Patent Publication Number: US-11398866-B2

Title: Optical semiconductor device, optical transmission module, and optical transceiver

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims priority to Japanese Patent Application No. 2020-086229 filed on May 15, 2020, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present disclosure are related to optical semiconductor devices, optical transmission modules, and optical transceivers. 
     2. Description of the Related Art 
     Optical semiconductor devices used in optical transmitters require a high-frequency transmission signal to be transmitted to a laser diode or an optical modulator, in order to generate an optical signal. For this reason, signal waveguides, such as coplanar strips and microstrip lines, are used. For example, semiconductor laser modules including microstrip lines for transmitting high-frequency driving signals to semiconductor lasers, are known. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the embodiments of the present disclosure, an optical semiconductor device includes
         an insulative base having a first surface and a second surface, the first surface being parallel to a first direction, the second surface crossing the first direction, the insulative base including a metallic pattern formed on the first surface, the metallic pattern including
           a grounding pattern configured to be grounded,   a transmission pattern having an input end, an output end, and a line electrically connected between the input end and the output end,   a first pattern, and   a second pattern,   wherein the first pattern is located between the second surface and the second pattern;   
           a semiconductor laser chip mounted on the first surface, the semiconductor chip having an electrode, and an emitting end located between the electrode and the second surface, the semiconductor laser chip being configured to emit an optical signal from the emitting end according to an electrical signal input to the electrode, the semiconductor laser chip being located between the transmission pattern and two patterns formed by the first pattern and the second pattern, respectively;   a first wire electrically connecting the output end of the transmission pattern to the electrode;   a second wire electrically connecting the electrode of the semiconductor laser chip to the first pattern;   an inductor provided on the first surface, the inductor being electrically connected between the first pattern and the second pattern, the inductor being formed by a meander wiring or a bonding wire;   a resistor provided on the first surface; and   a capacitor provided on the first surface;   wherein the resistor is electrically connected between the second pattern and the capacitor, and   wherein the capacitor is electrically connected between the resistor and the grounding pattern.       

     According to another aspect of the embodiments of the present disclosure, an optical transmission module includes
         the optical semiconductor device described immediately above; and   an optical system configured to receive the optical signal and output an optical signal corresponding to the input optical signal.       

     According to still another aspect of the embodiments of the present disclosure, an optical transceiver includes
         the optical transmission module described immediately above;   an optical reception module configured to convert an optical signal input from an external source into a received signal; and   a signal processing circuit configured to supply the electrical signal to the input end and process the received signal.       

     Other objects and further features of the present disclosure will be apparent from the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating an example of a configuration of an optical transceiver according to one embodiment. 
         FIG. 2  is a block diagram illustrating an example of a configuration of a signal processing circuit and an optical transmission module according to one embodiment. 
         FIG. 3  is a perspective view illustrating an example of a configuration of an optical semiconductor device according to a first embodiment. 
         FIG. 4  is a plan view illustrating the example of the configuration of the optical semiconductor device according to the first embodiment. 
         FIG. 5  is a circuit diagram illustrating the example of the configuration of the optical semiconductor device according to the first embodiment. 
         FIG. 6  is a perspective view illustrating an example of a configuration of an optical semiconductor device according to one comparative example. 
         FIG. 7  is a plan view illustrating the example of the configuration of the optical semiconductor device according to one comparative example. 
         FIG. 8  is a circuit diagram illustrating the example of the configuration of the optical semiconductor device according to one comparative example. 
         FIG. 9  is a plan view, on a partially enlarged scale, illustrating the example of the configuration of the optical semiconductor device according to the first embodiment. 
         FIG. 10  is a perspective view illustrating an example of the configuration of the optical semiconductor device according to a second embodiment. 
         FIG. 11  is a plan view illustrating the example of the configuration of the optical semiconductor device according to the second embodiment. 
         FIG. 12  is a perspective view illustrating an example of the configuration of the optical semiconductor device according to a third embodiment. 
         FIG. 13  is a plan view illustrating the example of the configuration of the optical semiconductor device according to the third embodiment. 
         FIG. 14  is a diagram illustrating an example of simulation results (for a case where a resistor is 50Ω) of the optical semiconductor device according to one comparative example. 
         FIG. 15  is a diagram illustrating the example of the simulation results (for a case where the resistor is 75Ω) of the optical semiconductor device according to one comparative example. 
         FIG. 16  is a diagram illustrating the example of the simulation results (for a case where the resistor is 100Ω) of the optical semiconductor device according to one comparative example. 
         FIG. 17  is a diagram illustrating an example of the simulation results (for the case where the resistor is 75Ω) of the optical semiconductor device according to the first embodiment. 
         FIG. 18  is a diagram illustrating the example of the simulation results (for the case where the resistor is 100Ω) of the optical semiconductor device according to the first embodiment. 
         FIG. 19  is a diagram illustrating the example of the simulation results (for a case where the resistor is 75Ω, and a second wire bonding is lengthened) of the optical semiconductor device according to the first embodiment. 
         FIG. 20  is a diagram illustrating the example of the simulation results (for a case where the resistor is 100Ω and the second wire bonding is lengthened) of the optical semiconductor device according to the first embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Next, examples of optical semiconductor devices, optical transmission modules, and optical transceivers according to embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to these embodiments, and various variations, modifications, and substitutions may be made without departing from the scope of the present disclosure.
     [Details of Optical transceiver According to One Embodiment]   

       FIG. 1  is a block diagram illustrating an example of a configuration of an optical transceiver according to one embodiment. An optical transceiver  501  illustrated in  FIG. 1  is a device which transmits and receives optical signals. For example, the optical transceiver  501  is connected to one end of an optical fiber, and communicates optically via the optical fiber with another optical transceiver which is connected to the other end of the optical fiber. The optical transceiver  501  may include an optical transmission module  201 , an optical reception module  401 , and a signal processing circuit  301 , for example. 
