JPH07122808A - Semiconductor laser modulation circuit device - Google Patents

Abstract

PURPOSE:To provide a semiconductor laser modulation circuit device wherein parasitic inductance can be lowered and a semiconductor laser can be modulated at high frequencies. CONSTITUTION:As a means for connecting an electrode of a semiconductor laser 1 to transmission paths 51, 52, a metallic surface of a heat sink 2 is used to directly connect them, and a metallic wire is made unnecessary. Furthermore, since an upper electrode of the semiconductor laser 1 and the transmission path 51 are connected through a metallic wire 32 via a metallic block 31 whose height is approximately the same as that of the upper electrode of the semiconductor laser 1, the length of a metallic wire can be shortened. Furthermore, since influence of stress which works on an upper electrode of a semiconductor laser is small, a sectional area of a metallic wire can be enlarged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ultra-high-speed optical communication and the like, and relates to a semiconductor laser device capable of high-speed modulation.

[0002]

2. Description of the Related Art In a semiconductor laser modulation circuit device for modulating a semiconductor laser at high speed, reflection characteristics at high frequencies
The improvement of the transfer characteristic usually depends on the mounting structure of the semiconductor laser which is connected to the modulation signal source device having the impedance of 50Ω.

For example, as an example of a mounting structure, Japanese Patent Laid-Open No.
There is -116990. The prior art of the mounting structure with reference to this will be described with reference to FIGS.
FIG. 4 is an equivalent circuit diagram showing a circuit configuration of a conventional semiconductor laser modulation circuit device. One ends of two transmission lines 51 and 52 are connected to the semiconductor laser 1, and the other end of the transmission line 52 is terminated by a terminator 7. On the other hand, the modulation signal source 9 is connected to the other end of the transmission path 51.

The semiconductor laser 1 is an element having an impedance in the range of approximately 3 to 8Ω, and the modulation signal source 9 is
It usually has an impedance of 50Ω. in this way,
If the impedance of the element sandwiched between the transmission lines 51 and 52 (semiconductor laser 1 in FIG. 4) is relatively small, the characteristic impedance of the transmission lines 51 and 52 is designed to be about 50Ω, so that the reflection due to the difference in impedance is caused. The effect can be expected to be small in practice.

FIG. 5 is a perspective view showing the structure of a conventional semiconductor laser modulation circuit device. In the figure, in order to embody the circuit diagram of FIG. 4, a heat sink 2, metal wires 32,
33, the substrates 41 and 42, the metal base 6, and the optical element 8 are added. The optical element 8 guides the optical output from the semiconductor laser 1 to the outside. The transmission line 51 forms a microstrip line with the substrate 41 and the metal base 6, and the transmission line 52 forms a microstrip line with the substrate 42 and the metal base 6. For connecting the transmission line 51 and the semiconductor laser 1, a metal wire 3
2 is used. The "metal wire" is used to obtain an electrical connection by a bonding technique, and a gold wire is usually used. In the following description, a cross section of which is circular and a ribbon whose cross section is spread laterally. I will include things like.

On the other hand, the heat sink 2 and the metal wire 33 are used to connect the transmission line 52 and the semiconductor laser 1.
The heat sink 2 is originally used for the purpose of radiating the heat generated by the semiconductor laser 1, and is made of a dielectric material having a good thermal conductivity, and the heat is radiated to the metal base 6 in FIG. The entire upper surface of the heat sink 2 is a metal surface, and the lower electrode of the semiconductor laser 1 and the metal wire 33 are electrically connected through this metal surface.

In FIG. 5, the transmission line 52 to which the lower electrode of the semiconductor laser 1 is connected is terminated, and the modulation signal is input to the transmission line 51 to which the upper electrode of the semiconductor laser 1 is connected. . In the following description, the same description is given for convenience, but a structure in which a modulation signal is input to the transmission line 52 to which the lower electrode of the semiconductor laser 1 is connected and the transmission line 51 to which the upper electrode of the semiconductor laser 1 is connected is terminated. However, there is no significant difference.

