JP2000223768A - Semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain generation of heat cycle, in a semiconductor laser device in which a semiconductor laser chip and a heat sink are integrated. SOLUTION: When the output of a semiconductor laser is stopped, or in the case of standby, or when pulse driving is turned off, heat equal to the amount of heat generated when a semiconductor laser chip 31 is operated is generated by a heat generating source 36. In this case, the difference of temperatures of the heat sink 32 and the semiconductor chip 31 is made equal to or nearly equal to the temperature difference when the semiconductor laser power is outputted or pulse driving is turned on. As a result, the number of times of heat cycle caused by fluctuation of temperature diference between the semiconductor laser chip 31 and the heat sink 32 is reduced as compared with the practical number of times of ON and OFF of the semiconductor laser.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device which suppresses a temperature change of a semiconductor laser chip.

[0002]

2. Description of the Related Art A semiconductor laser has an advantage that its oscillation efficiency is higher than other lasers. However, its oscillation efficiency, that is, the ratio of the power supplied to the semiconductor laser that contributes to the oscillation of laser light, is still high. , So far 30
About 40%. That is, 60 to 70% of the supplied power
Is not converted to light but becomes heat and is stored in the semiconductor laser chip. The accumulated heat may cause, for example, a change in the composition or melting of the compound semiconductor, and may cause breakdown of the semiconductor laser. Therefore, in order to prevent destruction due to heat, a semiconductor laser chip is usually mounted on a cooling heat sink.

FIG. 5 is a perspective view schematically showing a configuration of a conventional semiconductor laser device. The semiconductor laser chip 11 is bonded via a bonding material 15 to a submount 14 bonded to a heat sink 12 via a bonding material 13 and is integrated with the submount 14 and the heat sink 12.

[0004] The submount 14 is provided to reduce the thermal stress caused by a large difference between the coefficient of thermal expansion and the temperature difference between the semiconductor laser chip 11 and the heat sink 12. It has an intermediate coefficient of thermal expansion between the chip 11 and the heat sink 12. Therefore, the submount 14 may be omitted when the difference between the thermal expansion coefficient and the temperature difference between the semiconductor laser chip 11 and the heat sink 12 is small.

[0005] The bonding material 13 and the bonding material 15 mechanically bond between the submount 14 and the heat sink 12 and between the semiconductor laser chip 11 and the submount 14, respectively, and also bond them thermally.

[0006] The upper surface of the semiconductor laser chip 11 is connected to one electrode of a power supply 21 via a switch 22 for controlling current supply to the semiconductor laser chip 11. The other electrode of the power supply 21 is connected to, for example, the heat sink 12. This is because an electrode (not shown) provided on the lower surface of the semiconductor laser chip 11 is electrically connected to the heat sink 12 via the submount 14.

The switch 22 is set to an open circuit state (off) in order to stop the power supply to the semiconductor laser chip 11 when the output of the semiconductor laser is stopped or in a standby state. The laser chip 11 is turned on (closed) to supply power to the laser chip 11. When the semiconductor laser is pulse-driven, the switch 22 is turned on and off electrically or mechanically in order to intermittently supply power to the semiconductor laser chip 11.

[0008]

By the way, when power is not supplied to the semiconductor laser chip 11, that is, when the output of the semiconductor laser is stopped or in standby, or when the pulse drive is turned off, heat is not accumulated in the semiconductor laser chip 11. Therefore, the semiconductor laser chip 11 and the heat sink 1
The temperature difference between the two is small. On the other hand, when the semiconductor laser is output or when pulse driving is turned on, the temperature difference between the semiconductor laser chip 11 and the heat sink 12 increases because the density of heat accumulated in the semiconductor laser chip 11 is high. The temperature difference at this time is more remarkable as the semiconductor laser has a higher output.

