JP2020166166A - Optical device and optical transmitter/receiver using the same - Google Patents

Abstract

To provide an optical device that, even when an electro-optic substrate and a reflection member are joined, reduces an impact of internal stress generated in a joint portion of those, and has little fluctuation of optical loss or the like.SOLUTION: In an optical device in which a substrate 1 that has an optical waveguide 2 and a control electrode formed and has an electro-optic effect is joined with a reflection member R, the shape of a joint area where the reflection member and an end face of the substrate are joined is set so as to be symmetric in the extending direction of a short side with respect to a center point C1 of the arrangement shape of the end portion of the optical waveguide on the short side (side including a1 to a2) of the substrate or a point C2 where the axis of symmetry of the arrangement shape of a branched waveguide portion near the end intersects with the short side.SELECTED DRAWING: Figure 5

Description

The present invention relates to an optical device and an optical transmitter / receiver using the same, and more particularly to an optical device in which a reflective member is bonded to an electro-optical substrate on which an optical waveguide or a control electrode is formed, and an optical transmitter / receiver using the same.

In the field of optical communication and the field of optical measurement, various optical devices such as optical modulators are widely used. In the conventional optical device shown in FIG. 1, an optical waveguide 2 and a control electrode (not shown) are mounted on an electro-optical substrate 1 (substrate 1) having a substantially rectangular shape in a plan view, as in the optical modulator shown in Patent Document 1. It is formed, and two optical fibers (31, 32) for inputting and outputting light waves are directly connected to both short sides of a substantially rectangular shape. Reference numeral 4 is a housing for accommodating the substrate 1.

In the optical device as shown in FIG. 1, since the optical fiber is derived from both ends, not only the size of the device itself becomes large, but also when the optical device is incorporated into a unit such as an optical transmitter / receiver, the housing 4 The external optical fibers (31, 32) are bent and mounted, which causes a problem that the area for mounting the optical device becomes large.

In order to reduce the mounting area of the optical device, as shown in FIG. 2 in Patent Document 2, an input or output optical fiber (input optical fiber 31 in FIG. 2) connected to the optical device is provided with a lens. A method of bending at an arbitrary angle, for example, 90 degrees, using an optical path conversion element (reflecting member) 50 has been proposed. Reference numeral 51 is a ferrule for directly joining the optical fiber 31 to the optical path conversion element 50, and reference numeral 52 is a polarization synthesis means for polarization-synthesizing a plurality of light waves emitted from the optical waveguide 2.

Further, in Patent Document 3, as shown in FIG. 3, the input optical fiber 31 and the output optical fiber 32 are arranged on the same side wall with respect to the housing 4. A method of folding back an optical path using two prisms (R1 and R2) in the housing has been proposed. Reference numerals L1 to L3 are lenses for condensing or collimating, and reference numeral 53 indicates a polarization synthesizing means.

In an optical device as shown in FIG. 2, it is necessary to accurately adjust the angle and position with the optical path conversion element 50 with a lens, and to align the optical axis of the exit end of the optical fiber 31 with the incident end 21 of the optical waveguide 2. Become. However, the work related to this adjustment is extremely complicated and requires a lot of labor and time.

Moreover, when the substrate 1 and the optical path conversion element 50 are bonded to each other in the housing 4 with an adhesive or the like, the internal stress generated by the temperature change tends to be concentrated on the joint portion between the substrate 1 and the optical path conversion element 50. This is particularly remarkable when the substrate 1 and the optical path conversion element 50 are made of different materials. Therefore, the internal stress is transmitted to the end of the optical waveguide, and as a result, problems such as polarization distortion due to a change in the refractive index of the optical waveguide and misalignment of the optical axis occur.

Further, in the optical device as shown in FIG. 3, it is necessary to accurately match the positions and angles of the two prisms (R1 and R2) which are the optical path conversion means, which requires a lot of labor and time. Moreover, since the reflective surface is independent for each prism and each prism is adhesively fixed to the housing 4, the position and angle of the optical component change slightly due to temperature changes, and light loss fluctuations are likely to occur. Become.

Moreover, in optical devices such as optical modulators, the integration of optical waveguides is progressing, as in the so-called nested optical waveguides in which a plurality of Mach-Zehnder-type optical waveguides are combined in a nested manner, and the light modulation elements. In order to reduce the size of the substrate 1 constituting the substrate 1, light is simply branched from the short side end of the substrate 1 before the light is incident on the Mach-Zehnder interferometer section (hereinafter referred to as the MZ section) of the optical modulator or the MZ section. The distance to the branch is also extremely short. Therefore, the internal stress generated at the short side end portion of the substrate 1 is affected not only at the end portion but also at the MZ portion and the branch portion.

Japanese Unexamined Patent Publication No. 2004-125854 JP-A-2018-55017 JP-A-2018-720605

The problem to be solved by the present invention is to solve the above-mentioned problems, suppress the influence of internal stress generated at the joint portion between the electro-optical substrate and the reflective member, and suppress light loss and the like. It is to provide an optical device with little fluctuation.

