Optical modulator and optical semiconductor device

Abstract

To provide an optical modulator and optical semiconductor device, which reduce loss of a modulated signal due to reflection.SOLUTION: An optical modulator is provided, comprising a substrate, an optical modulation unit provided on the substrate and configured to modulate laser light, and a first termination unit with a first resistance film provided on the substrate. The optical modulation unit comprises a modulation electrode to be fed with a modulation signal, a signal pad connected to the modulation electrode and configured to be connected to a first wire for inputting the modulation signal to the optical modulation unit, and a first pad to be connected to a second wire set at a ground potential. The modulation electrode and one end of the first resistance film are connected to each other. The other end of the first resistance film and the first pad are connected to each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an optical modulator and an optical semiconductor device. [Background technology]

[0002] Patent Document 1 discloses a technique relating to a high-frequency circuit, a module in which the high-frequency circuit is mounted, and a communication device. The high-frequency circuit is configured by connecting a signal line that transmits a high-frequency signal to an element having a capacitance with a first bonding wire, and connecting the element having a capacitance to a termination resistor for impedance matching with a second bonding wire. In the high-frequency circuit, the magnitude of the characteristic impedance of the transmission line formed by the first bonding wire, the second bonding wire, and the element having a capacitance is larger than the magnitude of the characteristic impedance on the input side of the high-frequency signal. Also, in the high-frequency circuit, the magnitude of the inductance of the first bonding wire is smaller than the magnitude of the inductance of the second bonding wire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-308130 A Summary of the Invention [Problem to be solved by the invention]

[0004] As the speed and capacity of optical communication increases, a broadband optical modulator for optical semiconductor devices is desired. However, when the frequency of a modulated signal is high, such as 100 GHz or higher, electrical reflection of the modulated signal is likely to be large. When the reflection of the modulated signal is large, the loss of the modulated signal increases. This may result in, for example, the modulated signal not being transmitted sufficiently to the optical modulator.

[0005] An object of the present disclosure is to provide an optical modulator and an optical semiconductor device in which loss of a modulated signal due to reflection is reduced. [Means for solving the problem]

[0006] An optical modulator according to an embodiment of the present disclosure includes a substrate, an optical modulation section provided on the substrate for modulating laser light, and a first termination section provided on the substrate and having a first resistive film. The optical modulation section has a modulation electrode to which a modulation signal is supplied, a signal pad connected to the modulation electrode for connecting to a first wire for inputting the modulation signal to the optical modulation section, and a first pad for connecting to a second wire having a ground potential. The modulation electrode and one end of the first resistive film are connected to each other. The other end of the first resistive film and the first pad are connected to each other. Effect of the Invention

[0007] According to the present disclosure, it is possible to provide an optical modulator and an optical semiconductor device in which loss of a modulated signal due to reflection is reduced. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view showing a small-sized optical device for transmission according to a first embodiment of the present disclosure. [Diagram 2] FIG. 2 is a circuit diagram showing a circuit included in the small-sized optical device for transmission according to the first embodiment. [Diagram 3] FIG. 3 is a perspective view showing an optical semiconductor device included in the small-sized optical device for transmission according to the first embodiment. [Figure 4] FIG. 4 is a plan view showing the optical semiconductor device according to the first embodiment. [Diagram 5] FIG. 5 is an enlarged view showing the pad, the terminal portion, and the modulation electrode according to the first embodiment. [Figure 6] FIG. 6 is a cross-sectional view taken along the line VI-VI shown in FIG. [Figure 7] 7A to 7C are cross-sectional views showing some of the steps for manufacturing the optical semiconductor device shown in FIG. [Figure 8] FIG. 8 is a perspective view showing an optical semiconductor device according to the second embodiment. [Figure 9] FIG. 9 is a plan view showing an optical semiconductor device according to the second embodiment. [Figure 10] FIG. 10 is a perspective view showing an optical semiconductor device according to a first modification. [Figure 11] FIG. 11 is a plan view showing an optical semiconductor device according to a first modification. [Figure 12] FIG. 12 is a plan view showing an optical semiconductor device as a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [Description of the embodiments of the present disclosure] First, the contents of the embodiments of the present disclosure will be listed and described. [1] An optical modulator according to an embodiment of the present disclosure includes a substrate, an optical modulation section provided on the substrate for modulating laser light, and a first termination section provided on the substrate and having a first resistive film. The optical modulation section includes a modulation electrode to which a modulation signal is supplied, a signal pad connected to the modulation electrode for connecting to a first wire for inputting the modulation signal to the optical modulation section, and a first pad for connecting to a second wire having a ground potential. The modulation electrode and one end of the first resistive film are connected to each other. The other end of the first resistive film and the first pad are connected to each other.

