Semiconductor laser device and method for manufacturing the same

Abstract

The modulator-integrated semiconductor laser (100) comprises a semiconductor laser (101), and an electro-absorption modulator (102) and an optical attenuator (103) which are monolithically integrated in series at a subsequent stage of the semiconductor laser (101). The control unit (44) performs control in such a manner that the DC bias voltage applied to the optical attenuator (103) becomes larger as the temperature of the modulator-integrated semiconductor laser (100) rises.

Description

Technical Field

[0001] The present disclosure relates to a semiconductor laser device and a method for manufacturing the same. Background Art

[0002] In conventional uncooled modulator-integrated semiconductor lasers, two electro-absorption modulators having different absorption end wavelengths are integrated in series on the semiconductor laser. Thus, by modulating the laser light in mutually different temperature ranges, driving in a wide temperature range is achieved (for example, see Patent Document 1).

[0003] Patent Document 1: Japanese Patent Application Publication No. 2005-142230

[0004] However, in the conventional technology, in order to switch the input of the modulation signal to the two EA modulators when not in cooling use, complicated electrical wiring is required.

[0005] In addition, for semiconductor lasers, the higher the temperature, the lower the light output. Therefore, in the conventional modulator-integrated semiconductor lasers, in order to keep the average light output of the output end face constant regardless of the temperature, it is necessary to significantly reduce the DC bias current of the semiconductor laser on the low temperature side. If the DC bias current of the semiconductor laser is small, the laser oscillation becomes unstable during high-speed modulation, and there is a problem that the modulation waveform is degraded due to the return light from the output end face or other devices. Summary of the invention

[0006] The present disclosure is made to solve the above-mentioned problems, and its purpose is to obtain a semiconductor laser device and a manufacturing method thereof that can perform high-speed modulation of an uncooled modulator-integrated semiconductor laser in a wide temperature range without providing complex electrical wiring.

[0007] The semiconductor laser device involved in the present disclosure is characterized in that it comprises: a modulator-integrated semiconductor laser having a semiconductor laser, and an electro-absorption modulator and an optical attenuator which are monolithically integrated in a series manner on a subsequent stage of the semiconductor laser; and a control unit which controls in such a way that the DC bias voltage applied to the optical attenuator becomes larger as the temperature of the modulator-integrated semiconductor laser rises.

[0008] In the present disclosure, the DC bias voltage applied to the optical attenuator is controlled in such a way that the higher the temperature of the modulator integrated semiconductor laser rises, the larger it becomes. Thus, the average light output outputted from the output end face of the modulator integrated semiconductor laser becomes constant regardless of the temperature. Since it is not necessary to reduce the DC bias current of the semiconductor laser on the low temperature side, the modulation waveform will not deteriorate during high-speed modulation. Therefore, without providing complex electrical wiring, high-speed modulation of the non-cooled modulator integrated semiconductor laser can be performed within a wide temperature range. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a perspective view showing the modulator-integrated semiconductor laser according to the first embodiment.

[0010] Figure 2 It is along Figure 1 A cross-sectional view of a semiconductor laser cut along an AA line.

[0011] Figure 3 It is along Figure 1 A cross-sectional view of the electro-absorption modulator cut through BB.

[0012] Figure 4 It is along Figure 1 Cross-sectional view of the optical attenuator cut through CC.

[0013] Figure 5 It is along Figure 1 DD cutaway cross-sectional view.

[0014] Figure 6 This is a block diagram showing a semiconductor laser device according to the first embodiment.

[0015] Figure 7 This is a diagram showing the temperature dependency of the current / voltage of each portion for making the average light output from the emission end face of the modulator-integrated semiconductor laser according to the first embodiment constant.

[0016] Figure 8 It is a graph showing the wavelength dependence of two absorption coefficients and the laser oscillation wavelength.

[0017] Fig. 9 This is a diagram showing an adjustment algorithm for the bias current of the semiconductor laser, the electro-absorption modulator, and the DC bias voltage of the optical attenuator according to the first embodiment.

[0018] Fig.10 It is a cross-sectional view showing a modulator-integrated semiconductor laser according to the second embodiment.