[0008]

By the way, in the semiconductor laser modulation circuit device having the structure of FIG. 5 described above, due to the parasitic inductance due to the metal wires 32 and 33, the impedance increases and the multiple reflection increases as the frequency increases. However, there is a problem in that the high-frequency application efficiency to the semiconductor laser 1, that is, the transfer characteristic is deteriorated, along with the waveform deterioration and the like. The parasitic inductance is a circuit element that does not appear in the circuit diagram of FIG. 4, but is an important element that influences high frequency characteristics.

To reduce the parasitic inductance,
The cross-sectional area of the metal wire may be increased, a plurality of metal wires may be arranged and connected, or the length of the metal wire may be shortened. However, when the effective cross-sectional area is increased, the substances having different thermal expansion coefficients are physically and firmly bonded to each other. Therefore, for example, there is a drawback in that the semiconductor laser is distorted due to the stress exerted by the metal wire on the upper electrode of the semiconductor laser 1, and the normal operation is hindered. Next, with respect to the length, the shorter the length, the more improved, but there is a limit to the reduction of the metal wire length due to the dimensions of the semiconductor laser 1 and the heat sink 2.
As a result, there is a problem that the upper limit of the modulation frequency cannot be increased.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor laser modulation circuit device which can reduce the parasitic inductance and can modulate a semiconductor laser at a high frequency.

[0011]

In order to solve the above-mentioned problems, according to the invention of claim 1, a semiconductor laser having an upper electrode and a lower electrode, a heat sink in contact with the semiconductor laser, and a semiconductor laser of the semiconductor laser are provided. A semiconductor laser modulation circuit device comprising: a first transmission line whose one end is electrically connected to an upper electrode; and a second transmission line whose one end is electrically connected to a lower electrode of the semiconductor laser. The heat sink has a metal surface electrically connected to the lower electrode of the semiconductor laser, and the second transmission line is electrically connected to the lower electrode of the semiconductor laser via the metal surface. And

According to the invention described in claim 2,
In the semiconductor laser modulation circuit device described above, the semiconductor laser 1 has a metal block fixed on the first transmission line and having substantially the same height as an upper electrode of the semiconductor laser.
The upper electrode and the first transmission line are electrically connected by a metal wire.

In the invention according to claim 3, the invention according to claim 1
In the semiconductor laser modulation circuit device as described above, a substrate having substantially the same thickness as the heat sink, the first transmission path and the second transmission path are formed in an upper portion, and a lower surface of the substrate is in contact with a metal base, A hole reaching the metal base is provided, the heat sink is arranged in the hole, and the metal surface of the heat sink and the second transmission line are directly connected.

[0014]

According to the first aspect of the present invention, the lower electrode of the semiconductor laser and the second transmission line are directly connected to each other by a suitable metal surface of the heat sink. Therefore, no metal wire is required, and the connection length between the lower electrode and the second transmission line is shortened.

According to the second aspect of the present invention, the upper electrode of the semiconductor laser and the upper surface of the metal block having substantially the same height are connected by a metal wire. Therefore, the length of the metal wire can be shortened, and the influence of the stress acting on the upper electrode of the semiconductor laser is small, so that the cross-sectional area of the metal wire can be increased.

According to the third aspect of the invention, the metal surface of the heat sink is directly connected to the second transmission line by embedding the heat sink in the hole provided in the substrate. Therefore, the connection length is further shortened by the difference in height.

[0017]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a perspective view showing the structure of a semiconductor laser modulation circuit device which is an embodiment of the present invention. FIG. 2 is a sectional view showing the structure of part of the semiconductor laser modulation circuit device. Note that the portions corresponding to those in FIG. In FIGS. 1 and 2, all the surfaces of the heat sink 2 are made of metal. The lower electrode of the semiconductor laser 1 is provided in contact with the upper surface of the heat sink 2, and the transmission path 52 is provided in contact with the lower surface of the heat sink 2. That is, the lower electrode of the semiconductor laser 1 and the transmission line 52 are electrically connected. Similarly,
Even in the arrangement shown in FIG. 2, it goes without saying that a method of electrically connecting the lower electrode of the semiconductor laser 1 and the transmission line 52 can be easily considered even if the surface of the heat sink 2 is partially made of a metal surface.

