Optical waveguide element, optical modulation device using the same, and optical transmission device

Abstract

The purpose of the present invention is to provide an optical waveguide element in which electrode wiring can be simplified and maintained at a length longer than that of working electrode parts.　The optical waveguide element according to the present invention includes a substrate (1) on which an optical waveguide (10) is formed and an electrode which is disposed on the substrate and applies an electric field to the optical waveguide, said optical waveguide element being characterized in that: the electrode comprises working electrode parts (BE1, BE10, etc.) that are disposed in the vicinity of the optical waveguide, power feeding parts (BT1, BT10, etc.) that feed power to the electrode, and wiring parts (BW1, BW10, etc.) that link the working electrode parts and the power feeding parts; the electrode includes a plurality of the working electrode parts that are disposed at different positions on the substrate; and at least some of the wiring parts are disposed between at least some among the working electrode parts or the other wiring parts so as to overlap with an insulation layer (IN) therebetween.

Description

Technical Field

[0001] The present invention relates to an optical waveguide element, an optical modulation device using the same, and an optical transmission device, and particularly to an optical waveguide element having a substrate formed on a substrate and an electrode disposed on the substrate for applying an electric field to the optical waveguide.

Background Art

[0002] In the fields of optical measurement technology and optical communication technology, optical waveguide elements such as optical modulators are widely used. In an optical waveguide element, an electrode is disposed on a substrate on which an optical waveguide is formed, and an electric field is applied to the optical waveguide using the electrode to change the phase of light waves propagating through the optical waveguide. Hereinafter, the electrode portion for applying an electric field to the optical waveguide is referred to as an "active electrode portion".

[0003] In recent years, in order to reduce the mounting area of an optical modulation device, it is necessary to miniaturize the optical waveguide element itself. For this reason, as shown in Patent Document 1 or 2, the optical waveguide is arranged in a folded manner. FIG. 1 is a plan view showing an example of an optical waveguide element having a folded optical waveguide. FIG. 1 shows a state in which four Mach-Zehnder type optical waveguides are arranged in parallel and the entire optical waveguide is bent by 180 degrees.

[0004] In the region of the dotted line A of the optical waveguide, an electric field corresponding to a modulation signal is applied to the optical waveguide by an electrode (not shown) to perform a modulation operation. Separately from this modulation region, bias electrodes (BE1, BE10, etc.) are arranged in a part of the optical waveguide as shown in FIG. 1 to adjust the phase of light waves passing through each Mach-Zehnder type optical waveguide.

[0005] When a plurality of optical waveguides are arranged in parallel as shown in FIG. 1 and bias electrodes are provided for each optical waveguide, due to the relationship of wiring for supplying power to the active electrode portion disposed close to the optical waveguide, the length of the active electrode portion along the optical waveguide becomes short. For this reason, the DC bias voltage applied to the bias electrode becomes high, and the DC drift phenomenon is likely to occur.

[0006] Furthermore, a pad section for wire bonding is provided at the end of the chip for electrical connection to the outside. When using a folded optical waveguide as shown in Figure 1, the pad sections that supply power to each bias electrode are concentrated on one side of the chip, resulting in a greater concentration of wiring and a shorter length for the working electrode section. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2019-095698 [Patent Document 2] Japanese Patent Publication No. 2019-109442 [Overview of the project] [Problems that the invention aims to solve]

[0008] The problem that this invention aims to solve is to provide an optical waveguide element that solves the above-mentioned problems, simplifies electrode wiring, and allows for a longer electrode length in the working electrode section. Furthermore, it aims to provide an optical modulation device and an optical transmission device using this optical waveguide element. [Means for solving the problem]

[0009] To solve the above problems, the optical waveguide element, optical modulation device using the same, and optical transmission device of the present invention have the following technical features. (1) An optical waveguide element having a substrate on which an optical waveguide is formed and an electrode disposed on the substrate for applying an electric field to the optical waveguide, wherein the electrode is a bias electrode comprising a working electrode portion disposed near the optical waveguide, a power supply portion for supplying power to the electrode, and a wiring portion connecting the working electrode portion and the power supply portion, the optical waveguide is provided with a plurality of Mach-Zehnder type optical waveguides arranged in parallel, and a plurality of working electrode portions arranged in parallel on the substrate along a plurality of branch waveguides constituting each Mach-Zehnder type optical waveguide, an insulating layer covering the plurality of working electrode portions, the wiring portion disposed on the insulating layer, and the wiring portion and the working electrode portion connected by a conductive portion penetrating the insulating layer. Furthermore, at least a portion of the wiring section is joined to the substrate or a buffer layer placed on the substrate by a conductive portion that penetrates the insulating layer. It is characterized by being present.

