JP4964264B2 - Light modulator - Google Patents

Description

  The present invention relates to an optical modulator. More particularly, the present invention relates to a Mach-Zehnder type optical modulator.

  With the development of optical communication technology, a high-speed and highly stable optical modulator is required. A Mach-Zehnder type optical modulator is known as a high-speed optical modulator. In the Mach-Zehnder type optical modulator, the input light is branched, and a phase difference is given to the branched light to combine them, thereby obtaining modulated output light.

FIG. 1 shows a conventional Mach-Zehnder type optical modulator. The Mach-Zehnder type optical modulator 100 includes an input waveguide 112 on which input light is incident on an optical substrate 110 having an electro-optic effect (such as lithium niobate crystal (LiNbO ₃ , hereinafter referred to as LN)) 110, an input waveguide. A Y branching portion 114 that branches light from the waveguide, two arm waveguides 116a and 116b that guide the branched light, a Y multiplexing portion 118 that combines the light from these two arm waveguides, And an output waveguide 120 that outputs the combined light. These waveguides can be formed by selectively diffusing a metal such as Ti on the optical substrate. Thereafter, a buffer layer such as SiO ₂ is provided on the entire substrate surface, and metal electrodes 122a and 122b such as Au are formed on the arm waveguide. A high-frequency signal source 124 that modulates the optical modulator is connected to the electrodes 122a and 122b via a DC bias circuit 127. A termination resistor 170 and a DC block capacitor 171 are connected between these electrodes. The DC bias circuit 127 is connected to a DC power supply 128 for setting the operating point of the modulator.

  The input light incident on the input waveguide 112 is branched into two at the Y branching portion 114. While the branched light propagates through the arm waveguides 116a and 116b, the phase changes due to the influence of the electro-optic effect due to the modulation signal applied to the electrodes 122a and 122b. That is, the phase difference between the arm waveguides can be changed by the modulation signal applied to the electrodes. When the light from the arm waveguides 116a and 116b is multiplexed by the Y multiplexing unit 118, the light whose intensity is modulated is emitted from the output waveguide 120 according to the phase difference between these two lights (Patent Document 1). ).

JP 2001-154164 A Japanese Patent Laid-Open No. 5-100194

  In a conventional Mach-Zehnder type optical modulator, a capacitor 171 for DC block is connected to an electrode. The reason for this is that without this capacitor, the DC component is consumed as heat by the termination resistor, so the power consumption increases, and the generated heat is transmitted to the optical substrate such as LN, causing malfunction. is there. Another reason is that without this capacitor, a voltage drop occurs in the termination resistor when a DC bias is applied, and a higher voltage is required. This DC block capacitor increases the size and cost of the optical modulator.

  In order to reduce the capacitor for the DC block, a method of separately providing an electrode for setting the operating point of the optical modulator and directly applying a modulation signal to the modulation electrode is also known (Patent Document). 2). In this method, although the capacitor for the DC block can be reduced, an electrode for setting the operating point is newly required. This electrode increases the size and cost of the light modulator. If the operating point setting electrode is provided without increasing the size, the length of the modulation electrode is limited, the interaction length of the waveguide is shortened, and the high frequency characteristics are deteriorated.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an optical modulator that can be reduced in size by reducing the number of capacitors for DC blocks.

  In order to achieve the above object, the present invention provides a Mach-Zehnder type optical modulator comprising: a first substrate of an electro-optic material on which an arm waveguide is formed; And a second substrate on which at least one of a Y branch portion and a Y multiplexing portion coupled to the arm waveguide is formed, and the first substrate of the electro-optic material is formed on the arm waveguide A first electrode for modulation is provided, the second substrate is provided with a second electrode coupled to the first electrode, and the first and second electrodes are bonded with a dielectric adhesive. It is characterized by that.

  According to a second aspect of the present invention, there is provided the optical modulator according to the first aspect, wherein the adhesive is used for bonding the first and second substrates.

  According to a third aspect of the present invention, there is provided the optical modulator according to the first or second aspect, wherein the second electrode includes a termination resistor.

  According to a fourth aspect of the present invention, there is provided the optical modulator according to any one of the first to third aspects, comprising a plurality of Mach-Zehnder interferometers.

  According to a fifth aspect of the present invention, there is provided the optical modulator according to any one of the first to fourth aspects, wherein the second substrate is a quartz-based substrate.

  The invention according to claim 6 is the optical modulator according to any one of claims 1 to 5, wherein the first substrate is an optical substrate made of a lithium niobate crystal. To do.

