JP2004126108A - Semiconductor optical modulator and optical modulation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor optical modulator capable of making high-velocity optical modulation by an electric signal and to provide an optical modulation system. <P>SOLUTION: Terminal resistors (11 and 14) necessary for taking impedance matching with an electric signal line (20) are previously disposed as part of an element. Consequently, there is no more need for wires for connecting the element and the terminal resistors and optical modulation waveforms free of wavelength distortion can be obtained by averting the resonance by parasitic inductances. Further, a response can be speeded up by previously imparting the desired inductance (19) to the connection routes between the element and the terminal resistors. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor optical modulator and an optical modulation system, and more particularly to a semiconductor optical modulator and an optical modulation system capable of high-speed modulation by an electric signal.
[Prior art]
In recent years, the development of the Internet and the demand for data communication of a backbone of a mobile communication system have been remarkably increased, and accordingly, the capacity of an optical communication system has been rapidly increased. Although the communication capacity of the trunk system has reached 10 Gbps (gigabits per second), the development of an optical communication system at 40 Gbps has been actively performed with the aim of further increasing the capacity.
[0002]
An electroabsorption type semiconductor optical modulator can be monolithically integrated with a semiconductor laser serving as a light source, and a small optical transmitter can be provided. For this reason, it is widely used as a transmitter for intra-station and inter-station communication at 10 Gbps. Further, by reducing the element capacitance, operation at 40 Gbps is also possible.
[0003]
FIG. 10 is a schematic diagram showing a semiconductor optical modulator and peripheral circuits thereof studied by the present inventor in the course of reaching the present invention.
[0004]
That is, the semiconductor optical modulator 51 is mounted on a predetermined substrate together with the electric signal line 70 and the 50Ω termination resistor 71. These components are connected by wires 72 and 73 such as gold (Au).
[0005]
This semiconductor optical modulator 51 has a so-called “ridge waveguide structure”, and has a light absorption layer 53 formed on the entire surface on an n-type InP substrate 52 and a p-type light-emitting layer 53 formed in a mesa stripe shape thereon. And an InP cladding layer 54. In order to reduce the element capacitance, the element length in the optical axis direction is reduced to 100 μm, and the electrode pad 57 is formed as small as about 50 μm square, and at the same time, a resin 58 is buried under the electrode pad 57. . As a result, the parasitic capacitance is suppressed to 0.1 pF in the stripe portion and 0.05 pF in the electrode pad portion, and is reduced to 0.15 pF in the entire device.
[0006]
The semiconductor optical modulator 51 is mounted at an intermediate position between the electric signal line 70 and the terminating resistor 71 of 50Ω, and is connected to each of the Au wires 72 and 73 of 25 μmφ.
[0007]
Such a structure in which a semiconductor element such as an optical modulator or a light emitting element is connected to a terminating resistor via a wire is also disclosed in Patent Documents 1 to 3, for example.
[0008]
[Patent Document 1]
JP 2001-257435 A [Patent Document 2]
Japanese Patent Application Laid-Open No. 9-90302 [Patent Document 3]
JP-A-8-130237
[Problems to be solved by the invention]
However, in the case of these conventional examples and the optical modulation system illustrated in FIG. 10, there is a problem that a sufficiently high-speed modulation characteristic cannot be obtained due to a parasitic inductance of a wire connecting between components.
[0010]
That is, in consideration of the size of each component, the length of each of the Au wires 72 and 73 is required to be about 300 μm, and its inductance is limited to about 0.2 nH. Although the inductance can be reduced by connecting a plurality of Au wires, it is necessary to increase the electrode pad area, and the element capacity increases.
[0011]
FIG. 11 is a graph showing frequency response characteristics of the semiconductor optical modulation system of FIG. That is, the horizontal axis in the figure represents the frequency, the left vertical axis represents the amplitude, and the right vertical axis represents the phase. From the figure, it can be seen that this optical modulation system has a modulation band exceeding 50 GHz, but has peaking in the amplitude due to the resonance phenomenon between the wire inductance and the element capacitance.
[0012]
FIG. 12 is a waveform diagram showing an optical modulation waveform of the optical modulation system. Here, an optical modulation waveform when modulated by a 40 Gbps NRZ (Non Return to Zero) signal is shown.
