OPTICAL MODULATOR INTEGRATED SEMICONDUCTOR LASER AND SEMICONDUCTOR LIGHT-EMITTING DEVICE

An optical modulator integrated semiconductor laser includes a laser unit outputting a laser beam, an optical modulation unit modulating the laser beam, a signal pad for connection to a first wire for inputting a modulation signal to the optical modulation unit, and a first pad for connection to a second wire holding a ground potential.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority from Japanese Patent Application No. 2023-075845, filed on May 1, 2023, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an optical modulator integrated semiconductor laser and a semiconductor light-emitting device.

BACKGROUND

Patent Document 1 (Japanese Unexamined Patent Publication No. 2001-308130) discloses a technique of a high-frequency circuit, a module in which the high-frequency circuit is mounted, and a communicator. The high-frequency circuit has a configuration in which a signal line for transmitting a high-frequency signal is connected with a capacitive element by a first bonding wire and the capacitive element is connected with a termination resistor for matching impedance by a second bonding wire. In such a high-frequency circuit, a magnitude of a characteristic impedance of a transmission line formed by the first bonding wire, the second bonding wire, and the capacitive element is larger than a magnitude of a characteristic impedance on an input side of a high-frequency signal. In the high-frequency circuit, a magnitude of an inductance of the first bonding wire is smaller than a magnitude of an inductance of the second bonding wire.

SUMMARY

The present disclosure provides an optical modulator integrated semiconductor laser. The optical modulator integrated semiconductor laser includes: a laser unit including an active region and outputting a laser beam; an optical modulation unit including a modulation region and modulating the laser beam; and a first pad for connection to a wire holding a ground potential. The optical modulation unit includes a modulation electrode for transmitting or cutting off the laser beam based on an input modulation signal and a signal pad connected to the modulation electrode and configured for connection to another wire for inputting the modulation signal in the modulation region.

DETAILED DESCRIPTION

Problem to be Solved by Present Disclosure

With an increase in speed and capacity of optical communication, there is need for an increase in bandwidth of a semiconductor light-emitting element of a semiconductor light-emitting device. However, mismatch in input impedance is likely to occur due to the increase in bandwidth of an element. A loss of an input modulation signal increases, for example, in a junction of a transmission line in the semiconductor light-emitting device due to the mismatch in input impedance. Accordingly, for example, a modulation signal may not be satisfactorily transmitted to an optical modulation element.

Effects of Present Disclosure

According to the present disclosure, it is possible to provide an optical modulator integrated semiconductor laser and a semiconductor light-emitting device that can reduce a loss of a modulation signal due to mismatch in impedance.

DESCRIPTION OF EMBODIMENTS OF PRESENT DISCLOSURE

Details of embodiments of the present disclosure will be first described in a list.

[1] An optical modulator integrated semiconductor laser according to an embodiment of the present disclosure includes: a laser unit outputting a laser beam; an optical modulation unit modulating the laser beam; a signal pad for connection to a first wire for inputting a modulation signal to the optical modulation unit; and a first pad for connection to a second wire holding a ground potential.

The optical modulator integrated semiconductor laser according to [1] includes the signal pad and the first pad. Accordingly, wires can be connected to the signal pad and the first pad. The second wire connected to the first pad holds the ground potential. Accordingly, a modulation signal passing through the first wire connected to the signal pad advances along with the ground potential. Accordingly, it is possible to decrease mismatch in input impedance. As a result, it is possible to reduce a loss of a modulation signal due to mismatch in impedance.

[2] The optical modulator integrated semiconductor laser according to [1] may further include a second pad for connection to a third wire holding the ground potential. The third wire connected to the second pad holds the ground potential. Accordingly, a modulation signal passing through the first wire connected to the signal pad disposed between the first pad and the second pad is sandwiched in the ground potential. As a result, it is possible to further decrease mismatch in input impedance. Accordingly, it is possible to further reduce a loss of the modulation signal due to the mismatch in impedance.

[3] In the optical modulator integrated semiconductor laser according to [1], the first pad and the signal pad may be provided in the optical modulation unit. Accordingly, the first pad is disposed at a position close to the signal pad. As a result, a distance between the first wire through which the modulation signal passes and the second wire holding the ground potential becomes smaller, and it is possible to more easily achieve match in input impedance.