     The optical transmission module  201  may be a Transmitter Optical Sub Assembly (TOSA) which converts an electrical signal (or transmission signal) into an optical signal and transmits the converted optical signal outside the optical transceiver  501 , for example. The optical reception module  401  may be a Receiver Optical Sub Assembly (ROSA) which converts the optical signal input from the outside of the optical transceiver  501  into an electrical signal (or reception signal), for example. The signal processing circuit  301  supplies the transmission signal to the optical transmission module  201 , and receives the reception signal from the optical reception module  401 . The signal processing circuit  301  may be a Clock and Data Recovery (CDR) circuit, for example.
     [Details of Signal Processing Circuit and Light Transmission Module in One Embodiment]   

       FIG. 2  is a block diagram illustrating an example of a configuration of the signal processing circuit and the optical transmission module according to one embodiment. In  FIG. 2 , the signal processing circuit  301  includes a Digital Signal Processor (DSP)  302 , and a Laser Diode Driver (LDD)  303 , for example. The optical transmission module  201  includes an optical semiconductor device  11 , and an optical system  12 , for example. 
     The DSP  302  may be a circuit which generates an electrical signal (or transmission signal) including information (or transmission information) to be transmitted, and supplies the electrical signal (or transmission signal) to the LDD  303 . The DSP  302  may be an integrated circuit for signal processing, for example. The LDD  303  may be a driving circuit which supplies a driving signal IB to the optical semiconductor device  11 . The optical semiconductor device  11  may include a semiconductor laser, and an optical modulator, for example. The semiconductor laser outputs an optical signal according to the driving signal IB. The driving signal IB may be a DC bias current for oscillating the semiconductor laser, for example. The LDD  303  amplifies the electrical signal supplied from the DSP  302 , and supplies an amplified modulation signal SM to the optical semiconductor device  11 . The modulation signal SM is a high-frequency signal including the transmission information. For example, the modulation signal SM is input to the optical modulator which modulates the optical signal output from the semiconductor laser according to the modulation signal SM, and a modulated optical signal (or optical transmission signal) is output from the optical modulator. In this case, the driving signal IB may be a DC current, and the semiconductor laser may output Continuous Wave (CW) light as the optical signal, for example. The optical modulator modulates the CW light according to the modulation signal SM, and outputs the modulated optical signal. The driving signal IB may be generated by a circuit (for example, a current source) other than the LDD  303 , and supplied to the optical semiconductor device  11 . The optical semiconductor device  11  may be configured so that the semiconductor laser generates the optical transmission signal according to the driving signal IB and the modulation signal SM. In this case, the driving signal IB may be a DC bias current, and the modulation signal SM may be a high-speed drive current, for example. The DSP  302  may receive the electrical signal which is generated by the optical reception module  401  according to the optical signal (or optical reception signal) received by the optical transceiver  501  from the outside. The DSP  302  may subject the electrical signal supplied from the optical reception module  401  to a signal processing, and generate the electrical signal (or reception signal) including the information (or reception information) to be received. The received signal may be supplied to the inside of a host device which is mounted with the optical transceiver  501 , for example. 
     The optical semiconductor device  11  functions as a light source (or light emitting device) that is driven by the driving signal IB and the modulation signal SM, to output an optical signal (or light) La. The optical signal La is the light generated according to the driving signal IB and the modulation signal SM. As described above, the CW light may be generated by the driving signal IB, and the CW light may be modulated by the optical modulator according to the modulation signal SM, to generate the optical signal La. The optical system  12  may be a mechanism which includes a lens that receives the optical signal La from the optical semiconductor device  11 , and transmits an optical signal corresponding to the input (or received) optical signal La to the outside (for example, an optical fiber) of the optical transmission module  201 . For example, the optical system  12  may include a lens that converges the input optical signal La onto an end surface of the optical fiber.
     [Details of Optical Semiconductor Device According to First Embodiment]   

       FIG. 3  is a perspective view illustrating an example of a configuration of the optical semiconductor device according to a first embodiment.  FIG. 4  is a plan view illustrating the example of the configuration of the optical semiconductor device according to the first embodiment.  FIG. 5  is a circuit diagram illustrating the example of the configuration of the optical semiconductor device according to the first embodiment. The configuration of the optical semiconductor device according to the first embodiment will be described, by referring to  FIG. 3 ,  FIG. 4 , and  FIG. 5 . 
     For the sake of facilitating the understanding, the scale of each member in the drawings may differ from the actual scale. In this specification, three axis directions (that is, X-axis direction, Y-axis direction, and Z-axis direction) of a three-dimensional orthogonal coordinate system is used for the description, and a longitudinal direction of a carrier  31  is regarded as the X-axis direction, a width direction of the carrier  31  is regarded as the Y-axis direction, and a height direction (or thickness direction) of the carrier  31  is regarded as the Z-axis direction. 
     Directions such as parallel, perpendicular, orthogonal, horizontal, vertical, up and down, left and right, or the like, may tolerate deviations to a certain extent that do not impair or deteriorate effects of the disclosed technique. The X-axis direction, the Y-axis direction, and the Z-axis direction represent a direction parallel to the X-axis, a direction parallel to the Y-axis, and a direction parallel to the Z-axis, respectively. The X-axis direction and the Y-axis direction are orthogonal to each other. The Y-axis direction and the Z-axis direction are orthogonal to each other. The Z-axis direction and the X-axis direction are orthogonal to each other. An XY-plane, a YZ-plane, and a ZX-plane represent a virtual plane parallel to the X-axis direction and the Y-axis direction, a virtual plane parallel to the Y-axis direction and the Z-axis direction, and a virtual plane parallel to the Z-axis direction and the X-axis direction, respectively. 