[0010] (2) In the optical waveguide element described in (1) above, a first electrode layer is provided on the substrate. Applicable The insulating layer and the second electrode layer are arranged to overlap, the working electrode portion is formed in the first electrode layer, and at least a portion of the wiring portion is formed in the second electrode layer.

[0011] (3) The optical waveguide element described in (1) or (2) above, having a short-circuit wiring section that electrically connects different working electrode sections, the short-circuit wiring section , applicable insulating layer above Placed The short-circuit wiring portion and the working electrode portion are connected by a conductive portion that penetrates the insulating layer. It is characterized by having this feature.

[0012] (4) In the optical waveguide element described in (1) or (2) above, the insulating layer is characterized in that it covers the optical waveguide and is a film having a refractive index lower than that of the optical waveguide.

[0013] (5) The optical waveguide element described in (2) above, characterized in that a buffer layer is formed between the substrate and the first electrode layer.

[0017] ( 6 ) The above (1) to ( 5The optical waveguide device according to any one of

[0018] ( 7 ) above is an optical modulation device characterized in that the optical waveguide device is housed in a housing and includes an optical fiber for inputting or outputting light waves to or from the optical waveguide. 6 In the optical modulation device according to the above (

[0019] ( 8 ) above, the optical waveguide device includes a modulation electrode for modulating the light wave propagating through the optical waveguide, and an electronic circuit for amplifying a modulation signal input to the modulation electrode of the optical waveguide device is provided inside the housing. 6 ) or 7 ), an optical transmission device characterized by having the optical modulation device according to the above ([[]]) and an electronic circuit for outputting a modulation signal for causing the optical modulation device to perform a modulation operation.

Advantages of the Invention

[0020] In the present invention, in an optical waveguide device having a substrate on which an optical waveguide is formed and an electrode disposed on the substrate for applying an electric field to the optical waveguide, the electrode is a bias electrode including an active electrode portion disposed near the optical waveguide, a power supply portion for supplying power to the electrode, and a wiring portion connecting the active electrode portion and the power supply portion. The optical waveguide is arranged by juxtaposing a plurality of Mach-Zehnder type optical waveguides, and a plurality of the active electrode portions are arranged in parallel on the substrate along a plurality of branch waveguides constituting each Mach-Zehnder type optical waveguide. An insulating layer covering the plurality of active electrode portions is provided, the wiring portion is disposed on the insulating layer, and the wiring portion and the active electrode portion are connected by a conductive portion penetrating the insulating layer Furthermore, at least a portion of the wiring section is joined to the substrate or a buffer layer placed on the substrate by a conductive portion that penetrates the insulating layer. Therefore, it is possible to arrange the wiring portion so as to straddle the active electrode portion and other wiring portions, and it is possible to simplify the wiring. As a result, it is also possible to set a longer length for electrodes such as the bias electrode.

Brief Description of the Drawings

[0021] [Figure 1] It is a plan view showing a conventional optical waveguide device. [Figure 2] It is a plan view showing a first embodiment of the optical waveguide device of the present invention. [Figure 3] It is a figure showing the state of a partial cross-section of FIG. 2. [Figure 4] It is a figure showing the state of a partial cross-section of FIG. 2 and explaining an application example. [Figure 5] It is a figure showing the state of a partial cross-section of FIG. 2 and explaining another application example. [Figure 6] It is a plan view showing a second embodiment of the optical waveguide device of the present invention. [Figure 7] It is a plan view showing a third embodiment of the optical waveguide device of the present invention. [Figure 8] It is a plan view showing a fourth embodiment of the optical waveguide device of the present invention. [Figure 9] It is a plan view explaining the optical modulation device and the optical transmission device of the present invention.

Embodiments for Carrying Out the Invention

[0022] Hereinafter, the optical waveguide device of the present invention will be described in detail using preferred examples. As shown in FIGS. 2 to 8, the present invention is an optical waveguide device having a substrate 1 on which an optical waveguide 10 is formed and an electrode disposed on the substrate for applying an electric field to the optical waveguide. The electrode includes an active electrode portion (BE1, BE10, etc.) disposed in the vicinity of the optical waveguide, a power supply portion (BT1, BT10, etc.) for supplying power to the electrode, and a wiring portion (BW1, BW10, etc.) connecting the active electrode portion and the power supply portion. The optical waveguide device has a plurality of the active electrode portions disposed at different positions on the substrate, and at least a part of the wiring portion is disposed so as to overlap with at least a part of the active electrode portion or another wiring portion via an insulating layer (IN).