[0013]
As a result of measurement with a light receiving element having a sufficient band, an optical modulation waveform with a large overshoot OS was observed. This is based on the fact that the group delay has increased due to the resonance phenomenon. In the semiconductor optical modulator, since the conversion from electricity to light is performed nonlinearly, a slight voltage waveform distortion of the input electric signal is exaggerated in the optical waveform. Therefore, in order to prevent optical waveform distortion from occurring, it is necessary to minimize the group delay due to the resonance phenomenon. In particular, at the time of high-speed modulation up to 40 Gbps, it is necessary to reduce the inductance to about 0.1 nH or less, and it is difficult to realize the mounting by ordinary wire connection.
[0014]
As described above, when the semiconductor optical modulator of FIG. 10 was used, it was difficult to obtain a 40 Gbps modulation operation without optical waveform distortion.
[0015]
The present invention has been made based on the recognition of such a problem, and an object of the present invention is to provide a semiconductor optical modulator and an optical modulation system capable of performing sufficiently high-speed optical modulation by an electric signal.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, a first semiconductor optical modulator of the present invention is a semiconductor optical modulator that performs optical modulation based on an electric signal input via a line having a first characteristic impedance, A resistor having substantially the same impedance as the first characteristic impedance is provided.
[0017]
According to the above configuration, it is possible to provide a compact semiconductor optical modulator capable of performing sufficiently high-speed optical modulation by an electric signal.
[0018]
Here, a first electrode to which the electric signal is input and a second electrode connected to a constant potential are provided, one end of the resistor is connected to the first electrode, and one end of the resistor is connected to the first electrode. The other end can be connected to the second electrode.
[0019]
Further, a second semiconductor optical modulator according to the present invention includes a first conductivity type semiconductor layer, a light absorption layer provided on the first conductivity type semiconductor layer, and a light absorption layer provided on the light absorption layer. The second conductive type semiconductor layer, the first electrode connected to the first conductive type semiconductor layer, the second electrode connected to the second conductive type semiconductor layer, and the first conductive type semiconductor layer. And a resistor connected between the second electrode and the second electrode.
[0020]
According to the above configuration, it is possible to provide a compact semiconductor optical modulator capable of performing sufficiently high-speed optical modulation by an electric signal.
[0021]
In the second optical modulator, when the resistor has substantially the same impedance as the characteristic impedance of the line connected to the first electrode, it is not necessary to separately provide a terminating resistor.
[0022]
In addition, the semiconductor device may further include an insulating layer, and the resistor may be formed in a thin film on the insulating layer.
[0023]
Further, the resistor may be formed of a semiconductor of the same quality as at least one of the first conductivity type semiconductor layer, the light absorbing layer, and the second conductivity type semiconductor layer.
[0024]
In addition, a wiring path provided at least one of a wiring path between the first electrode and the resistor and a wiring path between the second electrode and the resistor, Then, it becomes easy to adjust the high frequency characteristics to a suitable range.
[0025]
In addition, when any one of the above optical modulators is integrated with a semiconductor laser, a compact and high-performance integrated semiconductor optical modulator can be provided.
[0026]
Further, assuming that the active layer of the semiconductor laser is integrated with the semiconductor laser and is formed continuously with the light absorbing layer, a so-called monolithic integrated semiconductor optical modulator can be provided.
[0027]
On the other hand, an optical modulation system according to the present invention is a semiconductor optical modulation device according to any one of claims 2 and 4 to 9 provided on a substrate, an electric signal line provided on the substrate, and the substrate. Wherein the electric signal line and the first electrode are connected, and the electric signal line has the first characteristic impedance.
[0028]
According to the above configuration, it is possible to provide an optical modulation system capable of performing sufficiently high-speed optical modulation by an electric signal.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0030]
(First Embodiment)
FIG. 1 is a schematic diagram illustrating a semiconductor optical modulator and a peripheral circuit according to a first embodiment of the present invention.
[0031]
That is, the semiconductor optical modulator 1 is mounted on a predetermined substrate together with the electric signal line 2 and is connected by a wire 21 made of gold (Au) or the like. In the present embodiment, the resistor 11 serving as a 50Ω termination resistor is integrated on the optical modulator 1. By integrating the terminating resistors in the modulator 1 in this manner, wires for connecting the terminating resistors are not required, the parasitic inductance is suppressed, and high-speed modulation can be performed.
[0032]
Hereinafter, the semiconductor optical modulator of this example will be described in detail.
