JP2017067986A - Optical waveguide element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide element capable of suppressing a phenomenon caused by a photorefractive effect of a substrate material.SOLUTION: The optical waveguide element includes a substrate 1 having an electro-optic effect and an optical waveguide 2 formed in the substrate 1, in which a light-absorbing member 3 that generates heat by absorption of light is disposed so as to cover an upper side of a waveguide portion on an input side (an input waveguide portion 21 and a branched portion 22) and a waveguide portion on an output side (a multiplexing portion 24 and an output waveguide portion 25).SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical waveguide device including a substrate having an electro-optic effect and an optical waveguide formed on the substrate.

In recent years, in the fields of optical communication and optical measurement, an optical waveguide is formed on a substrate having an electro-optic effect such as lithium niobate (LN) and a control electrode for controlling a light wave propagating in the optical waveguide is formed. Optical waveguide elements such as waveguide type optical modulators are widely used.
When the intensity of light incident on the optical modulator is increased for long-distance transmission, the extinction ratio is deteriorated, the optical loss is increased, and the bias point is changed. In particular, when the light input intensity is 10 mW or more, such a problem becomes significant.

These problems are mainly caused by interference between stray light leaking from the input unit that inputs light into the optical modulator and the optical waveguide in the optical modulator, and the signal light propagating in the optical waveguide, It is known that the photorefractive phenomenon occurs, and thereby the formation of a grating in the optical waveguide portion is a major cause.
The grating formed in such an optical waveguide part returns the signal light traveling in the optical waveguide in the direction opposite to the traveling direction, thereby deteriorating return loss or reflecting the signal light out of the optical waveguide. It will cause deterioration of the extinction ratio of light.

The photo reluctance phenomenon is a phenomenon in which the refractive index of a substance changes when exposed to light. Specifically, when a spatial light intensity distribution occurs due to light interference or the like due to the property of charge transfer in a substance caused by light, charge redistribution occurs according to the light intensity distribution. And an internal electric field changes locally by the uneven distribution of the electric charge produced by the redistribution of an electric charge. Since the internal electric field changes the refractive index of the substance, as a result, a refractive index distribution of the substance corresponding to the light intensity distribution is formed.
In addition, the photorefractive phenomenon has a characteristic that the refractive index gradually changes when the light is continuously applied to the material, and the scattering becomes stronger with time. Deterioration of optical modulator characteristics such as deterioration and increase of optical loss becomes remarkable.

  Therefore, various methods for alleviating the photoreductive phenomenon have been studied. For example, a method of forming a groove in an LN substrate to shield the optical waveguide from stray light and a method of filling the groove with a light absorbing material have been proposed (see Patent Document 1). However, there are concerns about deterioration of temperature characteristics due to groove formation (and filling of the light absorbing material) in the LN substrate and increase in optical waveguide loss due to roughness of the LN substrate surface due to impurity diffusion.

In addition, as another method for alleviating the photoreductive phenomenon, for example, utilization of Mg, Zn-added LiNbO ₃ , use at a high element temperature, and the like have been proposed (see Patent Documents 2 and 3). However, when an Mg, Zn-added LiNbO ₃ crystal is used for an LN modulator, the polarization inversion threshold value becomes low and the applied voltage that can be used becomes small, which is not suitable for integration. In addition, when the element temperature of the LN modulator is increased, it is difficult to apply it because power for temperature control is required and the DC drift phenomenon inherent to the LN modulator is increased.

JP 2004-93905 A Japanese Patent No. 4067845 Japanese Patent No. 4111075

  The problem to be solved by the present invention is to provide an optical waveguide device capable of solving the above-described problems and suppressing a phenomenon caused by a photorefractive effect of a substrate material.

In order to solve the above problems, the optical waveguide device of the present invention has the following technical features.
(1) In an optical waveguide device comprising a substrate having an electro-optic effect and an optical waveguide formed on the substrate, the optical waveguide includes an input waveguide portion to which light is input from the outside of the optical waveguide device A branch part that branches the light input to the input waveguide part into a plurality of branch waveguide parts, and covers at least the upper side of the input waveguide part and the part where the light intensity increases in the branch part. As described above, a light absorbing member that generates heat by light absorption is arranged.

(2) In the optical waveguide device according to the above (1), the light absorbing member covers at least the entire upper side of the input waveguide part, or a part of the input waveguide and the upper side of the branch part. It is characterized by being arranged in.