Therefore, each time the supply and stop of the power to the semiconductor laser chip 11 are repeated, the temperature difference between the semiconductor laser chip 11 and the heat sink 12 changes,
Therefore, a so-called heat cycle occurs. The thermal expansion coefficient of the semiconductor laser chip 11 and the heat sink 12
Thermal stress occurs between the semiconductor laser chip 11 and the heat sink 12 due to a difference in thermal expansion coefficient between the semiconductor laser chip 11 and the heat sink 12, and the generation of the thermal stress and the relaxation of the generated thermal stress are repeated by a heat cycle. .

For example, if the semiconductor laser chip 11 is made of GaAs
s (coefficient of thermal expansion: 6.5 ppm / K)
Heat sink 12 is made of Cu (coefficient of thermal expansion: 17 ppm /
K), the output per semiconductor laser chip
Assuming that the power is 1 W, the semiconductor laser chip 1 at the time of output is
Temperature difference ΔT1 between the heat sink 1 and the heat sink 12,
Between the semiconductor laser chip 11 and the heat sink 12
The difference from the temperature difference ΔT2 (that is, ΔT1-ΔT2) is
About 50 ° C., and the amount of strain between the two was 5 × 10 ^-FourTona
You.

By repeating the generation and relaxation of the thermal stress, the semiconductor laser chip 11 and the submount 14
And the joining materials 13 and 1 such as solder for joining between the submount 14 and the heat sink 12 respectively.
5, or when there is no sub-mount, the stress rupture limit of the joining material such as solder joining the semiconductor laser chip and the heat sink is reduced, and cracks are easily generated in the joining materials 13 and 15.

When a crack occurs in the bonding material 15, the contact area between the semiconductor laser chip 11 and the submount 14 decreases, and when a crack occurs in the bonding material 13, the contact area between the submount 14 and the heat sink 12 decreases. Become smaller. In each case, the resulting semiconductor laser chip 1
Since the heat conduction path between the semiconductor laser chip 11 and the heat sink 12 becomes narrow, the thermal resistance between the semiconductor laser chip 11 and the heat sink 12 increases, and the cooling efficiency of the semiconductor laser chip 11 decreases. Thereby, the semiconductor laser chip 11
Temperature rises and thermal destruction occurs.

As an example, FIG. 4 shows the relationship between the number of heat cycles Nf at which cracks occur in the PbSn solder joint and the amount of strain Δε. From this figure, it can be seen that the larger the strain amount Δε, the smaller the number Nf of crack initiation cycles. For example, in the above-mentioned example, the semiconductor laser chip 11 and the heat sink 12 are made of GaAs and Cu, respectively, and the amount of strain is 5 × 10 ⁻⁴ . 10,000 times.

The number of such crack initiation cycles Nf (10
When a semiconductor laser manufactured using a solder having 10,000 times) is applied to surveying and processing, for example, if the semiconductor laser is driven at a pulse rate of 1 Hz, it takes 1 hour at 30 hours of driving.
08,000 cycles (30 hours x 3600 seconds / hour x 1
Cycle / sec), which exceeds 100,000 times of crack generation cycle, resulting in thermal destruction.

On the other hand, the life of the semiconductor laser itself is generally about 10,000 hours. Therefore, in the case of the above-described example, the semiconductor laser device is destroyed in about 30 hours by using the pulse driving of the semiconductor laser at 1 Hz without using up the life of 10,000 hours.

Alternatively, such a semiconductor laser device is
In order to perform pulse driving for 000 hours, the pulse period is set to 0.0028 Hz (100,000 cycles / 10,
000 hours / 3600 seconds / hour).

That is, when the semiconductor laser is pulse-driven at a frequency higher than 0.0028 Hz, the life of the semiconductor laser device is determined by the heat destruction due to the heat cycle, rather than the life inherent in the semiconductor laser.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a semiconductor laser device capable of suppressing the occurrence of a heat cycle.

