Optical semiconductor module

Abstract

To obtain an optical semiconductor module in which a proper negative voltage is applied to an amplifying portion.SOLUTION: An optical semiconductor module includes: an optical semiconductor element including a light emitting portion and an amplifying portion that amplifies or absorbs light in an active layer according to a voltage applied between first electrodes, the optical semiconductor element outputting laser light; a voltage application section capable of applying a positive voltage or a negative voltage between the first electrodes and controlling an output current or an input current when applying the positive voltage or the negative voltage; a storage section storing a target value of the input current; and an overvoltage suppression circuit that prevents overvoltage from being applied to the amplifying portion between the first electrodes. The overvoltage suppression circuit includes: a current direction restriction section where, when a negative voltage is applied between the first electrodes, a first current flows to generate a first potential difference and, when a positive voltage is applied between the first electrodes, almost no current flows; and a potential difference applying section applying, to the current direction restriction section, a second potential difference corresponding to the first current. A sum of the first potential difference and the second potential difference when a negative voltage is applied between the first electrodes is equal to a potential difference between the first electrodes and lower than a withstand voltage of the amplifying portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical semiconductor module. [Background technology]

[0002] Conventionally, there has been known an optical semiconductor module that includes an optical semiconductor element having a laser region as a light-emitting section and an amplifier section that amplifies the light, and that is configured to output laser light, and that is configured so that when a reverse bias voltage is applied to the amplifier section, the amplifier section absorbs the laser light (for example, Patent Document 1).

[0003] In this type of optical semiconductor module, when the voltage application unit that applies voltage to the amplifier unit includes, for example, a current output type DAC (digital analog converter, hereinafter simply referred to as IDAC), and the current value is controlled when applying the voltage, the current value is controlled to a predetermined value with relatively high precision. Therefore, among multiple optical semiconductor modules, the individual differences (variations) in the current value in the voltage application unit are relatively small.

[0004] In contrast, individual differences (variations) in the current-voltage characteristics of the amplifier units when a reverse bias is applied in multiple optical semiconductor modules are relatively large due to, for example, manufacturing variations in optical semiconductor elements. In this case, for example, if there is variation in the resistance value of the amplifier units, in amplifier units with large resistance values, the voltage applied to the amplifier units in a reverse bias state may be greater than the withstand voltage of the amplifier units. In this case, there is a risk of damaging the amplifier units.

[0005] Patent Document 2 discloses an optical semiconductor module that has a configuration in which a voltage application unit controls a current value when applying a voltage to an amplifier unit, and that makes it possible to prevent the configuration from becoming large and complex while suppressing damage to the amplifier unit caused by the application of an excessively large voltage. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-144191 [Patent Document 2] Japanese Patent Application Publication No. 2023-151576 Summary of the Invention [Problem to be solved by the invention]

[0007] One object of the present invention is to provide an optical semiconductor module in which an appropriate negative voltage is applied to an amplifier section in a reverse bias state in a configuration in which a voltage application section controls a current value when applying a voltage to an amplifier section. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems and achieve the object, one aspect of the present invention is an optical semiconductor element that outputs laser light, the optical semiconductor element having a light-emitting unit that emits light and an amplifier unit that amplifies or absorbs light in an active layer in accordance with a voltage applied between first electrodes; a voltage application unit that is capable of applying a positive or negative voltage between the first electrodes and controls the output current or input current when the positive or negative voltage is applied; a memory unit that stores a target value of the input current; and an overvoltage suppression circuit that suppresses overvoltage from being applied to the amplifier unit between the first electrodes, the overvoltage suppression circuit having: a current direction regulating unit that allows a first current to flow and generates a first potential difference when a negative voltage is applied between the first electrodes, and that causes almost no current to flow when a positive voltage is applied between the first electrodes; and a potential difference applying unit that applies a second potential difference to the current direction regulating unit in accordance with the first current,

[0009] The current direction regulating unit may have a diode through which a forward current flows as the first current in a reverse bias state with respect to the active layer, the potential difference applying unit may have a resistor, and the current direction regulating unit and the potential difference applying unit may be connected in series.

[0010] The target value of the input current stored in the memory unit may be determined by a second current that flows in the amplifier unit in a reverse bias state with respect to the active layer, which is measured in advance, and a resistance value of the resistor.

[0011] The overvoltage suppression circuit may have a voltage monitor unit that monitors the sum of the first potential difference and the second potential difference, and the voltage application unit may control the input current based on the monitoring result by the voltage monitor unit.