On the side of the transmission line 51, the semiconductor laser 1
A metal block 31 having substantially the same height as that of the upper electrode is disposed in contact with the upper surface of the transmission path 51. Metal wire 3
2 electrically connects the upper surface of the metal block 31 and the upper electrode of the semiconductor laser 1. The length of the metal wire 32 having a small cross-sectional area is shorter than the distance between the transmission line 52 and the upper electrode of the semiconductor laser 1. The metal wire 3
Two or more wires 2 may be arranged side by side and connected, or a metal wire 32 having a larger cross-sectional area may be used. In this case, the parasitic inductance can be further reduced.

According to the first embodiment, by directly connecting the heat sink 2 to the transmission line 52, the metal wire 33 shown in FIG. 5 is unnecessary, the parasitic inductance is reduced, and the semiconductor laser 1 is driven at high speed. Can be modulated to. Further, since the upper electrode of the semiconductor laser 1 and the transmission line 51 are connected by the metal wire 32 via the metal block 31 having the same height as the upper electrode of the semiconductor laser 1, the length of the metal wire 32 is required. The minimum is sufficient, the parasitic inductance is reduced, and the semiconductor laser 1 can be modulated at high speed. In addition, since the stress applied to the upper electrode of the semiconductor laser 1 by the metal wire 32 is suppressed to the minimum, there is an advantage that the distortion of the semiconductor laser is prevented and the normal operation is not disturbed.

Next, a second embodiment of the present invention will be described with reference to FIG.
Will be described with reference to. FIG. 3 is a sectional view showing a partial configuration of the semiconductor laser modulation circuit device in the second embodiment. In the drawing, a hole portion 49 is provided in the substrate 4, and a part (almost all) of the heat sink 2 is provided in the hole portion 49.
Are arranged. The thick line portion shown is the metal surface 50. The lower electrode of the semiconductor laser 1 contacts the metal surface 50 on the upper surface of the heat sink 2, and the end of the transmission path 52 directly contacts the metal surface 50 on the upper surface of the heat sink 2.

The conductive material piece 34 is for ensuring the electrical connection between the end of the transmission path 52 and the metal surface 50 of the heat sink 2, and is made of conductive resin, solder, or a metal piece. Use as appropriate. The connection length between the lower electrode of the semiconductor laser 1 and the transmission line 52 is the lower limit of the geometrical distance determined by the size of the heat sink 2 in the structure shown in this embodiment.
Further, it is needless to say that the design of the metal surface 50 of the heat sink 2 can be easily considered other than the illustrated example with respect to the same arrangement of FIG.

In FIG. 3, when the height of the upper electrode of the semiconductor laser 1 and the transmission line 51 are not the same, the upper portion of the semiconductor laser 1 is connected via the metal block 31 as in FIG. 1 or 2. The electrodes and the transmission line 51 are connected by the metal wires 32. When the heights of the electrodes are almost the same, the influence of the stress acting on the upper electrode of the semiconductor laser 1 is small, and therefore, as shown in FIG. The block 31 may not be provided.

The above-described second embodiment has an advantage in heat dissipation as compared with the semiconductor laser modulation circuit device having the structure shown in FIG. In the semiconductor laser modulation circuit device, the materials that are usually used for the heat sink 2, the metal base 6, and the substrate 4 are, for example, diamond, copper, and alumina in that order, but the former two have about the same thermal conductivity. On the other hand, the substrate 4 is smaller than that by an order of magnitude. In the first embodiment shown in FIG. 2, the heat of the semiconductor laser 1 escapes from the heat sink 2 to the metal base 6 via the substrate 4. On the other hand, in the third embodiment shown in FIG. 3, the heat of the semiconductor laser 1 escapes from the heat sink 2 directly to the metal base 6. Therefore, the structure shown in FIG. 3 is advantageous in terms of heat dissipation.