     An optical semiconductor device  11 A illustrated in  FIG. 3 ,  FIG. 4 , and  FIG. 5  is an example of the optical semiconductor device  11  described above. The optical semiconductor device  11 A is a light emitting device which emits the optical signal La from a light emission end (or facet)  30   e . The optical signal La may be emitted from the light emission end  30   e  in a positive X-axis direction, for example. An optical axis of the optical signal La may be the X-axis direction, for example. The optical axis of the optical signal La may not perfectly match the X-axis direction, and may tolerate a deviation to a certain extent that does not impair or deteriorate the effects of the disclosed technique. The optical semiconductor device  11 A may include the carrier  31 , a semiconductor laser chip  30 , a first bonding wire  41 , a second bonding wire  42 , an inductor  40 , a resistor  37 , and a capacitor  51 . The first bonding wire  41  is an example of a first wire, and the second bonding wire  42  is an example of a second wire. The inductor  40  is an example of a meander wiring. 
     The carrier  31  is an example of an insulative base having a rectangular parallelepiped external shape. The carrier  31  may sometimes also be referred to as a base. The carrier  31  may have a rectangular parallelepiped external shape that extends in the longitudinal direction (or first direction). The rectangular parallelepiped shape may include generally rectangular parallelepiped shapes, and rectangular parallelepiped shapes having sides or corners that are chamfered, for example. The carrier  31  is made of a material that includes an insulating material, such as ceramics, glass, or the like, as a main component thereof. However, the carrier  31  may include a conductive portion (for example, an internal layer pattern, a via, or the like). 
     The carrier  31  may include, in the parallelepiped external shape, a parallelepiped body having a main (or principal) surface  31   a , a back surface  31   b , a pair of side surfaces  31   c  and  31   d , and a pair of end surfaces  31   e  and  31   f , for example. The main surface  31   a  is an example of a first surface parallel to the first direction. The first side may further be parallel to the width direction (or Y-axis direction). The back surface  31   b  is the surface opposite the main surface  31   a  along the height direction (or Z-axis direction). The pair of side surfaces  31   c  and  31   d  are arranged to face mutually opposite directions along a lateral direction (or Y-axis direction). The pair of end surfaces  31   e  and  31   f  are arranged to face mutually opposite directions along the longitudinal direction (or X-axis direction). The end surface  31   e  is an example of a second surface that is adjacent to the first surface and crosses the first direction. The end surface  31   e  is perpendicular to the first direction, for example. 
     The carrier  31  may include a conductive circuit pattern (or metallic pattern) formed on the main surface  31   a . In this example, the conductive circuit pattern formed on the main surface  31   a  includes a coplanar strip (or transmission pattern, or interconnect pattern)  32 , a first pattern  36 , a second pattern  39 , and a third pattern  52 . The carrier  31  may include a circuit pattern (or metallic pattern) on at least one of the back surface  31   b , the side surfaces  31   c  and  31   d , and the end surfaces  31   e  and  31   f.    
     The coplanar strip  32  is a waveguide extending in the longitudinal direction of the carrier  31 , for example. One end of the coplanar strip  32  is electrically connected to the semiconductor laser chip  30 , to supply the modulation signal SM to the semiconductor laser chip  30 . More particularly, the coplanar strip  32  includes an input end  33   a , an output end  33   b , and a wiring pattern (or signal line)  33  connected between the input end  33   a  and the output end  33   b . The coplanar strip  32  is an example of an interconnect pattern that transmits the modulation signal SM input to the input end  33   a  to the output end  33   b  via the wiring pattern  33 . The coplanar strip  32  may be a transmission line that is formed of the wiring pattern  33  disposed with a predetermined separation (or gap) from a grounding pattern (a portion of a grounding pattern  34  in this example) that is electrically connected to a ground potential. By utilizing a portion of the grounding pattern  34  as a ground plane of the coplanar strip  32 , it is possible to effectively utilize the limited area of the grounding pattern  34 , thereby enabling the size of the optical semiconductor device  11 A to be further reduced. On the main surface  31   a , the wiring pattern  33  is surrounded by the grounding pattern  34 , and is disposed with a gap from the surrounding grounding pattern  34 , thereby insulating the wiring pattern  33  from the grounding pattern  34 . For example, a characteristic impedance of the coplanar strip  32  can be varied by varying the size of the gap between the grounding pattern  34  and the wiring pattern  33 . 
     The grounding pattern  34  is an example of a conductive pattern that is electrically connected to the ground potential. The grounding pattern  34  may be a part of the conductive circuit pattern formed on the main surface  31   a , for example. The grounding pattern  34  may be a conductive metallic film, formed on the main surface  31   a  of the carrier  31 , and electrically connected to a reference potential, such as the ground potential. In this example, the grounding pattern  34  is provided on substantially the entire area of the main surface  31   a , except for areas where the wiring pattern (wiring)  33 , the first pattern  36 , the inductor (meander wiring)  40 , the second pattern  39 , and a third pattern  52  are to be formed. The grounding pattern  34  may be separated into a plurality of segments, instead of being formed by a single pattern. A bonding wire  47  may connect the grounding pattern  34  and a grounding pattern of the optical transmission module  201  to each other, on one side of the input end  33   a  of the coplanar strip  32  along the Y-axis direction. A bonding wire  48  may connect the grounding pattern  34  and the grounding pattern of the optical transmission module  201  to each other, on the other side of the input end  33   a  of the wiring pattern  33  along the Y-axis direction. For example, the grounding pattern  34  may be electrically connected to a grounding pattern or a grounding terminal of a package (not illustrated) of the optical transmission module  201  which accommodates the optical semiconductor device  11 A, via bonding wires  47  and  48 . 