[0019] Fig.11 This is a block diagram showing a semiconductor laser device according to the second embodiment.

[0020] Fig.12 This is a diagram showing the temperature dependency of the current / voltage of each portion so that the average light output from the emission end face of the modulator-integrated semiconductor laser according to the second embodiment becomes constant.

[0021] Fig.13 Graphs showing the photocurrent dependence of an electroabsorption modulator and an optical attenuator on a DC bias voltage.

[0022] Fig.14 This is a diagram showing an adjustment algorithm for the DC bias voltage of the electro-absorption modulator and the optical attenuator according to the second embodiment.

[0023] Fig.15 It is a cross-sectional view showing a modulator-integrated semiconductor laser according to the third embodiment.

[0024] Fig.16 This is a block diagram showing a semiconductor laser device according to a third embodiment.

[0025] Fig.17 This is a diagram showing the temperature dependency of the current / voltage of each portion so that the average light output from the emission end face of the modulator-integrated semiconductor laser according to the third embodiment becomes constant.

[0026] Fig.18 It is a cross-sectional view showing a modulator-integrated semiconductor laser according to a fourth embodiment.

[0027] Fig.19 It is a perspective view showing a modulator-integrated semiconductor laser according to the fifth embodiment. DETAILED DESCRIPTION

[0028] A semiconductor laser device and a method for manufacturing the same according to the embodiments will be described with reference to the accompanying drawings. The same or corresponding components are denoted by the same reference numerals in some cases, and repeated descriptions are omitted.

[0029] Implementation Method 1

[0030] Figure 11 is a perspective view showing a modulator-integrated semiconductor laser according to Embodiment 1. The modulator-integrated semiconductor laser 100 is a non-cooling type without a temperature control device, and has a semiconductor laser 101, an electro-absorption (EA: Electro-Absorption) modulator 102, and an optical attenuator 103, which are monolithically integrated on a semiconductor substrate. The semiconductor laser 101 is a distributed feedback laser diode (DFB-LD: Distributed feedback laser diode). The electro-absorption modulator 102 and the optical attenuator 103 are connected in series to the subsequent stage of the semiconductor laser 101. Separation regions 104a and 104b for electrical separation are provided between the semiconductor laser 101, the electro-absorption modulator 102, and the optical attenuator 103, respectively.

[0031] The semiconductor laser 101 has a surface electrode 201, the electro-absorption modulator 102 has a surface electrode 202, and the optical attenuator 103 has a surface electrode 203. In order to input a high-speed modulation signal to the electro-absorption modulator 102, the surface electrode 202 needs to be reduced in size. On the other hand, the optical attenuator 103 is DC driven, and in order to improve heat dissipation, the size of the surface electrode 203 and the contact area with the contact layer are preferably large. Therefore, the area of ​​the surface electrode 203 of the optical attenuator 103 is preferably larger than the area of ​​the surface electrode 202 of the electro-absorption modulator 102. In addition, the semiconductor laser 101, the electro-absorption modulator 102, and the optical attenuator 103 have a common back electrode 204.

[0032] Figure 2 It is along Figure 1 A cross-sectional view of a semiconductor laser cut along AA of FIG. A mesa strip 10 is formed along the direction of the optical axis of the laser. The semiconductor laser 101 has an n-type cladding layer 11, a diffraction grating layer 12, an n-type cladding layer 13, an active layer 14, a p-type cladding layer 15, a contact layer 16, a current blocking layer 17, an insulating film 18, a surface electrode 201, and a back electrode 204. The active layer 14 is a multi-quantum well structure.

[0033] Figure 3 It is along Figure 1 The cross-sectional view of the electro-absorption modulator cut along BB of FIG. The mesa strip 20 is formed continuously with the mesa strip 10 along the direction of the optical axis of the laser. The electro-absorption modulator 102 has an n-type cladding layer 11, a light absorbing layer 21, a p-type cladding layer 22, a contact layer 23, a current blocking layer 17, an insulating film 18, a surface electrode 202, and a back electrode 204. The light absorbing layer 21 has a multi-quantum well structure.