It is a figure which shows the structural example of a Mach-Zehnder type | mold optical modulator. It is a figure which shows the structural example of the Mach-Zehnder type | mold optical modulator by the 1st Embodiment of this invention. It is a figure which shows the structural example of the Mach-Zehnder type | mold optical modulator by the 2nd Embodiment of this invention. It is a figure for demonstrating the capacitance formed with an adhesive agent between the electrodes of the Mach-Zehnder type optical modulator of this invention. It is a figure which shows the structural example of the Mach-Zehnder type | mold optical modulator by the 3rd Embodiment of this invention. It is a figure which shows the structural example of the Mach-Zehnder type | mold optical modulator by the 4th Embodiment of this invention.

  In the optical modulator according to the present invention, two substrates are combined and bonded with an adhesive so that a dielectric layer is formed between an electrode disposed on one substrate and an electrode disposed on the other substrate. Thus, the dielectric layer can function as a capacitance for the DC block. As these substrates, for example, a substrate made of an electro-optical material such as lithium niobate crystal (LN) may be used on one side, and a paraelectric substrate such as quartz or silicon may be used on the other side. In this case, an arm waveguide of a Mach-Zehnder type optical modulator can be formed on the substrate of the electro-optic material, and a modulation electrode can be provided thereon.

  FIG. 2 shows an optical modulator according to the first embodiment of the present invention. The Mach-Zehnder type optical modulator 200 includes an LN substrate 210 made of an electro-optic material and a quartz substrate 230. The LN substrate 230 includes an input waveguide 212 into which input light is incident, a Y branch portion 214 that branches light from the input waveguide, and two arm waveguides 216a and 216b that guide the branched light. Is formed. The arm waveguides 216a and 216b of the LN substrate are provided with modulation electrodes 222a and 222b. The quartz substrate 230 has two arm waveguides 232a and 232b that are optically coupled to the two arm waveguides 216a and 216b of the LN substrate, and Y multiplexing that combines light from these two branch waveguides. A portion 234 and an output waveguide 236 that outputs the combined light are formed.

  A DC bias circuit 227 and an external high-frequency signal source 224 are connected to the electrodes 222a and 222b on the LN substrate. The DC bias circuit 227 is connected to a DC power source 228 for setting the operating point of the modulator. On the quartz substrate, electrodes 238a and 238b are provided and connected to an external termination resistor 270. The electrodes 222a and 222b are connected to the electrodes 238a and 238b on the quartz substrate using dielectric adhesives 226a and 226b. As will be described later, this adhesive forms a capacitance for DC block between these electrodes. In the present invention, the quartz substrate 230 may be a substrate different from the LN substrate 210 and may not be a quartz substrate.

  The input light incident on the input waveguide 212 is branched into two at the Y branch portion 214. The branched light propagates to the arm waveguides 216a and 216b. The phase of light propagating through the waveguides 216a and 216b of the LN substrate is modulated by a modulation signal applied to the electrodes 222a and 222b. The amount of phase modulation is determined by the applied voltage and action length of the modulation signal. Here, a DC component is superimposed on this modulation signal to set the operating point of the optical modulator 200. In the present invention, since the DC component is blocked by the capacitance formed by the adhesives 226a and 226b between the electrodes 222a and 222b of the LN substrate 210 and the electrodes 238a and 238b of the quartz substrate 230, the DC current is resisted. It can be prevented that it flows to 270 and is consumed as heat. Therefore, power consumption can be reduced. Further, since heat due to the DC component is not generated by the resistor, the operation of the optical modulator is stabilized. Furthermore, since there is no DC voltage drop due to resistance, the DC bias voltage can be reduced. Since the same function as the DC block capacitance is realized by a minute junction between the LN substrate and the quartz substrate, the capacitance for the DC block can be reduced without increasing the size of the LN substrate. Therefore, the apparatus can be miniaturized.

  Next, the light propagated through the waveguides 216a and 216b of the LN substrate is coupled to the arm waveguides 232a and 232b of the quartz substrate 230, and is multiplexed by the Y multiplexing unit 234, and the output light is emitted from the output waveguide 236. Is done.

  FIG. 3 shows an optical modulator according to the second embodiment of the present invention. In this embodiment, not only the output side substrate but also the input side substrate is formed of a substrate (for example, a quartz substrate) different from the LN substrate. Thereby, the capacitance using an adhesive agent can be formed in more places.