[0019]

According to the present invention, there is provided a semiconductor laser device comprising a semiconductor laser chip and a heat sink for cooling the semiconductor laser chip. When output is stopped or in standby, or when pulse drive is off,
A heat generating means is provided which generates heat so that the temperature difference between the heat sink and the semiconductor laser chip is close to the temperature difference between the output of the semiconductor laser and the ON state of the pulse drive.

According to the present invention, when the output of the semiconductor laser is stopped or on standby, or when the pulse drive is turned off, the heat generating means generates heat, and the temperature difference between the heat sink and the semiconductor laser chip at that time is reduced. Approaching the temperature difference at the time of output or pulse drive ON.

In the present invention, the heat generation means may be constituted by a heat generation source provided on a side of the semiconductor laser chip opposite to a side from which laser light is emitted.

According to the present invention, when the output of the semiconductor laser is stopped or in a standby state, or when the pulse drive is turned off, the semiconductor laser chip is provided by the heat generating source provided on the side opposite to the side on which the laser light is emitted from the semiconductor laser chip. Is heated, and the temperature of the semiconductor laser chip at that time approaches the temperature at the time of the output of the semiconductor laser or the ON state of the pulse drive.

In the present invention, the heat generating means may comprise a thin-film heat generating source interposed between the semiconductor laser chip and a heat sink.

According to the present invention, when the output of the semiconductor laser is stopped or on standby, or when the pulse drive is turned off, the semiconductor laser chip is formed by the thin-film heat source provided between the semiconductor laser chip and the heat sink. Heated,
The temperature of the semiconductor laser chip at that time approaches the temperature at the time of output of the semiconductor laser or at the time of pulse drive ON.

In the present invention, the heat generating means may be constituted by a radiant heat source provided on the opposite side of the heat sink with the semiconductor laser chip interposed therebetween and separated from the semiconductor laser chip.

According to the present invention, when the output of the semiconductor laser is stopped or on standby, or when the pulse drive is turned off, the radiant heat ray source is provided on the opposite side of the heat sink with the semiconductor laser chip interposed therebetween and separated from the semiconductor laser chip. As a result, the semiconductor laser chip is heated, and the temperature of the semiconductor laser chip at that time approaches the temperature at the time of output of the semiconductor laser or at the time of pulse drive ON.

The present invention also provides a semiconductor laser chip,
Heat generating means for generating heat so as to keep the temperature of the semiconductor laser chip constant or substantially constant.

According to the present invention, the temperature of the semiconductor laser chip is constantly or substantially kept constant by the heat generating means.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the semiconductor laser device according to the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG. 1 is a perspective view schematically illustrating a configuration of the semiconductor laser device according to the first embodiment of the present invention. This semiconductor laser device has a heat sink 3
The submount 34 is bonded on the submount 2 via a high thermal conductive bonding material (not shown) such as PbSn solder, and on the submount 34 via a high thermal conductive bonding material (not shown) such as PbSn solder. The semiconductor laser chip 31 and a heat generating source 36 serving as a heat generating unit are joined and integrated, and the heat generating source 36 emits a laser beam behind the semiconductor laser chip 31, that is, the semiconductor laser chip 31. It is a configuration arranged on the side opposite to the side.

The heat generating source 36 is configured to generate Joule heat when a current flows.
Made of electrical resistance. Generally, a high-resistance material such as tungsten or ceramics is used. In the case of a semiconductor, silicon oxide or the like is manufactured during the process. The heat generation amount of the heat generating source 36 is set to be equal to the heat generation amount when the semiconductor laser chip 31 is driven.

Semiconductor laser chip 31 and heat generating source 3
The power supply 21 for supplying a current to the power supply 6 has one electrode connected to the upper surface of the semiconductor laser chip 31 and the upper surface of the heat generating source 36, for example, and the other electrode connected to the heat sink 32, for example. The reason why the electrode of the power supply 21 is connected to the heat sink 32 is that the electrode (not shown) provided on the lower surface of the semiconductor laser chip 31 and the heat generation source 36 are electrically connected to the heat sink 32 via the submount 34 as in the related art. This is because they are connected to each other.