[4] A semiconductor light-emitting device according to another embodiment of the present disclosure includes: the optical modulator integrated semiconductor laser according to any one of [1] to [3]; and a transmission line connected to the optical modulation unit to transmit a modulation signal. The transmission line includes a signal line for transmitting the modulation signal and a ground potential line holding the ground potential. The signal pad is connected with the signal line by the first wire, and the first pad provided on one side of the signal pad is connected with the ground potential line by the second wire.

In the semiconductor light-emitting device according to [4], the first pad is connected to the ground potential line by the second wire. Accordingly, the second wire holding the ground potential can be provided in the optical modulator integrated semiconductor laser. The signal line is connected to the first wire. The ground potential line is connected to the second wire. In general, since the signal line and the ground potential line of the transmission line are arranged side by side, the first wire and the second wire are arranged side by side with each other. Accordingly, the modulation signal progresses side by side with the ground potential even after the modulation signal has gotten away from the signal line. As a result, it is possible to decrease mismatch in impedance between the signal line and the first wire. Accordingly, it is possible to reduce a loss of the modulation signal due to the mismatch in impedance.

[5] In the semiconductor light-emitting device according to [4], a second pad may be provided on another side of the signal pad. For example, when the second pad is connected with the ground potential line by the third wire, the third wire holds the ground potential. Accordingly, the first wire disposed along with the second wire and the third wire is sandwiched in the ground potential. Therefore, the modulation signal passing through the first wire progresses side by side with the ground potential. As a result, it is possible to further decrease mismatch in impedance between the signal line and the first wire. Accordingly, it is possible to further reduce a loss of the modulation signal due to the mismatch in impedance.

[6] The semiconductor light-emitting device according to [4] may further include: a termination unit provided on the opposite side of the transmission line with respect to the optical modulation unit and configured to reduce reflection of the modulation signal; a fourth wire; and a fifth wire. The termination unit includes a first wiring pattern, a resistor of which one end is connected to the first wiring pattern, and a second wiring pattern to which another end of the resistor is connected. The first wiring pattern is connected with the signal pad by the fourth wire. The second wiring pattern is connected with the first pad by the fifth wire. In this case, the fifth wire holds the ground potential. The fourth wire and the fifth wire are arranged side by side with each other. Accordingly, the modulation signal propagating in the fourth wire progresses side by side with the ground potential. As a result, it is possible to further decrease mismatch in impedance between the first wire and the fourth wire. Accordingly, it is possible to further reduce a loss of the modulation signal due to the mismatch in impedance.

[7] The semiconductor light-emitting device according to [6] may further include: a sixth wire; and a second pad provided on another side of the signal pad. The second wiring pattern may be connected with the second pad by the sixth wire. In this case, the third wire and the sixth wire hold the ground potential. Accordingly, the first wire arranged along with the second wire and the third wire is sandwiched in the ground potential. Similarly, the third wire arranged along with the fifth wire and the sixth wire is sandwiched in the ground potential. Accordingly, the modulation signal passing through the first wire and the third wire progresses side by side with the ground potential. As a result, it is possible to further decrease mismatch in impedance between the signal line and the first wire or the third wire. Accordingly, it is possible to further reduce a loss of the modulation signal due to the mismatch in impedance.

[8] In the semiconductor light-emitting device according to [7], the second wiring pattern may be connected to only the resistor, the fifth wire, and the sixth wire. Accordingly, since a current returning to the ground passes through only the fifth wire and the sixth wire, an amount of current of an input modulation current is balanced with an amount of current flowing in the wire holding the ground potential. As a result, it is possible to improve accuracy of match in input impedance.

[9] In the semiconductor light-emitting device according to [6], the second wiring pattern may be connected to only the resistor and the fifth wire. Accordingly, since a current returning to the ground passes through only the fifth wire, an amount of current of an input modulation current is balanced with an amount of current flowing in the wire holding the ground potential. As a result, it is possible to improve accuracy of match in input impedance.

[10] In the semiconductor light-emitting device according to [4] or [6], the first wire and the second wire may be provided in parallel with each other. By providing the first wire and the second wire to be parallel with each other, it is possible to more easily decrease mismatch in impedance between the signal line and the first wire. Accordingly, it is possible to further reduce a loss of the modulation signal due to mismatch in impedance.