[0012] The resistor may be a variable resistor, and the voltage application unit may control the resistance value of the variable resistor based on the target value stored in the storage unit. [Effects of the Invention]

[0013] According to the present invention, in a configuration in which the voltage application section controls the current value when applying the amplifier voltage, an optical semiconductor module can be obtained in which an appropriate negative voltage is applied to the amplifier in a reverse bias state. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is an exemplary schematic configuration diagram of an optical semiconductor module according to the first embodiment. [Figure 2] FIG. 2 is an exemplary circuit diagram of a part of the optical semiconductor module according to the first embodiment. [Figure 3] FIG. 3 is an exemplary schematic configuration diagram of the optical semiconductor module according to the second embodiment. [Figure 4] FIG. 4 is an exemplary schematic configuration diagram of an optical semiconductor module according to the third embodiment. [Figure 5] FIG. 5 is an exemplary circuit diagram of a part of the optical semiconductor module according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiment. Furthermore, in each drawing, the same or corresponding elements are appropriately designated by the same reference numerals, and redundant explanations will be omitted as appropriate.

[0016] [First embodiment] 1 is a schematic configuration diagram of an optical semiconductor module 10 according to a first embodiment. As shown in FIG. 1, the optical semiconductor module 10 includes a voltage application section 100, an optical semiconductor element 200, and an overvoltage suppression circuit 300.

[0017] The optical semiconductor device 200 includes a light emitting section 211 and an amplifier section 212 .

[0018] Two electrodes 221a and 221c are provided in light-emitting section 211. A voltage is applied to light-emitting section 211 from voltage application section 100 via these two electrodes 221a and 221c. A current flows through an active layer (not shown) in light-emitting section 211 in accordance with the voltage applied between the two electrodes 221a and 221c. This causes the active layer to emit light, and the emitted light oscillates within optical semiconductor device 200, causing laser light to be output from light-emitting section 211.

[0019] The amplifier 212 is provided with two electrodes 222p and 222m. A voltage is applied to the amplifier 212 from the voltage application unit 100 via the two electrodes 222p and 222m. The laser light input from the light emitting unit 211 is amplified in an active layer (not shown) in the amplifier 212 in accordance with a forward bias voltage applied between the two electrodes 222p and 222m. Furthermore, when a reverse bias voltage is applied between the two electrodes 222p and 222m by the voltage application unit 100, the laser light input from the light emitting unit 211 is absorbed in the active layer in the amplifier 212. Therefore, the amplifier 212 may also be referred to as an absorption unit. The electrodes 222p and 222m are an example of first electrodes.

[0020] The voltage application unit 100 includes a voltage source 110 , a first current variable unit 121 , a second current variable unit 122 , a first current detection unit 131 , a second current detection unit 132 , and a control unit 140 .

[0021] The voltage source 110 can apply a positive voltage to the electrodes 221a and 221c of the light-emitting unit 211. Furthermore, the voltage source 110 can switch between applying a positive voltage and a negative voltage with respect to the ground G to the electrodes 222p and 222m of the amplifier unit 212.

[0022] The first current detection unit 131 detects the current value of the current when a voltage is applied to the light-emitting unit 211. The first current variable unit 121 can change the current value of the current when a voltage is applied to the light-emitting unit 211.

[0023] The second current detection unit 132 detects the current value of the current when a voltage is applied to the amplification unit 212. The second current variable unit 122 can change the current value of the current when a voltage is applied to the amplification unit 212.

[0024] The control unit 140 controls the operation of the first current variable unit 121 so that the current value detected by the first current detection unit 131 becomes a desired current value. The control unit 140 controls the operation of the second current variable unit 122 so that the current value detected by the second current detection unit 132 becomes a desired current value.

[0025] The voltage application unit 100 is configured to include, as hardware, a microcontroller, an IDAC, a voltage source, and the like. The control unit 140 also includes a calculation unit 141 and a storage unit 142. The calculation unit 141 performs various calculation processes for implementing the processes executed by the control unit 140 and the functions of the control unit 140, and is configured, for example, by a CPU (Central Processing Unit) or a DSP (Digital Signal Processor). The storage unit 142 includes a portion configured, for example, by a ROM (Read Only Memory) in which various programs and data used by the calculation unit 141 to perform calculation processes are stored. The storage unit 142 also includes a portion configured, for example, by a RAM (Random Access Memory) that is used, for example, as a workspace when the calculation unit performs calculation processes and for storing the results of the calculation processes of the calculation unit.

