Semiconductor laser device inspection method and semiconductor laser device inspection device

Abstract

The inspection method of a semiconductor laser device is to use a semiconductor laser device formed by integrating a semiconductor laser (1), an electric field absorption modulator (2) to which the output of the semiconductor laser is input, and a photodetector (4) for detecting the laser intensity of a part of the laser light output by the semiconductor laser as an inspection object, and comprises: a step (ST1) of obtaining a transverse mode light output characteristic, which is a relationship between an injection current of the semiconductor laser and an output of the photodetector (4); a step (ST3) of obtaining a total light output characteristic, which is a relationship between an injection current of the semiconductor laser (1) and a photocurrent output by the electric field absorption modulator (2) while applying a reverse bias voltage to the electric field absorption modulator (2); and a step (ST4) of comparing the total light output characteristic with the transverse mode light output characteristic to determine whether the semiconductor laser device (100) to be inspected is transverse mode abnormal.

Description

Technical Field

[0001] The present application relates to a method for inspecting a semiconductor laser device and an apparatus for inspecting a semiconductor laser device. Background Art

[0002] As a signal transmission light source in optical communication, a semiconductor laser device that can respond to high-speed electrical signals is used. The semiconductor laser device outputs a laser whose intensity is modulated according to the received electrical signal. The laser is introduced into the optical fiber via a focusing lens, and the optical signal is transmitted through the optical fiber. In order to maintain the quality of the optical signal, single-mode optical fiber is generally used in the field of optical communication. Therefore, in order to obtain high optical coupling with the single-mode optical fiber, the semiconductor laser provided to the semiconductor laser device is also designed to output a single-mode laser.

[0003] Semiconductor lasers, due to their manufacturing deviations, sometimes produce disturbances in the oscillation mode called kink due to increased injection current (Iop). For example, in the case of a semiconductor laser with a waveguide structure of a gain-guided type, the transverse mode tends to become unstable because there is no refractive index difference to limit the light in the lateral direction. In a semiconductor laser with such a structure, if Iop is increased, the gain distribution near the light-emitting area where carrier consumption is intense is destroyed, resulting in the multi-mode of the transverse mode. Even if it is single-mode when driven at a low current, it will become multi-mode with multiple peaks when driven at a high current. If it changes from single-mode to multi-mode, the FFP (Far Field Pattern) of the laser beam changes. If the FFP changes at Iop within the actual use range, it will cause changes in the optical coupling efficiency between the output of the semiconductor laser device and the single-mode optical fiber, and the quality of the optical signal will decrease. Therefore, in the manufacturing process of a semiconductor laser device having a built-in semiconductor laser, it is preferred to immediately perform an inspection to confirm the quality of the transverse mode after the semiconductor laser device is manufactured based on the wafer process, and remove the semiconductor laser device with abnormal transverse mode as a defective product in advance at the early stage of the assembly process for assembling the semiconductor package. This can reduce the waste of component costs and processing fees that may be generated in the assembly process or the subsequent testing process.

[0004] As a means of removing such semiconductor lasers with abnormal transverse modes, the following method is disclosed in Patent Document 1: a photodetector is arranged in a manner to receive a part of the emitted light of the diffused semiconductor laser, and the Iop dependency (PI curve) of the light output is measured to detect the change of the transverse mode. Since the photodetector only receives a part of the diffused light emitted by the semiconductor laser, a linear PI curve is obtained when measuring a semiconductor laser with a stable transverse mode, but when measuring a semiconductor laser with an unstable transverse mode, since the proportion of the light received by the photodetector in the total emitted light changes, a non-linear PI curve is obtained, and the change of FFP can be detected.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 10-284780

[0006] In the method for distinguishing a semiconductor laser with unstable and abnormal transverse mode disclosed in Patent Document 1, a light detector configured to receive a portion of the emitted light of the semiconductor laser is required as an inspection device. Therefore, it is necessary to configure the semiconductor laser device to be inspected at a position that forms a certain relationship with the light detector, and the inspection sequence becomes cumbersome. In addition, according to the semiconductor laser, even if the transverse mode remains single-mode unchanged, the Iop dependence of the light output will not become completely linear, and it is impossible to accurately determine the semiconductor laser device with abnormal transverse mode only by the PI curve of a portion of the diffused light. Summary of the invention

[0007] The present application discloses a technology for solving the above-mentioned problems, and aims to provide a semiconductor laser device inspection method and a semiconductor laser device inspection device capable of accurately determining a semiconductor laser device with abnormal transverse mode.