Details of Embodiment of Present Disclosure

Specific examples of an optical modulator integrated semiconductor laser and a semiconductor light-emitting device according to the present disclosure will be described below with reference to the accompanying drawings. The present disclosure is not limited to these examples, is defined by the appended claims, and is intended to include all modifications within meanings and scopes equivalent to the claims. In the following description, the same elements in description with reference to the drawings will be referred to by the same reference signs, and repeated description thereof will be omitted. In the following description, connection means electrical connection and includes connection via an electronic component such as a resistor in addition to connection via conductive line of which an electrical resistance is substantially zero unless otherwise mentioned.

First Embodiment

FIG.1is a plan view illustrating a transmitting small-sized optical device A1according to a first embodiment of the present disclosure.FIG.2is a circuit diagram illustrating a circuit A2included in the transmitting small-sized optical device A1.FIG.3is a perspective view illustrating a semiconductor light-emitting device A included in the transmitting small-sized optical device A1.FIG.4is a plan view illustrating the semiconductor light-emitting device A. The configuration of the transmitting small-sized optical device A1will be described with reference toFIGS.1to4.

As illustrated inFIG.1, the transmitting small-sized optical device A1includes a package509, a substrate501(a chip-on carrier), a substrate502(a mount carrier), and a substrate503. The package509accommodates the substrate501, the substrate502, and the substrate503. A wiring pattern114, a wiring pattern115, a wiring pattern116, ground potential lines117and119, signal lines118and121, a wiring pattern111, a wiring pattern112, and a driver IC504are provided on the substrate503. The wiring pattern114, the wiring pattern115, the wiring pattern116, the ground potential line117, the signal line118, the wiring pattern111, and the wiring pattern112extend from one side wall of the package509toward the substrate502and are connected to an external circuit outside of the transmitting small-sized optical device A1via terminals which are not illustrated. The material of the substrate501is, for example, an insulator such as a resin. The material of the wiring pattern114, the wiring pattern115, the wiring pattern116, the ground potential lines117and119, the signal lines118and121, the wiring pattern111, and the wiring pattern112is, for example, a metal. The signal line118causes a high-frequency modulation signal input from the outside of the transmitting small-sized optical device A1to propagate. The ground potential line117holds a ground potential (a reference potential) input from the outside of the transmitting small-sized optical device A1. The signal line118and the ground potential line117constitute a transmission line. The ground potential line119and the signal line121also constitute a transmission line. An input terminal of the driver IC504is connected to the ground potential line117and the signal line118. An output terminal of the driver IC504is connected to the ground potential line119and the signal line121. The driver IC504amplifies the modulation signal from the signal line118and outputs the amplified modulation signal to the signal line121.

As illustrated inFIG.2, the substrate502is disposed along with the substrate503. A wiring pattern84, a wiring pattern85, a wiring pattern86, a ground potential line87, a signal line88, a thermistor506, a monitoring photodiode507, and a lens L are provided on the substrate502. The wiring pattern86is connected to the wiring pattern116by a wire96. The wiring pattern85is connected to the wiring pattern115by a wire95. The wiring pattern84is connected to the wiring pattern114by a wire94. The ground potential line87is connected to the ground potential line119by a wire97. The signal line88is connected to the signal line121by a wire98. The material of the substrate502is, for example, an insulator such as ceramics. The material of the wiring pattern84, the wiring pattern85, the wiring pattern86, the ground potential line87, and the signal line88is, for example, a metal. The thermistor506is provided on the wiring pattern86. The thermistor506indicates a resistance value depending on the temperature. The resistance value is detected by an external circuit outside of the transmitting small-sized optical device A1via the wiring pattern86, the wire96, and the wiring pattern116. The monitoring photodiode507is connected between the wiring pattern84and the ground potential line87. In order to make an average intensity of emission light M constant, the monitoring photodiode507detects backlight emitted from an optical modulator integrated semiconductor laser A3(which will be described later) of the semiconductor light-emitting device A. The monitoring photodiode507outputs an electrical signal based on the intensity of the backlight to the external circuit outside of the transmitting small-sized optical device A1via the wiring pattern84, the wire94, and the wiring pattern114. The lens L is optically coupled to a light emission end of the semiconductor light-emitting device A and collimates emission light M emitted from the optical modulator integrated semiconductor laser A3.