[0026] The voltage application unit 100 having such a configuration applies a voltage to the light emitting unit 211 via the electrodes 221a and 221c at a predetermined current value determined by the control unit 140, and also applies a voltage to the amplification unit 212 via the electrodes 222p and 222m at a predetermined current value determined by the control unit 140.

[0027] In this embodiment, when the amplifier 212 is used as an absorption unit, the voltage application unit 100 operates to apply a reverse bias voltage to the electrodes 222p and 222m of the amplifier 212. That is, the voltage application unit 100 applies a reverse bias voltage between the electrodes 222p and 222m of the amplifier 212 so as to obtain a desired light absorption state in the amplifier 212. In this case, the potential of the electrode 222p is lower than the potential of the electrode 222m.

[0028] The overvoltage suppression circuit 300 has a function of suppressing an overvoltage from being applied between the electrodes 222p and 222m to the amplifier 212. Specifically, the overvoltage suppression circuit 300 has a current direction regulation unit 301 and a potential difference application unit 302.

[0029] When a negative voltage (voltage in a reverse bias state) is applied between electrodes 222p and 222m of amplifier 212, current direction regulator 301 causes a first current to flow and generates a first potential difference. When a positive voltage (voltage in a forward bias state) is applied between electrodes 222p and 222m of amplifier 212, current direction regulator 301 causes almost no current to flow. Potential difference applying unit 302 applies a second potential difference corresponding to the first current to current direction regulator 301. As a result, the sum of the first potential difference and the second potential difference when a negative voltage is applied between electrodes 222p and 222m becomes equal to the potential difference between electrodes 222p and 222m.

[0030] 2 is an exemplary circuit diagram of a portion of the optical semiconductor module 10 according to the first embodiment. In this example, the current direction regulation unit 301 is a diode, and the potential difference application unit 302 is a resistor. The current direction regulation unit 301 and the potential difference application unit 302 are connected in series. The overvoltage suppression circuit 300 is provided in parallel with the amplifier unit 212.

[0031] When the voltage application unit 100 applies a positive voltage between the electrodes 222p and 222m, the voltage application unit 100 outputs a current C1 to the amplifier unit 212. In this case, almost no current flows through the overvoltage suppression circuit 300 due to the action of the current direction regulation unit 301. Therefore, the current C1 corresponds to the output current when a positive voltage is applied between the electrodes 222p and 222m.

[0032] On the other hand, when the voltage application unit 100 applies a negative voltage between the electrodes 222p and 222m, the voltage application unit 100 receives the current C21 flowing through the overvoltage suppression circuit 300 and the current C22 from the amplifier unit 212. In this case, the sum of the currents C21 and C22 corresponds to the input current to the voltage application unit 100 when applying a negative voltage between the electrodes 222p and 222m. The current C21 is an example of a first current, which is a forward current.

[0033] The current C22 from the amplifier 212 is generated due to the absorption of light by the amplifier 212. The current value of the current C22 depends, for example, on the frequency of the light emitted by the light-emitting unit 211. When the current C21 flows through the current direction regulator 301, a first potential difference corresponding to a forward voltage Vf is generated in the current direction regulator 301. The value of the forward voltage Vf is typically about 0.7 V, but is not limited to this. If the value of the current C21 is dIr and the resistance value of the resistor in the potential difference generator 302 is R, the potential difference generator 302 applies a second potential difference RdIr corresponding to the first current to the current direction regulator 301. As a result, a potential difference (Vf + RdIr), which is the sum of the first potential difference and the second potential difference, is generated across the overvoltage suppression circuit 300. As a result, the potential difference between the electrodes 222p and 222m is clamped to (Vf+RdIr), preventing a further overvoltage from being applied between the electrodes 222p and 222m. Note that (Vf+RdIr) is smaller than the withstand voltage when a negative voltage is applied to the amplifier unit 212. Hereinafter, (Vf+RdIr) may be referred to as the clamp voltage.

[0034] Here, current direction regulation units 301 such as diodes may have individual variations in the first potential difference, such as the forward voltage Vf. Furthermore, the first potential difference may fluctuate significantly depending on the ambient temperature. In contrast, optical semiconductor module 10 is provided with potential difference applying unit 302 that applies a second potential difference according to the first current. This compensates for the individual variations in the first potential difference in current direction regulation units 301 and the fluctuations depending on the ambient temperature, making it possible to apply an appropriate negative voltage to amplifier unit 212.