[0023] The substrate used in the optical waveguide element of the present invention can be a substrate utilizing materials that exhibit electro-optic effects, such as lithium niobate (LN), lithium tantalate (LT), or PLZT (lead lanthanum zirconate titanate), or a substrate doped with magnesium. Vapor-grown films made from these materials can also be used. Furthermore, semiconductor substrate materials can also be used. When using a dielectric substrate such as LN, an X-cut substrate in which electrodes are arranged on either side of the optical waveguide, or a Z-cut substrate in which electrodes are arranged on top of the optical waveguide, can be appropriately selected, as shown in Figure 2.

[0024] The thickness of the substrate 1 on which the optical waveguide is formed can be set to 10 μm or less, more preferably 5 μm or less, and even more preferably 1 μm or less. In such thin substrates, to increase the mechanical strength, a reinforcing substrate may be bonded and fixed to the underside of the substrate 1 either by direct bonding or via an adhesive layer such as resin. As the reinforcing substrate to be directly bonded, a substrate containing an oxide layer such as quartz or glass is preferably used, which has a lower refractive index than the optical waveguide or the substrate on which the optical waveguide is formed and a coefficient of thermal expansion similar to that of the optical waveguide, etc. Composite substrates in which a silicon oxide layer is formed on a silicon substrate abbreviated as SOI or LNOI, or composite substrates in which a silicon oxide layer is formed on an LN substrate can also be used. In this invention, the term "substrate on which an optical waveguide is formed" refers not only to the substrate that constitutes the optical waveguide portion, but also to the substrate integrated with the reinforcing substrate.

[0025] As a method for forming the optical waveguide 10, as shown in Figures 3 to 5, it is possible to use a rib-type optical waveguide in which the portion corresponding to the optical waveguide is convex on the substrate, such as by etching the substrate 1 or forming grooves on both sides of the optical waveguide. When using the thin plate substrate described above, the height of the rib-type optical waveguide is set to 4 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less or 0.4 μm or less. It is also possible to form a vapor-deposited film on a reinforcing substrate and process the film into the shape of an optical waveguide. In particular, when using a folded optical waveguide, an optical waveguide having a height and width of 1 μm or less is used.

[0026] Other optical waveguide methods include thermal diffusion of materials such as Ti into the substrate or the formation of high refractive index regions on the substrate surface using proton exchange methods. Furthermore, it is possible to strengthen optical confinement by thermal diffusion of materials such as Ti into a rib-type optical waveguide.

[0027] Next, various buffer layers (protective films) will be described. To suppress propagation loss due to surface roughness of the rib-type optical waveguide, it is possible to provide a resin film covering the optical waveguide. The resin film is composed of a permanent resist film or the like. It is also possible to form an SiO2 film on the optical waveguide to suppress absorption of light waves propagating through the waveguide by the electrodes. The resin film and SiO2 film are materials with a lower refractive index than the optical waveguide. Furthermore, in order to suppress the pyroelectric effect of the substrate, a film of Si or SiN may be formed on the substrate. The first electrode layer, described later, may be placed directly on the substrate or on top of the buffer layer mentioned above.

[0028] In this invention, resin films, SiO2 films, and the like can also be used as insulating layers (IN) as described later. The insulating layer is placed between the first electrode layer and the second electrode layer, and plays the role of electrically separating them. However, these films may be formed simultaneously with the conventional process of forming optical waveguide elements, or they may be placed by adding another process.

[0029] Electrodes are formed on the substrate 1. These electrodes include modulation electrodes consisting of a signal electrode and a ground electrode, and bias electrodes for applying a bias voltage. Highly conductive metals such as Au and Cu are used as electrode materials. Various methods can be used to form the electrodes, such as plating, vapor deposition, and sputtering. An underlayer of Ti or Nb can be provided between the electrode and the substrate 1, or between the substrate and the Si or SiO2 film placed on the substrate, to increase the adhesion strength between the electrode and the substrate.

[0030] The features of the present invention are that the electrode comprises, as shown in Figures 2 to 8, a working electrode section (see reference numerals beginning with BE) positioned near the optical waveguide, a power supply section (see reference numerals beginning with BT) that supplies power to the electrode from outside the optical waveguide element, and a wiring section (see reference numerals beginning with BW) connecting the working electrode section and the power supply section. The power supply section also serves as a power supply pad section to which a wire, which is a power supply line, is bonded. Furthermore, in the present invention, at least a portion of the wiring portion is arranged to overlap with other working electrode portions and at least a portion of other wiring portions via an insulating layer (IN), and is configured to straddle these working electrode portions and wiring portions.