A temperature control element (TEC)508(which is illustrated in onlyFIG.2) is provided on the rear side of the substrate502. One electrode of the TEC508is connected to the wiring pattern111by a wire91. The other electrode of the TEC508is connected to the wiring pattern112by a wire92. Electric power for driving the TEC508is input from an external circuit outside of the transmitting small-sized optical device A1via the wiring pattern111and the wiring pattern112. The external circuit outside of the transmitting small-sized optical device A1controls a magnitude of the electric power for driving the TEC508based on a peripheral temperature of the semiconductor light-emitting device A, that is, a resistance value of the thermistor506. Accordingly, the temperature of the optical modulator integrated semiconductor laser A3is maintained at a predetermined temperature, and the wavelength of emission light M emitted from the semiconductor light-emitting device A is maintained at a predetermined wavelength.

The substrate501is provided on the substrate502. A ground potential line66, a wiring pattern65, a bypass capacitor505, and a semiconductor light-emitting device A are provided on the substrate501. The material of the substrate501is, for example, an insulator such as ceramics. The material of the ground potential line66and the wiring pattern65is, for example, a metal. As illustrated inFIG.3, the semiconductor light-emitting device A includes an optical modulator integrated semiconductor laser A3, a ground pattern19, a transmission line200, and a termination unit300. The transmission line200includes a ground potential line17and a signal line18. The ground potential line17is provided on the optical modulator integrated semiconductor laser A3side with respect to the signal line18. The ground potential line17and the signal line18have an L-shape in a plan view. The ground pattern19has a rectangular shape in a plan view. The material of the ground potential line17, the signal line18, and the ground pattern19is, for example, a metal. The ground pattern19is connected to the ground potential line17. The ground potential line17is connected to the ground potential line87by a wire78. The ground potential line66is provided on the opposite side to the ground potential line17with respect to the ground pattern19. A ground terminal of the thermistor506is connected to the ground potential line66by a wire76. The bypass capacitor505is provided on the ground potential line66. A lower electrode of the bypass capacitor505is connected to the ground potential line66. An upper electrode of the bypass capacitor505is connected to the wiring pattern65by a wire55.

The optical modulator integrated semiconductor laser A3includes a laser unit1and an optical modulation unit100. The optical modulator integrated semiconductor laser A3is provided on the ground pattern19. The laser unit1includes an active region and generates a laser beam with an optical intensity which is temporally constant when a current is supplied to the active region. The optical modulation unit100modulates the laser beam output from the laser unit1and outputs the modulated emission light M. The backlight is a laser beam output from the laser unit1without passing through the optical modulation unit100. The laser unit1and the optical modulation unit100are monolithically formed in the optical modulator integrated semiconductor laser A3.

The laser unit1is provided near the substrate503with respect to the optical modulation unit100. The laser unit1includes an active region and outputs a laser beam. The laser unit1includes a drive electrode10, a pad7, and a pad12on the surface thereof. The drive electrode10extends in a laser resonating direction (a longitudinal direction of the optical modulation unit100) and supplies a current to the active region. The pad7is arranged side by side with the drive electrode10in a direction crossing an extending direction of the drive electrode10and is connected to the drive electrode10. The pad12is arranged on the opposite side to the pad7with respect to the drive electrode10and is connected to the drive electrode10. The pad7is connected to the upper electrode of the bypass capacitor505by a wire9. Accordingly, a drive current is supplied to the drive electrode10from the outside of the transmitting small-sized optical device A1via the wiring pattern115, the wiring pattern85, the wiring pattern65, the upper electrode of the bypass capacitor505, and the pad7. The wire9may be connected to the pad12instead of the pad7.

The optical modulation unit100includes a modulation electrode2, a pad3(a first pad), and a pad4(a signal pad). The optical modulation unit100includes a modulation region and modulates a laser beam by transmitting or cutting off the laser beam with supply of a current to the modulation region. The modulation electrode2supplies a modulation current (a modulation signal) to the modulation region. Accordingly, the modulation electrode2transmits or cuts off the laser beam based on the modulation signal input to the modulation region. The modulation electrode2extends in the same direction as the progressing direction of the laser beam in a plan view. On the top surface of the optical modulator integrated semiconductor laser A3, the modulation electrode2is provided at the center in a direction perpendicular to the progressing direction of the laser beam.

