JP7082418B2 - Semiconductor laser equipment - Google Patents

Description

The present invention relates to a technique for a semiconductor laser device.

The semiconductor laser device is premised on having a separate drive circuit for driving the semiconductor laser (Patent Document 1).

JP 2005-150684

An object of the present invention is to provide a semiconductor laser device including a drive circuit for driving a semiconductor laser in an integrated manner without enlarging the device.

In order to solve the above-mentioned problems, an end face light emitting semiconductor laser unit having an output side light emitting end for outputting a laser and a monitor side light emitting end for outputting a laser for monitoring the laser on a surface opposite to the output side light emitting end. The end face light emitting semiconductor laser unit is driven based on the light receiving element that receives the laser emitted from the monitor side light emitting end and the laser intensity received by the light receiving element, and the laser output from the end face light emitting semiconductor laser unit is output. It has a drive circuit to be controlled, a light receiving element, and a substrate on which the drive circuit is formed, and the light receiving element is an irradiation region on the substrate to which a laser emitted from a light emitting end on the monitor side is irradiated. This is a semiconductor laser device in which the entire light receiving surface is located only in a part of the region, and a part of the laser output from the light emitting end on the monitor side is received by the light receiving surface.

In the second aspect of the present invention, the drive circuit comprises a reference current source that generates a constant current reference current, a reference current generated by the reference current source, and a current output by the light receiving element in response to light reception. It has a forward rotation amplification unit that inputs a voltage value according to the difference and outputs a voltage gain of 1 or less.
It is preferable that the end face light emitting semiconductor laser unit is driven by a drive current corresponding to the output voltage from the normal rotation amplification unit.

In the third aspect of the present invention, the drive circuit specifies the normal rotation amplification unit in the feedback unit that feeds back to the input of the normal rotation amplification unit whose output from the normal rotation amplification unit has a voltage gain of 1 or less . It is preferable to perform a process of oscillating at a frequency .

In the fourth aspect of the present invention, the light receiving element, the drive circuit, and a bonding pad for connecting to the outside are configured as one integrated circuit on the substrate, and the bonding pad is attached to the bonding pad. A position where the bonding wire does not block the laser emitted from the light emitting end on the monitor side toward the light receiving element, and the bonding jig does not interfere with the structure around the substrate during bonding when the bonding wire is attached to the bonding pad. It is preferable to be arranged in.

In the fifth aspect of the present invention, it is preferable that the light receiving element is composed of a phototransistor.

According to the first aspect of the present invention, in the semiconductor laser device, the light receiving surface of the light receiving element is large enough to receive only a part of the laser output from the light emitting end on the monitor side. The size of the drive circuit can be sufficiently secured while enabling the formation of the drive circuit on the same substrate on which the is formed. As described above, the semiconductor laser device can be integrally provided with a drive circuit for driving the semiconductor laser without enlarging the device.

According to the second aspect of the present invention, in the semiconductor laser device, since the voltage gain is 1 or less, the oscillation of the amplification unit is suppressed, so that the number of external parts can be suppressed.

According to the third aspect of the present invention, the semiconductor laser apparatus can simultaneously realize the high frequency superimposition operation for noise reduction of the semiconductor laser and the operation of the drive circuit in one circuit.

According to the fourth aspect of the present invention, the semiconductor laser device secures the amount of light received by the laser in the light receiving element while making the light receiving element small, and secures the operation path of the bonding jig at the time of bonding. Can be realized.

According to the fifth aspect of the present invention, the semiconductor laser device secures a large light-receiving current while reducing the light-receiving element by using a phototransistor having a larger light-receiving current output according to the light-receiving intensity. can.

FIG. 1 is a perspective view showing an example of the overall configuration of a semiconductor laser device. FIG. 2 is a perspective view showing an overall configuration example of the semiconductor laser device with the cap removed. FIG. 3 is a plan view showing a configuration example of an integrated circuit. FIG. 4 is a diagram showing a configuration example of a drive circuit. FIG. 5 is a diagram showing another configuration example of the semiconductor laser device. FIG. 6 is a diagram showing another configuration example of the drive circuit.

An embodiment of the present invention will be described with reference to the drawings.

In this embodiment, a semiconductor laser device is mentioned.