[0010] In the optical modulator of [1] above, the modulation electrode, the first pad, and the first resistive film included in the first terminal portion are provided on the same substrate. Therefore, the distance of the conductive path between the modulation electrode and one end of the first resistive film can be made extremely short. This makes it possible to reduce electrical reflection of the modulation signal at one end of the first resistive film in the first terminal portion. Therefore, it is possible to realize an optical modulator in which loss of the modulation signal due to reflection is reduced.

[0011] [2] In the optical modulator of [1] above, the distance of the conductive path between the modulation electrode and one end of the first resistive film may be less than 1 / 4 of the wavelength of the modulated signal. According to the inventor's findings, even if the frequency of the input modulated signal is high, for example, 100 GHz or more, if the distance of the conductive path between the modulation electrode and one end of the first resistive film is less than 1 / 4 of the wavelength of the modulated signal, electrical reflection of the modulated signal at one end of the first resistive film of the first termination part is unlikely to be large. Therefore, the loss of the modulated signal due to reflection can be effectively reduced.

[0012] [3] The optical modulator of [1] or [2] may further include a second termination part having a second resistive film provided on a substrate. The optical modulation part may further include a second pad provided on the opposite side of the signal pad from the first pad for connection to a third wire having a ground potential. The modulation electrode and one end of the second resistive film may be connected to each other. The other end of the second resistive film and the second pad may be connected to each other. In the optical modulator of [3], the third wire connected to the second pad has a ground potential. Therefore, the modulated signal passing through the first wire connected to the signal pad arranged between the first pad and the second pad is sandwiched between the ground potential. This further reduces the mismatch of the input impedance, and further reduces the loss of the modulated signal due to the impedance mismatch. In addition, the modulation electrode, the second pad, and the second resistive film included in the second termination part are provided on the same substrate. Therefore, the distance of the conductive path between the modulation electrode and one end of the second resistive film can be extremely short. This makes it possible to reduce electrical reflection of the modulated signal at one end of the second resistive film in the second terminal portion, thereby making it possible to realize an optical modulator in which loss of the modulated signal due to reflection is further reduced.

[0013] [4] In the optical modulator of [3] above, the distance of the conductive path between the modulation electrode and one end of the second resistive film may be less than 1 / 4 of the wavelength of the modulation signal. This reduces the loss of the modulation signal due to reflection at the one end of the second resistive film, as in the optical modulator of [2] above.

[0014] [5] Any of the optical modulators in [1] to [4] above may further include a laser unit that is provided on the substrate and outputs laser light. This allows the laser unit and the optical modulation unit to be monolithically configured on the same substrate. This allows the transmission optical device to be miniaturized.

[0015] [6] An optical semiconductor device according to an embodiment of the present disclosure includes the optical modulator of [1] or [2] above, and a transmission line for transmitting a modulated signal. The transmission line includes a signal line for transmitting the modulated signal, and a first ground potential line having a ground potential and aligned with the signal line. The signal pad and the signal line are connected by a first wire. The first pad and the first ground potential line are connected by a second wire.

[0016] In the optical semiconductor device of [6] above, the first pad is connected to the ground potential line by the second wire. This allows the second wire having the ground potential to be provided on the optical modulator. The signal line is connected to the first wire. The ground potential line is connected to the second wire. This allows the first wire and the second wire to be arranged side by side. Therefore, the modulated signal travels side by side with the ground potential even after leaving the signal line. This reduces the impedance mismatch between the signal line and the first wire. Therefore, the loss of the modulated signal due to the impedance mismatch of the modulated signal is reduced.

[0017] [7] An optical semiconductor device according to an embodiment of the present disclosure includes the optical modulator of [3] or [4] above, and a transmission line for transmitting a modulated signal. The transmission line includes a signal line for transmitting the modulated signal, and a first ground potential line and a second ground potential line having a ground potential and aligned with the signal line. The signal pad and the signal line are connected by a first wire. The first pad and the first ground potential line are connected by a second wire. The second pad and the second ground potential line are connected by a third wire. The third wire is provided on the opposite side of the first wire to the second wire.

[0018] In the optical semiconductor device of [7] above, the second pad and the ground potential line are connected by the third wire, so that the third wire has a ground potential. Therefore, the first wire arranged in parallel with the second wire and the third wire is sandwiched between the ground potential. Therefore, the modulated signal passing through the first wire advances while being sandwiched between the ground potential. This further reduces the impedance mismatch between the signal line and the first wire. Therefore, the loss due to the impedance mismatch of the modulated signal is further reduced.

[0019] [Details of the embodiment of the present disclosure] Specific examples of the optical modulator and optical semiconductor device of the present disclosure will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. In the following description, the same elements in the description of the drawings will be given the same reference numerals, and duplicated descriptions will be omitted.