[0008] The inspection method of the semiconductor laser device disclosed in the present application takes the semiconductor laser device which integrates a semiconductor laser, an electric field absorption modulator, and a photodetector as the inspection object, the output of the semiconductor laser is input to the electric field absorption modulator, and the photodetector detects the laser intensity of a part of the laser output by the semiconductor laser. The inspection method of the semiconductor laser device comprises the following steps: a step of obtaining the transverse mode light output characteristic, wherein the transverse mode light output characteristic is the relationship between the injection current of the semiconductor laser and the output of the photodetector; a step of obtaining the total light output characteristic while applying a reverse bias voltage to the electric field absorption modulator, wherein the total light output characteristic is the relationship between the injection current of the semiconductor laser and the photocurrent output by the electric field absorption modulator; and a step of comparing the total light output characteristic with the transverse mode light output characteristic to determine whether the semiconductor laser device to be inspected is transverse mode abnormal.

[0009] The inspection device for a semiconductor laser device disclosed in the present application takes a semiconductor laser device that integrates a semiconductor laser, an electric field absorption modulator, and a photodetector as an inspection object, the output of the semiconductor laser is input to the electric field absorption modulator, and the photodetector detects the laser intensity of a part of the laser output by the semiconductor laser. The inspection device for a semiconductor laser device comprises: a semiconductor laser power supply that supplies an injection current to the semiconductor laser; an electric field absorption modulator power supply that supplies a reverse bias voltage to the electric field absorption modulator; a photodetector power supply that supplies a reverse bias voltage to the photodetector; and an inspection controller that is configured to control the semiconductor laser power supply, the electric field absorption modulator power supply, and the photodetector power supply, obtain a transverse mode light output characteristic that is a relationship between the injection current of the semiconductor laser and the output of the photodetector, and a total light output characteristic that is a relationship between the injection current of the semiconductor laser and the photocurrent output by the electric field absorption modulator, and compare the total light output characteristic with the transverse mode light output characteristic to determine whether the semiconductor laser device to be inspected is transverse mode abnormal.

[0010] The second inspection method of the semiconductor laser device disclosed in the present application takes a semiconductor laser device that integrates a semiconductor laser and an electric field absorption modulator as an inspection object, and the output of the semiconductor laser is input to the electric field absorption modulator. The second inspection method of the semiconductor laser device comprises the following steps: a step of obtaining a transverse mode light output characteristic, which is a relationship between an injection current of the semiconductor laser and an output of a photodetector that detects a portion of the laser intensity output by the semiconductor laser device that is the inspection object; a step of obtaining a total light output characteristic while applying a reverse bias voltage to the electric field absorption modulator, which is a relationship between the injection current of the semiconductor laser and the photocurrent output by the electric field absorption modulator; and a step of comparing the total light output characteristic with the transverse mode light output characteristic to determine whether the semiconductor laser device that is the inspection object has a transverse mode abnormality.

[0011] The third inspection method for a semiconductor laser device disclosed in the present application takes a semiconductor laser device having a semiconductor laser as an inspection object, and the third inspection method for a semiconductor laser device comprises the following steps: a step of obtaining a transverse mode light output characteristic, wherein the transverse mode light output characteristic is a relationship between an injection current of the semiconductor laser and an output of a photodetector that detects a portion of the laser intensity outputted by the semiconductor laser device that is the inspection object; a step of obtaining a total light output characteristic, wherein the total light output characteristic is a relationship between an injection current of the semiconductor laser and an output of a photodetector that detects the total laser intensity outputted by the semiconductor laser device that is the inspection object; and a step of comparing the total light output characteristic with the transverse mode light output characteristic to determine whether the semiconductor laser device that is the inspection object has a transverse mode abnormality.

[0012] According to the present application, there is an effect of being able to provide a semiconductor laser device inspection method and a semiconductor laser device inspection device that can accurately determine a semiconductor laser device in which a lateral mode has fluctuated. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 1 is a schematic diagram showing the structure of the inspection apparatus for semiconductor laser devices according to the first embodiment and the semiconductor laser device to be inspected.

[0014] Figure 2 1 is a plan view showing a semiconductor laser device to be inspected by the inspection apparatus for semiconductor laser devices according to the first embodiment.

[0015] Figure 3A , Figure 3B This is a diagram showing the radiation angle characteristics of laser light in a semiconductor laser device in which the transverse mode is normal.

[0016] Figure 4A , Figure 4B This is a diagram showing radiation angle characteristics of laser light from a semiconductor laser device with abnormal transverse mode.

[0017] Figure 5A , Figure 5B It is a diagram showing the total light output characteristics and the transverse mode output characteristics of laser light of a semiconductor laser device in which the transverse mode is normal.

[0018] Fig. 6A , Figure 6B The diagrams show total light output characteristics and transverse mode output characteristics of laser light in a semiconductor laser device with transverse mode abnormality.

[0019] Figure 7 This is a flowchart illustrating the procedure of the inspection method of the semiconductor laser device according to the first embodiment.

[0020] Figure 8 1 is a schematic diagram showing the structure of a semiconductor laser device inspection apparatus according to a second embodiment and a semiconductor laser device to be inspected.

[0021] Fig.9A , Fig. 9B This is a characteristic diagram for explaining the inspection method of the semiconductor laser device according to the third embodiment.