(3) In the optical waveguide device according to (1) or (2), the light absorbing member is a member having a predetermined width extending along the optical waveguide.

(4) The optical waveguide device according to any one of (1) to (3), wherein a through hole is provided along a portion of the light absorbing member along the optical waveguide.

(5) The optical waveguide element according to any one of (1) to (4), wherein the light absorbing member is grounded.

(6) The optical waveguide device according to any one of (1) to (5), wherein a spacer is provided between the optical waveguide and the light absorbing member.

(7) In the optical waveguide device according to any one of (1) to (6), the optical waveguide is synthesized by a synthesis unit that synthesizes light from the plurality of branch waveguide units, and the synthesis unit. An output waveguide portion for outputting the light to the outside of the optical waveguide element, and the light absorbing member so as to cover at least the upper side of the portion where the light intensity increases in the output waveguide portion and the synthesis portion Is arranged.

(8) In the optical waveguide device according to (7),
The light absorbing member is arranged so as to cover at least the entire upper side of the output waveguide portion or a part of the output waveguide and the upper side of the synthesis portion.

(9) In the optical waveguide device according to any one of (1) to (8), a plurality of the light absorption members are arranged along the optical waveguide, and light is absorbed by each of the plurality of light absorption members. The amount is small in the order of arrangement of the light absorbing members in the light propagation direction.

(10) In an optical waveguide device including a substrate having an electro-optic effect and an optical waveguide formed on the substrate, the optical waveguide is a plurality of input waveguides into which light is input from the outside of the optical waveguide device A combining unit that combines light input to the plurality of input waveguide units, and an output waveguide unit that outputs the light combined by the combining unit to the outside of the optical waveguide element, In the output waveguide portion and the combining portion, a light absorbing member that generates heat by light absorption is disposed so as to cover the upper side of the portion where the light intensity increases.

(11) The optical waveguide device according to any one of (1) to (10), further including a housing that accommodates the substrate, wherein an arrangement portion of the light absorbing member on the substrate is arranged from an inner surface of the housing It is characterized by being separated.

  The optical waveguide device of the present invention is an optical waveguide device including a substrate having an electro-optic effect and an optical waveguide formed on the substrate, and light is input to the optical waveguide from outside the optical waveguide device. A portion having an input waveguide portion and a branch portion for branching light input to the input waveguide portion into a plurality of branch waveguide portions, and a portion where the light intensity is increased in the input waveguide portion and the branch portion Since the light absorbing member that generates heat by light absorption is disposed so as to cover at least the upper side of the light, the photorefractive effect can be reduced by the heat generation of the light absorbing member by the light propagating through the optical waveguide, and the photorefractive effect can be reduced. The resulting phenomenon can be suppressed. Further, local heating can be performed only by arranging the light absorbing member at a location where the optical waveguide needs to generate heat, and there is no need to provide an additional power source for heating.

It is a figure which shows the 1st structural example of the optical waveguide element which concerns on one Embodiment of this invention. It is a figure which shows the temperature change of the input side board | substrate area | region at the time of changing input light quantity. It is a figure which shows the 2nd structural example of the optical waveguide element which concerns on one Embodiment of this invention. It is a figure which shows the 3rd structural example of the optical waveguide element which concerns on one Embodiment of this invention. It is a figure which shows the modification of the 3rd structural example of the optical waveguide element which concerns on one Embodiment of this invention. It is a figure which shows the 4th structural example of the optical waveguide element which concerns on one Embodiment of this invention. It is a figure which shows the 5th structural example of the optical waveguide element which concerns on one Embodiment of this invention. It is a figure which shows the 6th structural example of the optical waveguide element which concerns on one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 3 to 5, an optical waveguide device according to the present invention is an optical waveguide device including a substrate 1 having an electro-optic effect and an optical waveguide 2 formed on the substrate 1. A light absorbing member 3 that generates heat by light absorption is disposed so as to cover at least a part of the upper side of the optical waveguide 2.