(Constitution)
1 and 2 are diagrams showing a configuration example of the semiconductor laser device 1 according to the present embodiment. FIG. 1 is a perspective view showing an overall configuration example of the semiconductor laser device 1, and FIG. 2 is a perspective view showing an overall configuration example of the semiconductor laser device 1 with the cap 30 removed.

As shown in FIGS. 1 and 2, the semiconductor laser device 1 includes a stem 10, a mount portion 20, a cap 30, leads (also referred to as pins) 41, 42, 43, 44, and an integrated circuit 50.

The stem 10 has a substantially disk shape. The stem 10 is made of a metal material such as an Fe alloy. A plurality of notches 11a, 11b, 11c for positioning are formed on the outer peripheral surface 11 of the stem 10. A cap 30, a mount portion 20, and an integrated circuit 50 are provided on the upper surface 12 of the stem 10. Further, four leads 41, 42, 43, 44 are arranged on the lower surface side of the stem 10.

The cap 30 is made of metal and has a substantially elliptical cylindrical shape. The cap 30 covers the mount portion 20 and the integrated circuit 50 provided on the stem 10. The cap 30 is provided with a glass window 32 formed by joining a glass plate that transmits laser light to the central portion of the upper surface 31. The laser beam emitted from the light emitting end on the output side passes through the glass window 32 and is output to the outside. The cap 30 is fixed to the upper surface 12 of the stem 10 by a flange portion 33 provided on the outer periphery of the lower end portion.

The four leads 41, 42, 43, 44 are arranged at equal intervals on a circle centered on the central axis of the stem 10. In the first to third leads 41, 42, 43, the end portions 41a, 42a, 43a penetrate the stem 10 and are exposed on the upper surface 12 side of the stem 10. The first to third leads 41, 42, and 43 are attached to the stem 10 while penetrating the stem 10 with an insulating member 45 such as a glass material interposed therebetween. The ends 41a, 42a, 43a of the first to third leads 41, 42, 43 are located on both sides of the mounting surface 21 described later in the mounting portion 20 in the front direction and in the front direction, respectively. Further, the end portion of the fourth lead 44 (not shown) is fixed to the lower surface of the stem 10 with a brazing material or the like. As a result, the fourth lead 44 is electrically connected to the stem 10, and the stem 10 is grounded via the fourth lead 44. A mount portion 20 is provided on the upper surface 12 of the stem 10 substantially corresponding to the mounting position of the fourth lead 44.

The mount portion 20 has a substantially fan-shaped cross section and is erected on the upper surface 12 of the stem 10. The mount portion 20 is made of a metal material having good thermal conductivity such as Cu. The mount portion 20 is joined to the upper surface 12 of the stem 10 by a brazing material or the like. The mount portion 20 is formed with a mounting surface 21 facing the central axis side of the stem 10. A sub-mount portion 22 is provided on the mounting surface 21 of the mount portion 20. The integrated circuit 50 is provided on the upper surface 12 of the stem 10 in front of and in the vicinity of the mounting surface 21 of the mount portion 20.

The sub-mount portion 22 is a portion on which the LD chip 23 is mounted. The LD chip 23 is attached to the surface of the submount portion 22 facing the central axis side of the stem 10 by soldering or the like. The submount portion 22 has both a function of a heat sink for dissipating heat generated when the LD chip 23 emits light to the outside from the LD chip 23 and a function of a substrate for supporting the LD chip 23. The submount portion 22 is made of, for example, a ceramic such as AlN, SiC, or CuW. The submount portion 22 is electrically connected to the integrated circuit 50 by a bonding wire 75.

The LD chip 23 is an end face emitting semiconductor laser. The LD chip 23 has an output side light emitting end and a monitor side light emitting end. The light emitting end on the output side emits laser light in the direction in which the upper surface 12 of the stem 10 faces, that is, toward the glass window 32 side of the cap 30. On the other hand, the light emitting end on the monitor side is directed to the side opposite to the light emitting end on the output side, that is, toward the upper surface 12 side of the stem 10, and emits laser light. The LD chip 23 is positioned so that the center of a substantially elliptical cone-shaped laser beam emitted from the light emitting end on the monitor side coincides with the center of the light receiving surface 51a of the light receiving element (also referred to as a monitor light receiving element) 51 of the integrated circuit 50. Has been done. The LD chip 23 is electrically connected to the mount portion 20 via the bonding wire 71.