As described above, in the second embodiment, since the heat sink 2 is arranged in the hole 49 of the substrate 4, the end of the transmission line 52 directly contacts the metal surface 50 on the upper surface of the heat sink 2. Therefore, the metal wire 33 shown in FIG. 5 is not necessary, the parasitic inductance can be reduced, and the heat sink 2 is in thermal contact with the metal base 6, so that the heat dissipation of the semiconductor laser 1 is good and the semiconductor laser 1 can be operated at high speed. Can be modulated.

[0025]

As described above, according to the first aspect of the invention, the lower electrode of the semiconductor laser and the second transmission line are directly connected by the appropriate metal surface of the heat sink. Therefore, no metal wire is required, and the connection length between the lower electrode and the second transmission line is shortened. As a result, the parasitic inductance is reduced, and the semiconductor laser can be modulated at a high frequency.

According to the second aspect of the present invention, the upper electrode of the semiconductor laser and the upper surface of the metal block having substantially the same height as that of the upper electrode are connected by a metal wire. Therefore, the length of the metal wire can be shortened, and the influence of the stress acting on the upper electrode of the semiconductor laser is small, so that the cross-sectional area of the metal wire can be increased. As a result, the parasitic inductance is reduced, and the semiconductor laser can be modulated at a high frequency.

According to the third aspect of the invention, the metal surface of the heat sink and the second transmission line are directly connected by embedding the heat sink in the hole provided in the substrate. Therefore, the connection length is further shortened by the difference in height. As a result, the parasitic inductance can be reduced, and the heat sink is in thermal contact with the metal base, so that the heat dissipation of the semiconductor laser is good and the semiconductor laser can be modulated at a high frequency.

[Brief description of drawings]

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

FIG. 2 is a sectional view of the semiconductor laser modulation circuit device according to the first embodiment.

FIG. 3 is a sectional view of a semiconductor laser modulation circuit device according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a conventional semiconductor laser modulation circuit device.

FIG. 5 is a perspective view showing a structure of a conventional semiconductor laser modulation circuit device.

[Explanation of symbols]

 1 Semiconductor Laser 2 Heat Sink 4, 41, 42 Substrate 6 Metal Base 7 Terminator 8 Optical Element 9 Modulation Signal Source 31 Metal Block 32, 33 Metal Wire 49 Hole 50 Metal Surface 51 Transmission Line (First Transmission Line) 52 Transmission Path (second transmission path)

Claims (3)

[Claims] 1. A semiconductor laser having an upper electrode and a lower electrode, a heat sink in contact with the semiconductor laser, a first transmission line whose one end is electrically connected to an upper electrode of the semiconductor laser, and a semiconductor laser of the semiconductor laser. A semiconductor laser modulation circuit device comprising: a second transmission line whose one end is electrically connected to the lower electrode, wherein the heat sink has a metal surface electrically connected to the lower electrode of the semiconductor laser, The semiconductor laser modulation circuit device, wherein the second transmission line is electrically connected to the lower electrode of the semiconductor laser via the metal surface. 2. A metal block fixed on the first transmission line and having substantially the same height as an upper electrode of the semiconductor laser, wherein the upper electrode of the semiconductor laser 1 and the first transmission line are: The semiconductor laser modulation circuit device according to claim 1, wherein the semiconductor laser modulation circuit device is electrically connected by a metal wire. 3. A substrate having substantially the same thickness as that of the heat sink, the first transmission line and the second transmission line being formed in an upper portion, the lower surface of which is in contact with a metal base, and the metal base being in contact with the metal base. 2. The semiconductor laser modulation circuit device according to claim 1, wherein a hole reaching the hole is provided, the heat sink is arranged in the hole, and the metal surface of the heat sink and the second transmission line are directly connected. .