FIG. 1 shows a first configuration example of an optical waveguide device according to the present invention.
As the substrate 1 used for the optical waveguide element, it is preferable to use a substrate having an electro-optic effect such as LiNbO ₃ , LiTaO ₅ or PLZT (lead lanthanum zirconate titanate).
The optical waveguide 2 formed on the substrate 1 is formed, for example, by thermally diffusing a high refractive index material such as titanium (Ti) on a LiNbO ₃ substrate (LN substrate). A ridge-type optical waveguide in which irregularities along the optical waveguide 2 are formed on the substrate 1 can also be used. The substrate 1 may be an X cut type or a Z cut type.
The substrate on which the optical waveguide 2 is formed is polished on its back surface to a predetermined thickness (for example, 9 μm), and is attached to the holding substrate via an adhesive or the like.

The substrate 1 is formed with a signal electrode and a ground electrode that constitute a control electrode for controlling a light wave propagating through the optical waveguide 2. These electrodes can be formed by forming a Ti / Au electrode pattern on the surface of the substrate 1 and using a gold plating method or the like. Further, if necessary, it is possible to provide a buffer layer such as a dielectric SiO ₂ or a charge dispersion film on the surface of the substrate 1 after the optical waveguide is formed, and to form electrodes thereon.

  The optical waveguide 2 is connected to the light incident end of the optical waveguide 2 and has an input waveguide portion 21 to which light is input from the outside of the optical waveguide device, and a branch portion 22 that branches light from the input waveguide portion 21. , A plurality of working waveguide sections 23 in which the light branched by the branching section is controlled by the control electrode, a combining section 24 for synthesizing the light from each working waveguide section 23, and the optical waveguide 2. An output waveguide unit 25 is connected to the light emitting end and outputs the light combined by the combining unit 24 to the outside of the optical waveguide element.

The substrate 1 is further formed with a light absorbing member 3 that generates heat by light absorption. In the example of FIG. 1, a substrate region including a waveguide portion on the input side (input waveguide portion 21 and branching portion 22) and a substrate region including a waveguide portion on the output side (combining portion 24 and output waveguide portion 25). The light absorbing member 3 is formed so as to cover from above.
In the case of a single-structure Mach-Zehnder type waveguide composed of only one Mach-Zehnder interferometer as shown in FIG. It is assumed that a refraction effect will occur. For this reason, the light absorbing members 3 are formed at two locations of the input side substrate region and the output side substrate region.

  Although there is no particular designation regarding the material and formation method of the light absorbing member 3, when a metal film is used for the light absorbing member 3, for example, the material can be selected with reference to Table 1. Table 1 shows the amount of excess loss that occurs when a metal film is loaded on the surface of an Xcut LN substrate having a Ti diffusion waveguide. In the first configuration example, the light absorbing member 3 is formed by sputtering using Al as a material.

  FIG. 2 shows the temperature change of the input side substrate region when the input light quantity is changed. In this example, an Xcut LN substrate having a Ti diffusion waveguide shows the relationship between the input light amount and the chip temperature of the input side waveguide portion, the horizontal axis is the input light amount (dBm), and the vertical axis is Chip temperature (° C.). Further, the case where the film of the light absorbing member 3 is not provided is plotted by ◯, the case where the Al film is provided as the light absorbing member 3 is plotted by □, and the case where the Ti film is provided as the light absorbing member 3 is Δ Plotted with marks.

As shown in the figure, when the film of the light absorbing member 3 is not provided, the chip temperature is substantially constant even when the input light quantity is increased. However, when the Al film is provided, the input light quantity increases. When the Ti film is provided, the chip temperature is rapidly increased as the input light quantity is increased. That is, it can be seen that by arranging the light absorbing member 3 on the upper side of the optical waveguide 2, the heat generating effect of the light absorbing member 3 can be obtained by the light propagating through the portion.
Further, when the deterioration of the On / Off extinction ratio due to the presence or absence of the light absorbing member 3 was compared, it was confirmed that the deterioration of the On / Off extinction ratio was improved by providing the absorbing member 3.

  In the first configuration example shown in FIG. 1, the light absorbing member 3 is disposed so as to cover the entire area of the input side substrate region and the output side substrate region, but this is only an example. However, if a photorefractive phenomenon occurs in the branching section 22 or the combining section 24, the branching ratio or the combining ratio is affected, and there is a concern about deterioration of the extinction ratio. Therefore, at least the branching section 22 and the combining section 24 absorb light. It is preferable to form the member 3 and suppress the photorefractive phenomenon at that portion. Further, since the input waveguide section 21 and the output waveguide section 25 have higher light intensity than the working waveguide section 23, the light absorbing member 3 is formed also in these portions, and the photorefractive phenomenon of the portion is observed. It is preferable to suppress.