One end of the ground potential line17is connected to the ground potential line87by a wire77. One end of the signal line18is connected to the signal line88by a wire78. The other end of the ground potential line17is connected to the pad3by a wire15(a second wire). The other end of the signal line18is connected to the pad4by a wire16(a first wire). The wire15and the wire16are bonding wires formed of, for example, Au. A sectional diameter of the wire15and the wire16is, for example, 25 μm. The pad4is connected to the modulation electrode2. The pad3is provided on the laser unit1side (one side) with respect to the pad4. The pad3and the pad4are provided on the transmission line200side with respect to the modulation electrode2. The pad3is provided side by side with the pad4along the longitudinal direction of the modulation electrode2. The pad4is provided at the center in the progressing direction of the laser beam in the optical modulation unit100. The pad3and the pad4have a film shape and have a substantially rectangular shape in a plan view. The material of the pad3and the pad4is metal and is, for example, gold (Au). The wire15is provided along with the wire16. As illustrated inFIG.4, for example, the wire15and the wire16are provided in parallel with each other in a plan view. An interval between the wire15and the wire16is, for example, several tens of μm.

The termination unit300includes a first wiring pattern33, a termination resistor31, and a second wiring pattern32. The termination unit300is provided on the opposite side to the transmission line200with respect to the optical modulation unit100and reduces reflection of a modulation signal. One end of the termination resistor31is connected to the first wiring pattern33. The other end of the termination resistor31is connected to the second wiring pattern32. The first wiring pattern33is connected with the pad4by a wire35(a fourth wire). The second wiring pattern32is connected with the pad3by a wire34(a fifth wire). The wire34and the wire35are provided in parallel with each other. The wire34and the wire35are, for example, bonding wires. A sectional diameter of the wire34and the wire35is, for example, 25 μm. The second wiring pattern32is connected to the ground pattern19and thus holds the ground potential. The first wiring pattern33and the second wiring pattern32have a film shape and have a substantially rectangular shape in a plan view. The material of the first wiring pattern33and the second wiring pattern32is, for example, gold (Au). The termination resistor31has a rectangular shape in a plan view. The resistance value of the termination resistor31is, for example, 50Ω.

FIG.5is a sectional view along line V-V inFIG.4and illustrates a cross-section of the optical modulation unit100, which is perpendicular to the progressing direction of a laser beam. The optical modulator integrated semiconductor laser A3includes a top surface8and a bottom surface11. The optical modulation unit100includes an insulating film6on the top surface8. The pad4and the pad3are provided on the insulating film6. The pad3is electrically isolated from the pad4. A resistance value between the pad3and the pad4is, for example, several hundreds of Ω or larger. The material of the insulating film6is, for example, SiN or SiO2. The optical modulation unit100includes a p-InP layer101, a light absorbing layer102, a pair of semi-insulating InP regions103, and an n-InP layer104in addition to the modulation electrode2, the pad3, and the insulating film6. The light absorbing layer102and the p-InP layer101are provided on the n-InP layer104, and the light absorbing layer102is interposed between the n-InP layer104and the p-InP layer101. A part of the n-InP layer104, the light absorbing layer102, and the p-InP layer101are formed in a mesa shape on the remaining part of the n-InP layer104, and the pair of semi-insulating InP regions103are in contact with both side surfaces of the mesa to form a mesa buried structure. The lower electrode105is provided on the bottom surface11. The lower electrode105is in contact with the n-InP layer104. The top surface of the semi-insulating InP regions103constitute the top surface8. The insulating film6includes an opening at the center thereof, and the modulation electrode2is provided in the opening. The modulation electrode2is provided on the p-InP layer101and is in contact with the p-InP layer101. The n-InP layer104serves as a lower clad layer. The p-InP layer101serves as an upper clad layer and a contact layer.

Advantages of the semiconductor light-emitting device A having the aforementioned configuration will be described below through comparison with a comparative example illustrated inFIG.14. The wire15is connected between the pad3and the ground potential line17. Accordingly, the wire15holding the ground potential can be disposed side by side with the wire16. Since the wire16and the wire15are arranged side by side, a modulation signal progresses side by side with the ground potential even after the modulation signal has gotten away from the signal line18.