[0031] To realize a configuration in which the wiring section spans the working electrode section and other wiring sections, a first electrode layer (LY1), an insulating layer (IN), and a second electrode layer (LY2) are arranged on the substrate 1 so as to overlap, the working electrode section is formed on the first electrode layer, and at least a part of the wiring section is formed on the second electrode layer. Of course, the configuration is not limited to two electrode layers and one insulating layer sandwiched between them, but it is also possible to provide three or more electrode layers and arrange insulating layers between the overlapping electrode layers.

[0032] Figure 2 is a plan view illustrating the application of the present invention to a substrate 1 on which a folded optical waveguide 10 has been formed, similar to Figure 1. The area indicated by the dotted line A shows the portion where the modulation electrode is formed. The configuration of the present invention is applied to the bias electrode, with the working electrode portion (BE1, BE10, etc.) indicated by the dotted line formed in the first electrode layer (LY1), and the power supply portion (BT1, BT10, etc.) and wiring portion (BW1, BW10, etc.) formed in the second electrode layer (LY2). An insulating layer (IN), not shown, is placed between the two electrode layers.

[0033] The wiring section (BW1, etc.) and the working electrode section (BE1, etc.) are connected by conductive portions (through-holes) TH that penetrate the insulating layer. In section 2, the positions where the through-holes are formed are indicated by black circles.

[0034] Figure 3 shows a cross-sectional view perpendicular to the drawing of the wiring section (BW1) in Figure 2. In Figure 3, the working electrode sections (BE1 and BE10, or BE1 and BE10') are arranged so as to sandwich the optical waveguide 10. The wiring section (BW1) is positioned above the working electrode section via an insulating layer IN, and the wiring section (BW1) and the working electrode section (BE1) are electrically connected via through-holes TH. Similarly, the other wiring sections are positioned above the working electrode sections or optical waveguides via an insulating layer IN, and are electrically connected via through-holes TH above specific working electrode sections.

[0035] As is clear from comparing Figure 1 and Figure 2, in the present invention, the placement of the working electrode is not restricted by the routing of the electrode wiring, making it possible to secure a sufficient length of the working electrode along the optical waveguide. Moreover, even when the mounting area is minimized by miniaturizing the chip, a longer length of the working electrode can be secured than in conventional designs.

[0036] When wiring is arranged to span across an optical waveguide, the insulating layer covering the optical waveguide can be made of a material with a refractive index lower than that of the optical waveguide, such as resin or SiO2. This suppresses the problem of propagation loss caused by the wiring absorbing light waves propagating through the optical waveguide. In particular, when the optical waveguide has a structure in which multiple Mach-Zehnder type optical waveguides are arranged in parallel, the propagation loss of the Mach-Zehnder type optical waveguide greatly affects the modulation performance of the optical waveguide element, making the role of the insulating layer important.

[0037] Figures 4 and 5 show cross-sectional views of the wiring section (BW2) in Figure 2. As shown in Figure 4, the insulating layer (IN) can be provided only where necessary on the underside of the wiring section (BW2). Generally, when an electrode layer is placed on top of an insulating layer, there is a risk of the electrode layer peeling off due to the low adhesive strength between the insulating layer and the electrode layer. For this reason, in areas where an insulating layer is not needed, it is possible to omit the insulating layer and integrate the first electrode layer and the second electrode layer, or to form a through-hole (THA) with a conductive portion in a through-hole formed in a part of the insulating layer, and to bond the second electrode layer to the substrate 1 (or a buffer layer formed on the substrate 1) to prevent the second electrode layer from peeling off.

[0038] Furthermore, as shown in Figure 5, by widely distributing the insulating layer (IN) not only where it is needed but also where it is not, it becomes possible to suppress problems such as scattering of propagating light due to the presence or absence of an insulating layer covering the optical waveguide, and propagation loss due to changes in dielectric constant due to the presence or absence of an insulating layer between electrodes.