In order to solve the above problems, the optical device of the present invention has the following technical features.
(1) A substrate having an electro-optical effect and the substrate include a first surface having a long side facing each other and a short side facing each other in a plan view, and at least one of the first surfaces is on the first surface. An optical waveguide having an incident or exit end in contact with the short side of the optical waveguide and a control electrode for controlling a light wave propagating through the optical waveguide are formed, and the end of the optical waveguide is arranged. In an optical device having a reinforcing member arranged on the substrate along the short side and a reflecting member arranged on the outside of the substrate facing the end of the optical waveguide, the reflecting member is. The joint is joined to the end face of the substrate located on the short side and the end face of the reinforcing member at a joining region, and the reflective member and the end face of the substrate are joined when viewed in a plan view from the extending direction of the long side. The shape of the region is symmetrical to the central point of the arrangement shape of the end portion of the optical waveguide on the short side, or the arrangement shape of the branch waveguide portion for branching or merging near the end portion of the optical waveguide. It is an axis, and the axis of symmetry extending in the same direction as the long side is set to be symmetrical with respect to a point intersecting the short side in the extending direction of the short side.

(2) In the optical device according to (1) above, when viewed in a plan view from the extending direction of the long side, the reflective member surrounding the joint region at the joint portion between the reflective member and the substrate or the reinforcing member. It is characterized in that at least a part of the outer peripheral surface of the above and at least a part of the outer peripheral surface of the substrate or the reinforcing member surrounding the joint region are set to be continuous surfaces.

(3) In the optical device according to (1) above, the area of the joint region of the reflective member is smaller than the area of the end face region formed by the end face of the substrate and the end face of the reinforcing member.

(4) In the optical device according to (1) to (3) above, the reflecting member has at least two reflecting surfaces, and a light wave incident on or emitted from the optical waveguide is transmitted to the length of the substrate. It is characterized in that it is configured to convert the optical path in the direction of folding back with respect to the side direction.

(5) In the optical device according to (4) above, an optical path that is emitted from the optical waveguide and then folded back by the reflective member, or an optical path that is incident on the optical waveguide and before being folded back by the reflective member. The optical path of is set to pass above the plane formed by the first surface of the substrate.

(6) In the optical device according to any one of (1) to (5) above, the substrate and the reflective member are housed in a housing, and the substrate is fixed to the housing, but the substrate is fixed. The reflective member is not fixed.

(7) In the optical device according to any one of (1) to (6) above, the substrate, the reflective member, and the relay substrate are housed in a housing, and an electric signal input unit for inputting a high frequency signal of the control electrode. However, the high frequency signal is arranged on the side wall of the housing on the side where the reflection member is arranged with respect to the substrate, and the high frequency signal is transmitted from the electric signal input portion of the substrate via the relay line formed on the relay substrate. It is characterized in that it is transmitted to the input unit of the control electrode provided on the long side.

(8) The optical device according to any one of (1) to (7) above is an optical modulator, and is an optical transmitter / receiver including an optical receiver.

The present invention comprises a substrate having an electro-optical effect and the substrate having a first surface having long sides facing each other and short sides facing each other in a plan view, and at least on the first surface. An optical waveguide having an incident or exit end in contact with one of the short sides and a control electrode for controlling a light wave propagating through the optical waveguide are formed, and the end of the optical waveguide is arranged. In an optical device having a reinforcing member arranged on the substrate along the short side and a reflecting member arranged on the outside of the substrate facing the end of the optical waveguide, the reflecting member is The end face of the substrate located on the short side and the end face of the reinforcing member are joined at a joining region, and the reflective member and the end face of the substrate are joined when viewed in a plan view from the extending direction of the long side. The shape of the junction region is the center point of the arrangement shape of the end portion of the optical waveguide on the short side, or the arrangement shape of the branch waveguide portion for branching or merging near the end portion of the optical waveguide. Since it is an axis of symmetry and the axis of symmetry extending in the same direction as the long side is set to be symmetric in the extending direction of the short side with respect to the point where the short side intersects, the following effects are expected. it can.
Since the internal stress generated at the joint between the substrate and the reflective member is distributed symmetrically with respect to the center point of the arrangement of the optical waveguide at the end of the substrate, the internal stress transmitted to the optical waveguide at the end of the optical waveguide Is even on the left and right with respect to the end of the optical waveguide, the change in the polarization of the light wave is suppressed, and the deterioration of the quality of the modulated light can be reduced.
Further, the internal stress reaching the MZ portion and the branch portion of the optical waveguide is also distributed substantially symmetrically with respect to the axis of symmetry of the arrangement shape of the branch waveguide portion constituting the MZ portion and the branch portion. It is possible to suppress deterioration of the quality of the modulated light.