Further, this semiconductor laser device is
The switch 23 is provided for flowing the current supplied to only one of the semiconductor laser chip 31 and the heat generating source 36. This switch 23 is connected to the power supply 21
And the upper surface of the semiconductor laser chip 31 and the heat source 36
For example, in a current path leading to the upper surface.

The submount 34 is made of a material having a coefficient of thermal expansion substantially equal to the coefficient of thermal expansion of the semiconductor laser chip 31. For example, when the semiconductor laser chip 31
When the submount 34 is made of aAs, the submount 34 is made of a material such as copper tungsten (CuW) or aluminum nitride (AlN) having a relatively close thermal expansion coefficient to AlGaAs and a close thermal conductivity. I have.

Next, the operation of the first embodiment will be described. The switch 23 is switched to the semiconductor laser chip 31 side when the output of the semiconductor laser or the pulse drive is on, thereby generating a laser output. At this time, since no current flows through the heat generation source 36, no heat is generated. Therefore, the submount 34 is heated by heat generated by the semiconductor laser chip 31 at the time of laser output.

On the other hand, when the output of the semiconductor laser is stopped or on standby, or when the pulse drive is turned off, the switch 23 is turned off.
Is switched to the heat generation source 36 side. As a result, the output of the laser beam is stopped, and a current flows through the heat generating source 36 to generate heat. Therefore, the submount 34 is heated by the heat generated by the heat generation source 36.

Since the bonding material (not shown) between the submount 34 and the semiconductor laser chip 31 has a high thermal conductivity, when the submount 34 is heated by the heat source 36, the semiconductor laser The chip 31 is also heated to the same or substantially the same temperature as the submount 34. Therefore, no thermal distortion occurs between the semiconductor laser chip 31 and the submount 34.

Further, since the heat generation amount of the heat generating source 36 is set to be equal to the heat generation amount of the semiconductor laser chip 31 when the semiconductor laser chip 31 is driven, the sub-heating when the output of the semiconductor laser is stopped or in a standby state or when the pulse driving is off is performed. The temperature of the mount 34 is equal to or substantially equal to the temperature of the submount 34 when the semiconductor laser is output or when pulse driving is on.

That is, the amount of heating of the submount 34 by the heat generating source 36 when the output of the semiconductor laser is stopped or on standby, or when the pulse drive is turned off depends on the output of the semiconductor laser when the output of the semiconductor laser or the pulse drive is turned on. The amount by which the submount 34 is heated is the same or substantially the same. Since the temperature of the heat sink 32 is substantially constant even when the output of the semiconductor laser is stopped or in a standby state, or when the pulse drive is off, or when the output of the semiconductor laser or the pulse drive is on, the output of the semiconductor laser is stopped. However, the temperature difference between the heat sink 32 and the submount 34 does not change, and therefore, no heat cycle occurs between the heat sink 32 and the submount 34.

According to the first embodiment, when the output of the semiconductor laser is stopped or in standby, or when the pulse drive is turned off, the heat generating source 36 generates heat, and the heat sink 32 and the semiconductor laser chip 31 at that time are heated. The temperature difference of the semiconductor laser is the same or substantially the same as the temperature difference when the semiconductor laser is output or the pulse driving is on, so that the actual semiconductor laser is turned on (in a state of emitting light) and turned off (not emitting light). The number of heat cycles due to a change in the temperature difference between the semiconductor laser chip 31 and the heat sink 32 can be reduced with respect to the number of times (state). Therefore, the semiconductor laser chip 3
Since it is possible to prevent the stress rupture limit of the bonding material between the heat sink 1 and the heat sink 32 from being lowered, the semiconductor laser is
The laser can be used up to its original life without thermal destruction.

Further, according to the first embodiment, since the heat generation amount of the heat generating source 36 is the same as or approximately the same as the heat generation amount of the semiconductor laser chip 31, the semiconductor laser device can be operated only by switching the switch 23. The output of the semiconductor laser can be switched on and off while controlling the heat generation amount to be constant.