[0020] (First embodiment) Fig. 1 is a plan view showing a small-sized optical device for transmission A1 according to a first embodiment of the present disclosure. Fig. 2 is a circuit diagram showing a circuit A2 included in the small-sized optical device for transmission A1. The configuration of the small-sized optical device for transmission A1 will be described with reference to Figs. 1 and 2.

[0021] 1, the small-sized optical device for transmission A1 includes a package 509, a substrate 501 (chip-on-carrier), a substrate 502 (mount carrier), and a substrate 503. The package 509 accommodates the substrates 501, 502, and 503. The substrate 502 is arranged side by side with the substrate 503. The substrate 501 is arranged on the substrate 502. The material of the substrates 501 and 502 is an insulator such as ceramic.

[0022] On the substrate 503, the wiring patterns 111, 112, 114, 115, 116, the ground potential lines 117, 119, the signal lines 118, 121, and the driver IC 504 are provided. The wiring patterns 111, 112, 114, 115, 116, the ground potential lines 117, and the signal line 118 extend from one side wall of the package 509 toward the substrate 502, and are connected to a circuit outside the transmitting small optical device A1 via a terminal (not shown). The wiring patterns 111, 112, 114, 115, 116, the ground potential lines 117, 119, and the signal lines 118, 121 are made of, for example, metal. The signal line 118 propagates a high-frequency modulated signal input from outside the transmitting small optical device A1. The ground potential line 117 has a ground potential (reference potential) input from an external circuit 510 of the transmitting small optical device A1. The signal line 118 and the ground potential line 117 form a transmission line. The ground potential line 119 and the signal line 121 also form a transmission line.

[0023] An input terminal of the driver IC 504 is connected to a ground potential line 117 and a signal line 118. An output terminal of the driver IC 504 is connected to a ground potential line 119 and a signal line 121. The driver IC 504 amplifies the modulated signal from the signal line 118 and outputs the amplified modulated signal to the signal line 121.

[0024] FIG. 2 will be referred to together with FIG. 1. On the substrate 502, wiring patterns 84, 85, 86, a ground potential line 87, a signal line 88, a thermistor 506, a monitor photodiode 507, and a lens L are provided. The wiring pattern 86 is connected to the wiring pattern 116 by a wire 96. The wiring pattern 85 is connected to the wiring pattern 115 by a wire 95. The wiring pattern 84 is connected to the wiring pattern 114 by a wire 94. The ground potential line 87 is connected to the ground potential line 119 by a wire 97. The signal line 88 is connected to the signal line 121 by a wire 98. The wiring patterns 84, 85, 86, the ground potential line 87, and the signal line 88 are made of, for example, a metal. The wiring patterns 84, 85, 86, the ground potential line 87, and the signal line 88 are formed on an insulator by, for example, deposition and subsequent lift-off, or sputtering.

[0025] The thermistor 506 is provided on the wiring pattern 86. The thermistor 506 exhibits a resistance value that depends on temperature. This resistance value is detected by a circuit outside the transmitting small-sized optical device A1 via the wiring pattern 86, the wire 96, and the wiring pattern 116.

[0026] The monitor photodiode 507 is connected between the wiring pattern 84 and the ground potential line 87. In order to keep the average intensity of the emitted light M constant, the monitor photodiode 507 detects the backlight emitted from an optical modulator integrated semiconductor laser a (described later) of the optical semiconductor device A. The monitor photodiode 507 outputs an electric signal according to the intensity of the backlight to a circuit outside the transmitting small optical device A1 via the wiring pattern 84, the wire 94, and the wiring pattern 114. The lens L is optically coupled to the light emitting end of the optical semiconductor device A, and collimates the emitted light M emitted from the optical modulator integrated semiconductor laser a.

[0027] A temperature control element (TEC) 508 (shown only in FIG. 2) is provided on the back side of the substrate 502. One electrode of the TEC 508 is connected to the wiring pattern 111 by a wire 91. The other electrode of the TEC 508 is connected to the wiring pattern 112 by a wire 92. Power for driving the TEC 508 is input from a circuit external to the transmitting small optical device A1 via the wiring patterns 111 and 112. The circuit external to the transmitting small optical device A1 controls the magnitude of the power for driving the TEC 508 based on the ambient temperature of the optical semiconductor device A (i.e., the resistance value of the thermistor 506). This maintains the temperature of the optical modulator integrated semiconductor laser a at a predetermined temperature, and maintains the wavelength of the emitted light M output from the optical semiconductor device A at a predetermined wavelength.

[0028] A ground potential line 66, a wiring pattern 65, a bypass capacitor 505, and an optical semiconductor device A are provided on the substrate 501. One end of the ground potential line 66 is connected to a ground terminal of the thermistor 506 by a wire 76, and the other end of the ground potential line 66 is connected to a ground pattern 19 (described later). The material of the ground potential line 66 is, for example, a metal. The ground potential line 66 has a ground potential.