It is a figure which shows the conventional optical device (the optical fiber for input / output is arranged linearly). It is a figure which shows the conventional optical device (the optical fiber for input / output is arranged at a right angle). It is a figure which shows the conventional optical device (the optical fiber for input / output is folded and arranged). It is a figure explaining 1st Example which concerns on the optical device of this invention. It is a figure explaining the bonding state of the substrate and the reflective member in the optical device of this invention. It is a top view explaining the joining of the substrate of the optical device of this invention, and a reflection member. 6 is a cross-sectional view taken along the alternate long and short dash line XX'of the optical device of FIG. 6 is a cross-sectional view taken along the alternate long and short dash line YY'of the optical device of FIG. It is a figure which shows the application example (the 1) which concerns on FIG. It is a figure which shows the application example (the 2) which concerns on FIG. It is a figure explaining the case where the end portion of the optical waveguide deviates from the center in the short side direction of the substrate. 11 is a cross-sectional view taken along the alternate long and short dash line YY'of the optical device of FIG. It is a figure explaining another shape (the 1) of the reflective member. It is a figure explaining the bonding state of the substrate of FIG. 13 and a reflective member. It is a figure explaining the example which provided the mark in the reflective member used in FIG. It is a figure explaining another shape (the 2) of the reflective member. It is a figure explaining the notch of the reflection member used in FIG. It is a figure explaining the 2nd Example which concerns on the optical device of this invention. FIG. 8 is a cross-sectional view taken along the alternate long and short dash line XX'of the optical device of FIG. FIG. 8 is a cross-sectional view taken along the alternate long and short dash line YY'of the optical device of FIG. It is a figure which shows the application example (the 1) which concerns on FIG. It is a figure which shows the application example (the 2) which concerns on FIG. It is a figure explaining the 3rd Example which concerns on the optical device of this invention. It is a figure explaining the notch of the reflection member used in FIG. It is a figure explaining the 4th Example which concerns on the optical device of this invention. It is a figure explaining the 5th Example which concerns on the optical device of this invention. It is a figure explaining the 6th Example which concerns on the optical device of this invention.

Hereinafter, the optical device of the present invention will be described in detail with reference to suitable examples.
As shown in FIGS. 4 and 5, the optical device of the present invention has a substrate 1 having an electro-optical effect, and the substrate has a first surface having long sides facing each other and short sides facing each other in a plan view. An optical waveguide 2 having an incident or exit end in contact with at least one of the short sides on the first surface, and a control electrode for controlling the light wave propagating through the optical waveguide ( (Not shown) is formed, and the reinforcing member 10 arranged on the substrate along the short side where the end portion of the optical waveguide is arranged, and the substrate facing the end portion of the optical waveguide. In an optical device having a reflecting member R arranged outside the above, the reflecting member R is joined to the end face of the substrate located on the short side and the end face of the reinforcing member at a joining region, and the long side is extended. When viewed in a plan view from the direction, the shape of the joint region where the reflective member and the end face of the substrate are joined is the center point C1 of the arrangement shape of the end portion of the optical waveguide on the short side, or the optical light. It is the axis of symmetry of the arrangement shape of the branch waveguide section for branching or combining near the end of the waveguide, and with respect to the point C2 where the axis of symmetry extending in the same direction as the long side intersects the short side. It is characterized in that it is set to be symmetrical in the stretching direction of the short side.

Examples of the substrate 1 having an electro-optical effect used in the optical device of the present invention include crystal materials such as lithium niobate (LN), lithium tantalate, and lanthanum zirconate (PLZT), semiconductor substrates such as InP, and EO. A polymer material or the like can be used. As a method for forming the optical waveguide, for example, a high refractive index substance such as titanium (Ti) is thermally diffused on a lithium niobate substrate (LN substrate), a proton exchange method, or the like. It is also possible to form unevenness on the substrate 1 to form a ridge type waveguide.

The control electrode includes a modulation electrode that applies an electric field due to a modulation signal to the optical waveguide and a DC electrode that applies an electric field due to a DC bias voltage. These control electrodes can be formed by forming a Ti / Au electrode pattern on the surface of the substrate and by a gold plating method or the like. Further, if necessary, a buffer layer such as a dielectric SiO ₂ can be provided on the surface of the substrate after the optical waveguide is formed.

FIG. 4 is a plan view showing an example of the optical device of the present invention. In the optical device of FIG. 4, the input optical fiber 31 and the output optical fiber 32 are introduced into the housing from the same side wall of the housing 4, and form a folded optical path in the housing. The light emitted from the optical fiber 31 is collected by the condenser lens L at the incident end of the optical waveguide 2 formed on the substrate 1. Further, a reflection member R is provided to form a folded optical path. A reinforcing member 10 is joined and fixed on the substrate at the end on the short side side of the substrate 1, and a reflective member R is joined to the same end surface of the substrate 1 and the reinforcing member 10 with an adhesive. Hereinafter, an example of using the reinforcing member 10 will be mainly described, but it goes without saying that the basic idea of the present invention can be applied even when there is no reinforcing member. Further, the direction of the optical path (propagation direction of the light wave) may be opposite to that in FIG.