  In addition, about the waveguide part (input waveguide part 21 and the branching part 22) of an input side, and the waveguide part (synthesis | combination part 24 and the output waveguide part 25) of an output side, the whole (all areas) is light absorption member. It is not always necessary to cover with 3, and a portion where the light intensity is high may be covered with the light absorbing member 3. In the waveguide portion on the input side, it is assumed that the light intensity is increased in the entire input waveguide portion 21 or in a portion of the input waveguide 21 and the branch portion 22. What is necessary is just to provide the light absorption member 3 so that it may cover. Further, in the waveguide portion on the output side, it is assumed that the light intensity is increased in the entire output waveguide portion 25 or in a portion of the output waveguide portion 25 and the combining portion 24. What is necessary is just to provide the light absorption member 3 so that at least this may be covered.

FIG. 3 shows a second configuration example of the optical waveguide element according to the present invention.
In the second configuration example, the input-side waveguide portion (input waveguide portion 21 and branching portion 22) and the vicinity thereof, and the output-side waveguide portion (combining portion 24 and output waveguide portion 25) and the vicinity thereof are covered. As described above, a light absorbing member 3 having a predetermined width extending along the optical waveguide 2 is disposed. Thus, by limiting the arrangement of the light absorbing member 3 to the vicinity of the optical waveguide 2 and reducing the area of the portion that diffuses heat without contributing to the light absorption, the temperature of the optical waveguide 2 is made efficient. Can be raised. In the second configuration example, the light absorbing member 3 made of the same material as that in the first configuration example is used. However, the temperature rise of the optical waveguide 2 is higher than that in the first configuration example, and the suppression effect of the photorefractive phenomenon is improved. .

FIG. 4 shows a third configuration example of the optical waveguide element according to the present invention.
In the third configuration example, a plurality of slits in the direction intersecting with the optical waveguide 2 are provided along the optical waveguide 2 with respect to the light absorbing member 3 of the second configuration example. In this way, by providing a through hole such as the slit shown along the optical waveguide 2 in a part of the light absorbing member 3, light absorption at the location of the through hole can be suppressed. It becomes easy to adjust the calorific value. The light absorbing member 3 having such a shape is suitable when a material having a high light absorption efficiency such as a Ti film is used rather than using a material having a low light absorption efficiency such as an Al film.

  In FIG. 4, by providing a plurality of through holes in the light absorbing member 3, portions where the optical waveguide 2 is covered with the light absorbing member 3 and portions that are not covered are alternately formed in the arrangement section of the light absorbing member 3. The attenuation of light intensity and the amount of heat generated are adjusted, but the light absorbing member 3 can also be discretely arranged on the optical waveguide 2 as shown in FIG. In the arrangement section, the portion where the optical waveguide 2 is covered with the light absorbing member 3 and the portion which is not covered can be formed alternately, and the light intensity attenuation amount and the heat generation amount can be adjusted.

FIG. 6 shows a fourth configuration example of the optical waveguide element according to the present invention.
The optical waveguide 2 in the optical waveguide element of the fourth configuration example branches light from the input waveguide section 21 into two Mach-Zehnder type waveguide sections by the branch section 22 and propagates through each Mach-Zehnder type waveguide section. The light is output from the output waveguide section 25 provided for each Mach-Zehnder type waveguide section. In such a structure, the light intensity on the output side is weaker than the light intensity on the input side, and the photorefractive phenomenon is less likely to occur on the output side than on the input side. The light absorbing member 3 is disposed only in the waveguide section 21 and the branch section 22).

  Here, the light absorbing member 3 is arranged only in the waveguide portion on the input side (the input waveguide portion 21 and the branch portion 22), but the present invention is not limited to this. For example, a plurality of light absorbing members 3 may be arranged along the optical waveguide 2 and the amount of light absorbed by each light absorbing member 3 may be reduced in the order of arrangement of the light absorbing members 3 in the light propagation direction. Here, the light absorbing member 3 may be provided for all of the branch portion 22 on the input side and the subsequent branch portion 22 ′, or the light absorbing member 3 is provided for a part of these branch portions. It is good. In addition, for each branch portion, the light absorbing member 3 may be provided as a whole in the waveguide portion connected to the branch portion and the preceding stage, and the portion of which the light intensity is increased (for example, the stage before the branch portion) The light absorbing member 3 may be provided only on the entire waveguide portion or only on a part of the waveguide portion and a branching portion. The amount of light absorption may be adjusted by adjusting the area where the light absorbing member 3 covers the optical waveguide 2 or by selecting the material of the light absorbing member 3.