[0029] The bypass capacitor 505 is provided on the ground potential line 66. The bottom electrode of the bypass capacitor 505 is connected to the ground potential line 66. The top electrode of the bypass capacitor 505 is connected to the wiring pattern 65 by the wire 55. The material of the wiring pattern 65 is, for example, a metal.

[0030] Fig. 3 is a perspective view showing the optical semiconductor device A included in the small optical device for transmission A1. Fig. 4 is a plan view showing the optical semiconductor device A. As shown in Figs. 3 and 4, the optical semiconductor device A has an optical modulator integrated semiconductor laser a, a ground pattern 19, and a transmission line 200. The ground pattern 19 is provided on a substrate 501. The material of the ground pattern 19 is, for example, a metal. The ground pattern 19 has a ground potential.

[0031] The transmission line 200 includes a ground potential line 17 (first ground potential line) and a signal line 18. The ground potential line 17 is provided alongside the signal line 18 in a direction intersecting the direction in which the ground potential line 17 extends. The material of the ground potential line 17 and the signal line 18 is, for example, a metal. As shown in FIG. 1, one end of the ground potential line 17 is connected to a ground potential line 87 by a wire 77. The ground potential line 17 has a ground potential. As shown in FIG. 1, one end of the signal line 18 is connected to a signal line 88 by a wire 78. The signal line 18 transmits an amplified modulated signal.

[0032] The optical modulator integrated semiconductor laser a described in this embodiment is an example of an optical modulator of the present disclosure. The optical modulator integrated semiconductor laser a is provided on a ground pattern 19, and includes a substrate 6, a laser section 1, an optical modulation section 100, and a terminal section 300 (first terminal section). The substrate 6 has a rectangular parallelepiped shape. The laser section 1 is disposed on the substrate 6 on the substrate 503 side with respect to the optical modulation section 100. As shown in FIG. 1, the laser section 1 is sandwiched between a transmission line 200 and a ground potential line 66. The laser section 1 has an active region, and generates laser light having a constant optical intensity over time by supplying a current to the active region. The laser section 1 has a driving electrode 10 and a pad 7 on its surface. The driving electrode 10 extends along the laser resonance direction (the direction in which the laser section 1 and the optical modulation section 100 are arranged) and supplies a current to the active region. The pad 7 is arranged next to the driving electrode 10 in a direction intersecting the extending direction of the driving electrode 10, and is connected to the driving electrode 10. The pad 7 is connected to the upper electrode of the bypass capacitor 505 by a wire 9. As a result, a driving current is supplied to the driving electrode 10 from the outside of the transmitting small optical device A1 via the wiring pattern 115, the wiring pattern 85, the wiring pattern 65, the upper electrode of the bypass capacitor 505, and the pad 7.

[0033] The optical modulation section 100 is provided on the lens L side with respect to the laser section 1. The optical modulation section 100 modulates the laser light output from the laser section 1 and outputs the modulated emitted light M. The above-mentioned back light is the laser light output from the laser section 1 without passing through the optical modulation section 100. The laser section 1 and the optical modulation section 100 are monolithically formed on the substrate 6. The optical modulation section 100 includes a modulation electrode 2, a pad 3 (first pad), and a pad 4 (signal pad). The optical modulation section 100 has a modulation region, and modulates the laser light by transmitting or blocking the laser light according to the supply of current to the modulation region. The modulation electrode 2 supplies a modulation current (modulation signal) to the modulation region. As a result, the laser light is passed or blocked in the modulation region based on the input modulation signal. The modulation electrode 2 extends in the same direction as the traveling direction of the laser light in a plan view. On the upper surface of the optical modulator integrated semiconductor laser a, the modulation electrode 2 is provided approximately in the center in a direction perpendicular to the traveling direction of the laser light.

[0034] The pad 3 and the pad 4 are provided on the transmission line 200 side with respect to the modulation electrode 2. The pad 4 is provided in the center of the optical modulation section 100 in the traveling direction of the laser light. The pad 4 is connected to the modulation electrode 2, and is connected to a wire 16 (first wire) for inputting a modulation signal to the optical modulation section 100. The pad 3 is provided alongside the pad 4 along the longitudinal direction of the modulation electrode 2, and is provided on the laser section 1 side with respect to the pad 4. The pad 3 is connected to a wire 15 (second wire) having a ground potential. The pad 3 and the pad 4 are in the form of a film, and have a substantially rectangular shape in a plan view. The material of the pad 3 and the pad 4 is a metal, for example, gold (Au). The film thickness of the pad 3 and the pad 4 is, for example, 3 μm or more and 10 μm or less.