The integrated circuit 50 is provided on the upper surface 12 of the stem 10 in the central region of the stem 10.

FIG. 3 is a plan view showing a configuration example of the integrated circuit 50.

As shown in FIGS. 2 and 3, the light receiving element 51 and the drive circuit 60 are integrated in the integrated circuit (board) 50. Further, bonding pads 52, 53, 54, 55, 56 are formed in the integrated circuit 50.

The light receiving element 51 outputs a current (hereinafter referred to as a light receiving current) corresponding to the amount of light received (the intensity of light receiving). The light receiving element 51 is composed of a phototransistor. For example, a phototransistor has a characteristic of outputting a larger light-receiving current with respect to the amount of light received. Further, the phototransistor has a characteristic that the response speed of the output of the received light to the incident light is slower than that of the photodiode. The light receiving surface 51a of the light receiving element 51 is formed so that the area is as small as possible. Specifically, the light receiving element 51 is formed small so as to positively receive only a part of the laser light emitted from the light emitting end on the monitor side of the LD chip 23. As a result, the light receiving element 51 receives the laser light on the light receiving surface 51a located in a part of the irradiation region on the integrated circuit 50 to which the laser light emitted from the light emitting end on the monitor side of the LD chip 23 is irradiated. Receives a part of the light. The area of the integrated circuit 50 is, for example, about 0.25 mm2 to 1 mm2.

The bonding pads 52, 53, 54, 55, 56 serve as a portion for electrically connecting the integrated circuit 50 to the outside. In this example, the bonding pads 52, 53, 54, 55, 56 are formed at five locations. Bonding wires 72, 73, 74, 75, 76 are electrically connected to the bonding pads 52, 53, 54, 55, 56, and the bonding wires 72, 73, 74, 75, 76 are externally configured. It is electrically connected. In this example, as shown in FIG. 2, each bonding pad 52, 53, 54, 55, 56 is connected to the stem 10, the first to third leads 41 via the bonding wires 72, 73, 74, 75, 76. , 42, 43, and the submount portion 22 are electrically connected.

Regarding the positions of the bonding pads 52, 53, 54, 55, 56 in the integrated circuit 50, as shown in FIG. 3, the bonding pads 52, 53, 54, 55, 56 are located on the outer periphery of the light receiving element 51 and the drive circuit 60. It is formed at approximately equal intervals. Specifically, in the bonding pads 52, 53, 54, 55, 56, the bonding wires 72, 73, 74, 75, 76 attached to the bonding pads 52, 53, 54, 55, 56 are from the light emitting end on the monitor side. The bonding jig is a substrate at the time of bonding to attach the bonding wires 72, 73, 74, 75, 76 to the bonding pads 52, 53, 54, 55, 56 without blocking the laser beam emitted toward the light receiving element 51. It is arranged at a position that does not interfere with the surrounding structure, for example, the mount portion 20. Therefore, the bonding pads 52, 53, 54, 55, 56 are arranged with a certain distance from the mount portion 20.

The drive circuit 60 is an APC (Auto Power Control) drive circuit that controls the output of the LD chip 23.

FIG. 4 is a diagram showing a configuration example of the drive circuit 60. The drive circuit 60 has a reference current source 61 and an amplifier circuit (amplifier) 62.

The reference current source 61 has a reference power supply and a reference resistance, and is configured to generate a constant current.

The amplifier circuit 62 is a voltage follower amplifier circuit, that is, the voltage gain is 1 or less. A constant current from the reference current source 61 and a current (light receiving current) from the light receiving element 51 are input to the amplifier circuit 62, respectively. Here, the larger the current value from the light receiving element 51 with respect to the constant current value from the reference current source 61, the smaller the potential value at the connection point between the reference current source 61 and the cathode of the light receiving element 51. In this case, the output voltage value of the amplifier circuit 62 also becomes small, and the drive current value of the LD chip 23 output by the amplifier circuit 62 becomes small. On the other hand, the smaller the current from the light receiving element 51 with respect to the constant current from the reference current source 61, the larger the potential value at the connection point between the reference current source 61 and the cathode of the light receiving element 51. In this case, the output voltage value of the amplifier circuit 62 also increases, and the drive current value output by the amplifier circuit 62 also increases.