  The Mach-Zehnder type optical modulator 300 includes an LN substrate 310 made of electro-optic material and two quartz substrates 330 and 360. The quartz substrate 330 in the previous stage has an input waveguide 332 into which input light is incident, a Y branching portion 334 that branches light from the input waveguide, and two arm waveguides 336a and 336b that guide the branched light. And are formed. The LN substrate 310 is formed with two arm waveguides 312a and 312b that are optically coupled to the two arm waveguides 336a and 336b of the preceding quartz substrate. Electrodes 314a and 314b are provided. A DC power source 328 is connected to the modulation electrode 314b via a coil 329, and an operating point of the modulator can be set. The quartz substrate 360 at the subsequent stage includes two arm waveguides 362a and 362b that are optically coupled to the two arm waveguides 312a and 312b of the LN substrate, and Y that combines light from these two arm waveguides. A multiplexing unit 364 and an output waveguide 366 that outputs the combined light are formed.

  Further, electrodes 338a and 338b are provided on the previous stage quartz substrate and connected to an external high-frequency signal source 324. The electrodes 338a and 338b are connected to the electrodes 314a and 314b on the LN substrate using dielectric adhesives 326a and 326b. Similarly, electrodes 368a and 368b are provided on the latter-stage quartz substrate and connected to an external termination resistor 370. Similarly, the electrodes 368a and 368b are connected to the electrodes 314a and 314b on the LN substrate using dielectric adhesives 328a and 328b. As will be described later, this adhesive forms a capacitance for DC block between these electrodes. In the present invention, the quartz substrates 330 and 360 may be different from the LN substrate 310 and may not be a quartz-based substrate.

  The input light incident on the input waveguide 332 is branched into two by the Y branching unit 334. The branched light propagates to the arm waveguides 312a and 312b of the LN substrate 310 via the arm waveguides 336a and 336b. The phase of light propagating through the waveguides 312a and 312b of the LN substrate is modulated by a modulation signal applied to the electrodes 314a and 314b. The amount of phase modulation is determined by the applied voltage and action length of the modulation signal. Here, a DC component is superimposed on this modulation signal to set the operating point of the optical modulator 300. In the present invention, the capacitance formed by the adhesives 326 a and 326 b between the electrodes 338 a and 338 b of the quartz substrate 330 and the electrodes 314 a and 314 b of the LN substrate 310, and the electrodes 368 a and 368 b of the quartz substrate 360 and the LN substrate 310 are formed. Since the DC component is blocked by the capacitance formed by the adhesives 328a and 328b between the electrodes 314a and 314b, the DC current can be prevented from flowing through the resistor 370 and being consumed as heat. Therefore, power consumption can be reduced. Further, since heat due to the DC component is not generated by the resistor, the operation of the optical modulator is stabilized. Furthermore, since there is no DC voltage drop due to resistance, the DC bias voltage can be reduced. Since the same function as the DC block capacitance is realized by a minute junction between the LN substrate and the quartz substrate, the capacitance for the DC block can be reduced without increasing the size of the LN substrate. Therefore, the apparatus can be miniaturized. In the present invention, it is needless to say that it is not necessary to form a DC block capacitance at all of these four connection portions using an adhesive, and the effect can be obtained at any one of the locations.

  Next, the light propagated through the waveguides 312a and 312b of the LN substrate is coupled to the arm waveguides 362a and 362b of the quartz substrate 360, and is multiplexed by the Y multiplexing unit 364, and the output light is emitted from the output waveguide 366. Is done.

  FIG. 4 is an enlarged view of the joint portion between the electrodes in the first and second embodiments. The joint portion is formed by joining the first electrode 410 and the second electrode 430 with an adhesive 420. At this time, the capacitance C formed at the junction is given by the following equation.

  Here, ε is the dielectric constant of the adhesive, w is the width of the electrode, h is the height of the electrode, and d is the distance between the electrodes. When the dielectric constant ε of the adhesive is 2.25, the width w and height h of the electrode are 10 μm, and the distance d between the electrodes is 5 μm, the capacitance is approximately 45 μF.

  The cut-off frequency at the junction at this time is approximately 70 Hz according to the following equation when the termination resistance is 50Ω.

Thus, the capacitance for the DC block can be formed by bonding the electrodes with a dielectric adhesive. This adhesive can be used not only for bonding between electrodes but also for bonding between substrates. In this case, it is desirable that the adhesive has little loss with respect to light propagating through the waveguide. When the refractive index of the adhesive is about n = 1.5, the dielectric constant of the adhesive is ε≈n ² = 2.25. Such adhesives include acrylates, epoxies, silicones, and the like.