[0035] In particular, if the potential difference applying unit 302 is a resistor, the temperature-dependent change in resistance value, the amount of heat generated, and the size are smaller than those of a diode, so more suitable compensation can be performed.

[0036] The variations and fluctuations in the first potential difference caused by the potential difference applying unit 302 are compensated for, for example, as follows. That is, for each optical semiconductor module 10, the current C22 (denoted as Isoab) from the amplifier unit 212 when, for example, the voltage application unit 100 applies a negative voltage between the electrodes 222p and 222m is measured in advance. Isoab is an example of the second current. This measurement may be performed under various conditions (e.g., ambient temperature, or the frequency or power of the laser light output by the light-emitting unit 211). Then, from the measured Isoab and the resistance value R, a target value Ibias of the appropriate input current when the potential difference between the electrodes 222p and 222m is clamped to (Vf + RdIr) when a negative voltage is applied between the electrodes 222p and 222m is calculated. Here, Ibias = Isoab + dIr. This target value is then stored in the storage unit 142. That is, the target value of the input current stored in the memory unit 142 is determined by the second current Isoab flowing through the amplifier unit 212 in a reverse bias state, which is measured in advance, and the resistance value R of the resistor of the potential difference applying unit 302. This allows the control unit 140 to set a target value of the input current that will obtain an appropriate negative voltage between the electrodes 222p, 222m for each individual under various conditions, and to execute control.

[0037] According to the study of the present inventors, the higher the clamp voltage, the higher the light absorption ability of amplifier unit 212. Therefore, with regard to the clamp voltage, it is preferable to increase the clamp voltage to absorb the higher power of the laser light output from light emitting unit 211 under the condition that the clamp voltage is lower than the withstand voltage of amplifier unit 212.

[0038] Furthermore, for example, R may be determined so that Vf>RdIr holds true for Vf and RdIr. In this case, the clamp voltage of the amplifier 212 is determined mainly by Vf determined by the current direction regulating unit 301, and RdIr determined by the potential difference applying unit 302 has the function of finely adjusting the clamp voltage within a range that does not exceed the withstand voltage.

[0039] Furthermore, for example, R may be determined so that Vf and RdIr satisfy the relationship Vf≦RdIr. In this case, RdIr by the potential difference applying unit 302 has the function of adjusting the clamp voltage over a wide range so long as it does not exceed the withstand voltage. In this case, R(dIr) 2 It is necessary to take care that the resistance value of the potential difference applying unit 302 does not exceed the rated power.

[0040] [Second embodiment] Fig. 3 is a schematic diagram of an optical semiconductor module 10A according to a second embodiment. As shown in Fig. 3, the optical semiconductor module 10A has a configuration in which the overvoltage suppression circuit 300 in the configuration of the optical semiconductor module 10 shown in Fig. 1 is replaced with an overvoltage suppression circuit 300A. The overvoltage suppression circuit 300A has a configuration in which a voltage monitor unit 303 is added to the overvoltage suppression circuit 300.

[0041] The voltage monitor unit 303 has a function of monitoring the sum of the first potential difference and the second potential difference (for example, Vf+RdIr). The voltage monitor unit 303 can be configured, for example, by an inverting amplifier circuit using an operational amplifier. The voltage monitor unit 303 outputs the monitored potential difference to the control unit 140 of the voltage application unit 100. The control unit 140 of the voltage application unit 100 controls the input current (for example, Ibias=Isoab+dIr) based on the monitoring result by the voltage monitor unit 303. For example, the control unit 140 feedback-controls the input current so that the monitored potential difference becomes a target value of the potential difference stored in the storage unit 142.

[0042] In the optical semiconductor module 10A configured as described above, similar to the optical semiconductor module 10, it is possible to apply an appropriate negative voltage to the amplifier unit 212. Furthermore, in the optical semiconductor module 10A, it is possible to apply an appropriate negative voltage to the amplifier unit 212 without measuring Isoab in advance. Furthermore, in the optical semiconductor module 10A, even if the current direction regulating unit 301 and the potential difference applying unit 302 deteriorate over time and their characteristics change, it is possible to apply an appropriate negative voltage to the amplifier unit 212 by feedback controlling the input current.

[0043] [Third embodiment] Fig. 4 is a schematic diagram of an optical semiconductor module 10B according to a third embodiment. As shown in Fig. 4, the optical semiconductor module 10B has a configuration in which the overvoltage suppression circuit 300 in the configuration of the optical semiconductor module 10 shown in Fig. 1 is replaced with an overvoltage suppression circuit 300B. The overvoltage suppression circuit 300B has a configuration in which the potential difference applying unit 302 of the overvoltage suppression circuit 300 is replaced with a potential difference applying unit 302B.

