21, and the width of the submount 24 for the laser element 21. It is assumed to be substantially equivalent to Further, the depth of the light shielding member 23 may be such that the connection resistance with the upper surface electrode of the laser element 21 does not increase, and is, for example, substantially equal to the depth of the laser element 21.

(Manufacturing method) First, a high-melting-point solder 33 is applied to the surface of one of the metal thin films 23b of the light-shielding member 23, and as shown in FIG. Then, the laser element 21 is mounted on the upper surface of the solder 33 such that the upper electrode thereof is in contact with the upper surface electrode. Then, the temperature is raised to the melting temperature of the solder 33 and the light shielding member 23 and the laser element 21 are die-bonded. Next, the solder 34 is provided on the upper surface of the block 25.
The sub-mount 24 is placed via the sub-mount 24, and the integrated light-shielding member 23 and laser element 21 are further placed on the upper surface of the sub-mount 24 via the solder 35. At this time, FIG.
The back electrode of the laser element 21 is
Is placed upside down so as to be in contact with the solder 35 on the upper surface of. Thereafter, the temperature is raised to the melting temperature of the solders 33, 34, and 35, and the block 25 and the submount 24, and the submount 24 and the back surface electrode of the laser element 21, are die-bonded. Then, the integrated light shielding member 23, laser element 21, submount 24 and block 25 are integrated.
Is attached to a stem 26 to which a light receiving element 22 is attached in advance, and a bonding wire 31 is connected as shown in FIGS. 1, 2 and 5. Then, from the back of the stem 26, A
The semiconductor laser device is completed by connecting the PC control circuit SC and the drive circuit DC.

Here, since the light shielding member 23 is mounted on the laser element 21 using the solder 33 having a high melting point, if another chip or the like is to be mounted on the light shielding member 23, the solder 33 is used. Also, if a low melting point solder is used, a chip or the like can be soldered at a temperature lower than the melting temperature of the solder 33. That is, other functions can be easily added to the semiconductor laser device, and the degree of freedom in design increases. Also, by using the high melting point solder, it is possible to prevent the growth of whiskers (whisker-like projections) due to the change over time of the solder as compared with the case of using the low melting point solder, and it is possible to prevent the laser element from being short-circuited with other members. .

(Usage Method) In the above-described semiconductor laser device, when the laser element 21 is driven, both the front light ch1 and the rear light ch2 are generated as shown in FIG. Front light ch1
Has a linear relationship of one-to-one with the intensity of the rear light ch2, the rear light ch2 is received by the light receiving element 22 and the light receiving element 2
2 is detected by the APC control circuit SC, and the drive current to the laser element 21 in the drive circuit DC is controlled so that the monitor current is always constant.
APC control is performed so that the intensity of h1 is always constant.

Here, when the optical device is used by being coupled to an optical fiber or an optical disk through an optical system, there is reflection from the optical system, the optical fiber or the optical disk, and this is returned to the laser element 21 as return light ch3. Also,
The return light ch3 may include disturbance light. At this time, since the return light ch3 hits the front surface of the light shielding member 23 and is shielded, the light is prevented from entering the light receiving element 22. Therefore, when the rear light ch2 is received by the light receiving element 22 and APC controlled, the influence of the return light ch3 can be eliminated.
Accurate APC control becomes possible.

[Second Embodiment] FIG. 6 is a diagram showing a second embodiment of the present invention. The semiconductor laser device of the present embodiment
Edge-emitting laser element 21 (laser diode chip)
A light intensity monitoring light receiving element 22 (photodiode) disposed on a rear end face side (rear side) of the laser element 21; a front end face side (front) of the laser element 21 and the light receiving element 22;
In the first embodiment, the light shielding member is a metal plate and a metal thin film on both upper and lower surfaces thereof. However, the present embodiment is different from the first embodiment in that the light shielding member is constituted by a connection band 41 (conductive ribbon).

The connection band 41 is made of a metal having good conductivity such as plastically deformable gold, and one end of the connection band 41 is
The other end is connected to the post 32 of the stem 26 via solder or the like, respectively, to provide a power supply function to the laser element 21. Further, the width of the connection band 41 is formed to be larger than the diameter of the light receiving region 27 of the light receiving element 22. Here, the post 32 of the stem 26 is disposed above the light receiving element 22, and the connection band 41 is connected as described above, so that the light receiving area 2
7 is shielded by a connection strip 41. The other configuration is the same as that of the first embodiment, and the description is omitted.