FIG. 5 shows an optical modulator according to the third embodiment of the present invention. In this embodiment, an external termination resistor is integrated on the substrate. This termination resistor can be formed on the substrate using Ta ₂ N, NiCr, W or the like. Thereby, it is possible to reduce the size of the substrate and the surrounding electric circuit. Also, depending on the layout, the number of locations where the electrode intersects the waveguide is reduced, so that the influence of crosstalk can be reduced and good modulation characteristics can be achieved. Note that the termination resistor can be formed by sputtering, CVD (Chemical Vapor Deposition), vapor deposition, or the like.

  The Mach-Zehnder type optical modulator 500 includes an LN substrate 510 made of an electro-optic material and two quartz substrates 530 and 560. The quartz substrate 530 in the previous stage has an input waveguide 532 into which input light is incident, a Y branching portion 534 that branches light from the input waveguide, and two arm waveguides 536a and 536b that guide the branched light. And are formed. The LN substrate 510 is formed with two arm waveguides 512a and 512b that are optically coupled to the two arm waveguides 536a and 536b of the preceding quartz substrate. Electrodes 514a and 514b are provided. A DC power source 528 is connected to the modulation electrode 514b via a coil 529, and an operating point of the modulator can be set. The quartz substrate 560 at the rear stage has two arm waveguides 562a and 562b optically coupled to the two arm waveguides 512a and 512b of the LN substrate, and Y that multiplexes light from these two arm waveguides. A multiplexing unit 564 and an output waveguide 566 that outputs the combined light are formed.

  Electrodes 538a and 538b are provided on the previous stage quartz substrate and connected to an external high-frequency signal source 524. The electrodes 538a and 538b are connected to the electrodes 512a and 512b on the LN substrate using dielectric adhesives 526a and 526b. Similarly, electrodes 568a and 568b are provided on the subsequent quartz substrate, and are connected to a termination resistor 570 formed on the substrate. Similarly, the electrodes 568a and 568b are connected to the electrodes 514a and 514b on the LN substrate using dielectric adhesives 528a and 528b. As described above, this adhesive forms a DC blocking capacitance between the electrodes. In the present invention, the quartz substrates 530 and 560 may be different from the LN substrate 510 and may not be a quartz substrate.

  The input light incident on the input waveguide 532 is branched into two by the Y branching unit 534. The branched light propagates to the arm waveguides 512a and 512b of the LN substrate 510 via the arm waveguides 536a and 536b. The phase of light propagating through the waveguides 512a and 512b of the LN substrate is modulated by a modulation signal applied to the electrodes 514a and 514b. The amount of phase modulation is determined by the applied voltage and action length of the modulation signal. Here, a DC component is superimposed on this modulation signal, and an operating point of the optical modulator 500 is set. In the present invention, the capacitance formed by the adhesives 526 a and 526 b between the electrodes 538 a and 538 b of the quartz substrate 530 and the electrodes 514 a and 514 b of the LN substrate 510, and the electrodes 568 a and 568 b of the quartz substrate 560 and the LN substrate 510. Since the DC component is blocked by the capacitance formed by the adhesives 528a and 528b between the electrodes 514a and 514b, it is possible to prevent the DC current from flowing through the resistor 570 and being consumed as heat. Therefore, power consumption can be reduced. Further, since heat due to the DC component is not generated by the resistor, the operation of the optical modulator is stabilized. Furthermore, since there is no DC voltage drop due to resistance, the DC bias voltage can be reduced. Since the same function as the DC block capacitance is realized by a minute junction between the LN substrate and the quartz substrate, the capacitance for the DC block can be reduced without increasing the size of the LN substrate. Therefore, the apparatus can be miniaturized. In the present invention, it is needless to say that it is not necessary to form a DC block capacitance at all of these four connection portions using an adhesive, and the effect can be obtained at any one of the locations.

  Next, the light propagated through the waveguides 512a and 512b of the LN substrate is coupled to the arm waveguides 562a and 562b of the quartz substrate 560, and is multiplexed by the Y multiplexing unit 564, and the output light is emitted from the output waveguide 566. Is done.