[0035] The other end of the ground potential line 17 is in contact with the ground pattern 19 and is connected to the pad 3 by the wire 15. The other end of the signal line 18 is connected to the pad 4 by the wire 16. The wire 15 is provided in parallel with the wire 16. As shown in FIG. 4, in one example, the wire 15 and the wire 16 are provided parallel to each other in a plan view. The wire 15 and the wire 16 are bonding wires made of, for example, Au. The cross-sectional diameter of the wire 15 and the wire 16 is, for example, 25 μm. The distance between the wire 15 and the wire 16 is, for example, several tens of μm.

[0036] The termination section 300 is provided between the pad 3 and the modulation electrode 2. The termination section 300 has a resistive film 31 (first resistive film) and reduces reflection of the modulation signal. FIG. 5 is an enlarged view showing the pad 3, the termination section 300, and the modulation electrode 2 according to the first embodiment. The modulation electrode 2 and one end Y of the resistive film 31 are connected to each other via a wiring pattern 38. The other end of the resistive film 31 and the pad 3 are connected to each other. The distance (electrical length) L1 of the conductive path between the connection end X of the modulation electrode 2 and one end Y of the resistive film 31 is less than 1 / 4, less than 1 / 8, less than 1 / 10, or less than 1 / 12 of the wavelength of the modulation signal, and is 1 / 1000 or more. As a specific example, when the wavelength of the modulation signal is, for example, 1200 μm, L1 is less than 300 μm, less than 150 μm, less than 120 μm, or less than 100 μm, and is 1 μm or more. The resistive film 31 has a rectangular shape. The material of the resistive film 31 is a metal such as nickel chromium (NiCr), titanium tungsten (TiW), tantalum nitride (TaN), or platinum (Pt). The film thickness of the resistive film 31 is, for example, 100 nm to 300 nm. The resistive film 31 is made of a thin film resistive pattern formed by vapor deposition and subsequent lift-off, sputtering, or the like. When the impedance value of the light absorption layer is, for example, 90 Ω, the resistance value of the resistive film 31 is set to, for example, 110 Ω, so that the termination impedance value becomes 50 Ω. Note that the termination impedance value is generally often 50 Ω, but may be different from 50 Ω due to the addition of a capacitor or inductor, or adjustment of the resistance value.

[0037] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 4. The optical modulation section 100 has a passivation film 101 and a seed layer 103 (SEED layer) on a substrate 6. The substrate 6 is provided on the ground pattern 19 in contact with the ground pattern 19. The substrate 6 is made of, for example, SI-InP, n-InP, or a dielectric. The passivation film 101 is provided on the substrate 6. The material of the passivation film 101 is an insulator such as SiO2 or SiN. The thickness of the passivation film 101 is, for example, 300 nm or more and 500 nm or less. The resistive film 31 is provided on the passivation film 101. The pad 3 and the wiring pattern 38 are provided on the passivation film 101, and have a portion provided on the resistive film 31 and a portion provided in an area where the resistive film 31 is not present. A seed layer 103 is provided between the pad 3 and the wiring pattern 38 and the passivation film 101, and between the pad 3 and the wiring pattern 38 and the resistive film 31. The material of the seed layer 103 is, for example, gold (Au). The layer thickness of the seed layer 103 is, for example, 100 nm or more and 200 nm or less. The pad 3 and the wiring pattern 38 are not in contact with each other, and the resistive film 31 has a portion exposed from the pad 3 and the wiring pattern 38.

[0038] FIG. 7 is a cross-sectional view showing a part of the process for manufacturing the optical semiconductor device A shown in FIG. 4. A part of the manufacturing process for the optical semiconductor device A will be described. In the optical modulation section 100, first, a substrate 6 is prepared. Next, a passivation film 101 is formed on the substrate 6. After that, a resist mask (not shown) is formed on the surface of the passivation film 101 by photolithography, and a resistive film 31 is formed on the passivation film 101. Next, a seed layer 103 is formed on the surfaces of the resistive film 31 and the passivation film 101. After that, a resist mask 104 with an opening 3A and an opening 4A is formed on the surface of the seed layer 103 by photolithography. Next, a pad 3 is formed in the opening 3A by gold plating the opening 3A and the opening 4A, and a wiring pattern 38 is formed in the opening 4A. Finally, the resist mask 104 is removed from the optical modulation section 100, and the seed layer 103 is removed using the pad 3 and the wiring pattern 38 as a mask. As a result, the pad 3, the terminal section 300, and the wiring pattern 38 in FIG. 6 are formed.