[0044] 5 is an exemplary circuit diagram of a portion of an optical semiconductor module 10B according to the third embodiment. In this example, the current direction regulating unit 301 is a diode, and the potential difference applying unit 302B is a variable resistor.

[0045] The control unit 140 of the voltage application unit 100 controls the resistance value of the variable resistor of the potential difference applying unit 302B based on the target value stored in the memory unit 142. For example, the control unit 140 feedback-controls the resistance value so that the sum of the first potential difference and the second potential difference becomes the target value stored in the memory unit 142 while setting the input current to a fixed value.

[0046] In the optical semiconductor module 10B configured as described above, an appropriate negative voltage can be applied to the amplifier unit 212, similar to the optical semiconductor module 10. Furthermore, in the optical semiconductor module 10B, even if the current direction regulating unit 301 and the potential difference applying unit 302 deteriorate over time and their characteristics change, the optical semiconductor module 10B can still apply an appropriate negative voltage to the amplifier unit 212.

[0047] In the above embodiment, the same action and effect can be obtained not only when an overvoltage due to an individual difference between optical semiconductor modules is applied, but also when an overvoltage such as a surge voltage is applied.

[0048] In the above embodiment, the current direction regulating unit has one diode, but may have two or more diodes. In the above embodiment, the potential difference applying unit 302 has one resistor, but may have two or more resistors.

[0049] Furthermore, the present invention is not limited to the above-described embodiments. The present invention also includes configurations in which the above-described components are appropriately combined. Further effects and modifications can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited to the above-described embodiments, and various modifications are possible.

[0050] For example, the overvoltage suppression circuit may be configured as another equivalent circuit that provides the same action and effect. [Explanation of symbols]

[0051] 10, 10A, 10B: Optical semiconductor module 100: Voltage application section 110: Voltage source 121: First current variable section 122: Second current variable section 131: First current detection unit 132: Second current detection unit 140: Control unit 141: Arithmetic section 142: Storage section 200: Optical semiconductor element 211: Light-emitting part 212: Amplification unit 221a, 221c, 222m, 222p: Electrode 300, 300A, 300B: Overvoltage suppression circuit 301: Current direction regulation section 302, 302B: Potential difference applying part 303: Voltage monitor unit C1, C21, C22: Current G: Ground

Claims

1. an optical semiconductor element that outputs laser light and includes a light-emitting portion that emits light and an amplifier portion that amplifies or absorbs light in an active layer in response to a voltage applied between first electrodes; a voltage application unit that is capable of applying a positive voltage or a negative voltage between the first electrodes and that controls an output current or an input current when the positive voltage or the negative voltage is applied; a storage unit that stores the target value of the input current; an overvoltage suppression circuit that suppresses application of an overvoltage to the amplifier between the first electrodes; Equipped with the overvoltage suppression circuit includes a current direction regulating unit that allows a first current to flow and generates a first potential difference when a negative voltage is applied between the first electrodes, and allows almost no current to flow when a positive voltage is applied between the first electrodes, and a potential difference applying unit that applies a second potential difference to the current direction regulating unit according to the first current, wherein the sum of the first potential difference and the second potential difference when a negative voltage is applied between the first electrodes is equal to the potential difference between the first electrodes and is lower than the withstand voltage of the amplifier unit.

2. 2. The optical semiconductor module according to claim 1, wherein the current direction regulating unit has a diode through which a forward current flows as the first current in a reverse bias state with respect to the active layer, the potential difference applying unit has a resistor, and the current direction regulating unit and the potential difference applying unit are connected in series.

3. 3. The optical semiconductor module according to claim 2, wherein the target value of the input current stored in the memory unit is determined by a second current flowing in the amplifier unit in a reverse bias state with respect to the active layer, which is measured in advance, and a resistance value of the resistor.

4. 2. The optical semiconductor module according to claim 1, wherein the overvoltage suppression circuit has a voltage monitor unit that monitors the sum of the first potential difference and the second potential difference, and the voltage application unit controls the input current based on a monitoring result by the voltage monitor unit.

5. 3. The optical semiconductor module according to claim 2, wherein the resistor is a variable resistor, and the voltage application unit controls the resistance value of the variable resistor based on the target value stored in the storage unit.

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