[0039] Figure 6 shows a case where power is supplied to the working electrode not only by the wiring extending from the power supply unit, but also by using a short-circuit wiring unit to electrically connect different working electrode units. Specifically, the working electrode unit (BE10) is electrically connected to the wiring unit (BW101) extending from the power supply unit, while the working electrode unit (BE10') is electrically connected to the working electrode unit (BE10) by a short-circuit wiring unit (BP1). To prevent the short-circuit wiring section (BP1) from being electrically connected to the working electrode section (BE1), an insulating layer (not shown) is placed between the short-circuit wiring section and at least a portion of the working electrode section (BE1), so that the two are not directly connected.

[0040] This short-circuit configuration increases the flexibility of electrode wiring, enabling more compact wiring. Furthermore, by adding an additional short-circuit section to the electrode wiring shown in Figure 2, electrical connections between different working electrodes can be made more reliable. Additionally, by electrically connecting the working electrodes at multiple points, it is possible to suppress the working electrodes from functioning as antennas against noise. In Figure 6, the short-circuit section (BP1) is formed in the second electrode layer (LY2), but it is also possible to provide it in the first electrode layer and arrange it, for example, to bypass the working electrode section (BE1), thereby electrically connecting the working electrode sections BE10 and BE10'. Alternatively, a short-circuit section that electrically connects the working electrode sections BE10' and BE20 can be provided in the first electrode layer. The more working electrodes connected at the same potential the short-circuit wiring section has, the simpler the wiring structure becomes.

[0041] In Figure 7, the power supply section and the wiring sections connected to it (BW102, BW302) can be formed in the first electrode layer, unlike other power supply sections and wiring sections. In this case, however, it is necessary to avoid placing an insulating layer above the power supply section formed in the first electrode layer in order to connect the power supply lines, such as by wire bonding.

[0042] Figure 8 shows the case where the same electric field is applied to the same optical waveguide before and after the folded optical waveguide. By simply adjusting the position of the through-hole TH that electrically connects the wiring section (BW7, BW70) and the working electrode section (BE7~BE80'), wiring can be easily performed.

[0043] Regarding the thickness of each electrode layer and insulating layer used in this invention, it is desirable that the thickness of each layer be in the relationship first electrode layer < insulating layer < second electrode layer in order to prevent the patterns of each layer from being interrupted by steps in the laminated portion and to ensure sufficient dielectric strength between electrode layers.

[0044] The first electrode layer is intended to form electrodes positioned close to the optical waveguide and modulation electrodes using high-frequency signals, and therefore, a highly precise manufacturing process is expected to be used. In such processes, it is difficult to form thick layers of photoresist or other materials used for pattern formation. Therefore, a thickness of 2 μm or less is desirable.

[0045] The thickness of the insulating layer should preferably be 2 μm or more to compensate for the voltage withstand capability and to prevent light absorption by the second electrode layer. Furthermore, the second electrode layer is preferably at least 1 μm thicker than the insulating layer in order to prevent disconnection at the etched areas (stepped areas) of the insulating layer.

[0046] As described above, bias electrodes are preferred over modulation electrodes that propagate high-frequency signals as the electrodes to which the present invention is applied. Furthermore, when used as a modulation electrode, it is preferable to apply the configuration of the present invention to the wiring of the ground electrode rather than the signal electrode.

[0047] The above description has mainly focused on cases where the input / output sections and the working section (the region containing the working electrode) of the optical waveguide are formed on the same substrate, but the present invention is not limited to this. For example, in Figure 1, a substrate such as LN may be used in the area containing the working electrode, while the branched waveguide section (to the left of the working electrode BE10) and the folded optical waveguide of the Mach-Zehnder type optical waveguide may be formed on a different substrate such as a Si substrate or a quartz substrate, and these may be connected to each other. Alternatively, the substrates containing the working electrode may be divided and connected to each other. Furthermore, a light source or the like may be connected to the substrate.

[0048] Next, we will describe examples of applying the optical waveguide element of the present invention to optical modulation devices and optical transmitting devices. Figure 9 shows an optical waveguide element having an optical waveguide 10 formed by bending a single Mach-Zehnder type optical waveguide, but it is not limited to this and it is also possible to use optical waveguide elements with more Mach-Zehnder type optical waveguides, such as those shown in Figure 2. Furthermore, it goes without saying that it can be applied to devices for sensor applications and high-bandwidth-coherent driver modulators (HB-CDM).