The reflective member R in FIG. 4 has two reflective surfaces formed therein, but the number of reflective surfaces is not limited to two, and may be three or more or one. By using a reflective member having a plurality of reflective surfaces, it is possible to reduce fluctuations in light loss due to temperature changes, as compared with the case where each reflective surface is formed by a separate reflective member.
Further, the reflecting member having two or more reflecting surfaces may be formed by one prism, or two or more prisms having one reflecting surface are prepared separately from the housing. You may use the one fixedly arranged on the fixing member of. This makes it possible to increase the tolerance for the angular deviation of the optical axis.
Further, as shown in the conventional example of FIG. 2, the reflecting member R can also add a lens function to a part of the reflecting surface.

FIG. 5 is an enlarged view of the joint portion between the substrate 1 and the reflective member R. In FIG. 5, the reinforcing member is not shown in order to make it easier to see the arrangement of the optical waveguide 2. The portion of the dotted line A indicates a portion where the substrate 1 and the reflective member R are joined by an optical adhesive or the like. In the present invention, the region of the dotted line A where the substrate (reinforcing member) and the reflective member are joined to each other is referred to as a "joining portion". In the portion of the dotted line A, internal stress is generated by curing and shrinking the adhesive in the joint region. In addition, the adhesive also squeezes out near the outer periphery of the joint region, and the adhesive cures and shrinks, so that internal stress is generated. The internal stress is applied to the incident end of the optical waveguide 2 exposed on the joint surface, and causes a change in the refractive index of the optical waveguide (distortion of polarization, change in polarization state, etc.). As a result, the extinction ratio and the modulation efficiency deteriorate, and the quality of the modulated light deteriorates.
Further, when the ends of a plurality of optical waveguides are exposed on the joint surface (for example, see FIG. 27), the relative polarization state between the optical waveguides is different because the change of the refractive index is different for each optical waveguide. It is very different and may cause further deterioration of the quality of the modulated light.

Further, in recent optical modulators and the like, reflecting the needs for miniaturization of optical devices, as shown in FIG. 5, the branch portion of the MZ portion of the optical waveguide is arranged near the short side end portion of the substrate 1. The distance S between the branch waveguide portion such as the light wave junction or the Y-shaped branching portion or the Y-shaped junction portion of the optical waveguide and the short side end portion is small. As an example of the "Y-shaped branching portion", before the incident on the first branching portion of the nested waveguide or the X polarization MZ portion and the Y polarization MZ portion such as the DP-QPSK modulator. This corresponds to a branch portion that simply branches light for X polarization and Y polarization. Therefore, the internal stress due to the adhesive protruding from the joint portion A may reach the branch waveguide portion. Therefore, when an unbalanced internal stress is applied to the branched waveguide section, the branching ratio becomes asymmetrical, a different phase difference is generated for each modulation section, and adverse effects such as distortion of the modulated signal occur. Such an adverse effect becomes particularly remarkable when the substrate includes a modulation section composed of a plurality of MZ sections and different modulations are performed by the plurality of modulation signals.

In order to solve the above-mentioned problems in the joint portion A, in the optical device of the present invention, the shape of the joint region where the reflective member R and the end face of the substrate 1 are joined is the shape of the upper surface (first surface) of the substrate 1. On the short side (the line connecting the points a1 and a2 in FIG. 5 is a part of the short side), with respect to the center point C1 of the arrangement shape of the end portion of the optical waveguide exposed on the joint surface. , It is set to be symmetrical in the stretching direction of the short side.

Further, the shape of the junction region is a branched waveguide for branching or merging near the end of the optical waveguide, which extends in the same direction as the long side of the substrate 1 when viewed in a plan view on the short side. The axis of symmetry of the arrangement shape of the portion; see the two-point chain line in FIG. 5) may be set to be symmetrical with respect to the point C2 that intersects the short side in the extending direction of the short side.

When the center point C1 and the intersection C2 described above coincide with each other, the reference points of symmetry are the same points, but when the positions of the two are different as shown in FIG. 5, the points are added to the end of the optical waveguide. It is possible to select either the center point C1 or the intersection C2 as a reference point depending on whether the internal stress or the internal stress applied to the branch waveguide portion of the MZ portion or the branch portion is emphasized.

With this setting, the internal stress can be distributed symmetrically with respect to the points C1 or C2, and the imbalance of the internal stress with respect to the end portion of the optical waveguide, the MZ portion, and the branch waveguide portion of the optical waveguide can be eliminated. It becomes possible. As a result, the optical device due to changes in the refractive index at the ends of the optical waveguide (distortion of polarization, etc.) and unbalanced stress on the branched waveguide when the adhesive is cured or when the environmental temperature changes after curing. Deterioration of modulation characteristics can be suppressed.