FIG. 7 shows a fifth configuration example of the optical waveguide element according to the present invention.
In the fifth configuration example, an optical waveguide element (LN) is connected to the subsequent stage of the planar lightwave circuit (PLC). That is, a plurality of lights branched by the planar lightwave circuit (PLC) are respectively input to a plurality of input waveguides 21 included in the optical waveguide element (LN), and a plurality of working guides connected to the respective input waveguides 21 are connected. After the control by the control electrode in the waveguide portion 23, the light is synthesized by each synthesis portion 24 ′ at the subsequent stage, and further synthesized by the synthesis portion 24, and then the optical waveguide element (LN) is output from the output waveguide portion 25. It is structured to be output to the outside. In such a structure, the light intensity on the output side is stronger than the light intensity on the input side, and the photorefractive phenomenon is more likely to occur on the output side than on the input side. 24 and the output waveguide portion 25) are disposed only on the light absorbing member 3.

  Here, the light absorbing member 3 is arranged only in the output-side waveguide portion (the combining portion 24 and the output waveguide portion 25). However, the output-side combining portion 24 and the preceding combining portion 24 ′ are arranged. It is good also as a structure provided with respect to all, and it is good also as a structure which provides the light absorption member 3 with respect to a part of these synthetic | combination parts. In addition, for each combining unit, the light absorbing member 3 may be provided as a whole in the waveguide unit connected to the combining unit and the subsequent stage, of which the light intensity increases (for example, in the latter part of the combining unit) The light absorbing member 3 may be provided in the entire waveguide portion or only in a part of the waveguide portion and the combining portion.

FIG. 8 shows a sixth configuration example of the optical waveguide element according to the present invention.
FIG. 8 shows a state in which the substrate 1 is housed in the housing 4, (a) is a side sectional view, and (b) is a plan sectional view. In this example, a pedestal 41 having a predetermined height is provided on the bottom surface portion of the housing 4, and the substrate 1 is placed on the pedestal 41, so that the substrate 1 is not limited to the top surface and side surfaces of the housing 4. It is also separated from the bottom. Further, the arrangement portion of the light absorbing member 3 on the substrate 1 is protruded from the pedestal 41 so as not to contact the pedestal 41. Thus, by dissociating the arrangement portion of the light absorbing member 3 in the substrate 1 from the inner surface portion of the housing 4, it is possible to suppress the diffusion of heat by the housing 4 and to efficiently raise the temperature of the optical waveguide 2. it can. In this example, the distance between the substrate 1 and the inner surface portion of the housing 4 is about 1 to 2 mm. However, the inner surface portion of the substrate 1 and the housing 4 depending on how the substrate 1 is mounted on the housing 4. What is necessary is just to decide the interval.

  As described above, by arranging the light absorbing member 3 so as to cover at least a part of the upper side of the optical waveguide 2, the photorefractive effect is reduced by the heat generated by the light absorbing member 3 by the light propagating through the optical waveguide 2. And the phenomenon caused by the photorefractive effect can be suppressed. Moreover, local heating can be performed only by arranging the light absorbing member 3 at a place where the optical waveguide 2 needs to generate heat, and there is no need to provide an additional power source for heating.

In addition, since there is a concern about charge-up of the light absorbing member 3, it is preferable to connect the light absorbing member 3 to the ground potential so that heat does not escape from the light absorbing member 3.
In each of the above configuration examples, the light absorbing member 3 is formed directly on the upper side of the optical waveguide 2. However, by providing a spacer between the optical waveguide 2 and the light absorbing member 3, the light absorption efficiency can be improved. Adjustments may be made. That is, for example, a spacer is formed on the optical waveguide 2 by (reactive) sputtering, and then the light absorbing member 3 is formed by vapor deposition. As the spacer, various materials can be used. For example, when a film made of a material having a lower refractive index than LN, such as SiO ₂ , SiN, Al ₂ O _3, etc., the amount of light absorption decreases as the film becomes thicker. For example, when a film made of a material having a higher refractive index than LN such as TiO ₂ , Si, Cu ₂ O, or the like is used, the amount of light absorption varies depending on the thickness of the film. That is, the light absorption efficiency can be appropriately adjusted according to the spacer material and its thickness.