In this way, when the current value from the light receiving element 51 becomes larger than the constant current value from the reference current source 61, the drive circuit 60 reduces the drive current value of the LD chip 23, and vice versa. When the current value from the light receiving element 51 becomes smaller than the constant current value from 61, the drive current value of the LD chip 23 is increased so that the drive current value becomes constant. As a result, the intensity of the laser beam emitted from the LD chip 23 is kept constant.

Further, when high frequency superimposition is required, the drive circuit 60 can process the amplifier circuit 62 to oscillate in the feedback unit that feeds back the output from the amplifier circuit 62 to the input of the amplifier circuit 62. As a configuration for that purpose, the drive circuit 60 inserts a feedback circuit 63, which is a circuit element, into the feedback path of 100% negative feedback so that the phase gain satisfies the oscillation condition at a specific frequency, and oscillates the amplifier circuit 62.

For example, the feedback circuit 63 is a two-stage CR delay circuit having the same 3 dB attenuation frequency as the bandwidth of the amplifier circuit 62. As a result, positive feedback occurs in the vicinity of the 3 dB attenuation frequency and the oscillation condition can be satisfied, and the amplifier circuit 62 oscillates. As a result, in the control loop of the APC, the negative feedback operation in which the oscillated high frequency is not fed back due to the frequency characteristic of the light receiving element 51 and the average value of the laser output is kept constant is realized.

(Effect in this embodiment)
(1) The semiconductor laser device 1 is large enough for the light receiving surface (light receiving portion) 51a of the light receiving element 51 to receive only a part of the laser light output from the light emitting end on the monitor side of the LD chip 23. It is smaller than the area of the light receiving surface of the conventional light receiving element.

As a result, the semiconductor laser device 1 according to the present embodiment can sufficiently secure the size of the drive circuit 60 while enabling the formation of the drive circuit 60 on the same substrate on which the light receiving element 51 is formed. .. In this way, the semiconductor laser device 1 can integrate the drive circuit 60 that drives the semiconductor laser without increasing the size of the device.

Further, the semiconductor laser device 1 is provided as a low-priced, compact and lightweight semiconductor laser device.

Further, reducing the area of the light receiving surface 51a of the light receiving element 51 causes a decrease in the light receiving current output by the light receiving element 51. However, in the semiconductor laser device 1, since the drive circuit 60 is formed in the same integrated circuit as the light receiving element 51 and is configured on the same substrate, the influence of external noise is reduced and the S / N ratio can be secured. As a result, it is possible to secure security against the influence of the decrease in the received light current on the drive current value of the LD chip 23. Further, the semiconductor laser device 1 can compensate for the decrease in the received light current by the amplifier circuit 62.

(2) In the semiconductor laser device 1, since the voltage gain is 1 or less, the oscillation of the amplification unit is suppressed, so that the number of external parts can be suppressed.

For example, in a conventional semiconductor laser device, a circuit is used in which the light receiving current of a light receiving element is voltage-converted by a current-voltage conversion circuit and the drive current of the LD chip is increased or decreased so that the voltage becomes the same as the reference voltage. However, in such a configuration, in order to prevent oscillation of the circuit to be amplified, a large-capacity capacitor that is difficult to integrate monolithically is required, and it is necessary to connect the capacitor to the outside. As a result, the conventional semiconductor laser device requires an external connection terminal for an external component, resulting in high cost.

On the other hand, in the semiconductor laser device 1 according to the present embodiment, the oscillation of the amplification unit is suppressed, so that an external capacitor or the like is not required, and the number of external parts can be suppressed.

(3) By oscillating the amplification unit, the semiconductor laser device 1 can simultaneously realize the high frequency superimposition operation for noise reduction of the semiconductor laser and the operation of the drive circuit in one circuit.

(4) In the semiconductor laser device 1, by appropriately arranging the bonding pads 52, 53, 54, 55, 56, it is possible to secure the amount of laser light received by the light receiving element while reducing the size of the light receiving element. It is possible to secure the operation path of the bonding jig at the time of bonding.

(5) The semiconductor laser device 1 can secure a large light-receiving current value while reducing the size of the light-receiving element 51 by using a phototransistor whose light-receiving current output is larger than the light-receiving intensity as the light-receiving element 51.