Regarding the branched waveguide section, the nested optical waveguide and the optical waveguide of the DP-QPSK modulator are provided with a plurality of stages of the branched waveguide section. In the present invention, the axis of symmetry is set by focusing on the branched waveguide portion closest to the short side of the substrate.
However, when a plurality of MZ portions are arranged in parallel, such as a nested optical waveguide or a multi-wavelength modulator (the wavelength used differs between the MZ portions), the center of the junction region in the short side direction is It may be arranged on the axis of symmetry of the arrangement shape of a plurality of MZ portions.
Further, when the branch portion of the parent MZ portion is arranged near the short side side of the substrate as in the nested optical waveguide, the center of the junction region in the short side direction is closest to the end portion of the optical waveguide. It may be arranged on the axis of symmetry of the parent MZ portion of.
As a result, the stress affecting the plurality of MZ portions becomes substantially symmetric with respect to the axis of symmetry, so that the bias of modulation characteristic deterioration can be reduced.

As shown in FIG. 4, the substrate 1 and the reflective member R are housed in the housing 4. In the housing, the substrate 1 is fixed to the housing 4, but the reflective member R is not fixed to the housing 4. Therefore, even when the temperature inside the housing changes, the stress generated from the fixed portion is eliminated as compared with the case where the reflective member R is fixed to the housing 4, so that the stress source applied to the substrate 1 via the reflective member R is used. Can be reduced.

Further, especially when the linear expansion coefficient of the housing 4 and the reflective member R are different, even if the reflective member R expands and contracts due to a temperature change, the reflective member R is not fixed to the housing 4, so that the internal stress due to the expansion and contraction occurs. Can be suppressed from being added to the substrate 1. Therefore, even if the temperature inside the housing 4 changes, deterioration of the modulation characteristics of the optical device can be suppressed.

Further, by joining the lens barrel accommodating the condenser lens L to the reflecting member R and fixing the lens barrel at a predetermined position of the housing 4, the reflecting member R is formed on both the substrate 1 and the lens barrel. It can also be configured to support.
Further, from the viewpoint of suppressing deterioration of the modulation characteristics when the temperature inside the housing 4 changes, the configuration in which the lens barrel and the reflecting member R are not fixed to the housing 4 is changed from the housing 4 to the lens barrel and the reflecting member R. It is more preferable because it can eliminate the influence of the stress of.
A refractive index distribution type (GRIN) lens can also be used as the condenser lens L. In particular, since a small refractive index distribution type lens having an outer diameter close to the outer diameter of the optical fiber is lightweight, it is more suitable when the condenser lens L is not fixed to the housing 4 but fixed only to the reflective member R.
The refractive index distribution type lens may be fused and fixed to the optical fiber without using the lens barrel, or may be fixed to the optical fiber by using the lens barrel.

The shape of the joint region between the substrate 1 or the reinforcing member 10 and the reflecting member R will be described in detail below. FIG. 6 is a plan view showing the substrate 1, the reinforcing member 10, and the reflecting member R in the optical device of FIG. 4 in an extracted manner.
However, in FIG. 4, the position of the end portion (the end portion on the left end side of the substrate 1) of the optical waveguide 2 formed on the substrate 1 substantially coincides with the center of the short side of the substrate 1, whereas in FIG. No. 6 is different in that the position C1 of the end portion of the optical waveguide 2 does not coincide with the center of the short side of the substrate 1.
Further, FIG. 7 shows a cross-sectional view taken along the alternate long and short dash line XX of FIG. 6, and FIG. 8 shows a sectional view taken along the alternate long and short dash line YY'of FIG. In FIGS. 6 to 8, the shape of the junction region is set with the end C1 of the optical waveguide 2 as a reference point.

In the example of FIG. 8, the thickness of the reflective member R (thickness in the vertical direction of the drawing) is the same as the sum of the thickness of the substrate 1 and the thickness of the reinforcing member 10. Therefore, the upper surface of the reflective member R forms a continuous plane with the upper surface of the reinforcing member 10. Further, the lower surface of the reflective member R forms a continuous plane with the lower surface of the substrate 1. As described above, in FIG. 8, continuous surfaces are formed along the two sides of the reflective member R.

As described above, in the joint portion between the reflective member R and the substrate 1 or the reinforcing member 10, at least a part of the outer peripheral surface surrounding the joint region (shaded portion) of the reflective member and the joint portion of the substrate or the reinforcing member. At least a part of the outer peripheral surface surrounding the area is set to be a continuous surface. By providing such a continuous surface, it becomes easy to wipe off the adhesive that has squeezed out at the joint portion. Wiping off the squeezed adhesive leads to less generation of internal stress due to curing shrinkage of the adhesive.

Further, designing to form a continuous surface makes it possible to align the reflective member R with the substrate 1 or the reinforcing member 10 with reference to the side of each member, which also contributes to facilitation of assembly work. ..

FIG. 9 shows an example in which the thickness d (vertical direction of the drawing) of the reflective member is made thinner than that of FIG. In this case, one surface of the reflective member R (here, the lower surface of the reflective member R) forms a surface continuous with one surface of the substrate 1 (here, the lower surface of the substrate 1).

FIG. 10 shows an example in which the thickness d of the reflective member R is made thicker than that in FIG. In this case as well, the lower surface of the reflective member R coincides with one surface of the substrate 1. Therefore, a continuous surface is formed along one side.