[0039] The effects obtained by the optical semiconductor device A having the above configuration will be described. FIG. 12 is a plan view showing an optical semiconductor device D as a comparative example. The optical semiconductor device D differs from the optical semiconductor device A in the following points. The optical semiconductor device D includes an optical modulator integrated semiconductor laser d and a terminal section 320 instead of the optical modulator integrated semiconductor laser a. The optical modulator integrated semiconductor laser d has an optical modulation section 130 instead of the optical modulation section 100. The optical modulation section 130 is disposed on the lens side (not shown) with respect to the laser section 1. The optical modulation section 130 does not include the pad 3, the wires 15 and 24, and the terminal section 300. The terminal section 320 is disposed on the substrate 501 on the opposite side of the transmission line 200 with respect to the optical modulation section 130. The terminal section 320 includes wiring patterns 34 and 36 and a resistive film 33 arranged along the arrangement direction of the laser section 1 and the optical modulation section 130. The resistive film 33 is disposed between the wiring patterns 34 and 36. The wiring pattern 34 is connected to the pad 4 by a wire 35. The wiring pattern 36 is in contact with the ground pattern 19. In the optical semiconductor device D, since the termination portion 320 is provided outside the optical modulator integrated semiconductor laser d, the length of the transmission path from one end W of the resistive film 33 of the termination portion 320 to the connection point V of the wire 16 and the pad 4 becomes large. In that case, since the impedance mismatch becomes large, the electrical reflection of the modulated signal at the resistive film 33 is likely to become large due to the broadband of the optical modulator integrated semiconductor laser. In contrast, in the optical semiconductor device A, the modulating electrode 2, the pad 3, and the resistive film 31 included in the termination portion 300 are provided on the same substrate 6. Therefore, the distance L1 of the conductive path between the connection end X of the modulating electrode 2 and one end Y of the resistive film 31 can be reduced. Therefore, in the optical semiconductor device A, the electrical reflection of the modulated signal at the resistive film 31 of the termination portion 300 is unlikely to become large. Therefore, it is possible to realize an optical modulator integrated semiconductor laser a in which the loss of the modulated signal is reduced.

[0040] Also, in the optical semiconductor device A, the pad 3 is connected to the ground potential line 17 by the wire 15. This allows the wire 15 having the ground potential to be provided on the optical modulator integrated semiconductor laser a. The signal line 18 is connected to the wire 16. The ground potential line 17 is connected to the wire 15. This allows the wire 15 and the wire 16 to be arranged side by side. Therefore, the modulated signal travels side by side with the ground potential even after leaving the signal line 18. This reduces the impedance mismatch between the signal line 18 and the wire 16. Therefore, the loss of the modulated signal due to the impedance mismatch of the modulated signal is reduced.

[0041] As in this embodiment, the distance L1 of the conductive path between the connection end X of the modulation electrode 2 and one end Y of the resistive film 31 may be less than ¼ of the wavelength of the modulated signal. According to the inventor's knowledge, even if the frequency of the input modulated signal is high, for example, 100 GHz or more, if the distance of the conductive path between the connection end X of the modulation electrode 2 and one end Y of the resistive film 31 is less than ¼ of the wavelength of the modulated signal, the electrical reflection of the modulated signal at one end Y of the resistive film 31 is unlikely to be large. Therefore, the loss of the modulated signal due to reflection can be effectively reduced. In addition, in 100 Gbps communication, the value of ¼ of the wavelength of the modulated signal is, for example, 300 μm, and it is desirable that the distance L1 is, for example, 100 μm or less.

[0042] As in this embodiment, in the optical semiconductor device A, the resistive film 31 may contain at least one material included in the group consisting of nickel chromium, titanium tungsten, tantalum nitride, and platinum. This improves the adhesion between the resistive film 31 and the passivation film 101. In addition, a desired resistance value can be achieved.

[0043] As in this embodiment, the wire 15 and the wire 16 may be provided parallel to each other in the optical semiconductor device A. By providing the wire 15 and the wire 16 parallel to each other, the impedance mismatch between the signal line 18 and the wire 16 is further reduced. Therefore, the loss of the modulated signal due to the impedance mismatch is further reduced.

[0044] As in this embodiment, the laser section 1 that outputs laser light may be provided on the substrate 6. This allows the laser section 1 and the optical modulation section 100 to be monolithically configured on the same substrate 6, thereby making it possible to miniaturize the transmitting small optical device A1.

[0045] Second embodiment Fig. 8 is a perspective view showing an optical semiconductor device B according to the second embodiment. Fig. 9 is a plan view showing the optical semiconductor device B. The optical semiconductor device B differs from the optical semiconductor device A in the following points, but is the same as the optical semiconductor device A in other points. The optical semiconductor device B includes an optical modulator-integrated semiconductor laser b instead of the optical modulator-integrated semiconductor laser a, and a transmission line 210 instead of the transmission line 200. The optical modulator-integrated semiconductor laser b has an optical modulation section 110 instead of the optical modulation section 100. The other configurations of the optical modulator-integrated semiconductor laser b are the same as those of the optical modulator-integrated semiconductor laser a.