[0022] Fig. 10A , Fig. 10B This is a characteristic diagram for explaining the inspection method of the semiconductor laser device according to the fourth embodiment.

[0023] Figures 11A to 11E This is a diagram for explaining a method for inspecting a semiconductor laser device according to a fifth embodiment.

[0024] Fig.12 It is a schematic diagram showing the structure of a semiconductor laser device inspection apparatus according to Embodiment 6 and a semiconductor laser device to be inspected.

[0025] Fig.13 It is a schematic diagram showing the structure of a semiconductor laser device inspection apparatus according to a seventh embodiment and a semiconductor laser device to be inspected.

[0026] Fig.14 This is a flowchart for explaining the procedure of the inspection method of the semiconductor laser device according to the seventh embodiment.

[0027] Fig.15 This is a block diagram showing an example of the hardware configuration of the inspection controller of the present application. DETAILED DESCRIPTION

[0028] Implementation Method 1

[0029] Figure 1 1 is a schematic diagram showing the configuration of a semiconductor laser device inspection apparatus 11 and a semiconductor laser device 100 to be inspected according to Embodiment 1. The semiconductor laser device inspection apparatus 11 is shown in a block diagram, and the semiconductor laser device 100 is shown in a schematic side cross-sectional view. Figure 2 A top view of the semiconductor laser device 100 is shown, and Figure 1 The semiconductor laser device 100 is Figure 2 The cross-sectional view at the position AA' of FIG. 1 is shown. The semiconductor laser device 100 integrates a semiconductor laser (also called LD) 1 and an electric field absorption modulator (also called EAM) 2 into a single chip, and couples the optical waveguides of the two. Therefore, the laser light output by LD1 is introduced into EAM2 with low loss. In addition, near the chip end face (front end face) on the output side of EAM2, that is, on the EAM2 side, a window structure 31 having a lower refractive index than that of EAM2 is formed. The laser light output by LD1 is radiated while diffusing toward the window structure 31 through EAM2. A photodetector (also called PD) 4 serving as a light monitor is formed near the window structure 31 in a manner that receives a portion of the diffused light.

[0030] Both EAM2 and PD4 absorb incident light by applying a reverse bias voltage and output a photocurrent. Thereafter, the photocurrent output by EAM2 is set to Iea, and the photocurrent output by PD4 is set to Im. The inspection device 11 for a semiconductor laser device comprises: an LD (semiconductor laser) power supply 5 for supplying an injection current to LD1, an EAM (electric field absorption modulator) power supply 6 for supplying a reverse bias voltage to EAM2, and a PD (photodetector) power supply 7 for supplying a reverse bias voltage to PD4. The LD power supply 5 comprises a current detector 51 for detecting the current flowing to LD1, namely, the LD injection current Iop, and the EAM power supply 6 comprises a photocurrent detector 61 for detecting Iea. Furthermore, the PD power supply 7 comprises a photocurrent detector 71 for detecting Im. These current detectors 51, photocurrent detectors 61, and photocurrent detectors 71 can of course also be provided separately from their respective power supplies. The inspection device 11 for semiconductor laser devices further includes an inspection controller 10 that controls the LD power supply 5 , the EAM power supply 6 , and the PD power supply 7 to obtain data of Iop, Iea, and Im.

[0031] Under normal circumstances, the photocurrent outputted by EAM2 and PD4 is designed to be proportional to the input optical power. Therefore, if the optical power incident on EAM2 and PD4 increases linearly, the photocurrents Iea and Im outputted by the two also increase linearly.

[0032] Since EAM2 and the optical waveguide of LD1 are formed continuously and coupled with low loss, EAM2 absorbs most of the laser light outputted by LD1. On the other hand, PD4 receives part of the laser light diffused in the window structure 31 and absorbs only part of the transverse mode of the laser light outputted by LD1.

[0033] exist Figure 3A as well as Figure 3B The figure shows the radiation angle of the output laser when the lateral mode is driven at low current and when the lateral mode is driven at high current in the case of a semiconductor laser device with normal lateral mode and the lateral mode does not vary depending on Iop. When the lateral mode is normal, there is no variation in the radiation angle and the FFP does not vary when the lateral mode is driven at low current and when the lateral mode is driven at high current. Figure 4A as well as Figure 4B The figure shows the radiation angle of the output laser when driven by low current and when driven by high current in the case of a semiconductor laser device with a transverse mode abnormality in which the transverse mode varies depending on Iop. In the case of a transverse mode abnormality, it is single-mode when driven by low current, but becomes multi-mode when driven by high current, and the radiation mode of light changes from that when driven by low current, and the FFP changes.