  FIG. 6 shows an optical modulator according to the fourth embodiment of the present invention. In this embodiment, an optical modulator is composed of a plurality of Mach-Zehnder interferometers. Thus, in an optical modulator composed of a plurality of Mach-Zehnder interferometers, the effect of the present invention by forming a capacitance using an adhesive and forming a termination resistor on the substrate becomes remarkable.

  The Mach-Zehnder type optical modulator 600 includes an LN substrate 610 made of electro-optic material and two quartz substrates 630 and 660. The quartz substrate 630 in the previous stage has an input waveguide 632 into which input light is incident, a Y branch portion 634 that branches light from the input waveguide, and Y branch portions 634-1 and 634 that further branch the branched light. -2 are formed. The LN substrate 610 is formed with four arm waveguides 612-1a, 612-1b, 612-2a, and 612-2b to which light from the Y branch portions 634-1 and 634-2 of the preceding quartz substrate is coupled. The LN substrate arm waveguides are provided with modulation electrodes 614-1a, 614-1b, 614-2a, and 614-2b, respectively. DC power sources 628-1 and 628-2 are connected to the modulation electrodes 614-1a and 614-2b through the coils 629-1 and 629-2, respectively, and the operating point of the modulator is set. can do. The quartz substrate 660 at the rear stage includes a Y multiplexing unit 664-1 that is optically coupled to the two arm waveguides 612-1a and 612-1b of the LN substrate, and a two-arm waveguide 612-2a of the LN substrate. , 612-2b optically coupled to Y-coupling unit 664-2, Y-coupling unit 664 for further multiplexing the light from the two multiplexing units, and an output waveguide for outputting the combined light 666.

  Further, electrodes 638-1a, 638-1b, 638-2a, and 638-2b are provided on the previous stage quartz substrate, and are connected to external high-frequency signal sources 624-1 and 624-2. The electrodes 638-1a, 638-1b, 638-2a, and 638-2b are electrodes 614-1a and 616-2a on the LN substrate using dielectric adhesives 626-1a, 626-1b, 626-2a, and 626-2b. It is connected to 614-1b, 614-2a, and 614-2b. Similarly, electrodes 668-1 a, 668-1 b, 668-2 a, and 668-2 b are provided on the subsequent quartz substrate and are connected to termination resistors 670-1 and 670-2 formed on the substrate. Yes. Similarly, electrodes 668-1a, 668-1b, 668-2a, 668-2b are electrodes 614 on the LN substrate using dielectric adhesives 628-1a, 628-1b, 628-2a, 628-2b. -1a, 614-1b, 614-2a, and 614-2b. As described above, this adhesive forms a DC blocking capacitance between the electrodes. In the present invention, the quartz substrates 630 and 660 may be different from the LN substrate 610 and may not be a quartz substrate.

  The input light incident on the input waveguide 632 is branched into two by the Y branch portion 634. The branched light is further branched into two at the Y branch portions 634-1 and 634-2, and propagates to the arm waveguides 612-1a, 612-1b, 612-2a, and 612-2b of the LN substrate 610, respectively. . The light propagating through the waveguides 612-1a, 612-1b, 612-2a, and 612-2b of the LN substrate is caused by the modulation signal applied to the electrodes 614-1a, 614-1b, 614-2a, and 614-2b. Its phase is modulated. The amount of phase modulation is determined by the applied voltage and action length of the modulation signal. Here, a DC component is superimposed on this modulation signal, and an operating point of the optical modulator 600 is set. In the present invention, between the electrodes 638-1a, 638-1b, 638-2a, 638-2b of the quartz substrate 630 and the electrodes 614-1a, 614-1b, 614-2a, 614-2b of the LN substrate 610. The capacitance formed by the adhesives 626-1a, 626-1b, 626-2a, and 626-2b, and the electrodes 668-1a, 668-1b, 668-2a, and 666-2b of the quartz substrate 660 and the electrodes of the LN substrate 610 The DC component is blocked by the capacitance formed by the adhesives 628-1a, 628-1b, 628-2a, and 628-2b between 614-1a, 614-1b, 614-2a, and 614-2b. The DC current can be prevented from flowing through the resistors 670-1 and 670-2 and being consumed as heat. Therefore, power consumption can be reduced. Further, since heat due to the DC component is not generated by the resistor, the operation of the optical modulator is stabilized. Furthermore, since there is no DC voltage drop due to resistance, the DC bias voltage can be reduced. Since the same function as the DC block capacitance is realized by a minute junction between the LN substrate and the quartz substrate, the capacitance for the DC block can be reduced without increasing the size of the LN substrate. Therefore, the apparatus can be miniaturized. In the present invention, it is not necessary to form a capacitance for the DC block in all of these eight connection portions using the adhesive, and it goes without saying that the effect can be obtained at any one position for each Mach-Zehnder interferometer. Nor.