[0046] The optical modulator integrated semiconductor laser b further includes a terminal end 310 (second terminal end) in addition to the terminal end 300, and the optical modulation section 110 further includes a pad 5 (second pad) in addition to the pads 3 and 4. The pad 5 is provided on the substrate 6 on the opposite side of the pad 3 with respect to the pad 4, and is connected to a wire 22 (third wire) having a ground potential. The pad 5 is in the form of a film and has a substantially rectangular shape in a plan view. The material of the pad 5 is a metal, for example, gold (Au). The film thickness of the pad 5 is, for example, 3 μm or more and 10 μm or less.

[0047] The termination section 310 has a resistive film 32 (second resistive film) and reduces reflection of the modulated signal. The termination section 310 is provided on the substrate 6. One end of the resistive film 32 is connected to the modulated electrode 2 via the wiring pattern 37. The other end of the resistive film 32 is connected to the pad 5. The distance (electrical length) L2 of the conductive path between the connection end P of the modulated electrode 2 and one end Q of the resistive film 32 is less than 1 / 4, less than 1 / 8, less than 1 / 10, or less than 1 / 12 of the wavelength of the modulated signal, and is 1 / 1000 or more. As a specific example, when the wavelength of the modulated signal is, for example, 1200 μm, L2 is less than 300 μm, less than 150 μm, less than 120 μm, or less than 100 μm, and is 1 μm or more. The resistive film 32 has a rectangular shape. The material of the resistive film 32 is a metal such as nickel chromium (NiCr), titanium tungsten (TiW), tantalum nitride (TaN), or platinum (Pt). The film thickness of the resistive film 32 is, for example, 100 nm to 300 nm. The resistive film 32 is formed by deposition, lift-off, sputtering, or the like. When the impedance value of the light absorption layer is, for example, 90 Ω, the resistance value of the resistive film 32 is, for example, 220 Ω, so that the termination impedance value becomes 50 Ω. Note that the termination impedance value is generally often 50 Ω, but may be different from 50 Ω due to the addition of a capacitor or inductor, or adjustment of the resistance value.

[0048] The transmission line 210 has a signal line 18, a ground potential line 17, and a ground potential line 23 (second ground potential line). The ground potential line 23 is connected to the pad 5 by a wire 22. The signal line 18 transmits a modulated signal, and the ground potential line 17 and the ground potential line 23 have a ground potential.

[0049] The wire 22 is provided on the opposite side of the wire 16 to the wire 15. The wire 22 is, for example, a bonding wire made of Au. The cross-sectional diameter of the wire 22 is, for example, 25 μm.

[0050] In the optical semiconductor device B having the above configuration, when the pad 5 and the ground potential line 23 are connected by the wire 22, the wire 22 has a ground potential. Therefore, the wire 16 arranged in parallel with the wire 15 and the wire 22 is sandwiched between the ground potential. Therefore, the modulated signal passing through the wire 16 advances while being sandwiched between the ground potential. This further reduces the impedance mismatch between the signal line 18 and the wire 16. Therefore, the loss due to the impedance mismatch of the modulated signal is further reduced. In addition, the modulated electrode 2, the pad 5, and the resistive film 32 are provided on the same substrate 6. Therefore, the distance L2 of the conductive path between the connection end P of the modulated electrode 2 and one end Q of the resistive film 32 can be extremely short. This makes it possible to reduce the electrical reflection of the modulated signal at the one end Q of the resistive film 32. Therefore, it is possible to realize an optical modulator in which the loss of the modulated signal due to reflection is further reduced.

[0051] As in this embodiment, the distance L2 of the conductive path between the connection end P of the modulation electrode 2 and one end Q of the resistive film 32 may be less than ¼ of the wavelength of the modulation signal. This makes it possible to effectively reduce the loss of the modulation signal due to reflection at the one end Q of the resistive film 32.

[0052] (First Modification) Fig. 10 is a perspective view showing an optical semiconductor device C according to a first modification. Fig. 11 is a plan view showing the optical semiconductor device C. The optical semiconductor device C differs from the optical semiconductor device A in the following points, but is the same as the optical semiconductor device A in other points. The optical semiconductor device C includes an optical modulator-integrated semiconductor laser c instead of the optical modulator-integrated semiconductor laser a, and a transmission line 220 instead of the transmission line 200. The optical modulator-integrated semiconductor laser c has an optical modulation section 120 instead of the optical modulation section 100. The other configurations of the optical modulator-integrated semiconductor laser c are the same as those of the optical modulator-integrated semiconductor laser a.