[0034] exist Figure 5A as well as Figure 5BThe Iop dependence of Iea (hereinafter referred to as the Iea-I curve, or the total light output characteristic) and the Iop dependence of Im (hereinafter referred to as the Im-I curve, or the transverse mode light output characteristic) when the transverse mode is normal are shown respectively. When the transverse mode does not change due to Iop, the ratio of the light received by EAM2 to the total laser output and the ratio of the light received by the photodetector PD4 to the total laser output do not change, so the Iea-I curve and the Im-I curve obtain similar waveforms. Figure 5A , Figure 5B In the figure, as an example, the Iea-I curve and the Im-I curve of a semiconductor laser whose luminous efficiency is saturated in the high current region are shown, but both are linear in the low current region and non-linear in the high current region, and become similar waveforms.

[0035] exist Fig. 6A as well as Figure 6B An example of the Iea-I curve and the Im-I curve in the case of abnormal transverse mode is shown respectively. Since EAM2 receives most of the transverse mode, even if the transverse mode changes, the change in the ratio of the light received by EAM2 to the total laser output is small. On the other hand, since the photodetector PD4 only receives a part of the transverse mode, if the transverse mode changes, the change in the ratio of the light received by the photodetector PD4 to the total laser output is large. Therefore, the Iea-I curve and the Im-I curve obtain different waveforms. Fig. 6A as well as Figure 6B ,and Figure 5A as well as Figure 5B Similarly, the Iea-I curve and the Im-I curve are shown in the case of a semiconductor laser in which the luminous efficiency of LD1 is saturated in a high current region. Fig. 6A The Iea-I curve shown becomes Figure 5A Same as above, only in the high current region the waveform becomes nonlinear, but Figure 6B The Im-I curve shown in the figure becomes nonlinear in a smaller current region, and the two become different waveforms.

[0036] Based on the above, by measuring both the Iea-I curve and the Im-I curve and determining the element with a large difference between the two as a transverse mode anomaly, it is possible to eliminate semiconductor laser devices with transverse mode anomalies in which the transverse mode varies depending on Iop.

[0037] Figure 7 This is a flowchart summarizing the inspection method of the semiconductor laser device according to the first embodiment. Figure 1 as well as Figure 2The semiconductor laser device 100 shown is the inspection object. First, the inspection controller 10 controls the LD power supply 5, changes the injection current Iop of the LD, and measures the output of the PD4, that is, the photocurrent Im, to obtain the transverse mode light output characteristic, that is, the Im-I curve (step ST1). At this time, in order to allow the laser to pass through the EAM2, it is preliminarily set to a state where no reverse bias voltage is applied to the EAM2, or a reverse bias voltage is applied to the degree that does not absorb the laser light significantly. Next, the inspection controller 10 controls the EAM power supply 6, and applies a reverse bias voltage to the EAM2 to the degree that absorbs light (step ST2). In the state where the reverse bias voltage is applied to the EAM2, the inspection controller 10 controls the LD power supply 5, changes the injection current Iop of the LD, and measures the output of the EAM2, that is, the photocurrent Iea, to obtain the total light output characteristic, that is, the Iea-I curve (step ST3). Next, the obtained transverse mode light output characteristic and the total light output characteristic are compared to determine whether the LD of the semiconductor laser device of the inspection object is transverse mode abnormal (step ST4). Among them, steps ST2 and ST3 can also be performed before step ST1. In this case, when executing step ST1 , the EAM 2 is of course set in advance to a state where no reverse bias voltage is applied or a reverse bias voltage is applied to a degree that does not significantly absorb the laser light in order to allow the laser light to pass through the EAM 2 .

[0038] For example Fig.15 As shown, the above steps can actually be realized by the operation processing device 21 in the inspection controller 10 having the operation processing device 21, the storage device 22, and the input / output interface 23 executing the program stored in the storage device 22. That is, the inspection controller 10 sends a control signal to each power supply through the input / output interface 23, obtains data such as each current value, and determines the transverse mode abnormality.

[0039] As above, use Figure 1 The semiconductor laser device inspection device shown in FIG. Figure 7The inspection method shown can accurately determine whether LD1 of the semiconductor laser device 100 to be inspected is abnormal in the transverse mode. In particular, the intensity of a part of the laser light output by the semiconductor laser LD1 is measured by the photodetector, i.e., PD4, of the semiconductor laser device 100 to obtain the transverse mode light output characteristics, and the total light output characteristics equivalent to the total laser output are obtained by using the electric field absorption modulator EAM2 of the semiconductor laser device 100. Therefore, there is no need to use an additional photodetector as an inspection device. In addition, in the case of a semiconductor laser device in which LD1 is a normal transverse mode element and the Iea-I curve, i.e., the total light output characteristics, has nonlinear characteristics even in the area outside the saturation area, if the normal or abnormal is determined only by the transverse mode light output characteristics, it is possible to determine that the transverse mode is abnormal even when the transverse mode is normal. However, even in such a semiconductor laser device, by comparing the total light output characteristics and the transverse mode light output characteristics, it is possible to accurately determine whether the transverse mode is abnormal.