     The wiring pattern  33  may be a conductive metallic film that guides the modulation signal SM. The wiring pattern  33  extends in the X-axis direction from a position near one end surface  31   f  of the carrier  31  to a position near the other end surface  31   e  (second surface). More particularly, the wiring pattern  33  extends in the first direction (positive X-axis direction in this example) from the input end  33   a  to the output end  33   b . The wiring pattern  33  electrically connects the input end  33   a  to the output end  33   b . The wiring pattern  33  may include not only a linear portion parallel to the first direction, but may include a portion that is partially non-parallel to the first direction. 
     A portion of the wiring pattern  33  positioned near the end surface  31   f  may be the input end  33   a , for example. The input end  33   a  may be a pad to be used for wire bonding, for example. A bonding wire  46  may electrically connect the input end  33   a  to an external input terminal of the package of optical transmission module  201 , for example. The modulation signal SM may be input to the input end  33   a  from the signal processing circuit  301 , via the external input terminal and the bonding wire  46 , for example. The input end  33   a  may have a sufficiently large area that is required to bond a tip end of the bonding wire  46  thereon, for example. The input end  33   a  may be a conductive metallic film, similar to the wiring pattern  33 . The input end  33   a  is adjacent to the grounding pattern  34  via a gap. When the optical semiconductor device  11 A is viewed in the Z-axis direction (that is, in a plan view of the main surface  31   a ), the grounding pattern  34  may be formed so as not to cross the bonding wire  46 . 
     A portion of the wiring pattern  33  positioned near the end surface  31   e  may be the output end  33   b  that is disposed between the input end  33   a  and the end surface  31   e . The output end  33   b  may be a pad to be used for wire bonding. The output end  33   b  may be electrically connected to the input end  33   a  via the wiring pattern  33 . The output end  33   b  may be a conductive metallic film, similar to the wiring pattern  33 . 
     The semiconductor laser chip  30  may be a semiconductor optical integrated device having a monolithic structure in which a laser diode (not illustrated) and a semiconductor optical modulator  30   d  (refer to  FIG. 5 ) are integrated on a semiconductor substrate. The semiconductor laser chip  30  may sometimes also be referred to as an Electro-Absorption Modulated Laser (EML) chip. The semiconductor laser chip  30  may include a pad  30   a , a pad  30   c , a back electrode which will be described later, and the light emission end  30   e , for example. The pad  30   a  may be an electrode connected to an anode electrode of the laser diode, for example. The pad  30   c  may be an electrode connected to an anode electrode of the semiconductor optical modulator  30   d , for example. The semiconductor laser chip  30  emits the optical signal La from the light emission end  30   e . The optical signal La is emitted in the X-axis direction, for example. Accordingly, the optical axis of the optical signal La may coincide with the X-axis direction. An angular deviation of the optical axis of the optical signal La with respect to the X-axis direction may be tolerated to a certain extent that does not impair or deteriorate the effects of the disclosed technique, so that it is possible to obtain an optical coupling between the optical semiconductor device  11 A and the optical system  12  having a coupling efficiency higher than or equal to a predetermined efficiency, or the like. 
     The pad  30   a  may receive a DC bias current, for example. The DC bias current is a DC current for causing the laser diode to generate laser light. This DC bias current corresponds to the driving signal IB supplied from the LDD  303  of the signal processing circuit  301  via wires and bonding wires that are not illustrated, for example. The pad  30   c  may receive the high-frequency modulation signal SM, for example. These pads  30   a  and  30   c  may be formed on a semiconductor substrate by gold plating, for example. The semiconductor laser chip  30  may be mounted on the grounding pattern  34  formed on the main surface  31   a , at a position near the one end surface  31   e  along the longitudinal direction of the carrier  31 . In other words, the back electrode (or cathode electrode) formed on the back of the semiconductor laser chip  30 , which is common to the laser diode and the semiconductor optical modulator  30   d  of the semiconductor laser chip  30 , is bonded to the grounding pattern  34  via a conductive adhesive such as solder or the like. The conductive adhesive may include gold tin (AuSn), for example. Hence, the back electrode is electrically connected to the grounding pattern  34 , and the semiconductor laser chip  30  is mounted on the main surface  31   a  of the carrier  31 . 
     The semiconductor laser chip  30  may generate the optical signal La according to the modulation signal SM that is input to the pad  30   c . The semiconductor laser chip  30  may output the generated optical signal La from the light emission end  30   e  in the positive X-axis direction. As described above, the optical axis of the optical signal La may be inclined with respect to the X-axis direction to a certain extent that does not impair or deteriorate the effects of the disclosed technique. The modulation signal SM is an example of an electrical signal that is input to the pad  30   c . The pad  30   c  is an example of a signal electrode. 
     The first bonding wire  41  may connect the output end  33   b  of the coplanar strip  32  and the pad  30   c  of the semiconductor laser chip  30  to each other. The first bonding wire  41  may be made of a conductive material, such as gold (Au) or the like, for example. The first bonding wire  41  may transmit the modulation signal SM from the output end  33   b  to the pad  30   c . The first bonding wire  41  may include a first end  41   a  connected to the output end  33   b , and a second end  41   b  connected to the pad  30   c . The pad  30   c  may have a sufficiently large area that is required to bond the second end  41   b  of the first bonding wire  46  thereon. 
     The second bonding wire  42  may connect the pad  30   c  and the first pattern  36  to each other. The second bonding wire  42  may be made of a conductive material, such as gold (Au) or the like, for example. The first bonding wire  41  may be used to electrically terminate the modulation signal SM by the resistor  37  which will be described later. The second bonding wire  42  may include a third end  42   a  connected to the pad  30   c , and a fourth end  42   b  connected to the first pattern  36 . 