In any of FIGS. 8 to 10, the shape of the joint region (hatched portion) is optically formed on the short side (the boundary line between the substrate 1 and the reinforcing member 10 in the drawing) of the upper surface (first surface) of the substrate 1. It is set to be symmetrical with respect to the center point of the waveguide 2. Of course, it is also possible to set the reference point of symmetry with respect to the extending direction of the short side at the point where the axis of symmetry of the branched waveguide portion near the end of the optical waveguide intersects the short side.

FIG. 6 shows an example in which the position of the end portion (the end portion on the left end side of the substrate 1) of the optical waveguide 2 formed on the substrate 1 deviates from the center of the short side of the substrate 1. The present invention is not limited to such a substrate, and as shown in the conventional example of FIG. 1, the position of the end portion of the optical waveguide and the position of the point where the above-mentioned axis of symmetry and the short side intersect are the said of the substrate 1. Needless to say, the one located in the center of the short side can also be adopted.

FIG. 11 shows an example in which the axis of symmetry (dashed line) of the branch portion of the optical waveguide 2 formed on the substrate 1 is deviated from the center of the short side of the substrate 1. FIG. 12 is a cross-sectional view taken along the alternate long and short dash line YY'in FIG.

In FIGS. 11 and 12, the shape of the joint region (hatched portion in FIG. 12) is the center of the extending direction (horizontal direction in the drawing) of the short side of the substrate 1 with the above-mentioned axis of symmetry (dashed line) and the short side. The intersection (C2) with is arranged. Of course, it is also possible to configure the shape of the junction region so that the end portion (C1) of the optical waveguide is located at the center of the short side in the extending direction.

Further, as shown in FIG. 11, the position of the end of the optical waveguide (C1) and the position of the point where the above-mentioned axis of symmetry and the short side intersect (C2) are from the center of the short side of the substrate 1 toward the short side. When the displaced substrate 1 is adopted, the reflective member R is shifted and arranged in the displaced direction at the position of the intersecting point or the like, so that the width w of the reflective member R can be narrowed, resulting in a result. As a result, the overall size of the reflective member R can also be made compact.

13 to 15 are views for explaining another shape (No. 1) of the reflective member. The area of the joint region of the reflective member R is such that the joint region of the reflective member R (the shaded portion in FIG. 14) falls within the range of the end face region formed by the end face of the substrate 1 and the end face of the reinforcing member 10. It is set to be smaller than the area of the end face area. In the case of the reflective member R of FIG. 13, the adhesive protrudes around the joint region, but the area of the joint region is small, so that the influence of internal stress due to the curing shrinkage of the adhesive and the change in the environmental temperature after curing is affected. It is possible to reduce it.

Another feature of the reflective member R in FIG. 13 is that the folded optical path formed by the reflective member is configured to spread by an angle θ, not parallel to the direction in which the light wave propagates through the optical waveguide. Such a configuration can also be adopted in the reflection member R of FIG. With this configuration, it is possible to secure a space for mounting optical components such as a collimator lens and a polarizer in the vicinity of the reflecting member R without increasing the size of the reflecting member R.

As shown in FIG. 15, the reflective member R often has a total length (the length of the region not joined to the substrate 1) T2 excluding T1 longer than the length T1 of the joining region. With a reflective member having a shape having asymmetry, positioning at the time of joining becomes more difficult. Therefore, as shown in FIG. 15, the mark 7 of the reflective member is separately formed on the end portion of the optical waveguide 2 of the substrate 1 and the upper surface of the reinforcing member 10 by providing a mark such as a marking line as shown by reference numeral 7. By aligning with the mark, the optical component can be easily positioned.

FIG. 16 is a layout drawing of a reflective member R having another shape (No. 2), a substrate 1, and a reinforcing member 10, and FIG. 17 is a diagram for explaining another shape (No. 2) of the reflective member R. ..
A notch-shaped step 8 is formed in the reflective member R, and the step is brought into contact with the corner of the substrate 1 or the reinforcing member 10 to join the reflective member R to the substrate 1 or the like. By using the step 8 as a mark in this way, the reflective member R can be mechanically positioned.

18 to 22 are diagrams illustrating a second embodiment of the optical device of the present invention. As shown in FIGS. 18 and 19, the folded optical path (dotted arrow in FIG. 19) formed by the reflective member R is set to pass above the plane formed by the first surface (upper surface) of the substrate 1. ing.
Further, in FIGS. 18 to 22, the shape of the junction region (hatched portion in FIGS. 20 to 22) is the intersection (C2) between the axis of symmetry of the branch portion of the optical waveguide (two-dot chain line in FIG. 18) and the short side of the substrate 1. ) Is arranged so as to be located at the center of the short side of the substrate 1 in the stretching direction.