[0040] Implementation Method 2

[0041] Figure 8 1 is a schematic diagram showing the structure of the inspection device 11 of the semiconductor laser device of the second embodiment and the semiconductor laser device 101 as the inspection object. In the present second embodiment, the structure of the inspection device 11 of the semiconductor laser device is the same as that of the first embodiment. The semiconductor laser device 101 as the inspection object is formed by integrating LD1 and EAM2 into a single chip, and coupling the optical waveguides of the two with low loss. In addition, a window structure 32 having a refractive index lower than that of LD1 is formed near the chip end face (rear end face) on the LD1 side. The laser output by LD1 is radiated while diffusing toward the window structure 32. PD4 as a light detector is formed near the window structure 32 to receive a part of the diffused light.

[0042] In the second embodiment, the EAM2 receives most of the transverse mode of the laser light outputted by the LD1, while the PD4 receives only a part of the transverse mode. Therefore, as in the first embodiment, by measuring both the Iea-I curve and the Im-I curve, and determining and removing semiconductor laser devices with large differences between the two as transverse mode abnormalities, it is possible to remove semiconductor laser devices with transverse mode abnormalities in which the transverse mode varies depending on Iop. The order of the inspection method of the semiconductor laser device in the second embodiment is the same as that in the first embodiment. Figure 7 same.

[0043] The advantages of the semiconductor laser device 101, which is the inspection object of the second embodiment, over the semiconductor laser device 100, which is the inspection object of the semiconductor laser device inspection device of the first embodiment, are described. Since the semiconductor laser device 100, which is the inspection object of the first embodiment, is a structure in which the PD4 receives the output light of the EAM2, there is a problem that the APC (Auto Power Control) control becomes complicated. The so-called APC control means: feedback is applied to the injection current injected into LD1 so that the photocurrent (i.e., the amount of light received) output by the monitor becomes constant. Through this control, the change over time of the intensity of the optical signal output by the semiconductor laser LD1 can be suppressed. Here, when the semiconductor laser device is assembled into the optical communication system, the semiconductor laser device does not always output the optical signal, but sometimes temporarily stops the operation according to the time. At this time, the following problem can be imagined: if an electrical signal with an optical signal intensity close to zero is applied to the EAM2, the photocurrent (the amount of light received) of the PD4 in the semiconductor laser device 100, which is the inspection object of the first embodiment, drops sharply, so the injection current injected into LD1 rises sharply due to the APC control, and LD1 fails. In order to avoid this situation, it is necessary to perform such control that, when temporarily stopping, not only EAM2 but also LD1 is stopped at the same time. On the other hand, in the semiconductor laser device 101 to be inspected in Embodiment 2, since PD4 directly receives the output light of LD1, even if an electrical signal for temporarily stopping is applied to the EAM2 side, the amount of light received by PD4 does not change, and the injection current injected into LD1 does not change sharply, and the above-mentioned problem does not occur. Therefore, simple APC control can be applied.

[0044] Both the semiconductor laser device 100 shown in Embodiment 1 and the semiconductor laser device 101 shown in Embodiment 2 are configured such that PD 4 detects a portion of the spatial distribution of the laser light outputted from LD 1 that is generated by the transverse mode, and thus the change in the transverse mode can be detected by PD 4. Therefore, both the semiconductor laser device 100 shown in Embodiment 1 and the semiconductor laser device 101 shown in Embodiment 2 can be used as the inspection object of the semiconductor laser device inspection device 11 and the semiconductor laser device inspection method described in Embodiment 1.

[0045] Implementation 3

[0046] In the third to fifth embodiments, a specific method of determining a semiconductor laser device having a transverse mode abnormality will be described. Fig.9A as well as Fig. 9B 1 is a diagram for explaining the inspection method of the semiconductor laser device according to the third embodiment. It shows the Iea-I curve ( Fig.9A ) and the Im-I curve ( Fig. 9B ).like Fig.9A As shown in FIG. 1 , in the Iea-I curve as the total light output characteristic, an extreme value due to saturation can be observed. On the other hand, in the Im-I curve as the transverse mode light output characteristic, due to the instability of the transverse mode, as shown in FIG. Fig. 9B As shown in , multiple extrema can sometimes be observed. In the case of stable transverse modes, e.g. Figure 5B As shown in FIG. 1 , the number of extreme values ​​in the Im-I curve is the same as that in the Iea-I curve. Therefore, the number of extreme values ​​of each of the Iea-I curve and the Im-I curve is compared. If the two are consistent, it is considered that the transverse mode is stable. If they are inconsistent, it is considered that the transverse mode is unstable. Here, the extreme value can be determined as the value of the position where the sign of the differential value of the characteristic curve is reversed. Fig.9A as well as Fig. 9B In the example, Fig.9A The number of extreme values ​​of the Iea-I curve in is 1, but Fig. 9B The number of extreme values ​​of the Im-I curve in is 3, and the two do not coincide with each other, so it can be determined that the semiconductor laser device having such characteristics is a semiconductor laser device with abnormal transverse mode.