[0034] Figure 4 It is along Figure 1The cross-sectional view of the optical attenuator cut along CC of FIG. The mesa strip 30 is formed continuously with the mesa strips 10 and 20 along the direction of the optical axis of the laser. The optical attenuator 103 has an n-type cladding layer 11, a light absorbing layer 31, a p-type cladding layer 32, a contact layer 33, a current blocking layer 17, an insulating film 18, a surface electrode 203, and a back electrode 204. The light absorbing layer 31 also has a multi-quantum well structure, and attenuates the light output by the electric absorption effect similarly to the light absorbing layer 21 of the electro-absorption modulator 102.

[0035] Figure 5 It is along Figure 1 DD cut-away cross-sectional view. The semiconductor laser 101, the separation region 104a, the electro-absorption modulator 102, the separation region 104b, and the optical attenuator 103 are connected in series along the direction of the laser light axis. In the separation regions 104a and 104b, the contact layer and the electrode are removed, and an insulating film 18 is provided on the surface. The mesa strips are formed continuously.

[0036] In this example, although the optical attenuator 103 is an embedded structure based on the current blocking layer 17 of a semi-insulating material, it can also be a transistor structure formed by stacking pnp type or npn type, or a thyristor structure formed by stacking npnp type or pnpn type. In addition, instead of using the embedded structure, a ridge structure or a high table structure can be used. In addition, the semiconductor laser 101 and the electro-absorption modulator 102 are not limited to the embedded structure, and other structures can also be used. In addition, although the case of using an n-type substrate including an n-type cladding layer 11 is shown in this example, a p-type substrate can also be used.

[0037] Figure 6 1 is a block diagram showing a semiconductor laser device according to Embodiment 1. The driving unit 40 applies a DC bias current to the semiconductor laser 101. The driving unit 41 applies a DC bias voltage and a modulation signal to the electro-absorption modulator 102. The driving unit 42 applies a DC bias voltage to the optical attenuator 103. The thermistor 43 detects the temperature of the modulator-integrated semiconductor laser 100. Based on the temperature detected by the thermistor 43, the control unit 44 reads the value of the lookup table 45 and controls the current / voltage of the driving units 40, 41, and 42.

[0038] Figure 71 is a diagram showing the temperature dependence of the current / voltage of each part so that the average light output outputted from the output end face of the modulator integrated semiconductor laser involved in Embodiment 1 becomes constant. The DC bias current of the semiconductor laser 101 is constant and has nothing to do with the temperature. The DC bias voltage of the electro-absorption modulator 102 is selected in such a way that the extinction ratio becomes constant at each temperature. The DC bias voltage of the optical attenuator 103 is selected in such a way that the average light output becomes constant under such conditions.

[0039] Figure 8 It is a diagram showing the wavelength dependence of two absorption coefficients and the laser oscillation wavelength. Generally speaking, when the difference between the laser oscillation wavelength and the absorption end wavelength is large, such as absorption end wavelength 1, the absorption coefficient at the laser oscillation wavelength becomes smaller. When the difference between the laser oscillation wavelength and the absorption end wavelength is small, such as absorption end wavelength 2, the absorption coefficient at the laser oscillation wavelength becomes larger. Therefore, by increasing the difference between the laser oscillation wavelength and the absorption end wavelength, the loss can be reduced. On the other hand, when the loss is small, the extinction ratio at the same voltage becomes smaller. In the case of the optical attenuator 103 driven by a DC bias voltage, a relatively large voltage can be applied. However, since the electro-absorption modulator 102 needs to be driven by a modulation signal with a small amplitude voltage, it is necessary to reduce the difference between the laser oscillation wavelength and the absorption end wavelength. Therefore, it is preferred to make the absorption end wavelength of the light absorption layer 31 of the optical attenuator 103 shorter than the absorption end wavelength of the light absorption layer 21 of the electro-absorption modulator 102. Thus, the loss of light output can be reduced.