     The first pattern  36  may be a conductive pattern disposed opposite the output end  33   b  of the coplanar strip  32 , with respect to the semiconductor laser chip  30 . Alternatively, the semiconductor laser chip  30  may be positioned between the coplanar strip  32  and the first pattern  36  on the main surface  31   a . The first pattern  36  may be a pad for connecting a circuit formed on the main surface  31   a  and the pad  30   c  by wire bonding, for example. The pad  30   c  may be positioned between the output end  33   b  and the first pattern  36  on the main surface  31   a , for example. 
     The second pattern  39  may be a conductive pattern disposed opposite the output end  33   b  of the coplanar strip  32  with respect to the semiconductor laser chip  30 , and opposite the end surface  31   e  with respect to the first pattern  36 . Alternatively, the semiconductor laser chip  30  may be positioned between the coplanar strip  32  and two patterns (first pattern  36  and second pattern  39 ) on the main surface  31   a . The first pattern  36  may be positioned between the second pattern  39  and the end surface  31   e  on the main surface  31   a . The second pattern  39  may be a pattern that connects the inductor  40  or a bonding wire which will be described later, to the resistor  37 . 
     The inductor  40  is an example of the meander wiring provided on the first surface. The inductor  40  includes a fifth end  40   a  electrically connected to the first pattern  36 , and a sixth end  40   b  electrically connected to the second pattern  39 . The inductor  40  may include a meander-shaped wire including hairpin turns. The inductor  40  extends in the X-axis direction from the first pattern  36  to the second pattern  39 , and may be a conductive wiring pattern formed on the main surface  31   a . For example, the fifth end  40   a  and the sixth end  40   b  may be disposed along the X-axis direction. The inductor  40  may include a plurality of rectangular wave-like undulating wiring patterns including hairpin turns, extending in the Y-axis direction. An inductance of the inductor  40  may be varied by varying the number of rectangular wave-like undulating wiring patterns and the length of each rectangular wave-like undulating wiring pattern, for example. 
     The resistor  37  is an example of a resistive element provided on the first surface. The resistor  37  may include a seventh end  37   a , and an eighth end  37   b . The seventh end  37   a  may be electrically connected to the second pattern  39 . The eighth end  37   b  may be electrically connected to the grounding pattern  34  via the capacitor  51 . Accordingly, the resistor  37  may be electrically connected between the second pattern  39  and the capacitor  51 . The eighth end  37   b  may be electrically connected to the third pattern  52 . The resistor  37  may be surface mounted on the first surface by solder reflow, for example, in order to make these electrical connections and also fix the resistor  37  on carrier  31 . More particularly, the seventh end  37   a  is bonded to the second pattern  39  by a solder material, and the eighth end  37   b  is bonded to the third pattern  52  by a solder material. The resistor  37  may be any of a chip resistor, a thin film resistor, and other types of devices having a resistance value, for example. In the case of the thin film resistor, a conductive film may be formed directly on the main surface  31   a  by deposition, for example. The thin film resistor does not require the bonding using the solder material. 
     The resistor  37  may function as a terminating resistor of the coplanar strip  32 . A resistance value of the resistor  37  may be greater than the value of a characteristic impedance value (for example, 50Ω) of the coplanar strip  32 , for example. 
     The capacitor  51  is an example of a capacitor provided on the first surface. In this example, the capacitor  51  has a rectangular shape that extends in the longitudinal direction, for example. The capacitor  51  may be disposed on the main surface  31   a , so that the longitudinal direction of the capacitor  51  is parallel to the Y-axis direction, for example. The capacitor  51  may include one end electrically connected to the third pattern  52 , and the other end electrically connected to the grounding pattern  34 . Accordingly, capacitor  51  may be electrically connected between the resistor  37  and the grounding pattern  34 . The coplanar strip  32 , which transmits the high-frequency modulation signal SM, is terminated to the ground potential via the resistor  37  and the capacitor  51 . 
     Accordingly, in the optical semiconductor device  11 A, the inductance of the wiring between the second bonding wire  42  and the resistor  37  can be increased, by providing the inductor  40  between the second bonding wire  42  and the resistor  37 . Hence, the inductance of the wiring between the second bonding wire  42  and the resistor  37  in the optical semiconductor device  11 A increases compared to that of an optical semiconductor device  111  according to one comparative example in which a wiring  4  between the second bonding wire  42  and the resistor  37  is linear, as illustrated in  FIG. 6 ,  FIG. 7 , and  FIG. 8 , for example. Accordingly, by employing the inductor  40 , it is possible to secure a high inductance between the second bonding wire  42  and the resistor  37 , even if an area sandwiched between the first pattern  36  and the second pattern  39  is relatively narrow. Because the inductance of the wiring is increased by the inductor  40 , an amplitude of the modulation signal SM input to the pad  30   c  of the semiconductor laser chip  30  can be increased within a desired frequency range. This effect of increasing the amplitude of the modulation signal SM corresponds to peaking that improves the bandwidth in a frequency domain where the intensity of particularly the high-frequency signal begins to decrease, in frequency characteristics of the high-frequency signal. Hence, it is possible to provide a broadband optical semiconductor device  11 A, a broadband optical transmission module  201 , and a broadband optical transceiver  501 , by reducing attenuation in the high-frequency band of the modulation signal SM input to the semiconductor laser chip  30 . 