[0047] Implementation 4

[0048] Fig. 10A as well as Fig. 10B 1 is a diagram for explaining the inspection method of the semiconductor laser device according to the fourth embodiment. It shows the Iea-I curve ( Fig. 10A ) and the Im-I curve as the transverse mode light output characteristic ( Fig. 10B ).like Fig. 10A As shown, in the Iea-I curve, an extreme value caused by saturation is observed, while in the Im-I curve, due to the instability of the transverse mode, an extreme value is sometimes observed at an injection current Iop that is smaller than the injection current Iop corresponding to the extreme value of the Iea-I curve. When the transverse mode is stable, the extreme value of the Im-I curve also appears at the same Iop position as the extreme value of the Iea-I curve. Therefore, for each of the Iea-I curve and the Im-I curve, the Iop where the extreme value appears is measured. If the two are consistent, it can be regarded as the transverse mode is stable. If they are inconsistent, it can be regarded as unstable. Fig. 10A , Fig. 10B In the example, the Iop with an extreme value in the Iea-I curve is Iop1, and the Iop with an extreme value in the Im-I curve is Iop2. As long as Iop1 and Iop2 are consistent, it can be determined that the transverse mode of the semiconductor laser device under inspection is stable, and thus it can be determined to be a qualified product. On the other hand, when Iop1 and Iop2 are inconsistent, it can be determined that the semiconductor laser device under inspection has an abnormal transverse mode.

[0049] In implementation mode 3 Fig. 9B In the Im-I curve shown in FIG. 1 , since there are multiple extreme values, it is difficult to determine the location of the extreme values. Fig. 10B In the Im-I curve shown, since the number of extreme values ​​is 1, if the determination method of transverse mode abnormality described in Embodiment 3 is used to determine the semiconductor laser device having such characteristics, the transverse mode abnormality cannot be determined. Therefore, it is preferable to use Embodiments 3 and 4 together to determine the transverse mode abnormality.

[0050] Implementation method 5

[0051] FIG. 11A to FIG. 11E This is a diagram for explaining a method for inspecting a semiconductor laser device according to a fifth embodiment. Fig.11A The Iea-I curve is obtained as the total light output characteristic when the inspection object is a semiconductor laser device with unstable lateral mode, and Fig. 11B The Im-I curve represents the transverse mode light output characteristic. Fig. 11C The curve representing the differential value of the Iea-I curve, Fig.11D The curve representing the differential value of the Im-I curve, Fig.11E A curve representing the value of the product of the differential value of the Iea-I curve and the differential value of the Im-I curve. In the fifth embodiment, the product of the differential values ​​of the Iea-I curve and the Im-I curve is obtained, and in the region above the injection current at which LD1 starts laser oscillation, i.e., the threshold current (Ith), when the sign is positive, it is determined that the transverse mode is stable, and when it is negative, it is determined that the transverse mode is unstable.

[0052] For example, if the transverse mode is stable and both the Iea-I curve and the Im-I curve are similar linear waveforms, the product of the differential values ​​always takes a positive value in the region above Ith. Fig. 11B In the case where the Im-I curve is a nonlinear waveform different from the Iea-I curve, Fig.11E Thus, in the region of Ith and above, the product of the differential values ​​is not always positive, but a region of negative value occurs. A semiconductor laser device having such a characteristic can be determined as a transverse mode abnormality.

[0053] According to this embodiment 5, there is the following advantage: regardless of the case where the number of extreme values ​​in the Iea-I curve and the Im-I curve is different as in embodiment 3, or the case where the number of extreme values ​​in the Iea-I curve and the Im-I curve is the same but the positions of the extreme values ​​are different as in embodiment 4, it can be determined as a transverse mode abnormality.

[0054] Implementation 6

[0055] Fig.12 A schematic diagram showing the structure of a semiconductor laser device inspection device 12 and a semiconductor laser device 102 as an inspection object in Embodiment 6. Embodiment 6 is an embodiment in which a semiconductor laser device 102 without a photodetector is used as an inspection object. The semiconductor laser device 102 integrates a semiconductor laser (LD) 1 and an electric field absorption modulator (EAM) 2 into a single chip and couples the optical waveguides of the two. The semiconductor laser device 102 does not have a photodetector. Therefore, the inspection device 12 for the semiconductor laser device is provided with a photodetector (PD) 40, and the PD40 is arranged at a position that receives only a part of the spatial distribution of the laser light output by the semiconductor laser device 102, that is, a part of the transverse mode. The PD40 is controlled by a PD power supply 70 having a photocurrent detector 71.

[0056] According to this structure, the photocurrent output by PD40 performs the same operation as the photocurrent Im of the photodetector (PD) 4 described in Embodiment 1 and Embodiments 3 to 5. Therefore, by comparing the photocurrent Iea of ​​EAM2 and the photocurrent of PD40, it is possible to determine the semiconductor laser device 102 with abnormal transverse mode by the same method as the method described in Embodiment 1 and Embodiments 3 to 5.