20 to 22 show the arrangement of the joint portion between the reflective member R and the substrate 1 and the like.
FIG. 20 shows a case where the width of the substrate 1 (reinforcing member 10) and the thickness of the reflective member R (thickness in the lateral direction of the drawing) are the same. The outer peripheral surface surrounding the joint region (hatched portion) forms a continuous surface with three sides, that is, the left and right side surfaces of the substrate 1 (reinforcing member 10) and the lower surface side of the substrate 1. When there are many such continuous surfaces, it is possible to easily wipe off the adhesive protruding from the joint region to the vicinity of the outer periphery of the substrate 1, and it is possible to suppress the influence of internal stress due to curing shrinkage of the adhesive.

When the thickness d (thickness in the horizontal direction of the drawing) of the reflective member R is reduced as shown in FIG. 21, the adhesive protrudes to the left and right of the reflective member R, but the area of the joint portion becomes small, so that the inside due to curing shrinkage of the adhesive It is possible to reduce the influence of stress.
Further, when the thickness d (thickness in the horizontal direction of the drawing) of the reflective member R is increased as shown in FIG. 22, the adhesive protrudes from the left and right side surfaces of the substrate 1 (reinforcing member 10). However, since the protruding portions of these adhesives are the left and right sides of the outer peripheral portion of the joint portion, the stress from the protruding portion of the adhesive applied to the end portion of the optical waveguide can be made substantially the same.
Further, since the protruding portion of the adhesive is separated from the MZ portion and the branched waveguide portion of the optical waveguide as compared with the configuration of FIG. 21, it is possible to reduce the influence of the internal stress of the adhesive.

Further, since the folded optical path (dotted arrow) formed by the reflecting member R is set to pass above the plane formed by the first surface (upper surface) of the substrate 1, the input light is set as shown in FIG. The area of the optical device can be reduced (miniaturized) as compared with the configuration in which the fiber 31 is arranged on the side surface of the substrate 1.
When the short side of the substrate 1 is viewed from the stretching direction of the long side of the substrate 1, the reflection direction of the reflective member R may be an oblique direction instead of the vertical or horizontal direction of the substrate 1.

23 and 24 are diagrams illustrating a third embodiment of the optical device of the present invention. Here, two substrates 1 on which an optical waveguide and a control electrode (not shown) are formed are optically coupled via a reflection member R. Needless to say, the bonding region between the reflective member R and each substrate 1 is set so as to satisfy the various conditions described above. Further, as shown in FIG. 24, by providing the groove portion 80 which is a notch portion in the reflective member R, the adhesive protruding from the joint portion between the substrate 1 and the reflective member R can be released to the groove portion 80, and the substrate 1 can be released. It is possible to suppress the spread of the adhesive on the side surface of the.
For this reason, the effect of stress generated by the curing shrinkage of the adhesive that has squeezed out on the end of the optical waveguide is reduced, and defects such as polarization distortion due to changes in the refractive index of the optical waveguide and misalignment of the optical axis are suppressed. be able to.

FIG. 25 is a diagram illustrating a fourth embodiment according to the optical device of the present invention. Here, two MZ portions and branch waveguide portions related to optical modulation are formed in the vicinity of the end portion of the substrate 1. When the MZ portion or the branched waveguide portion having a plurality of such modulation portions is near the end portion of the substrate 1, the MZ portion or the branched waveguide portion closest to the end portion is focused on, and the MZ portion or the branched waveguide portion is focused on. The axis of symmetry of the arrangement shape of the optical waveguide in the waveguide section (the axis of symmetry in the propagation direction of the light wave or the direction of the long side of the substrate; the two-point chain line in FIG. 25) is specified, and the intersection of the axis of symmetry and the junction region (the axis of symmetry and the axis of symmetry). It is preferable to set the shape of the joint region as described above based on (intersection point with the short side of the substrate) C2. In the case of FIG. 25, since there are a plurality of end portions of the optical waveguide, it is also possible to specify the center point C1 of the arrangement shape of the end portions and set the shape of the junction region.

FIG. 26 is a diagram illustrating a fifth embodiment according to the optical device of the present invention. Here, as in FIG. 25, two MZ portions and branch waveguide portions related to optical modulation are formed in the vicinity of the end portion of the substrate 1. In FIG. 26, in order to divide the joint region between the reflective member R and the substrate 1 into two, a recess is formed in a part of the joint surface of the reflective member R. The shape of the upper junction region in FIG. 26 is set based on C2, which is the intersection of the symmetry axis of the branched waveguide portion related to the upper optical waveguide 2 and the junction region (the intersection of the symmetry axis and the short side of the substrate). It has been Further, the shape of the lower joint region in FIG. 26 is set based on the center point C1'of the arrangement shape of the end portion of the lower optical waveguide 2'. Of course, the shape of the lower junction region may also be set based on the intersection C2'of the symmetry axis of the branched waveguide portion related to the lower optical waveguide 2'and the junction region.