[0053] In the optical modulation section 120, the pad 3 is disposed on the opposite side of the pad 4 from the laser section 1, and the pad 4 is disposed on the laser section 1 side from the pad 3. That is, in the optical modulation section 120, the positions of the pad 3 and the pad 4 are swapped with respect to the optical modulation section 100. The termination section 300 is disposed on the opposite side of the pad 4 from the laser section 1.

[0054] In the transmission line 220, the signal line 18 is disposed on the laser unit 1 side with respect to the ground potential line 17, and the ground potential line 17 is disposed on the opposite side of the signal line 18 from the laser unit 1. That is, in the transmission line 220, the position of the signal line 18 and the position of the ground potential line 17 are interchanged with respect to the transmission line 200.

[0055] The optical semiconductor device C having the above configuration also provides the same effects as those of the optical semiconductor device A.

[0056] The optical modulator and optical semiconductor device according to the present disclosure are not limited to the above-mentioned embodiment and each modified example, and various other modifications are possible. For example, in the above-mentioned embodiment, the wire 15 and the wire 16 are parallel to each other, but the wire 15 and the wire 16 may be inclined to each other. Similarly, in the first modified example, the wire 22 and the wire 16 may be inclined to each other. Even in that case, the above-mentioned effect can be achieved by arranging the wire 15 and the wire 16 side by side (or by sandwiching the wire 16 between the wire 15 and the wire 22).

[0057] In the above embodiment, the ground potential line 17 of the transmission line 200 is provided on the substrate 502 alongside the signal line 18, but the form of the transmission line is not limited to this. For example, even if the transmission line is configured as a so-called microstrip line in which the ground potential line is provided on the back surface of the substrate 501, the above-mentioned effects can be achieved. [Explanation of symbols]

[0058] 1...Laser section 2...Modulation electrode 3~5,7…Pad 3A,4A…Aperture 6,501~503…Substrate 9,15,16,22,24,25,35,55,76~78,91,92,94~98…Wire 10...Drive electrode 17, 23, 66, 87, 117, 119...Ground potential lines 18,88,118,121...Signal line 19…Grand pattern 31~33…Resistance film 34, 36~38, 65, 84~86, 111, 112, 114~116...Wiring pattern 100, 110, 120...Optical modulation section 101...passivation film 103…Seed layer 104...Resist mask 200, 210…Transmission lines 300, 310, 320...Terminal section 504...Driver IC 505...Bypass capacitor 506…Thermistor 507...Monitor photodiode 508…TEC 509…Package 510…Circuit A to D: Optical semiconductor device a-d...Optical modulator integrated semiconductor laser A1: Small optical device for transmission A2…Circuit L…Lens M…Outgoing light P,X…Connection end V…Connection point Q,W,Y…one end L1,L2…distance

Claims

1. A substrate; a light modulation unit provided on the substrate and configured to modulate a laser beam; a first termination portion provided on the substrate and having a first resistive film; Equipped with The optical modulation unit is a modulation electrode to which a modulation signal is applied; a signal pad connected to the modulation electrode and for connection to a first wire for inputting the modulation signal to the optical modulation unit; a first pad for connection to a second wire having a ground potential; having the modulation electrode and one end of the first resistive film are connected to each other, The other end of the first resistive film and the first pad are connected to each other.

2. The optical modulator according to claim 1 , wherein a distance of a conductive path between the modulation electrode and the one end of the first resistive film is less than ¼ of a wavelength of the modulation signal.

3. a second termination portion provided on the substrate and having a second resistive film; The optical modulation unit is a second pad provided on an opposite side of the signal pad from the first pad for connection to a third wire having the ground potential; the modulation electrode and one end of the second resistive film are connected to each other; The optical modulator according to claim 1 , wherein the other end of the second resistive film and the second pad are connected to each other.

4. 4. The optical modulator according to claim 3, wherein a distance of a conductive path between the modulation electrode and the one end of the second resistive film is less than 1 / 4 of a wavelength of the modulation signal.

5. 4. The optical modulator according to claim 1, further comprising a laser unit provided on said substrate and outputting said laser light.

6. An optical modulator according to claim 1; a transmission line for transmitting the modulated signal; Equipped with The transmission line is A signal line for transmitting the modulated signal; a first ground potential line having the ground potential and arranged alongside the signal line; having the signal pad and the signal line are connected by the first wire; the first pad and the first ground potential line are connected by the second wire.

7. An optical modulator according to claim 3; a transmission line for transmitting the modulated signal; Equipped with The transmission line is A signal line for transmitting the modulated signal; a first ground potential line and a second ground potential line having the ground potential and arranged in parallel with the signal line; having the signal pad and the signal line are connected by the first wire; the first pad and the first ground potential line are connected by the second wire; the second pad and the second ground potential line are connected by the third wire; The third wire is provided on an opposite side of the first wire to the second wire.

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