  Next, the light propagated through the waveguides 612-1a and 612-1b of the LN substrate is multiplexed by the Y multiplexing unit 664-1 of the quartz substrate 660, and the waveguides 612-2a and 612-2b of the LN substrate are transmitted. The propagated light is multiplexed by the Y multiplexing unit 664-2 of the quartz substrate 660. The lights from the Y multiplexing units 664-1 and 664-2 are further combined by the Y multiplexing unit 664, and output light is emitted from the output waveguide 666.

While the present invention has been described with respect to several specific embodiments, the embodiments described herein are merely illustrative in view of the many possible embodiments to which the principles of the present invention can be applied. It is not intended to limit the scope of the invention. For example, in the above embodiment, the LN substrate is described as an example of the electro-optic material substrate. However, the principle of the present invention is that lithium tantalate (LiTaO ₃ ), KTN (KTa _1-x Nb _x O ₃ ), KTP (KTiOPO ₄ ), PZT (lead zirconate titanate), or the like can be used. Further, the case where the paraelectric quartz substrate is used on the output side of the optical modulator and the case where it is used on both the input side and the output side has been described. The effect of can be obtained. Furthermore, in the above embodiment, a circuit such as a directional coupler, a coupler, or a multimode interference coupler (MMI) may be used instead of the Y branch. As described above, the configuration and details of the embodiment exemplified here can be changed without departing from the gist of the present invention. Further, the illustrative components and procedures may be changed, supplemented, or changed in order without departing from the spirit of the invention.

100, 200, 300, 500, 600 Mach-Zehnder type optical modulator 110 Optical substrate 112, 212, 332, 532, 632 Input waveguide 114, 214, 334, 534, 564, 634, 634-1, 634-2 Y branch 116a, 116b, 216a, 216b, 232a, 232b, 312a, 312b, 336a, 336b, 362a, 362b, 512a, 512b, 536a, 536b, 562a, 562b, 612-1a, 612-1b, 612-2a, 612 -2b Arm waveguide 118, 234, 364, 664, 664-1, 664-2 Y combiner 120, 236, 366, 566, 666 Output waveguide 124, 224, 324, 524, 624-1, 624 2 High-frequency signal source 127, 227 DC bias circuit 28, 228, 328, 628-1, 628-2 DC power supply 170, 270, 370, 570, 670-1, 670-2 Termination resistor 171 DC block capacitor 210, 310, 510, 610 LN substrate 222a, 222b , 238a, 238b, 314a, 314b, 338a, 338b, 368a, 368b, 410, 430, 514a, 514b, 538a, 538b, 568a, 568b, 614-1a, 614-1b, 614-2a, 614-2b, 638 -1a, 638-1b, 638-2a, 638-2b, 668-1a, 668-1b, 668-2a, 668-2b Electrodes 226a, 226b, 326a, 326b, 328a, 328b, 420, 526a, 526b, 528a , 528b, 626-1a, 626 1b, 626-2a, 626-2b, 628-1a, 628-1b, 628-2a, 628-2b Adhesive 230, 330, 360, 530, 560, 630, 660 Quartz substrates 329, 529, 629-1, 629-2 coil

Claims (6)

A Mach-Zehnder type optical modulator,
A first substrate of electro-optic material on which an arm waveguide is formed;
A second substrate on which at least one of a Y branching portion and a Y multiplexing portion coupled to the arm waveguide is formed, and
The first substrate of the electro-optic material includes a first electrode for modulation formed on the arm waveguide, and the second substrate includes a second electrode coupled to the first electrode. And the first and second electrodes are joined by a dielectric adhesive. The optical modulator according to claim 1, comprising:
The optical modulator, wherein the adhesive is used for joining the first and second substrates. The optical modulator according to claim 1 or 2,
The optical modulator, wherein the second electrode includes a termination resistor. The optical modulator according to any one of claims 1 to 3,
An optical modulator comprising a plurality of Mach-Zehnder interferometers. An optical modulator according to any one of claims 1 to 4,
The optical modulator, wherein the second substrate is a quartz-based substrate. An optical modulator according to any one of claims 1 to 5,
The optical modulator, wherein the first substrate is an optical substrate made of a lithium niobate crystal.

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