[0033]
This semiconductor optical modulator 1 also has a "ridge waveguide structure", and has a light absorption layer 3 formed on the entire surface of an n-type InP substrate 2 and a p-type InP formed on the n-type InP substrate 2 in a mesa stripe shape. And a cladding layer 4. A p-type InGaAsP contact layer 5 is also laminated on the cladding layer 4 in a stripe shape, and a p-side ohmic electrode 6 is formed thereon. An n-side ohmic electrode 9 is formed on the back side of the InP substrate 2, and an n-side ohmic electrode 10 is connected to the front side of the substrate 2.
[0034]
In order to reduce the element capacitance, the element length in the optical axis direction (longitudinal direction of the mesa stripe) is reduced to 100 μm, and the p-side electrode pad 7 is formed as small as 50 μm square, and at the same time, both sides of the mesa are made of resin. 8, the electrode pad 7 is provided thereon. As a result, the parasitic capacitance is suppressed to 0.1 pF in the stripe portion and 0.05 pF in the electrode pad portion, and is reduced to 0.15 pF in the entire device.
[0035]
In the present invention, the resistor 11 is formed on the resin 8 on the opposite side of the p-side ohmic electrode 6 from the electrode pad 7. Here, the impedance of the resistor 11 is formed to be, for example, 50Ω in accordance with the characteristic impedance of the electric signal line 20. That is, the resistor 11 corresponding to the terminating resistor 71 described above with reference to FIG. 10 is integrated in the semiconductor optical modulator 1.
[0036]
The resistor 11 is connected to the n-side ohmic electrode 10 by a wiring 18 made of gold (Au) or the like, and is connected to the ground (GND) via the n-type InP substrate 2 and the n-side ohmic electrode 9 on the back side thereof. Have been.
[0037]
The resistor 11 can be formed of various thin-film metal materials or semiconductor materials. For example, it can be formed of a thin film nickel-chromium (NiCr) alloy or the like. If a nickel-chromium alloy is used, a sheet resistance of 50 ohms can be obtained with a thickness of about 0.03 microns. Therefore, for example, when the width of the wiring 18 is 10 μm, if the resistor 11 made of a nickel-chromium alloy having a thickness of 0.03 μm and a width and a length of about 10 μm is formed, 50 ohms is obtained. can get. Further, the resistor 11 can be formed by using, for example, platinum (Pt) in addition to the nickel-chromium alloy.
[0038]
Such a resistor 11 can be formed, for example, by combining a thin film deposition process such as evaporation or sputtering with a processing process using photolithography.
[0039]
In the semiconductor optical modulator 1 of this example, since the resistor 11 serving as a terminating resistor is integrated, the electric signal line 20 and the electrode pad 7 are connected by the Au wire 21 when assembling the optical modulation system. Just good. Although a slight parasitic inductance exists between the electric signal line 20 and the electrode pad 7, there is almost no inductance component between the electric signal line 20 and the terminal pad 11 because the resistor 11 is formed inside the chip in advance. As a result, high-speed modulation characteristics can be significantly improved.
[0040]
FIG. 2 is a graph illustrating a frequency response characteristic of the semiconductor optical modulation system according to the present embodiment. That is, the horizontal axis in the figure represents the frequency, the left vertical axis represents the amplitude, and the right vertical axis represents the phase. From the figure, it can be seen that when the optical modulator of the present embodiment is used, no peaking due to the resonance phenomenon is observed, and a smooth frequency response characteristic can be obtained.
[0041]
FIG. 3 is a waveform diagram showing an optical modulation waveform of the optical modulation system. Here also, the optical modulation waveform when modulated with a 40 Gbps NRZ (Non Return to Zero) signal is shown.
[0042]
A good modulation waveform with a sufficiently open eye is obtained without causing waveform distortion such as overshoot. That is, according to the present invention, by incorporating the resistor 11 functioning as a terminating resistor in the semiconductor optical modulator 1, a wire connecting these components is not required, the parasitic inductance is suppressed, and the high-speed modulation characteristic is improved. Can be greatly improved.
[0043]
FIG. 4 is a schematic diagram illustrating a modification of the present embodiment. That is, FIGS. 3A to 3C are cross-sectional views of main parts in which the vicinity of the resistor 11 integrated in the semiconductor optical modulator 1 is enlarged.
[0044]
In the specific example of FIG. 4A, the resistor 11 is formed on the side surface of the resin 8.
[0045]
Further, in the case of the specific example of FIG. 2B, the resin 8 is provided to extend to the upper surface of the substrate 2, and the resistor 11 is formed on the extending portion.