[0057] According to the sixth embodiment, a photodetector is required as the inspection device 12 for semiconductor laser devices, but the semiconductor laser device 102 having the EAM 2 but not having the photodetector is used as the inspection object, and the total light output characteristics can be obtained by measuring the photocurrent of the EAM 2. Therefore, by comparing the total light output characteristics with the transverse mode light output characteristics, it can be determined with high accuracy whether the semiconductor laser device to be inspected has transverse mode abnormality.

[0058] Implementation 7

[0059] Fig.131 is a schematic diagram showing the structure of a semiconductor laser device inspection device 13 and a semiconductor laser device 103 as an inspection object according to Embodiment 7. Embodiment 7 is an embodiment in which a semiconductor laser device 103 having only a semiconductor laser (LD) 1 as a light emitting element and having neither an electric field absorption modulator (EAM) nor a photodetector is used as an inspection object. Since the inspection object does not have a photodetector, the inspection device 13 of the semiconductor laser device is provided with a first photodetector (first PD) 41, which is arranged at a position to receive only a part of the spatial distribution of the laser light emitted from the front end face of the semiconductor laser device 103, that is, a part of the transverse mode. In addition, a first PD power source 73 is provided, which applies a reverse bias voltage to the first PD 41, and a photocurrent detector 74 is provided. Furthermore, since the inspection object does not have an EAM, the inspection device 13 of the semiconductor laser device is provided with a second photodetector (second PD) 42, which is arranged at a position to receive all the laser light emitted from the rear end face of the semiconductor laser device 103. In addition, a second PD power source 75 for applying a reverse bias voltage to the second PD 42 and a photocurrent detector 76 are provided.

[0060] According to the above structure, the photocurrent output by PD41 performs the same operation as the photocurrent Im of PD4 described in Embodiment 1 and Embodiments 3 to 5. In addition, the photocurrent output by PD42 performs the same operation as the photocurrent Iea of ​​EAM2 described in Embodiment 1 and Embodiments 3 to 5. Therefore, Fig.14 As shown in the flowchart, the inspection controller 10 controls the LD power supply 5, changes the injection current Iop injected into the LD1, and measures the photocurrents of the first PD 41 and the second PD 42, thereby obtaining the transverse mode light output characteristics and the total light output characteristics (step ST11). And, by comparing the total light output characteristics and the transverse mode light output characteristics in the same way as the methods described in the first embodiment and the third to fifth embodiments, it can be determined whether there is a transverse mode abnormality (step ST4).

[0061] According to the seventh embodiment, two photodetectors are required as the inspection device 13 for the semiconductor laser device, but a semiconductor laser device 103 having neither an EAM nor a photodetector is used as the inspection object. By comparing the total light output characteristics and the transverse mode light output characteristics, it is possible to determine with high precision whether the semiconductor laser device of the inspection object has a transverse mode abnormality.

[0062] Although various illustrative embodiments and examples are described in this application, the various features, forms and functions described in one or more embodiments are not limited to the application of a specific embodiment, and can also be applied to the embodiments alone or in various combinations. Therefore, countless unillustrated variations can be imagined within the technical scope disclosed in the specification of this application. For example, it includes the case where at least one constituent element is deformed, added or omitted, and also includes the case where at least one constituent element is extracted and combined with constituent elements of other embodiments.

[0063] Description of Reference Numerals

[0064] 1...semiconductor laser (LD); 2...electric absorption modulator (EAM); 4, 40...photodetector (PD); 41...first PD; 42...second PD; 5...LD (semiconductor laser) power supply; 6...EAM (electric absorption modulator) power supply; 7, 70...PD (photodetector) power supply; 73...first PD power supply; 75...second PD power supply; 31, 32...window structure; 11, 12, 13...inspection device for semiconductor laser device; 100, 101, 102, 103...semiconductor laser device.

Claims

1. A method for inspecting a semiconductor laser device, wherein a semiconductor laser device that integrates a semiconductor laser, an electric field absorption modulator, and a photodetector is used as an inspection object, wherein the electric field absorption modulator is input with the output of the semiconductor laser, and the photodetector detects the laser intensity of a part of the laser light output by the semiconductor laser. It is characterized in that The semiconductor laser device inspection method comprises the following steps: The step of obtaining a transverse mode light output characteristic, wherein the transverse mode light output characteristic is a relationship between an injection current of the semiconductor laser and an output of the photodetector; A step of obtaining a total light output characteristic, which is a relationship between an injection current of the semiconductor laser and a photocurrent output by the electric field absorption modulator, while applying a reverse bias voltage to the electric field absorption modulator; as well as, The step of comparing the total light output characteristic with the transverse mode light output characteristic to determine whether the semiconductor laser device to be inspected is abnormal in the transverse mode.

2. The inspection method of a semiconductor laser device according to claim 1, characterized in that: The semiconductor laser device as the inspection object has a window structure on the front end surface of the semiconductor laser device, and the photodetector is arranged at a position to receive a part of the laser light diffused in the window structure.