[0040] Calculated through inspection during manufacturing Figure 7 The temperature dependence of the current / voltage of each part shown is calculated, and the driving conditions at each temperature are stored in the lookup table 45. If the condition is set so that the range of the DC bias voltage of the optical attenuator 103 becomes wider than the range of the DC bias voltage of the electro-absorption modulator 102, it is easy to achieve both the reduction of the optical output variation between temperatures and the reduction of the optical loss.

[0041] Fig. 9 1 is a diagram showing an adjustment algorithm for the bias current of the semiconductor laser, the DC bias voltage of the electro-absorption modulator, and the optical attenuator involved in Embodiment 1. First, the thermistor 43 detects the temperature of the modulator-integrated semiconductor laser 100. Next, the control unit 44 reads the detected temperature and uses the lookup table 45 to read the DC bias current of the semiconductor laser 101, the DC bias voltage of the electro-absorption modulator 102, and the optical attenuator 103 corresponding to the temperature. The control unit 44 sets the DC bias current of the semiconductor laser 101, the DC bias voltage of the electro-absorption modulator 102, and the optical attenuator 103 respectively in such a way that they become the read values. Since Figure 7The graph is a function that increases monotonically with respect to temperature within a specified range, so it can be set to a unique voltage value and current value. In addition, this function is obtained by checking each element. Although the DC bias current of semiconductor laser 101 is set to a constant condition in the present embodiment, it can also be adjusted according to the temperature.

[0042] In manufacturing the modulator-integrated semiconductor laser 100 of the present embodiment, the light absorption layer 31 of the optical attenuator 103 and the light absorption layer 21 of the electro-absorption modulator 102 are integrated by butt joint growth. Alternatively, the light absorption layer 31 of the optical attenuator 103 and the light absorption layer 21 of the electro-absorption modulator 102 may be epitaxially grown simultaneously using a selective growth mask.

[0043] In the present embodiment, the DC bias voltage applied to the optical attenuator 103 is controlled in such a way that the more the temperature of the modulator integrated semiconductor laser 100 rises, the greater the DC bias voltage becomes. Thus, the average light output from the output end face of the modulator integrated semiconductor laser 100 becomes constant regardless of the temperature. Since it is not necessary to reduce the DC bias current of the semiconductor laser on the low temperature side, the modulation waveform will not deteriorate during high-speed modulation. Therefore, without providing complex electrical wiring, high-speed modulation of the modulator integrated semiconductor laser 100 of the non-cooling type can be performed in a wide temperature range.

[0044] Implementation Method 2

[0045] Fig.10 1 is a cross-sectional view showing a modulator-integrated semiconductor laser according to Embodiment 2. In Embodiment 1, an optical attenuator 103 is integrated at the rear stage of the electro-absorption modulator 102, but in this embodiment, an optical attenuator 103 is integrated at the front stage of the electro-absorption modulator 102. The optical attenuator 103 attenuates the output light of the semiconductor laser 101. The electro-absorption modulator 102 modulates the output light of the optical attenuator 103. The output light of the electro-absorption modulator 102 is output from the emission end face of the modulator-integrated semiconductor laser 100. Thus, since the intensity of the optical signal input to the electro-absorption modulator 102 can be reduced to an appropriate level, the noise of the modulated optical signal can be reduced compared to Embodiment 1.

[0046] Fig.11 1 is a block diagram showing a semiconductor laser device according to Embodiment 2. The photocurrent detector 46 detects the photocurrent flowing in the optical attenuator 103. The control unit 44 reads the value of the lookup table 45 based on the detected photocurrent and sets the current / voltage of each part.

[0047] Fig.12This is a diagram showing the temperature dependence of the current / voltage of each part so that the average light output outputted from the output end face of the modulator-integrated semiconductor laser involved in Embodiment 2 becomes constant. The photocurrent is measured in a state where a DC bias voltage optimized at each temperature is applied to the optical attenuator 103. The temperature dependence of the DC bias current of the semiconductor laser 101, the DC bias voltage of the electro-absorption modulator 102, the DC bias voltage of the optical attenuator 103, and the photocurrent flowing in the optical attenuator 103 are obtained through inspection during manufacturing.