[0046]
On the other hand, in the case of the specific example shown in FIG. 3C, almost the entire wiring path from the stripe-shaped p-side ohmic electrode 6 to the n-side ohmic electrode 10 on the substrate is formed as the resistor 11. With this configuration, even when a material having a low specific resistance is used as the material of the resistor 11, an effect that a predetermined termination resistance (for example, 50Ω) can be easily obtained.
[0047]
As described above, as illustrated in FIGS. 4A to 4C, the size and arrangement of the resistor 11 in the present embodiment can be appropriately determined according to the shape of the semiconductor optical modulator 1 and the like.
[0048]
(Second embodiment)
Next, as a second embodiment of the present invention, a semiconductor optical modulator including a resistor formed using a part of a semiconductor layer forming an optical modulator will be described.
[0049]
FIG. 5 is a schematic diagram illustrating the semiconductor optical modulator according to the present embodiment and its peripheral circuits. In this figure, the same elements as those described above with reference to FIGS. 1 to 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.
[0050]
In the case of the modulator of this specific example, the resistor 14 is formed using a part of the p-type InP cladding layer 4. That is, on the side of the mesa stripe, the p-type InP cladding layer 14 is patterned and arranged in an island shape via the resin 8, and the p-side ohmic electrodes 12 and 13 are provided on both ends of the upper surface via the contact layer 6 respectively. It is connected. That is, the termination resistance is formed inside the element by using the bulk resistance of the p-type InP cladding layer 14.
[0051]
The p-side ohmic electrode 6 on the mesa stripe includes a wiring 18, a p-side ohmic electrode 12, a p-type InP cladding layer 14, a p-side ohmic electrode 13, an n-ohmic electrode 10, a wiring 18, an n-type InP substrate 2, and an n-side ohmic. It is connected to ground (GND) via the electrode 9.
[0052]
The resistivity of the p-type InP cladding layer 14 is usually about 0.1 Ωcm. For example, a bulk resistor of about 50Ω can be formed in a small size of about several μm square. Therefore, the increase in the parasitic capacitance due to the provision of the resistance region can be almost ignored.
[0053]
Also in the present embodiment, when assembling the optical modulation system, it is only necessary to mount the semiconductor optical modulator 1 and the electric signal line 20 on a predetermined substrate and connect them with the wires 21. Then, as described above with respect to the first embodiment, it is possible to obtain a smooth frequency response characteristic and a good modulation waveform without waveform distortion.
[0054]
In forming the resistor in this embodiment, the resistance is set to 50Ω including not only the bulk resistance of the p-type InP cladding layer 14 but also the ohmic resistance of the contact layer 5 and the p-type ohmic electrodes 12 and 13. Just adjust it.
[0055]
Further, FIG. 5 shows a specific example in which the resistor 14 is formed using a part of the p-type InP clad layer 4, but the present invention is not limited to this. It is also possible to form a resistor using any one of the absorption layer 3, the contact layer 6, and the like. However, isolation may be required as appropriate so that electrical leakage or interference does not occur with the light modulation portion.
[0056]
(Third embodiment)
Next, as a third embodiment of the present invention, a semiconductor optical modulator in which a predetermined inductance is given to a wiring path connecting a resistor to improve a response characteristic will be described. FIG. 6 is a schematic diagram illustrating the semiconductor optical modulator according to the present embodiment and its peripheral circuits. Also in this figure, the same elements as those described above with reference to FIGS. 1 to 5 are denoted by the same reference numerals, and detailed description is omitted.
[0057]
In the case of this specific example, the wiring 19 between the p-side ohmic electrode 6 and the resistor 11 is formed by an appropriately bent elongated pattern, and functions as an “inductance providing section”. By doing so, a minute inductance of, for example, about 0.1 nH can be given to the wiring 19.
[0058]
FIG. 7 is a graph showing the frequency response characteristics of the semiconductor optical modulator of this example. Looking at the amplitude response characteristics, it can be seen that a modulation band exceeding 50 GHz can be obtained while maintaining the smoothness of the frequency response. This is the effect of giving an inductance of about 0.1 nH to the wiring 19 and causing a slight resonance in the high-frequency operation.
[0059]
FIG. 8 is a waveform diagram showing an optical modulation waveform of an optical modulation system using the semiconductor optical modulator of this example. Here also, the optical modulation waveform when modulated with a 40 Gbps NRZ (Non Return to Zero) signal is shown.
[0060]
In the figure, no waveform distortion is observed in the modulation waveform, and a good modulation waveform having a sufficiently open eye is obtained. That is, in the optical modulator of this specific example, it can be seen that the increase in the group delay is suppressed.