For example, in the first embodiment, PbSn solder is used as a bonding material between the semiconductor laser chip 31 and the submount 34 and between the submount 34 and the heat sink 32, and the output per chip is reduced by 1%.
In the case of about W, assuming that the semiconductor laser is used for 10 hours a day and the power of the entire semiconductor laser device is turned on / off five times a day, the number of heat cycles per day is five. Therefore, the typical lifetime of a semiconductor laser is 10,000.
The number of heat cycles occurring in 1,000 days corresponding to the use of time is 5,000, which is 100,000 cracking cycles when the amount of strain of the PbSn solder joint is 5 × 10 ^−4. Therefore, the semiconductor laser can be used for its original life without causing thermal destruction due to the heat cycle.

The above-mentioned effect is obtained by setting the semiconductor laser to kHz.
This is particularly effective when pulse driving is performed at a frequency lower than the order. The reason is that the fluctuation width of the temperature difference between the heat sink 32 and the semiconductor laser chip 31 in the case of pulse driving at a frequency of kHz or less is larger than the fluctuation width in the case of pulse driving at a frequency of kHz or more. .

That is, in the case of pulse driving at a frequency of the order of kHz or less, the next pulse current is supplied to the semiconductor laser chip 31 after the temperature of the semiconductor laser chip 31 has dropped to some extent during the output stop period of the semiconductor laser. The temperature of the semiconductor laser chip 31 rises. On the other hand, when the frequency is higher than kHz, the output stop time of the semiconductor laser is short, so that the next pulse current is supplied to the semiconductor laser chip 31 before the temperature of the semiconductor laser chip 31 decreases to some extent, and the temperature of the semiconductor laser chip 31 is reduced again. Rises. Therefore, the fluctuation width of the temperature difference due to the on / off operation of the semiconductor laser is larger in the case of pulse driving at a frequency of kHz or less than in the case of pulse driving at a frequency of kHz or more. The effect of the effect is higher.

In the first embodiment, the heat source 36 is provided behind the semiconductor laser chip 31.
It may be provided on the side surface and the upper surface of the semiconductor laser chip 31.

Embodiment 2 FIG. 2 is a perspective view schematically showing a configuration of the semiconductor laser device according to the second embodiment of the present invention. The second embodiment is different from the first embodiment in that a thin-film heat generating source 37 is used as a heat generating means and is interposed between a semiconductor laser chip 31 and a heat sink 32 by partially exposing the upper surface thereof. And one electrode of the power supply 21 is connected to the exposed portion via the switch 23. Other configurations are the same as those in the first embodiment, and thus, the same components are denoted by the same reference numerals as in the first embodiment, and description thereof is omitted.

The heat generating source 37 is configured to generate Joule heat when a current flows.
For example, it is made of electric resistance. Generally, a high-resistance material such as tungsten or ceramics is used. In the case of a semiconductor, silicon oxide or the like is manufactured during the process. The heat generation amount of the heat generation source 37 is set to be equal to the heat generation amount when the semiconductor laser chip 31 is driven. The heat source 37
Has a heat conduction function of transmitting heat generated from the semiconductor laser chip 31 to the heat sink 32.

Next, the operation of the second embodiment will be described. The switch 23 is switched to the semiconductor laser chip 31 side when the output of the semiconductor laser or the pulse drive is on, thereby generating a laser output. At this time, since no current flows through the heat generation source 37, no heat is generated. Therefore, the submount 34 is heated by heat generated by the semiconductor laser chip 31 at the time of laser output. Further, the heat of the submount 34 is transmitted to the heat sink 32 via the heat source 37.