[0049] As shown in Figure 9, the optical waveguide element has an optical waveguide 10 formed on a substrate 1 and a modulation electrode (not shown) that modulates the light wave propagating through the optical waveguide 10, and is housed in a housing CA. Furthermore, by providing an optical fiber (F) that inputs and outputs light waves to the optical waveguide, an optical modulation device MD can be constructed. In Figure 9, the optical fiber F is optically coupled to the optical waveguide 10 in the optical waveguide element using an optical block 3 equipped with an optical lens, a lens barrel OL, etc. However, it is not limited to this, and the optical fiber may be introduced into the housing through a through-hole that penetrates the side wall of the housing, and the optical fiber may be directly joined to an optical component or substrate, or an optical fiber with a lens function at the end of the optical fiber may be optically coupled to the optical waveguide in the optical waveguide element.

[0050] An optical transmitter (OTA) can be configured by connecting an electronic circuit (digital signal processor DSP) that outputs a modulation signal So to the optical modulation device MD to perform modulation operations on the optical modulation device MD. In order to obtain the modulation signal S to be applied to the optical waveguide element, it is necessary to amplify the modulation signal So output from the digital signal processor DSP. For this reason, in Figure 9, a driver circuit DRV is used to amplify the modulation signal. The driver circuit DRV and the digital signal processor DSP can be placed outside the housing CA, but they can also be placed inside the housing CA. In particular, by placing the driver circuit DRV inside the housing, it is possible to further reduce the propagation loss of the modulation signal from the driver circuit. [Industrial applicability]

[0051] As described above, the present invention makes it possible to provide an optical waveguide element that simplifies electrode wiring and allows for a longer working electrode section. Furthermore, it makes it possible to provide an optical modulation device and an optical transmission device using this optical waveguide element. [Explanation of Symbols]

[0052] 1. Substrate (thin plate, film) for forming an optical waveguide 3 Optical Blocks 10 Optical waveguide BE1,BE10,BE10' Working electrode part BW1, BW10 Wiring Section BT1, BT10 Power supply section (pad section) BP1 Short-circuit wiring section LY1 1st electrode layer LY2 2nd electrode layer IN insulating layer F Optical Fiber OL lens barrel CA cabinet MD Optical Modulation Device DRV driver circuit DSP (Digital Signal Processor) OTA Optical Transmitter

Claims

1. An optical waveguide element having a substrate on which an optical waveguide is formed, and electrodes disposed on the substrate for applying an electric field to the optical waveguide, The electrode is a bias electrode comprising a working electrode portion positioned near an optical waveguide, a power supply portion for supplying power to the electrode, and a wiring portion connecting the working electrode portion and the power supply portion. The optical waveguide is configured by arranging multiple Mach-Zehnder type optical waveguides in parallel, and arranging multiple working electrode sections in parallel on the substrate along multiple branch waveguides that constitute each Mach-Zehnder type optical waveguide. The facility includes an insulating layer covering the plurality of working electrode portions, The wiring portion is placed on the insulating layer, and the wiring portion and the working electrode portion are connected by a conductive portion that penetrates the insulating layer. An optical waveguide element characterized in that at least a portion of the wiring is joined to the substrate or a buffer layer disposed on the substrate by a conductive portion that penetrates the insulating layer.

2. In the optical waveguide element according to claim 1, The first electrode layer, the insulating layer, and the second electrode layer are arranged on the substrate so as to overlap each other. The working electrode portion is formed in the first electrode layer, An optical waveguide element characterized in that at least a portion of the wiring portion is formed in the second electrode layer.

3. In the optical waveguide element according to claim 1 or 2, It has a short-circuit wiring section that electrically connects different working electrode sections, The optical waveguide element is characterized in that the short-circuit wiring portion is arranged on the insulating layer, and the short-circuit wiring portion and the working electrode portion are connected by a conductive portion that penetrates the insulating layer.

4. In the optical waveguide element according to claim 1 or 2, The optical waveguide element is characterized in that the insulating layer covers the optical waveguide and is a film having a refractive index lower than that of the optical waveguide.

5. An optical waveguide element according to claim 2, characterized in that a buffer layer is formed between the substrate and the first electrode layer.

6. An optical waveguide element according to any one of claims 1 to 5 is an optical modulation device characterized in that the optical waveguide element is housed in a housing and comprises an optical fiber that inputs or outputs an optical wave to the optical waveguide.

7. An optical modulation device according to claim 6, characterized in that the optical waveguide element is provided with a modulation electrode for modulating a light wave propagating through the optical waveguide, and the housing has an electronic circuit for amplifying a modulation signal input to the modulation electrode of the optical waveguide element.

8. An optical transmitting device comprising an optical modulation device according to claim 6 or 7, and an electronic circuit that outputs a modulation signal for causing the optical modulation device to perform a modulation operation.

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