FIG. 27 is a diagram illustrating a sixth embodiment according to the optical device of the present invention. Here, taking advantage of the characteristics of the folded optical path of the optical device of the present invention described above, the electric signal input / output terminal is arranged on the side wall of the housing 4 which is opposite to the substrate 1 side of the reflective member R. Specifically, the substrate 1, the reflective member R, and the relay substrate 9 are housed in the housing 4, and the electric signal input unit 40 that inputs a high frequency signal to the control electrode on the substrate 1 reflects the substrate 1 with respect to the substrate 1. It is arranged on the side wall of the housing 4 on the side where R is arranged. Then, the high frequency signal input to the electric signal input unit 40 is provided on the long side side (upper side of the drawing) of the substrate 1 via a relay line (not shown) formed on the relay substrate 9 (alumina or the like). It is transmitted to the input section (not shown) of the control electrode. If necessary, an electric signal input unit that supplies a DC bias voltage and an electric signal output unit that outputs a detection signal that detects propagating light or synchrotron radiation of the optical waveguide 2 can be added.

When the relay board 9 is made of alumina or the like, the transmission loss of the high frequency signal is smaller than the transmission loss on the board 1.
Therefore, as shown in FIG. 27, the relay board 9 is formed into an L shape, and the relay line (not shown) is arranged from the board 1 to the long side side (upper side of the figure) of the board 1 where the reflection member R does not protrude. Therefore, each component can be efficiently arranged, and a high-frequency signal can be efficiently transmitted to the control electrode provided on the long side side (upper side of the drawing) of the substrate 1 with a small transmission loss.
When the folded optical path in the reflective member R does not pass through the side surface of the substrate 1 on the long side as shown in FIGS. 18 to 22, the L-shaped relay substrate 9 and the relay line (not shown) are the substrate 1. It may be arranged on either long side (upper side or lower side in FIG. 27).

It is also possible to configure an optical transmitter / receiver by configuring the above-mentioned optical device as an optical modulator and further incorporating an optical receiver in the same device.

As described above, according to the present invention, even when the electro-optical substrate and the reflective member are joined, the influence of the internal stress generated at the joint portion between the two is suppressed, and the optical device with less fluctuation such as light loss and the like. It is possible to provide an optical device that suppresses deterioration of the quality of the modulated light.

1 Electro-optical substrate 2 Optical waveguide 4 Housing 10 Reinforcing member 31, 32 Optical fiber L, L1 to L3 Lens R Reflective member

Claims (8)

A substrate with an electro-optical effect and
The substrate comprises a first surface having a long side facing each other and a short side facing each other in a plan view.
On the first surface, an optical waveguide having an incident or exit end tangent to at least one of the short sides and a control electrode for controlling a light wave propagating through the optical waveguide are formed.
A reinforcing member arranged on the substrate along the short side on which the end of the optical waveguide is arranged.
In an optical device having a reflective member arranged on the outside of the substrate facing the end of the optical waveguide.
The reflective member is joined to the end face of the substrate located on the short side and the end face of the reinforcing member at a joining region.
When viewed in a plan view from the extending direction of the long side, the shape of the joint region where the reflective member and the end face of the substrate are joined is the center point of the arrangement shape of the end portion of the optical waveguide on the short side. Or, a point of symmetry of the arrangement shape of the branch waveguide for branching or merging near the end of the optical waveguide, and the axis of symmetry extending in the same direction as the long side intersects the short side. An optical device characterized in that it is set to be symmetrical with respect to the stretching direction of the short side. In the optical device according to claim 1, when viewed in a plan view from the extending direction of the long side, at the joint portion between the reflective member and the substrate or the reinforcing member, the outer peripheral surface of the reflective member surrounding the joint region An optical device characterized in that at least a part thereof and at least a part of an outer peripheral surface of the substrate or the reinforcing member surrounding the joint region are set to be continuous surfaces. The optical device according to claim 1, wherein the area of the joint region of the reflective member is smaller than the area of the end face region formed by the end face of the substrate and the end face of the reinforcing member. In the optical device according to claims 1 to 3, the reflecting member has at least two reflecting surfaces, and a light wave incident on or emitted from the optical waveguide is folded back in the long side direction of the substrate. An optical device characterized by being configured to transform an optical path in a direction. In the optical device according to claim 4, the optical path after being emitted from the optical waveguide and then folded back by the reflective member, or the optical path incident on the optical waveguide and before being folded back by the reflective member is An optical device characterized in that it is set to pass above a plane formed by a first surface of the substrate. In the optical device according to any one of claims 1 to 5, the substrate and the reflective member are housed in a housing, and the substrate is fixed to the housing, but the reflective member is fixed. An optical device characterized by no. In the optical device according to any one of claims 1 to 6, the substrate, the reflective member, and the relay substrate are housed in a housing, and an electric signal input unit for inputting a high frequency signal of the control electrode is provided with respect to the substrate. The high frequency signal is provided on the side wall of the housing on the side where the reflection member is arranged, and the high frequency signal is provided on the long side side of the substrate from the electric signal input portion via the relay line formed on the relay substrate. An optical device characterized in that it is transmitted to an input unit of the control electrode. The optical transmitter / receiver according to any one of claims 1 to 7, wherein the optical device is an optical modulator and further includes an optical receiver.

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