FIG.14is a perspective view illustrating a semiconductor light-emitting device F according to a comparative example. The semiconductor light-emitting device F illustrated inFIG.14includes an optical modulation unit100F instead of the optical modulation unit100according to this embodiment. The semiconductor light-emitting device F does not include the wire15and the wire34according to this embodiment. The optical modulation unit100F is different from the optical modulation unit100in that the pad3is not provided and a pad4F is provided and is the same as the optical modulation unit100in the other points. The pad4F is provided on the opposite side to the pad4with respect to the modulation electrode2and is connected to the modulation electrode2. In this comparative example, the wire35is connected to the pad4F. In this comparative example, high-frequency characteristics are improved by performing design such that a characteristic impedance value of a transmission line210from an external drive circuit to the semiconductor light-emitting device F is close to a value of the termination resistor31. However, the ground potential line17and the ground potential line23of the transmission line210are provided in only a region ‘a’ including the transmission line210and are not provided in a region ‘b’ including the optical modulation unit100F. Accordingly, a modulation signal input to the semiconductor light-emitting device F and getting away from the signal line18and progressing in the wire16progresses away from the ground potential line17and the ground potential line23after passing through a junction between the transmission line210(the region ‘a’) and the optical modulation unit100F (the region ‘b’). Accordingly, an input impedance is less likely to be matched, and mismatch in impedance between the signal line18and the wire16is likely to increase. When mismatch in impedance increases, the modulation signal is reflected by a boundary (a change point P) between the signal line18and the wire16and thus a loss of the modulation signal increases. Accordingly, there is concern the modulation signal may not be satisfactorily transmitted to the modulation electrode2.

In the semiconductor light-emitting device A according to the first embodiment of the present disclosure, the wire16holding the ground potential is arranged side by side with the wire15as described above. Accordingly, the modulation signal progresses side by side with the ground potential even after the modulation signal has gotten away from the signal line18. As a result, the characteristic impedance of the wire16becomes close to a predetermined value (for example, 50Ω), and mismatch in impedance between the signal line18and the wire16decreases. Accordingly, it is possible to reduce a loss of the modulation signal (for example, a modulation signal of a high-frequency region equal to or higher than several tens of GHz) due to mismatch in impedance. The wire34is connected to the pad3and thus holds the ground potential. In addition, the wire34and the wire35are arranged side by side with each other. Accordingly, the modulation signal propagating in the wire35progresses side by side with the ground potential. As a result, the characteristic impedance of the wire35becomes close to a predetermined value (for example, 50Ω), and mismatch in impedance between the wire16and the wire35decreases. Accordingly, it is possible to further reduce a loss of the modulation signal due to mismatch in impedance.

As in this embodiment, the optical modulation unit100may include the insulating film6on the top surface8, and the pad3and the pad4may be provided on the insulating film6. When the pad3and the pad4are provided on the insulating film6, the pad3and the pad4can be electrically isolated from each other. Accordingly, it is possible to prevent a modulation signal input to the pad4from leaking into the pad3. As a result, it is possible to efficiently allow the modulation signal input to the pad4to reach the modulation electrode2.

As in this embodiment, the pad3may be electrically isolated from the pad4. The pad3holds the ground potential. Accordingly, by electrically isolating the pad3and the pad4, it is possible to prevent the modulation signal input to the pad4from leaking into the pad3. As a result, it is possible to efficiently allow the modulation signal input to the pad4to reach the modulation electrode2.

As in this embodiment, the pad3may be provided in the optical modulation unit100. Accordingly, the pad3is disposed at a position closer to the pad4. As a result, a distance between the wire16through which the modulation signal passes and the wire15holding the ground potential becomes smaller, and match in input impedance is further facilitated.

As in this embodiment, the wire15and the wire16may be provided in parallel with each other. Accordingly, it is possible to more easily reduce mismatch in impedance between the signal line18and the wire16. As a result, it is possible to further reduce a loss of the modulation signal due to mismatch in impedance.

FIG.6is a perspective view illustrating a semiconductor light-emitting device B according to a first modification.FIG.7is a plan view illustrating the semiconductor light-emitting device B. The semiconductor light-emitting device B is different from the semiconductor light-emitting device A in the following points and is the same in the other points. The semiconductor light-emitting device B includes a termination unit301instead of the termination unit300of the semiconductor light-emitting device A. The termination unit301includes a first wiring pattern33, a termination resistor31, and a second wiring pattern32. Unlike the first embodiment, in this modification, the second wiring pattern32is not connected to a ground pattern19. A resistance value between the second wiring pattern32and the ground pattern19is, for example, several hundreds of (or more.

In this modification, since the second wiring pattern32and the ground pattern19are not connected to each other, the whole amount of current of a modulation current returning to the ground via the termination resistor31passes through the wire34, and thus the amount of current of the input modulation current is balanced with the amount of current flowing in a wire holding the ground potential. As a result, it is possible to improve accuracy of match in input impedance.