     In addition, as illustrated in  FIG. 4 , in the optical semiconductor device  11 A, a distance between the first pattern  36  and the end surface  31   e  is shorter than a distance between the pad  30   c  and the end surface  31   e . Thus, in the X-axis direction, a distance between the first pattern  36  and the second pattern  39  becomes long compared to a case where the distance between the first pattern  36  and the end surface  31   e  is longer than the distance between the pad  30   c  and the end surface  31   e , or a case where both the first pattern  36  and the pad  30   c  are separated from the end surface  31   e  by approximately the same distance (refer to  FIG. 7 ). The longer distance between the first pattern  36  and the second pattern  39  enables the inductance of the connecting wiring between the second bonding wire  42  and the resistor  37  to be increased. 
     Further, along the X-axis direction of the optical semiconductor device  11 A, the distance between the pad  30   c  and the end surface  31   e  is shorter than the distance between the output end  33   b  and the end surface  31   e , as illustrated in  FIG. 4 . For this reason, the positional relationship of three positions, namely, a center portion of the first pattern  36 , a center portion of the pad  30   c , and a center portion of the output end  33   b , does not represent a V-shape which curves at the center position of the pad  30   c , but approaches a linear arrangement. Hence, the bonding of the first bonding wire  41  and the second bonding wire  42  by a wire bonding device can be facilitated, and a wire bonding time can be reduced. As illustrated in  FIG. 4 , according to the optical semiconductor device  11 A, in the plan view of the main surface  31   a , the center portion of the first pattern  36 , the center portion of the pad  30   c , and the center portion of the output end  33   b  are arranged linearly. Thus, the bonding of the first bonding wire  41  can be followed by the bonding of the second bonding wire  42 , thereby reducing the wire bonding time. 
     In order to reduce the power consumption of the signal processing circuit  301 , it is effective to reduce a driving amplitude (amplitude of the signal output from the DSP  302  or LDD  303 ) of the DSP  302  or the LDD  303 , for example. When a voltage amplitude of a signal is reduced, for example, a power supply voltage of the circuit which generates the signal can be reduced, thereby enabling the power consumption to be reduced. According to one method, by increasing the resistance value of a terminating resistor (for example, the resistor  37 ), the amplitude of the modulation signal SM can be secured (or increased) even if a driving capability of the DSP  302  or the LDD  303  is reduced. On the other hand, the inductance of the second bonding wire  42  on the terminating end can cause the peaking of the frequency characteristics, thereby broadening the band that can be processed. However, increasing the resistance value of the terminating resistor weakens the peaking caused by the inductance of the second bonding wire  42 , thereby reducing the band of modulation signal SM input to the pad  30   c  of the semiconductor laser chip  30 . For this reason, as the resistance value of the terminating resistor increases, the inductance on the termination end needs to be increased in order to secure the band that can be processed. However, the inductance of the second bonding wire  42  depends on the length of the wire, and in actual practice, may be approximately 600 pH at the most, for example. Because the size of the carrier  31  is limited to a size with a width L 1  of approximately 0.7 mm at the most, for example, which enables integration into and mounting onto the optical transmission module  201 , it may be difficult to mount an inductor element, such as a chip coil or the like. 
     On the contrary, in the optical semiconductor device  11 A according to the first embodiment, the inductance between the semiconductor laser chip  30  and the terminating resistor  37  can be increased, by combining the inductance of the inductor  40  and the inductance of the second bonding wire  42 . Accordingly, in a carrier structure having a small size, the high frequency band can be maintained, even if the resistance value of the terminating resistor is increased. In addition, because the resistance value of the terminating resistor can be increased, the driving capability of the DSP  302  or the LDD  303  can be reduced, thereby enabling the power consumption of the signal processing circuit  301  to be reduced. When the resistance value of the terminating resistor is changed from 50Ω to 100Ω, for example, the amplitude of the modulation signal SM input to the pad  30   c  can be increased (or peaked) to the same value as before changing the resistance value in the high-frequency band, even if the driving capability of the DSP  302  is reduced to approximately 78%, for example. 
     A component size of the carrier  31  is the size that enables a plurality of carriers  31  to be integrated into the optical transmission module  201 , with the width L 1  of 0.7 mm, and a length L 2  of 1.7 mm, for example. The capacitance (earth capacitance) between the inductor  40  on the main surface  31   a  and the grounding pattern in contact with the back surface  31   b  can be reduced, by making a thickness L 3  of the carrier  31  greater than or equal to 0.45 mm, for example. 
       FIG. 9  is a plan view, on a partially enlarged scale, illustrating a peripheral portion of the semiconductor laser chip  30  in the example of the configuration of the optical semiconductor device according to the first embodiment. The inductance can be increased by increasing the wiring length of the inductor  40 , however, the peaking is weakened when an earth capacitance  53  (refer to  FIG. 5 ) is formed between the inductor  40  and the grounding pattern  34 . From a viewpoint of reducing the earth capacitance  53 , a minimum distance L 4  between the inductor  40  and the grounding pattern  34  is preferably 15 μm or greater, more preferably 20 μm or greater, and even more preferably 30 μm or greater. If the minimum distance L 4  is less than 15 μm, the earth capacitance  53  increases considerably, and the peaking is reduced due to the increase in the inductance. In addition, if the minimum distance L 4  is less than 15 μm, manufacturing variation or inconsistency of the peaking increases, thereby making it difficult to manage or control the frequency characteristics among the individual products. An upper limit of the minimum distance L 4  is not particularly limited, but from a viewpoint of securing a mounting area for each component, the minimum distance L 4  is preferably ¼ the width L 1  along the Y-axis direction of the carrier  31  or less, for example. The minimum distance L 4  is preferably 15 μm or greater, also in the case of an inductor  40 A and a third bonding wire  54  described below. 