[0061]
As described above, in order to expand the modulation band without increasing the group delay, the resonance phenomenon due to the parasitic impedance must be controlled with extremely high precision. According to the present embodiment, by controlling the pattern of the wiring 19, the minute inductance is previously formed inside the element, so that a wide modulation band can be realized without causing waveform distortion.
[0062]
Note that, also in the present embodiment, the structure shown in FIG. 6 is merely an example, and the pattern shape and thickness of the wiring 19 (inductance providing section) can be appropriately determined according to required inductance. Further, the wiring 18 extending from the resistor 11 to the n-side ohmic electrode 10 can be similarly provided with an inductance by giving a predetermined pattern shape and a wiring width.
[0063]
(Fourth embodiment)
Next, a semiconductor optical modulator integrated with a laser serving as a light source will be described as a fourth embodiment of the present invention.
[0064]
FIG. 9 is a schematic diagram illustrating a semiconductor optical modulator / semiconductor laser integrated device and peripheral circuits according to the present embodiment. Also in this figure, the same elements as those described above with reference to FIGS. 1 to 8 are denoted by the same reference numerals, and detailed description is omitted.
[0065]
In the case of this specific example, the semiconductor optical modulator 1 and the semiconductor laser 15 are monolithically integrated. In the case of the specific example shown in the figure, the structure of the portion of the semiconductor optical modulator 1 and the mounting method thereof are the same as those described above with respect to the first embodiment. However, the present embodiment is not limited to this specific example, but also includes the semiconductor optical modulator according to the second or third embodiment integrated with a laser.
[0066]
On the upper surface of the semiconductor optical modulator 1, a striped n-side ohmic electrode 6A and an electrode pad 7A are provided.
[0067]
On the other hand, the semiconductor laser 15 can have the same laminated structure as the optical modulator 1. That is, a light absorption layer 3 is provided on an n-type InP substrate 2, and a p-type InP cladding layer 4 and a p-type InGaAsP contact layer 5 patterned in a stripe shape are further laminated thereon. Both sides of the mesa stripe are buried with resin 8 like the optical modulator 1. An n-side ohmic electrode 6B in the form of a stripe is formed on the upper surface of the contact layer 6, and electrode pads 7B are connected to both sides thereof.
[0068]
A laser power supply line 23 is provided near the laser 15, and is connected to the electrode pad 7 </ b> B by a wire 22. Then, when a current is injected through this wiring path, the laser light absorbing layer 3 functions as an active layer, and laser oscillation occurs.
[0069]
The obtained laser light is subjected to predetermined modulation in the light absorption layer 3 of the light modulator 1, and is emitted as modulated light from the emission end on the near side in the drawing.
[0070]
According to the present embodiment, by integrating the semiconductor optical modulator 1 and the semiconductor laser 15 in a monolithic manner, it is possible to provide a small-sized optical transmitter capable of performing a 40 Gbps modulation operation.
[0071]
The embodiment of the invention has been described with reference to the examples. However, the present invention is not limited to these specific examples.
[0072]
For example, in the above-described specific examples, an InGaAsP / InP-based optical semiconductor element has been described as an example. However, the present invention can be applied to various material systems such as a GaAlAs / GaAs-based and GaInNAs / GaAs-based. Can be.
[0073]
Further, in the specific examples described above, examples in which the present invention is applied to a single element-shaped semiconductor optical modulator and an integrated element with a semiconductor laser have been described, but other examples include an optical switch, an optical amplifier, and an optical waveguide. The same effects can be obtained by applying the present invention to an integrated element structure in the same manner.
[0074]
Furthermore, the conductivity type of the semiconductor substrate or other parts is not limited to the specific examples, and the n-type and p-type may be appropriately reversed. Further, a semi-insulating substrate may be used as the semiconductor substrate.
[0075]
Further, the light absorption layer may have a multiple quantum well structure or a bulk structure, and the element sectional structure is not limited to the ridge waveguide structure. Further, the present invention can be similarly applied to an element structure having a traveling-wave-type electrode to obtain the same operation and effect.
[0076]
In addition, various modifications can be made without departing from the spirit of the present invention.
【The invention's effect】
As described in detail above, according to the present invention, by forming a terminating resistor in advance inside a device of a semiconductor optical modulator, wire connection between the device and the terminating resistor can be omitted. As a result, it is possible to avoid the resonance phenomenon due to the parasitic inductance and obtain an optical modulation waveform without waveform distortion.