[0048] Fig.13 is a graph showing the dependence of photocurrent on DC bias voltage for electroabsorption modulators and optical attenuators. Fig.12 The DC bias voltage of the electro-absorption modulator 102 and the optical attenuator 103 is converted into a function of the photocurrent and stored in the lookup table 45.

[0049] Fig.14 1 is a diagram showing an adjustment algorithm for the DC bias voltage of the electro-absorption modulator and the optical attenuator according to Embodiment 2. First, the photocurrent detector 46 detects the photocurrent flowing in the optical attenuator 103. Next, the control unit 44 reads the detected photocurrent and uses the lookup table 45 to read the DC bias voltage of the electro-absorption modulator 102 and the optical attenuator 103 corresponding to the photocurrent. The control unit 44 sets the DC bias voltage of the electro-absorption modulator 102 and the optical attenuator 103 to the read value. Fig.13 The graph of is a monotonically increasing function with respect to the photocurrent within a specified range, so a unique voltage value can be set for the photocurrent.

[0050] Implementation 3

[0051] Fig.15 1 is a cross-sectional view showing a modulator integrated semiconductor laser involved in Embodiment 3. In the separation region 104a between the semiconductor laser 101 and the optical attenuator 103, and the separation region 104b between the optical attenuator 103 and the electro-absorption modulator 102, transparent waveguides 105a and 105b as passive waveguides are respectively provided. In addition, although passive waveguides are provided on both sides, passive waveguides can also be provided only on either side. Although the electro-absorption modulator 102 becomes the light emission end face, a passive waveguide can also be provided between the electro-absorption modulator 102 and the emission end face. That is, a passive waveguide is provided between any one of the semiconductor laser 101, the electro-absorption modulator 102, the optical attenuator 103, and the emission end face. Thus, the loss of light in the waveguide can be reduced. In addition, a window structure that reduces the reflectivity of the end face can also be provided between the electro-absorption modulator 102 and the emission end face.

[0052] Fig.16 : is a block diagram showing a semiconductor laser device according to Embodiment 3. Based on the temperature detected by the thermistor 43 , the control unit 44 reads the value of the lookup table and sets the current / voltage of each part.

[0053] Fig.17 1 is a diagram showing the temperature dependence of the current / voltage of each part so that the average light output outputted from the output end face of the modulator integrated semiconductor laser involved in Embodiment 3 becomes constant. In this embodiment, the DC bias current of the semiconductor laser 101 is also adjusted according to the temperature. Thus, the average light output can be set to a target value in a wider temperature range.

[0054] Implementation 4

[0055] Fig.18 1 is a cross-sectional view showing a modulator-integrated semiconductor laser according to Embodiment 4. In this embodiment, the light absorption layer 21 of the electro-absorption modulator 102 and the light absorption layer 31 of the optical attenuator 103 have the same layer structure. In this case, the light absorption layer 31 of the optical attenuator 103 and the light absorption layer 21 of the electro-absorption modulator 102 can be epitaxially grown simultaneously using a selective growth mask. Thus, the number of epitaxial growths during manufacturing can be reduced.

[0056] Implementation method 5

[0057] Fig.19 1 is a perspective view showing a modulator-integrated semiconductor laser according to Embodiment 5. In this embodiment, in order to improve the heat dissipation in the optical attenuator 103, the process table width in the optical attenuator 103 is made wider than that in the electro-absorption modulator 102. Therefore, the contact area between the contact layer 33 of the optical attenuator 103 and the surface electrode 203 becomes larger than the contact area between the contact layer 23 of the electro-absorption modulator 102 and the surface electrode 202. As a result, on the high temperature side where it is difficult to obtain light output, the temperature rise of the light absorption layer 31 of the optical attenuator 103 caused by the photocurrent can be suppressed, thereby reducing the loss of light.

[0058] Description of Reference Numerals

[0059] 21...light absorption layer of electroabsorption modulator; 23, 33...contact layer; 31...light absorption layer of optical attenuator; 43...thermistor; 44...control unit; 45...lookup table; 100...modulator integrated semiconductor laser; 101...semiconductor laser; 102...electroabsorption modulator; 103...optical attenuator; 105a, 105b...transparent waveguide (passive waveguide); 202, 203...surface electrode.