3. The inspection method of a semiconductor laser device according to claim 1, characterized in that: The semiconductor laser device to be inspected has a window structure on the rear end face side of the semiconductor laser device, and the photodetector is arranged at a position to receive a part of the laser light diffused in the window structure.

4. The inspection method of a semiconductor laser device according to any one of claims 1 to 3, characterized in that: The number of extreme values ​​of the characteristic curve of the transverse mode light output characteristic and the number of extreme values ​​of the characteristic curve of the total light output characteristic are compared to determine whether the semiconductor laser device to be inspected has transverse mode abnormality.

5. The inspection method of a semiconductor laser device according to any one of claims 1 to 3, characterized in that: The position of the extreme value of the characteristic curve of the transverse mode light output characteristic is compared with the position of the extreme value of the characteristic curve of the total light output characteristic to determine whether the semiconductor laser device to be inspected has transverse mode abnormality.

6. The inspection method of a semiconductor laser device according to any one of claims 1 to 3, characterized in that: The product of the differential value of the characteristic curve of the transverse mode light output characteristic and the differential value of the characteristic curve of the total light output characteristic is obtained to determine whether the semiconductor laser device to be inspected has transverse mode abnormality.

7. A semiconductor laser device inspection device, wherein the semiconductor laser device is an integrated semiconductor laser, an electric field absorption modulator, and a photodetector as an inspection object, the electric field absorption modulator is input with the output of the semiconductor laser, and the photodetector detects the laser intensity of a part of the laser light output by the semiconductor laser, It is characterized in that The semiconductor laser device inspection device comprises: A semiconductor laser power supply for supplying injection current to the semiconductor laser; An electric field absorption modulator power supply for supplying a reverse bias voltage to the electric field absorption modulator; a photodetector power supply for supplying a reverse bias voltage to the photodetector; and The inspection controller is configured to control the semiconductor laser power supply, the electric field absorption modulator power supply, and the photodetector power supply, obtain the transverse mode light output characteristic as the relationship between the injection current of the semiconductor laser and the output of the photodetector, and the total light output characteristic as the relationship between the injection current of the semiconductor laser and the photocurrent output by the electric field absorption modulator, and compare the total light output characteristic with the transverse mode light output characteristic to determine whether the semiconductor laser device under inspection is transverse mode abnormal.

8. The inspection device for a semiconductor laser device according to claim 7, wherein: The inspection controller is configured to compare the number of extreme values ​​of the characteristic curve of the transverse mode light output characteristic with the number of extreme values ​​of the characteristic curve of the total light output characteristic to determine whether the semiconductor laser device to be inspected has transverse mode abnormality.

9. The inspection device for a semiconductor laser device according to claim 7, wherein: The inspection controller is configured to compare the position of the extreme value of the characteristic curve of the transverse mode light output characteristic with the position of the extreme value of the characteristic curve of the total light output characteristic to determine whether the semiconductor laser device to be inspected has a transverse mode abnormality.

10. The inspection device for a semiconductor laser device according to claim 7, wherein: The inspection controller is configured to determine whether the semiconductor laser device to be inspected has a transverse mode abnormality by obtaining a product of a differential value of a characteristic curve of the transverse mode light output characteristic and a differential value of a characteristic curve of the total light output characteristic.

11. A method for inspecting a semiconductor laser device, comprising: taking a semiconductor laser device that integrates a semiconductor laser and an electric field absorption modulator as an inspection object, wherein the electric field absorption modulator is input with the output of the semiconductor laser, It is characterized in that The semiconductor laser device inspection method comprises the following steps: A step of obtaining a transverse mode light output characteristic, the transverse mode light output characteristic being a relationship between an injection current of the semiconductor laser and an output of a photodetector that detects a laser intensity of a portion of laser light outputted by the semiconductor laser device as an inspection object; A step of obtaining a total light output characteristic, which is a relationship between an injection current of the semiconductor laser and a photocurrent output by the electric field absorption modulator, while applying a reverse bias voltage to the electric field absorption modulator; as well as The step of comparing the total light output characteristic with the transverse mode light output characteristic to determine whether the semiconductor laser device to be inspected is abnormal in the transverse mode.

12. A method for inspecting a semiconductor laser device, comprising: taking a semiconductor laser device having a semiconductor laser as an inspection object; It is characterized in that The semiconductor laser device inspection method comprises the following steps: A step of obtaining a transverse mode light output characteristic, the transverse mode light output characteristic being a relationship between an injection current of the semiconductor laser and an output of a photodetector that detects a laser intensity of a portion of laser light outputted by the semiconductor laser device as an inspection object; a step of obtaining a total light output characteristic, the total light output characteristic being a relationship between an injection current of the semiconductor laser and an output of a photodetector that detects the total laser intensity of the laser light outputted by the semiconductor laser device to be inspected; as well as The step of comparing the total light output characteristic with the transverse mode light output characteristic to determine whether the semiconductor laser device to be inspected is abnormal in the transverse mode.

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