On the other hand, when the output of the semiconductor laser is stopped or on standby, or when the pulse drive is off, the switch 23 is turned off.
Is switched to the heat generation source 37 side. As a result, the output of the laser beam is stopped, and a current flows through the heat generating source 37 to generate heat. Therefore, the submount 34 is heated by the heat generated by the heat source 37,
(Not shown) between the semiconductor laser chip 31 and the semiconductor laser chip 31
Has a high thermal conductivity, the semiconductor laser chip 31 is also heated to the same or substantially the same temperature as the submount 34. Therefore, no thermal distortion occurs between the semiconductor laser chip 31 and the submount 34.

The amount of heat generated by the heat generating source 37 is set to be equal to the amount of heat generated when the semiconductor laser chip 31 is driven. The temperature of the mount 34 is equal to or substantially equal to the temperature of the submount 34 when the semiconductor laser is output or when pulse driving is on. Therefore, even if the output of the semiconductor laser is stopped,
Since the temperature difference between the heat sink 32 and the submount 34 does not change, no heat cycle occurs between the heat sink 32 and the submount 34.

According to the second embodiment, when the output of the semiconductor laser is stopped or on standby, or when the pulse driving is turned off, the heat generating source 37 generates heat, and the heat sink 32 and the semiconductor laser chip 31 at that time are heated. Is substantially or the same as the temperature difference at the time of output of the semiconductor laser or the ON state of the pulse drive, and therefore, the semiconductor laser chip 31 and the heat sink 32 are different from the actual number of ON / OFF operations of the semiconductor laser. , The number of heat cycles due to the fluctuation of the temperature difference between the two can be reduced. Therefore, since the stress rupture limit of the bonding material between the semiconductor laser chip 31 and the heat sink 32 can be prevented from being lowered, the semiconductor laser can be used up to its original life without causing thermal destruction. it can.

Further, according to the second embodiment, since the heat generation amount of the heat generating source 37 is the same as or substantially the same as the heat generation amount of the semiconductor laser chip 31, the semiconductor laser device can be operated only by switching the switch 23. The output of the semiconductor laser can be switched on and off while controlling the heat generation amount to be constant.

Although the heat source 37 is provided between the heat sink 32 and the submount 34 in the second embodiment, the semiconductor laser chip 31 and the submount 3
4 may be provided.

Embodiment 3 FIG. FIG. 3 is a perspective view schematically showing a configuration of the semiconductor laser device according to the third embodiment of the present invention. The third embodiment is different from the first embodiment in that a radiant heat ray source 38 is used as heat generating means, and is provided on the opposite side of the heat sink 32 with the semiconductor laser chip 31 interposed therebetween, away from the semiconductor laser chip 31, The point is that the power source 21 is connected to the radiant heat ray source 38 via the switch 23. Other configurations are the same as those in the first embodiment, and thus, the same components are denoted by the same reference numerals as in the first embodiment, and description thereof is omitted.

The radiant heat ray source 38 generates heat by a configuration like an incandescent lamp, for example, and is made of, for example, electric resistance. The amount of heat generated by the radiation heat source 38 is set to be equal to the amount of heat generated when the semiconductor laser chip 31 is driven. The radiant heat ray source 38 is fixed inside a package (not shown) containing the semiconductor laser chip 31, the submount 34, and the heat sink 32, for example.

Next, the operation of the third embodiment will be described. The switch 23 is switched to the semiconductor laser chip 31 side when the output of the semiconductor laser or the pulse drive is on, thereby generating a laser output. At this time, since no current flows through the radiant heat ray source 38, no heat is generated. Therefore, the submount 34 is heated by heat generated by the semiconductor laser chip 31 at the time of laser output.

On the other hand, when the output of the semiconductor laser is stopped or on standby, or when the pulse drive is turned off, the switch 23 is turned off.
Is switched to the radiation heat source 38 side. As a result, the output of the laser beam stops, and a current flows through the radiant heat ray source 38 to generate heat. Accordingly, the semiconductor laser chip 31 is heated by the heat generated by the radiation heat ray source 38. However, since the bonding material (not shown) between the submount 34 and the semiconductor laser chip 31 has high thermal conductivity, the submount 34 is also heated to the same or substantially the same temperature as the semiconductor laser chip 31. Therefore, the semiconductor laser chip 31
No thermal distortion occurs between the submount 34 and the submount 34.