Claims

1. A semiconductor laser device, characterized in that: have: A modulator-integrated semiconductor laser having a semiconductor laser, and an electro-absorption modulator and an optical attenuator monolithically integrated in series at a subsequent stage of the semiconductor laser; and a control unit configured to control the optical attenuator so that the DC bias voltage applied as a reverse bias to the optical attenuator increases as the temperature of the modulator-integrated semiconductor laser increases, thereby controlling the average light output output from the output end face of the modulator-integrated semiconductor laser to be constant regardless of the temperature; The DC bias current of the semiconductor laser is constant regardless of temperature, The control unit reads a DC bias current of the semiconductor laser corresponding to the temperature from a lookup table to set the DC bias current, reads a DC bias voltage of the electro-absorption modulator corresponding to the temperature from the lookup table to set the DC bias current, and reads a DC bias voltage of the optical attenuator corresponding to the temperature from the lookup table to set the DC bias voltage. The lookup table stores temperature dependencies of the DC bias current of the semiconductor laser, the DC bias voltage of the electro-absorption modulator, and the DC bias voltage of the optical attenuator obtained through inspection during manufacturing.

2. The semiconductor laser device according to claim 1, wherein The modulator-integrated semiconductor laser has no temperature control device.

3. The semiconductor laser device according to claim 1 or 2, characterized in that: A thermistor for detecting the temperature of the modulator-integrated semiconductor laser is also provided.

4. The semiconductor laser device according to claim 1 or 2, characterized in that: The electro-absorption modulator modulates the output light of the semiconductor laser. The optical attenuator attenuates the output light of the electro-absorption modulator. The output light of the optical attenuator is output from the output end face of the modulator integrated semiconductor laser.

5. The semiconductor laser device according to claim 1 or 2, characterized in that: The optical attenuator attenuates the output light of the semiconductor laser. The electro-absorption modulator modulates the output light of the optical attenuator. The output light of the electro-absorption modulator is output from the output end face of the modulator-integrated semiconductor laser.

6. The semiconductor laser device according to claim 1 or 2, characterized in that: The absorption end wavelength of the light absorption layer of the optical attenuator is shorter than the absorption end wavelength of the light absorption layer of the electro-absorption modulator.

7. The semiconductor laser device according to claim 1 or 2, characterized in that: The area of ​​the electrode of the optical attenuator is larger than the area of ​​the electrode of the electro-absorption modulator.

8. The semiconductor laser device according to claim 1 or 2, characterized in that: The DC bias voltage adjustment range of the optical attenuator is wider than the DC bias voltage adjustment range of the electro-absorption modulator.

9. The semiconductor laser device according to claim 1 or 2, characterized in that: The light absorbing layer of the electro-absorption modulator and the light absorbing layer of the optical attenuator have different layer structures.

10. The semiconductor laser device according to claim 1 or 2, characterized in that: The light absorbing layer of the electro-absorption modulator and the light absorbing layer of the optical attenuator have the same layer structure.

11. The semiconductor laser device according to claim 1 or 2, characterized in that: The modulator-integrated semiconductor laser has a passive waveguide between any one of the semiconductor laser, the electro-absorption modulator, the optical attenuator, and an output end face.

12. The semiconductor laser device according to claim 1 or 2, characterized in that: The contact area between the contact layer of the optical attenuator and the electrode is larger than the contact area between the contact layer of the electro-absorption modulator and the electrode.

13. A method for manufacturing a semiconductor laser device, the method for manufacturing a semiconductor laser device according to any one of claims 1 to 12, characterized in that: The light absorbing layer of the optical attenuator and the light absorbing layer of the electro-absorption modulator are integrated by butt-jointing growth.

14. A method for manufacturing a semiconductor laser device, the method for manufacturing a semiconductor laser device according to any one of claims 1 to 12, characterized in that: The light absorbing layer of the optical attenuator and the light absorbing layer of the electro-absorption modulator are epitaxially grown simultaneously using a selective growth mask.