(6) In the semiconductor laser device 1, the center of the elliptical cone-shaped laser light emitted from the light emitting end on the monitor side is positioned so as to coincide with the center of the light receiving surface 51a of the light receiving element 51, and the light receiving element 51 is positioned to coincide with the center of the light receiving surface 51a. It is located near the center of the light beam. As a result, in the semiconductor laser device 1, even if the relative positions of the light flux center of the laser light and the light receiving element 51 deviate due to the positional error during die bonding, the light receiving element 51 can sufficiently receive the laser light.

In the above embodiment, the amplifier circuit 60 constitutes, for example, an amplifier unit.

(Modification example, etc.)
As another example of the above embodiment, the semiconductor laser device 1 can also be configured as a semiconductor laser device in a resin mold type package formed by a resin mold.

FIG. 5 is a diagram showing another configuration example of the semiconductor laser device 1. As shown in FIG. 5, in the semiconductor laser device 1, an integrated circuit 110 in which a light receiving element 111 and a drive circuit 112 are integrated is arranged on a submount substrate 100, and an LD chip 120 is arranged on the integrated circuit 11. Is placed. In the integrated circuit 110, bonding pads 131, 132, 133, 134, 135 are formed on the outer periphery of the light receiving element 51 and the drive circuit 60. In the semiconductor laser device 1, the leads 141, 142, 143 and the like and the bonding pads 131, 132, 133, 134, 135 and the like are electrically connected by bonding wires 151, 152, 153, 154, 155 and the like. .. In the semiconductor laser device 1, the light receiving element 111 is formed small so as to positively receive only a part of the laser light emitted from the light emitting end on the monitor side of the LD chip 23. Further, the semiconductor laser device 1 may be configured with only the integrated circuit 110 by eliminating the submount substrate.

Further, as another example of the above embodiment, the light receiving element 51 can be a photodiode.

Further, as another example of the above embodiment, as shown in FIG. 6, the drive circuit 60 may be configured so that the feedback circuit does not have frequency dependence when high frequency superimposition is not required.

Further, although the embodiments of the present invention have been disclosed, it is clear that some skill in the art can make changes without departing from the scope of the present invention. All such modifications and equivalents are intended to be included in the following claims.

1 Semiconductor laser device, 10 stems, 20 mounts, 23 LD chips, 41, 42, 43, 44 leads, 50 integrated circuits, 51 light receiving elements, 51a light receiving surfaces, 60 drive circuits, 61 reference current sources, 62 amplification circuits, 63 Feedback circuit

Claims (5)

An end face emitting semiconductor laser unit having an output side light emitting end that outputs a laser and a monitor side light emitting end that outputs a laser for monitoring the laser on the surface opposite to the output side light emitting end.
A light receiving element that receives the laser emitted from the light emitting end on the monitor side and
A drive circuit that drives the end face light emitting semiconductor laser unit based on the intensity of the laser received by the light receiving element and controls the laser output from the end face light emitting semiconductor laser unit.
It has the light receiving element and the substrate on which the drive circuit is formed.
In the light receiving element, the entire light receiving surface is located only in a part of the irradiation region on the substrate to which the laser emitted from the light emitting end on the monitor side is irradiated, and the light receiving surface is from the light emitting end on the monitor side. A semiconductor laser device that receives a part of the output laser. In the drive circuit, a voltage value corresponding to a difference between a reference current source that generates a constant current reference current, a reference current generated by the reference current source, and a current output by the light receiving element in response to light reception is input. It has a forward rotation amplification unit that outputs with a voltage gain of 1 or less.
The semiconductor laser device according to claim 1, wherein the end face light emitting semiconductor laser unit is driven by a drive current corresponding to an output voltage from the normal rotation amplification unit. A claim that the drive circuit performs a process of oscillating the normal rotation amplification unit at a specific frequency in a feedback unit that feeds back to an input of the normal rotation amplification unit whose output from the normal rotation amplification unit has a voltage gain of 1 or less. 2. The semiconductor laser device according to 2. The light receiving element, the drive circuit, and a bonding pad for connecting to the outside are configured as one integrated circuit on the substrate.
In the bonding pad, the bonding jig attached to the bonding pad does not block the laser emitted from the light emitting end on the monitor side toward the light receiving element, and the bonding jig is attached to the bonding pad at the time of bonding. The semiconductor laser device according to any one of claims 1 to 3, which is arranged at a position that does not interfere with the structure around the substrate. The semiconductor laser device according to any one of claims 1 to 4, wherein the light receiving element is composed of a phototransistor.

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