     The inductor  40  includes a rectangular wave-like undulating portion  40   c  between the fifth end  40   a  and the sixth end  40   b . The minimum distance L 4  corresponds to a distance between the rectangular wave-like undulating portion  40   c  of the inductor  40  and an outer edge  34   a  of the grounding pattern  34 . The rectangular wave-like undulating portion  40   c  includes a wiring pattern in the Y-axis direction on both ends of the wiring pattern in the X-axis direction. By providing the wiring pattern in the Y-axis direction, the wiring length of the inductor  40  can be increased. A plurality of undulating wiring patterns are formed by connecting a plurality of patterns in the Y-axis direction and a plurality of patterns in the X-axis direction. The rectangular wave-like undulating portion  40   c  includes the plurality of undulating wiring patterns. From a viewpoint of reducing the increase in the capacitance between the wiring patterns in the Y-axis direction adjacent to each other in the X-axis direction, a spacing L 5  of the rectangular wave-like undulating portion  40   c  along the X-axis direction is preferably in a range that is 15 μm or greater and 60 μm or less, and more preferably in a range that is 20 μm or greater and 55 μm or less. The spacing L 5  corresponds to the distance between adjacent wiring patterns in the Y-axis direction. From a viewpoint of reducing the increase in the earth capacitance  53 , a line width L 6  of the wiring of the rectangular wave-like undulating portion  40   c  is preferably in a range that is 5 μm or greater and 30 μm or less, and more preferably in a range that is 10 μm or greater and 25 μm or less.
     [Details of Second Embodiment of Present Disclosure]   

     A specific example of the optical semiconductor device according to a second embodiment of the present disclosure will be described below, with reference to the drawings. In the following, a description of the configuration and effects similar to those of the first embodiment may be omitted or simplified, by incorporating the description given heretofore. 
       FIG. 10  is a perspective view illustrating an example of the configuration of the optical semiconductor device according to the second embodiment.  FIG. 11  is a plan view illustrating the example of the configuration of the optical semiconductor device according to the second embodiment. An optical semiconductor device  11 B illustrated in  FIG. 10  and  FIG. 11  is an example of the optical semiconductor device  11  described above. The optical semiconductor device  11 B differs from the optical semiconductor device  11 A in that a portion of the inductor  40 A is provided on the side surface  31   d  of the carrier  31 . In  FIG. 10  and  FIG. 11 , the illustration of some components, such as the bonding wires or the like, is omitted. 
     The side surface  31   d  is an example of a third surface adjacent to the first surface and the second surface. Because a portion of the inductor  40 A is provided on the side surface  31   d , the inductance of the connecting wiring between the first pattern  36  and the second pattern  39  can be secured, even if the area sandwiched between the first pattern  36  and the second pattern  39  is relatively narrow. A distance between the wiring pattern provided on the side surface  31   d , and the surrounding grounding pattern or grounded conductor, is preferably set greater than or equal to the minimum distance L 4  described above.
     [Details of Third Embodiment of Present Disclosure]   

     A specific example of the optical semiconductor device according to a third embodiment of the present disclosure will be described below, with reference to the drawings. In the following, a description of the configuration and effects similar to those of the first embodiment may be omitted or simplified, by incorporating the description given heretofore. 
       FIG. 12  is a perspective view illustrating an example of the configuration of the optical semiconductor device according to the third embodiment.  FIG. 13  is a plan view illustrating the example of the configuration of the optical semiconductor device according to the third embodiment. An optical semiconductor device  11 C illustrated in  FIG. 12  and  FIG. 13  is an example of the optical semiconductor device  11  described above. The optical semiconductor device  11 C differs from the optical semiconductor device  11 A in that the inductor inserted between the first pattern  36  and the second pattern  39  is the third bonding wire  54 . 
     The third bonding wire  54  illustrated in  FIG. 12  and  FIG. 13  includes a wire end  54   a  electrically connected to the first pattern  36 , and a wire end  54   b  electrically connected to the second pattern  39 . For example, the wire bonding device may bond the wire end  54   a  to the first pattern  36 , and the wire end  54   b  to the second pattern  39 . The third bonding wire  54  is an example of an inductor provided on the first surface, the wire end  54   a  is an example of a fifth end, and the wire end  54   b  is an example of a sixth end. The third bonding wire  54  extends in the X-axis direction from the first pattern  36  to the second pattern  39 . The third bonding wire  54  is a conductive wiring member provided on the main surface  31   a , so as to curve in an upward direction (Z-axis direction) above the main surface  31   a.    
     Accordingly, in the optical semiconductor device  11 C, the inductance between the second bonding wire  42  and the resistor  37  is increased, by providing the third bonding wire  54  between the second bonding wire  42  and the resistor  37 . By employing the third bonding wire  54 , a high inductance can be secured between the second bonding wire  42  and the resistor  37 , even if the area sandwiched between the first pattern  36  and the second pattern  39  is relatively narrow. Because the inductance between the pad  30   c  of the semiconductor laser chip  30  and the resistor  37  increases considerably due to the third bonding wire  54 , it is possible to increase the intensity (or amplitude) of the modulation signal SM input to the pad  30   c  of the semiconductor laser chip  30  in the desired high-frequency range. Hence, it is possible to provide a broadband optical semiconductor device  11 C, a broadband optical transmission module  201 , and a broadband optical transceiver  501 , by reducing attenuation in the high-frequency band of the modulation signal SM input to the semiconductor laser chip  30 .