15. A semiconductor laser device, characterized in that: have: A modulator-integrated semiconductor laser having a semiconductor laser, and an electro-absorption modulator and an optical attenuator monolithically integrated in series at a subsequent stage of the semiconductor laser; and a control unit configured to control the optical attenuator so that the DC bias voltage applied as a reverse bias to the optical attenuator increases as the temperature of the modulator-integrated semiconductor laser increases, thereby controlling the average light output output from the output end face of the modulator-integrated semiconductor laser to be constant regardless of the temperature; The DC bias current of the semiconductor laser is constant regardless of temperature, The control unit reads a DC bias current of the semiconductor laser corresponding to the photocurrent flowing in the optical attenuator from a lookup table to set the DC bias current, reads a DC bias voltage of the electro-absorption modulator corresponding to the photocurrent from the lookup table to set the DC bias current, and reads a DC bias voltage of the optical attenuator corresponding to the photocurrent from the lookup table to set the DC bias current. The DC bias current of the semiconductor laser, the DC bias voltage of the electro-absorption modulator, the DC bias voltage of the optical attenuator, and the temperature dependence of the photocurrent flowing in the optical attenuator are determined through inspection during manufacturing, and the DC bias voltage of the electro-absorption modulator and the DC bias voltage of the optical attenuator are converted into functions of the photocurrent and stored in the lookup table.

16. The semiconductor laser device according to claim 15, wherein: The modulator-integrated semiconductor laser has no temperature control device.

17. The semiconductor laser device according to claim 15 or 16, characterized in that: A thermistor for detecting the temperature of the modulator-integrated semiconductor laser is also provided.

18. The semiconductor laser device according to claim 15 or 16, characterized in that: The electro-absorption modulator modulates the output light of the semiconductor laser. The optical attenuator attenuates the output light of the electro-absorption modulator. The output light of the optical attenuator is output from the output end face of the modulator integrated semiconductor laser.

19. The semiconductor laser device according to claim 15 or 16, characterized in that: The optical attenuator attenuates the output light of the semiconductor laser. The electro-absorption modulator modulates the output light of the optical attenuator. The output light of the electro-absorption modulator is output from the output end face of the modulator-integrated semiconductor laser.

20. The semiconductor laser device according to claim 15 or 16, characterized in that: The absorption end wavelength of the light absorption layer of the optical attenuator is shorter than the absorption end wavelength of the light absorption layer of the electro-absorption modulator.

21. The semiconductor laser device according to claim 15 or 16, characterized in that: The area of ​​the electrode of the optical attenuator is larger than the area of ​​the electrode of the electro-absorption modulator.

22. The semiconductor laser device according to claim 15 or 16, characterized in that: The DC bias voltage adjustment range of the optical attenuator is wider than the DC bias voltage adjustment range of the electro-absorption modulator.

23. The semiconductor laser device according to claim 15 or 16, characterized in that: The light absorbing layer of the electro-absorption modulator and the light absorbing layer of the optical attenuator have different layer structures.

24. The semiconductor laser device according to claim 15 or 16, characterized in that: The light absorbing layer of the electro-absorption modulator and the light absorbing layer of the optical attenuator have the same layer structure.

25. The semiconductor laser device according to claim 15 or 16, characterized in that: The modulator-integrated semiconductor laser has a passive waveguide between any one of the semiconductor laser, the electro-absorption modulator, the optical attenuator, and an output end face.

26. The semiconductor laser device according to claim 15 or 16, characterized in that: The contact area between the contact layer of the optical attenuator and the electrode is larger than the contact area between the contact layer of the electro-absorption modulator and the electrode.

27. A method for manufacturing a semiconductor laser device, the method for manufacturing a semiconductor laser device according to any one of claims 15 to 26, characterized in that: The light absorbing layer of the optical attenuator and the light absorbing layer of the electro-absorption modulator are integrated by butt-jointing growth.

28. A method for manufacturing a semiconductor laser device, the method for manufacturing a semiconductor laser device according to any one of claims 15 to 26, characterized in that: The light absorbing layer of the optical attenuator and the light absorbing layer of the electro-absorption modulator are epitaxially grown simultaneously using a selective growth mask.

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