[0077]
As a result, it is possible to provide an optical modulator that is compact and capable of high-speed modulation operation, and the industrial advantage is great.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a semiconductor optical modulator and a peripheral circuit according to a first embodiment of the present invention.
FIG. 2 is a graph illustrating a frequency response characteristic of the semiconductor optical modulation system according to the first embodiment of the present invention.
FIG. 3 is a waveform diagram illustrating an optical modulation waveform of the optical modulation system according to the first embodiment of the present invention.
FIG. 4 is a schematic diagram illustrating a modification of the first embodiment of the present invention.
FIG. 5 is a schematic diagram illustrating a semiconductor optical modulator and peripheral circuits according to a second embodiment of the present invention.
FIG. 6 is a schematic diagram illustrating a semiconductor optical modulator and its peripheral circuits according to a third embodiment of the present invention.
FIG. 7 is a graph illustrating frequency response characteristics of a semiconductor optical modulator according to a third embodiment of the present invention.
FIG. 8 is a waveform diagram illustrating an optical modulation waveform of an optical modulation system using the semiconductor optical modulator according to the third embodiment.
FIG. 9 is a schematic diagram showing a semiconductor optical modulator / semiconductor laser integrated device and its peripheral circuits according to a fourth embodiment of the present invention.
FIG. 10 is a schematic diagram showing a semiconductor optical modulator and peripheral circuits thereof studied by the present inventors in the process leading to the present invention.
FIG. 11 is a graph showing frequency response characteristics of the semiconductor optical modulation system of FIG.
FIG. 12 is a waveform chart showing an optical modulation waveform of the optical modulation system of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Semiconductor optical modulator 2 Substrate 3 Light absorption layer (active layer)
4 Cladding layer 5 Contact layer 6, 6A, 6B Ohmic electrode 7, 7A, 7B Electrode pad 8 Resin 9 Ohmic electrode 10 Ohmic electrode 11 Resistor (terminal resistance)
12, 13 Ohmic electrode 14 Cladding layer 14 Resistor 15 Semiconductor laser 18, 19 Wiring 20 Electric signal line 21, 22 Wire 23 Laser power supply line 51 Semiconductor optical modulator 52 Substrate 53 Light absorbing layer 54 Cladding layer 57 Electrode pad 58 Resin 70 electric signal line 71 terminating resistor 72 wire

Claims (10)

A semiconductor optical modulator that performs optical modulation based on an electric signal input through a line having a first characteristic impedance,
A semiconductor optical modulator comprising a resistor having substantially the same impedance as the first characteristic impedance. A first electrode to which the electric signal is input;
A second electrode connected to a constant potential;
With
2. The semiconductor optical modulator according to claim 1, wherein one end of the resistor is connected to the first electrode, and the other end of the resistor is connected to the second electrode. A first conductivity type semiconductor layer;
A light absorption layer provided on the first conductivity type semiconductor layer;
A second conductivity type semiconductor layer provided on the light absorption layer;
A first electrode connected to the semiconductor layer of the first conductivity type;
A second electrode connected to the second conductivity type semiconductor layer;
A resistor connected between the first electrode and the second electrode;
A semiconductor optical modulator comprising: The semiconductor optical modulator according to claim 3, wherein the resistor has substantially the same impedance as a characteristic impedance of a line connected to the first electrode. Further comprising an insulating layer,
5. The semiconductor optical modulator according to claim 3, wherein the resistor is formed in a thin film on the insulating layer. 6. The resistor according to claim 3, wherein the resistor is formed of a semiconductor having the same quality as at least one of the first conductivity type semiconductor layer, the light absorption layer, and the second conductivity type semiconductor layer. A semiconductor optical modulator according to any one of the preceding claims. An inductance applying unit is provided in at least one of a wiring path between the first electrode and the resistor and a wiring path between the second electrode and the resistor. The semiconductor optical modulator according to any one of claims 2 to 6. The semiconductor optical modulator according to claim 1, wherein the semiconductor optical modulator is integrated with a semiconductor laser. Integrated with a semiconductor laser,
The semiconductor optical modulator according to any one of claims 3 to 7, wherein an active layer of the semiconductor laser is formed continuously with the light absorbing layer. Board and
An electric signal line provided on the substrate,
The semiconductor optical modulator according to any one of claims 2 and 4 to 9 provided on the substrate;
With
The electric signal line is connected to the first electrode,
The optical modulation system, wherein the electric signal line has the first characteristic impedance.

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