Since the amount of heat generated by the radiant heat source 38 is set to be equal to the amount of heat generated when the semiconductor laser chip 31 is driven, the sub-heating when the output of the semiconductor laser is stopped or in a standby state or when the pulse drive is turned off is turned off. The temperature of the mount 34 is
The temperature becomes the same or substantially the same as the temperature of the submount 34 when the semiconductor laser is output or when the pulse drive is on.
Therefore, even if the output of the semiconductor laser is stopped, the heat sink 3
Since the temperature difference between the submount 2 and the submount 34 does not change, no heat cycle occurs between the heat sink 32 and the submount 34.

According to the third embodiment, when the output of the semiconductor laser is stopped or on standby, or when the pulse drive is turned off, the radiant heat source 38 generates heat, and the heat sink 32 and the semiconductor laser chip 31 at that time are heated. Is substantially or the same as the temperature difference at the time of output of the semiconductor laser or the ON state of the pulse drive, and therefore, the semiconductor laser chip 31 and the heat sink 32 are different from the actual number of ON / OFF operations of the semiconductor laser. , The number of heat cycles due to the fluctuation of the temperature difference between the two can be reduced. Therefore, since the stress rupture limit of the bonding material between the semiconductor laser chip 31 and the heat sink 32 can be prevented from being lowered, the semiconductor laser can be used up to its original life without causing thermal destruction. it can.

Further, according to the third embodiment, the heat value of the radiant heat ray source 38 is the same as or approximately the same as the heat value of the semiconductor laser chip 31. The output of the semiconductor laser can be switched on and off while controlling the heat generation amount to be constant.

In the above, the present invention relates to the submount 34
Can be applied to a semiconductor laser device having a configuration in which the semiconductor laser chip 3 is omitted.
The power supply for the heat generating means may be provided independently of the power supply for the first unit, for example, by detecting the on / off state of the output of the semiconductor laser using a photodiode for monitoring or the like, and controlling the on / off of the power supply for the heat generating means based on the detected state. Alternatively, the temperature difference between the semiconductor laser chip 31 and the heat sink 32 may be accurately detected using a temperature detecting means such as a thermocouple or a radiation thermometer, and the heat generating means may be feedback-controlled based on the detected temperature difference.

Further, an integrated circuit in which the semiconductor laser chip 31, the heat generating means and the power supply circuit are integrated may be manufactured. In this case, since the heat generating means can be provided in a localized manner as compared with the case where the semiconductor laser chip 31 and the heat generating means are separated from each other, the occurrence of thermal distortion can be further reduced.

[0063]

As described above, according to the present invention, when the output of the semiconductor laser is stopped or on standby, or when the pulse drive is turned off, the heat generating means generates heat, and the heat sink and the semiconductor laser at that time are generated. Since the temperature difference with the chip approaches the temperature difference when the semiconductor laser is output or the pulse drive is on, the difference between the temperature of the semiconductor laser chip and the heat sink with respect to the actual number of times the semiconductor laser is turned on and off. The number of heat cycles due to fluctuation can be reduced. Therefore, it is possible to prevent the stress rupture limit of the bonding material between the semiconductor laser chip and the heat sink from being lowered, so that the semiconductor laser can be used up to the original life of the laser.

According to the next invention, when the output of the semiconductor laser is stopped or on standby, or when the pulse drive is turned off,
The semiconductor laser chip is heated by a heat source provided on the side opposite to the side from which the semiconductor laser chip emits laser light, and the temperature of the semiconductor laser chip at that time is the temperature at the time of output of the semiconductor laser or at the time of pulse drive ON. Therefore, the number of heat cycles can be reduced even when a heat generation source is provided on the side of the semiconductor laser chip opposite to the side from which laser light is emitted. Therefore, since the stress breakdown limit of the bonding material does not decrease, the semiconductor laser can be used up to its original life.