FIG.8is a perspective view illustrating a semiconductor light-emitting device C according to a second modification.FIG.9is a plan view illustrating the semiconductor light-emitting device C. The semiconductor light-emitting device C is different from the semiconductor light-emitting device A in the following points and is the same in the other points. The semiconductor light-emitting device C includes a transmission line210instead of the transmission line200in the embodiment and further includes a wire22(a third wire). The wire22is provided in parallel with the wire15and the wire16. The wire22is, for example, a bonding wire. A diameter of a cross-section of the wire22is 25 μm, for example. The optical modulator integrated semiconductor laser A3of the semiconductor light-emitting device C includes an optical modulation unit110instead of the optical modulation unit100in the embodiment. The optical modulation unit110further includes a pad5(a second pad) in addition to the configuration of the optical modulation unit100. The pad5is provided on the opposite side to (the other side of) the pad3with respect to the pad4and is provided side by side with the pad3and the pad4along the longitudinal direction of the modulation electrode2. The pad5is provided near the transmission line210with respect to the modulation electrode2. The transmission line210further includes a ground potential line23in addition to the ground potential line17and the signal line18according to the embodiment. The signal line18is provided between the ground potential line17and the ground potential line23. Accordingly, the transmission line210constitutes a coplanar line. The pad5is connected to the ground potential line23by a wire22. The pad5has a film shape and has a substantially rectangular shape in a plan view. The material of the pad5is, for example, gold (Au). The wire22is provided on the opposite side to the wire15with respect to the wire16. The wire22is provided side by side with the wire16. For example, the wire16and the wire22are provided in parallel with each other in a plan view.

The semiconductor light-emitting device C further includes a termination unit310and a wire36(a sixth wire). The wire34, the wire35, and the wire36are provided in parallel with each other. The wire34, the wire35, and the wire36are, for example, bonding wires. A sectional diameter of the wire34, the wire35, and the wire36is, for example, 25 μm. The termination unit310is provided on the opposite side to the transmission line210with respect to the optical modulation unit110and reduces reflection of the modulation signal. The termination unit310includes the first wiring pattern33, the termination resistor31, and the second wiring pattern52. The second wiring pattern52has a U-shape in a plan view. One end of the termination resistor31is connected to the first wiring pattern33. The other end of the termination resistor31is connected to the center of the second wiring pattern52. The first wiring pattern33is connected with the pad4by the wire35. One end of the second wiring pattern52is connected with the pad3by the wire34. The other end of the second wiring pattern52is connected with the pad5by the wire36. The second wiring pattern52holds the ground potential because one end and the other end thereof are connected to the ground pattern19. The material of the first wiring pattern33and the second wiring pattern52is, for example, gold (Au). The termination resistor31has a rectangular shape in a plan view. The resistance value of the termination resistor31is, for example, 50Ω.

In this modification, the wire22is connected between the ground potential line23and the pad5. The wire22holds the ground potential. Accordingly, the wire16arranged side by side with the wire15and the wire22is sandwiched in the ground potential. In this case, a modulation signal passing through the wire16advances while being sandwiched by the ground potential. Accordingly, the characteristic impedance of the wire16becomes close to a predetermined value (for example, 50Ω), and mismatch in impedance between the signal line18and the wire16further decreases. Accordingly, it is possible to further reduce a loss of a modulation signal (for example, a modulation signal of a high-frequency region equal to or higher than several tens of GHz) due to mismatch in impedance. The wire34and the wire36are connected to the pad3and the pad5, respectively, and thus hold the ground potential. Accordingly, the wire35arranged side by side with the wire34and the wire36is sandwiched in the ground potential. Therefore, the modulation signal passing through the wire35advances while being sandwiched by the ground potential. Accordingly, the characteristic impedance of the wire35becomes closer to a predetermined value (for example, 50Ω), and mismatch in impedance between the wire16and the wire35further decreases. As a result, it is possible to further reduce a loss of the modulation signal due to mismatch in impedance.

FIG.10is a perspective view illustrating a semiconductor light-emitting device D according to a third modification.FIG.11is a plan view illustrating the semiconductor light-emitting device D. The semiconductor light-emitting device D is different from the semiconductor light-emitting device C in the following points and is the same in the other points. The semiconductor light-emitting device D includes a termination unit311instead of the termination unit310of the semiconductor light-emitting device C. The termination unit311includes a first wiring pattern33, a termination resistor31, and a second wiring pattern54. Unlike the second modification, in this modification, the second wiring pattern54and the ground pattern19are not connected to each other. A resistance value between the second wiring pattern54and the ground pattern19is, for example, several hundreds of Ω or more.