In this embodiment, the return light ch3 from the front
When the light enters, the return light ch3 hits the front surface of the connection band 41 as a light shielding member and is blocked, so that the light is prevented from entering the light receiving element 22 as in the first embodiment. Therefore, when the rear light ch2 is received by the light receiving element 22 and APC controlled, the influence of the return light ch3 can be eliminated.
Accurate APC control becomes possible.

In this embodiment, since power is supplied through the connection band 41, there is no need to connect a bonding wire other than the connection band 41.

Third Embodiment FIGS. 7 and 8 show a third embodiment of the present invention. The semiconductor laser device of this embodiment includes an edge-emitting laser element 21 (laser diode chip), a light-intensity monitoring light-receiving element 22 (photodiode) disposed on the rear end face side (rear side) of the laser element 21, The second embodiment is similar to the first embodiment in that a light-shielding member 23 for shielding light is provided between the front end face side (front) of the laser element 21 and the light receiving element 22. In the embodiment, the width of the light shielding member 23 is
In this embodiment, the width of the light receiving region 2 of the light receiving element 22 is smaller than the width of the laser element 21.
The difference is that the diameter is larger than the diameter of 7. In this embodiment, the bonding wire 31 connected between the stem 26 and the post 32 is directly connected to the exposed upper surface of the laser element 21. That is, while the light shielding member 23 functions as a conductive member in the first embodiment, the light shielding member 23 does not need to function as a conductive member in the present embodiment. Cost can be reduced. Further, since the laser element 21 is directly connected by the bonding wire 31, the electrical resistance can be reduced as compared with the first embodiment in which the light shielding member 23 is interposed in the electrical connection.

In this embodiment, the return light ch3 from the front
When the light enters, the return light ch3 impinges on the front surface of the light shielding member 23 and is blocked, so that the light is prevented from entering the light receiving element 22 as in the first embodiment. Therefore, when the rear light ch2 is received by the light receiving element 22 and APC is controlled, the influence of the return light ch3 can be eliminated, and the APC with high accuracy
Control becomes possible.

[Modifications] (1) As shown in FIGS. 3 to 5, in the first embodiment, the light shielding member is constituted by the metal plate and the metal thin film on the upper and lower surfaces of the metal plate. You may comprise only a board.

[0022]

According to the first aspect of the present invention, since the light-shielding member is mounted on the laser element using the first solder having a high melting point, it is desired to mount a chip or the like on the light-shielding member. On the other hand, if a low-melting point solder is used for mounting, chips and the like can be soldered at a temperature lower than the melting temperature of the first solder. That is, other functions can be easily added to the semiconductor laser device, and the degree of freedom in design increases. Also,
By using the high melting point solder, it is possible to prevent the occurrence of whiskers due to the change over time of the solder and to prevent a short circuit with other members of the laser element as compared with the case of using the low melting point solder.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a semiconductor laser device according to a first embodiment of the present invention.

FIG. 2 is a front view showing a main part of the semiconductor laser device according to the first embodiment of the present invention.

FIG. 3 is a perspective view illustrating a manufacturing process of the semiconductor laser device according to the first embodiment of the present invention.

FIG. 4 is a perspective view illustrating a manufacturing process of the semiconductor laser device according to the first embodiment of the present invention.

FIG. 5 is a perspective view illustrating a manufacturing process of the semiconductor laser device according to the first embodiment of the present invention.

FIG. 6 is a perspective view showing a semiconductor laser device according to a second embodiment of the present invention.

FIG. 7 is a perspective view showing a semiconductor laser device according to a third embodiment of the present invention.

FIG. 8 is a front view showing a main part of a semiconductor laser device according to a third embodiment of the present invention.

FIG. 9 is a side sectional view of a conventional semiconductor laser device.

[Explanation of symbols]

21 laser element, 22 light receiving element, 23 light shielding member,
24, 25 mounting member, 27 light receiving area, 34, 3
5 First solder, 41 connection strip.

Claims (1)

[Claims] 1. A step of mounting a light shielding member on a top surface of a laser element via a first solder, a step of mounting a laser element on a top surface of a mount member via a second solder, and after the laser element. Interposing the light shielding member between the front end surface side of the laser element and the light receiving element by disposing a light intensity monitoring light receiving element on an end face side, wherein the step of mounting the light shielding member comprises: A method for manufacturing a semiconductor laser device, wherein a first solder having a higher melting point than the second solder is used.