     [Simulation Results]   

       FIG. 14 ,  FIG. 15 , and  FIG. 16  illustrate examples of simulation results for the optical semiconductor device  111  in one comparative example illustrated in  FIG. 6 ,  FIG. 7 , and  FIG. 8 , respectively.  FIG. 14 ,  FIG. 15 , and  FIG. 16  respectively illustrate the frequency characteristics of the signal intensity, that is, an Electro-Optic (EO) response, of the optical signal La with respect to the signal intensity of the modulation signal SM input to the input end  33   a . The EO response represents a ratio of the signal intensity of optical signal La with respect to the signal intensity of the modulation signal SM. A value of the EO response is expressed in decibels (dB) in  FIG. 14 ,  FIG. 15 , and  FIG. 16 . The value of the EO response may be calculated based on the signal intensity of the optical signal La at a frequency F=0 Hz.  FIG. 14 ,  FIG. 15 , and  FIG. 16  illustrate the simulation results for cases where the resistance value of the resistor  37  is 50 Ω, 75Ω, and 100 Ω, respectively. The abscissa indicates the frequency F of the modulation signal SM input to the input end  33   a , and the ordinate indicates the EO response. In the frequency characteristics of the EO response, the lower the position along the ordinate, the greater the loss (conversion loss) during the conversion of the modulation signal SM into the optical signal La. In  FIG. 14 , a curve (solid line) indicating the frequency characteristics crosses a dashed line parallel to the abscissa, indicating a value which is decreased by approximately −3 dB from a value when the frequency F is 1 GHz, at a point m 3 . The frequency F at this point m 3  may also be referred to as a 3 dB-band. Similarly, in  FIG. 15 , the frequency F at the point m 3  is the 3 dB-band. In  FIG. 16 , there is no point m 3 , and the frequency F at a point m 2  is the 3 dB-band. Further, in the simulation results illustrated in  FIG. 14 ,  FIG. 15 , and  FIG. 16 , the wiring length of the second bonding wire  42  is set to 670 μm, and the inductance at the terminating end is set to 618 pH@30 GHz (=329 pH (second bonding wire  42 )+289 pH (4 connecting wirings). 
     As the resistance value of the resistor  37  is increased to 50Ω (refer to  FIG. 14 ), 75Ω (refer to  FIG. 15 ), and 100Ω (refer to  FIG. 16 ), the peaking (increasing effect) of the frequency characteristics deteriorates, and the degree of decrease in the EO response with increasing frequency F increases. For example, when the resistance value of the resistor  37  is set to 50Ω (refer to  FIG. 14 ), the peaking is observed at the point m 2 , and the 3 dB-band is 36 GHz. However, when the resistance value of the resistor  37  is increased to 100Ω (refer to  FIG. 16 ), the peaking is no longer observed, and the 3 dB-band decreases to 27 GHz. 
     On the other hand,  FIG. 17  and  FIG. 18  illustrate examples of the simulation results for the optical semiconductor device  11 A according to the first embodiment illustrated in  FIG. 3 ,  FIG. 4 , and  FIG. 5 , respectively.  FIG. 17  and  FIG. 18  respectively illustrate the frequency characteristics of the signal intensity, that is, the Electro-Optic (EO) response, of the optical signal La with respect to the signal intensity of the modulation signal SM input to the input end  33   a . The value of the EO response is expressed similarly to  FIG. 14 ,  FIG. 15 , and  FIG. 16 .  FIG. 17  and  FIG. 18  illustrate cases where the resistance value of the resistor  37  is 75 Ω and 100Ω, respectively. In the simulation results illustrated in  FIG. 17  and  FIG. 18 , the wiring length of the second bonding wire  42  is set to 670 μm (same as in  FIG. 15  and  FIG. 16 ), and the inductance at the terminating end is set to 730 pH@30 GHz (=329 pH (second bonding wire  42 )+401 pH (inductor  40 )). 
     When the resistance value of the resistor  37  is 75Ω,  FIG. 17  has a higher peaking effect than  FIG. 15 , and a −3 dB-band extends to the high-frequency side. When the resistance value of the resistor  37  is 100Ω,  FIG. 18  has a −3 dB-band extending to the high-frequency side when compared to  FIG. 16 . Thus, by employing the inductor  40  as the terminating inductor, the inductance between the pad  30   c  of the semiconductor laser chip  30  and the resistor  37  can be increased, thereby enabling a broadband optical semiconductor device, a broadband optical transmission module, and a broadband optical transceiver to be provided. 
       FIG. 19  and  FIG. 20  also illustrate examples of the simulation results for the optical semiconductor device  11 A according to the first embodiment illustrated in  FIG. 3 ,  FIG. 4 , and  FIG. 5 , respectively.  FIG. 19  and  FIG. 20  illustrate cases where the resistance value of the resistor  37  is 75Ω and 100Ω, respectively. The wiring length of the second bonding wire  42  is set to 1200 μm, and the inductance at the terminating end is set to 101 pH@30 GHz (=600 pH (second bonding wire  42 )+401 pH (inductor  40 )). 
     When the resistance value of the resistor  37  is 75Ω,  FIG. 19  has a higher peaking effect and the −3 dB-band extends to the high-frequency side, when compared to  FIG. 15 . When the resistance value of the resistor  37  is 100Ω,  FIG. 20  has a higher peaking effect and the −3 dB-band extends to the high-frequency side, when compared to  FIG. 16 . As described above, by employing the inductor  40  as the inductor at the terminating end, and extending the second bonding wire  42  (increasing the inductance of the second bonding wire  42 ), the inductance at the terminating end can be increased, thereby enabling a broadband optical semiconductor device, a broadband optical transmission module, and a broadband optical transceiver to be provided. 
     Hence, according to the embodiments of the present disclosure described above, it is possible to reduce attenuation in the high-frequency range of the electrical signal input to the semiconductor laser chip. 
     While the embodiments have been described, it will be understood that various variations, modifications, and substitutions may be made without departing from the spirit and scope of the present disclosure. Hence, combinations and substitutions of a part or all of each embodiment with another embodiment may be made, as appropriate. 
     For example, an interconnect pattern that transmits the electrical signal input to the input end  33   a  to the output end  33   b  via the wiring pattern  33  is not limited to the coplanar strip, and other transmission lines, such as microstrips, microstrip lines, or the like, may be used.