According to the next invention, when the output of the semiconductor laser is stopped or on standby, or when the pulse drive is turned off,
The semiconductor laser chip is heated by the thin-film heat source interposed between the semiconductor laser chip and the heat sink, and the temperature of the semiconductor laser chip at that time becomes the temperature at the time of output of the semiconductor laser or at the time of pulse drive ON. Therefore, the number of heat cycles can be reduced even when a thin-film heat source is provided between the semiconductor laser chip and the heat sink. Therefore, since the stress breakdown limit of the bonding material does not decrease, the semiconductor laser can be used up to its original life.

According to the next invention, when the output of the semiconductor laser is stopped or on standby, or when the pulse drive is turned off,
On the other side of the heat sink across the semiconductor laser chip,
The semiconductor laser chip is heated by a radiant heat ray source provided away from the semiconductor laser chip, and the temperature of the semiconductor laser chip at that time approaches the temperature at the time of output of the semiconductor laser or when pulse driving is on, so that the semiconductor laser chip is The number of heat cycles can also be reduced when a radiant heat ray source is provided on the opposite side of the heat sink between them. Therefore, since the stress breakdown limit of the bonding material does not decrease, the semiconductor laser can be used up to its original life.

According to the next invention, the temperature of the semiconductor laser chip is constantly or substantially kept constant by the heat generating means, so that even if the semiconductor laser is switched on and off, the temperature between the semiconductor laser chip and the heat sink is maintained. Since the temperature difference does not change at all or hardly changes, the number of heat cycles can be reduced with respect to the actual number of on / off times of the semiconductor laser. Therefore, it is possible to prevent the stress rupture limit of the bonding material between the semiconductor laser chip and the heat sink from being lowered, so that the semiconductor laser can be used up to the original life of the laser.

[Brief description of the drawings]

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

FIG. 2 is a perspective view schematically illustrating a configuration of a semiconductor laser device according to a second embodiment of the present invention;

FIG. 3 is a perspective view schematically illustrating a configuration of a semiconductor laser device according to a third embodiment of the present invention;

FIG. 4 is a characteristic diagram showing the relationship between the number of heat cycles at which a crack occurs in a PbSn solder joint and the amount of strain.

FIG. 5 is a perspective view schematically showing a configuration of a conventional semiconductor laser device.

[Explanation of symbols]

31 semiconductor laser chip, 32 heat sink, 36
Heat generating source (heat generating means), 37 Thin-film heat generating source (heat generating means), 38 radiant heat ray source (heat generating means).

Claims (5)

[Claims] 1. A semiconductor laser device in which a semiconductor laser chip and a heat sink for cooling the semiconductor laser chip are integrated, wherein a heat sink is provided when the output of the semiconductor laser is stopped or on standby, or when pulse driving is turned off. A semiconductor laser device comprising: heat generating means for generating heat so that the temperature difference between the semiconductor laser chip and the semiconductor laser chip approaches the temperature difference between the output of the semiconductor laser and the ON state of the pulse drive. 2. The semiconductor laser device according to claim 1, wherein said heat generating means comprises a heat generating source provided on a side of said semiconductor laser chip opposite to a side from which laser light is emitted. 3. The semiconductor laser device according to claim 1, wherein said heat generating means comprises a thin-film heat generating source interposed between a semiconductor laser chip and a heat sink. 4. The heat generating means according to claim 1, wherein said heat generating means comprises a radiant heat ray source provided on a side opposite to the heat sink with the semiconductor laser chip interposed therebetween and separated from the semiconductor laser chip. Semiconductor laser device. 5. A semiconductor laser device comprising: a semiconductor laser chip; and heat generating means capable of generating heat to keep the temperature of the semiconductor laser chip constant or substantially constant.