Moreover, in each said structural example, although the metal film was used as the light absorption member 3, you may use the other material which generate | occur | produces heat by light absorption. For example, oxygen-deficient metal oxide, semiconductor, or the like can be used as the light absorbing member 3. There is also a method of adjusting light absorption using a structure such as a metamaterial.
Further, the polarization plane adjustment that adjusts the polarization plane of the input light to the optical waveguide 2 using the characteristic that the amount of heat generated by the light absorption amount of the light absorbing member 3 changes according to the polarization plane of the light propagating through the optical waveguide 2. The amount of heat generated by the light absorption amount of the light absorbing member 3 may be adjusted by providing a mechanism and adjusting the polarization plane of the input light by the polarization plane adjustment mechanism.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described contents, and it is needless to say that the design can be changed as appropriate without departing from the gist of the present invention.

  As described above, according to the present invention, it is possible to provide a light modulation element that can suppress a phenomenon caused by a photorefractive effect of a substrate material.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Optical waveguide 3 Light absorption member 4 Case 21 Input waveguide part 22,22 'Branch part 23 Action waveguide part 24,24' Synthesis | combination part 25 Output waveguide part 41 Base

Claims (11)

In an optical waveguide device comprising a substrate having an electro-optic effect and an optical waveguide formed on the substrate,
The optical waveguide has an input waveguide portion to which light is input from the outside of the optical waveguide element, and a branch portion that branches light input to the input waveguide portion into a plurality of branch waveguide portions,
An optical waveguide element, wherein a light absorbing member that generates heat by light absorption is disposed so as to cover at least the upper side of a portion where the light intensity increases in the input waveguide portion and the branch portion. The optical waveguide device according to claim 1,
The optical waveguide element, wherein the light absorbing member is disposed so as to cover at least the entire upper side of the input waveguide section or a part of the input waveguide and the upper side of the branch section. In the optical waveguide device according to claim 1 or 2,
The optical waveguide element, wherein the light absorbing member is a member having a predetermined width extending along the optical waveguide. In the optical waveguide device according to any one of claims 1 to 3,
An optical waveguide device, wherein a through hole is provided in a part of the light absorbing member along the optical waveguide. In the optical waveguide device according to any one of claims 1 to 4,
The waveguide element, wherein the light absorbing member is grounded. The optical waveguide device according to any one of claims 1 to 5,
An optical waveguide element comprising a spacer provided between the optical waveguide and the light absorbing member. The optical waveguide device according to any one of claims 1 to 6,
The optical waveguide includes a combining unit that combines light from the plurality of branch waveguide units, and an output waveguide unit that outputs the light combined by the combining unit to the outside of the optical waveguide element.
An optical waveguide element, wherein the light absorbing member is disposed so as to cover at least the upper side of the portion where the light intensity increases in the output waveguide portion and the combining portion. In the optical waveguide device according to claim 7,
The optical waveguide element, wherein the light absorbing member is arranged so as to cover at least the entire upper side of the output waveguide part or a part of the output waveguide and the upper side of the synthesis part. The optical waveguide device according to any one of claims 1 to 8,
A plurality of the light absorbing members are arranged along the optical waveguide,
An optical waveguide device characterized in that the amount of light absorbed by each of the plurality of light absorbing members is small in the order of arrangement of the light absorbing members in the light propagation direction. In an optical waveguide device comprising a substrate having an electro-optic effect and an optical waveguide formed on the substrate,
The optical waveguide is synthesized by a plurality of input waveguide portions to which light is input from the outside of the optical waveguide element, a synthesis portion for synthesizing light input to the plurality of input waveguide portions, and the synthesis portion. An output waveguide portion that outputs the light to the outside of the optical waveguide element,
An optical waveguide element, wherein a light absorbing member that generates heat by light absorption is disposed so as to cover an upper side of a portion where the light intensity increases in the output waveguide portion and the combining portion. The optical waveguide device according to any one of claims 1 to 10,
A housing for accommodating the substrate;
An optical waveguide element characterized in that an arrangement portion of the light absorbing member on the substrate is separated from an inner surface of the casing.

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