In this modification, since the second wiring pattern54and the ground pattern19are not connected to each other, the whole amount of current of a modulation current returning to the ground via the termination resistor31passes through the wire34or the wire36, and thus the amount of current of the input modulation current is balanced with the amount of current flowing in a wire holding the ground potential. As a result, it is possible to improve accuracy of match in input impedance.

FIG.12is a perspective view illustrating a semiconductor light-emitting device E according to a fourth modification.FIG.13is a plan view illustrating the semiconductor light-emitting device E according to the fourth modification. The semiconductor light-emitting device E is different from the semiconductor light-emitting device D in the following points and is the same in the other points. The optical modulator integrated semiconductor laser A3of the semiconductor light-emitting device E includes an optical modulation unit120instead of the optical modulation unit110. The semiconductor light-emitting device E further includes a wire41, a wire43, a wire44, and a wire46instead of the wire34and the wire36. The wire41, the wire43, the wire44, and the wire46are, for example, bonding wires. A sectional diameter of the wire41, the wire43, the wire44, and the wire46is, for example, 25 μm. The optical modulation unit120further includes a pad42and a pad45. The pad42and the pad45are provided near the termination unit311with respect to the modulation electrode2(that is, the opposite side to the pad3and the pad5with respect to the modulation electrode2). The pad42and the pad45are provided side by side along the longitudinal direction of the modulation electrode2. The pad42is provided near the laser unit1with respect to the pad45. The material of the pad42and the pad45is, for example, gold (Au). The pad42is connected to one end of the second wiring pattern54by the wire41and is connected to the pad3by the wire43. The pad45is connected to the other end of the second wiring pattern54by the wire44and is connected to the pad5by the wire46. The pad42and the pad45have a film shape and have a substantially rectangular shape in a plan view. The wire43and the wire41are provided in parallel with the wire35in a plan view. The wire35is provided in parallel with the wire46and the wire44in a plan view.

A distance between the wire35and both the wire43and the wire41can be stably maintained by the pad42. A distance between the wire35and both the wire44and the wire46can be stably maintained by the pad45. The wire43, the wire41, the wire44, and the wire46hold the ground potential. Accordingly, the wire35arranged side by side with these wires is sandwiched in the ground potential. Therefore, the modulation signal passing through the wire35advances while being sandwiched by the ground potential. Accordingly, the characteristic impedance of the wire35becomes closer to a predetermined value (for example, 50Ω), and mismatch in impedance between the wire16and the wire35further decreases. As a result, it is possible to further reduce a loss of the modulation due to mismatch in impedance.

The optical modulator integrated semiconductor laser and the semiconductor light-emitting device according to the present disclosure are not limited to the aforementioned embodiment and the aforementioned modifications and can be modified in various forms. For example, in the embodiment, the pad3is provided in the optical modulation unit100, but the arrangement of the pad3is not particularly limited in the optical modulator integrated semiconductor laser A3. For example, the pad3may be provided in the laser unit1.

In the embodiment, the pad3is provided on the insulating film6, and thus the pad3is not directly connected to the ground potential of the optical modulator integrated semiconductor laser A3. The present disclosure is not limited to this embodiment, and for example, the pad3may be provided on the n-InP layer104and may be in contact with the n-InP layer104. Since the pad3is connected to the ground potential via the wire15, the aforementioned advantages can be achieved with a configuration in which the pad3is connected to a part holding the ground potential such as the n-InP layer104.

In the embodiment, the wire15and the wire16are parallel to each other, but the wire15and the wire16may not be parallel to each other. Similarly, in the first modification, the wire22and the wire16may not be parallel to each other. In this case, the aforementioned advantages can be achieved by arranging the wire15and the wire16side by side with each other (or with the wire16interposed between the wire15and the wire22).

In the embodiment, an example in which the ground potential line17of the transmission line200is provided on the substrate502side by side with the signal line18has been described above, but the configuration of the transmission line is not limited thereto. For example, even when the transmission line is configured as a so-called micro strip line in which the ground potential line is provided on the bottom surface of the substrate501, the aforementioned advantages can be achieved.