WO2025163891A1 - Optical waveguide element, optical waveguide device, and optical transmission apparatus - Google Patents

Abstract

The present invention achieves realization of an optical waveguide element having high functionality by improving the degree of freedom of arrangement of functional elements on a substrate without increasing the size of the substrate.　The optical waveguide element comprises: a substrate; an optical waveguide formed on one main surface of the substrate; and a reinforcement block disposed on the one main surface of the substrate so as to extend along one end surface of the substrate, which is a light entrance/exit surface at which light is input into the optical waveguide and output from the optical waveguide. The reinforcement block is constituted of a plurality of rectangular parallelepiped blocks or constituted of a single block having a shape obtained by removing at least one portion of a single rectangular parallelepiped from said single rectangular parallelepiped.

Description

Optical waveguide element, optical waveguide device, and optical transmitter

The present invention relates to an optical waveguide element, an optical waveguide device, and an optical transmitter.

In high-speed/large-capacity optical fiber communication systems, optical modulators incorporating an optical modulation element as an optical waveguide element, which is composed of an optical waveguide formed on a substrate and a control electrode that controls the light wave propagating through the optical waveguide, are widely used. As optical waveguide elements that perform optical modulation, semiconductor optical modulation elements using semiconductor substrates such as InP substrates and LN optical modulation elements using _LiNbO3 (hereinafter also referred to as LN) as a substrate have been put to practical use.

Optical waveguide elements built into driver-integrated LN modulators (CDM, Coherent Driver Modulators), which have been developed in recent years, or mounted directly on optical transceivers, are increasingly being required to be compact, in addition to offering higher performance such as lower power consumption, higher speeds, and wider bandwidths. To meet these demands, the optical waveguides used in these optical waveguide elements are often ridge- or rib-shaped, which provide strong light confinement. This allows for low-loss folding in the waveguide direction, and the high-density arrangement of functional elements such as associated high-frequency electrodes, DC electrodes, and light-receiving elements for optical monitoring (e.g., photodiodes (PDs)) achieves both high functionality and compactness.

The ridge-type and rib-type optical waveguides used in the above-mentioned optical waveguide elements have a mode field diameter (MFD) for propagating light of 3 μm or less. However, optical components such as optical fibers that are bonded to the end face of the optical waveguide have an MFD of around 10 μm. Therefore, a spot size converter (SSC) is installed at the output end of the optical waveguide element to increase the MFD.

Furthermore, to ensure the bonding strength between the end face of the optical waveguide element and the optical component, such as an optical fiber, that is bonded to that end face, and to prevent chipping or scratches on the optical waveguide when the end face is polished, a rectangular glass block (reinforcement block) is placed at the end of the optical waveguide element across the entire width of the substrate of the optical waveguide element, covering the optical waveguide containing the SSC. This reinforcing block is usually fixed to the substrate with an adhesive. Because this adhesive also functions as a cladding layer for the SSC, the reinforcing block plays an important role in constructing the optical waveguide element.

Patent Document 1 discloses an optical waveguide element that includes a reinforcing block at the edge of the substrate and a light-receiving element for monitoring light on the surface of the substrate. In this optical waveguide element, the light-guiding direction of the optical waveguide that guides light to the light-receiving element is bent back, allowing the light-receiving element to be mounted on the part of the substrate surface where no reinforcing block is provided.

The above configuration allows for increased functionality without increasing the size of the substrate, making it suitable for use in modulators such as the CDM mentioned above, where device size is standardized. However, from the perspective of further increasing functionality and reducing the size of the substrate, it would be advantageous to be able to place functional components such as photodetectors between the reinforcing block and the substrate.

Functional elements arranged on the substrate of an optical waveguide element may include, in addition to the light receiving element, an SSC, a buffer layer, a thick film electrode for high-frequency signals, an electrode pad (wiring electrode portion), and a thin film electrode for DC or low-frequency signals.

However, when thick functional elements such as light-receiving elements, electrode pads, and thick-film electrodes are placed between the reinforcing block and the substrate, the thickness of the adhesive layer between the reinforcing block and the substrate must be increased to the same thickness as these functional elements. Such a thick adhesive layer can cause problems such as cracks due to thermal expansion and contraction caused by ambient temperature fluctuations.

Japanese Patent Application Laid-Open No. 2021-162642

The objective of this invention is to improve the degree of freedom in arranging functional elements on a substrate, thereby enabling the realization of highly functional optical waveguide elements without increasing the size of the substrate.

One aspect of the present invention is an optical waveguide element comprising a substrate, an optical waveguide formed on one main surface of the substrate, and a reinforcing block arranged on the one main surface of the substrate so as to be aligned with an end face of the substrate, the end face being a light input/output surface that inputs light to the optical waveguide and outputs light from the optical waveguide, wherein the reinforcing block is either composed of a plurality of rectangular blocks, or composed of a single block having a shape obtained by removing at least a portion of a single rectangular block from the single rectangular block.
According to another aspect of the present invention, the reinforcing block is a single block having a shape obtained by removing at least a portion of a single rectangular prism from the single rectangular prism, and the removed portion, which is the portion of the reinforcing block removed from the single rectangular prism, is formed at a position other than directly above the end of the optical waveguide where light enters and exits through the light entrance and exit surface of the substrate.
According to another aspect of the present invention, the removed portion is at least one notch formed in at least one surface of the reinforcing block.
According to another aspect of the present invention, the removed portion, which is at least one notch portion, is formed on a surface of the reinforcing block that faces a surface of the substrate that is aligned with the light incident/exit surface.
According to another aspect of the present invention, the removal portion, which is at least one notch portion, is formed on a surface of the reinforcing block facing the main surface of the substrate.
According to another aspect of the present invention, the removed portion is a through hole provided in the reinforcing block and opening in a direction perpendicular to the main surface of the substrate.
According to another aspect of the present invention, the reinforcing block has a surface that faces the surface of the substrate along the light incident/exit surface and that forms a concave curved surface.
According to another aspect of the present invention, the reinforcing block has a pentagonal shape in plan view when viewed from a normal direction to the main surface of the substrate.
According to another aspect of the present invention, the reinforcing block has a trapezoidal shape in plan view when viewed from a normal direction to the main surface of the substrate.
According to another aspect of the present invention, the optical waveguide includes an optical input waveguide that propagates input light input through the optical input/output surface of the substrate, and an optical output waveguide that propagates output light output through the optical input/output surface of the substrate toward the optical input/output surface, the optical input waveguide and the optical output waveguide including a spot size conversion section in which the cross-sectional size of the optical waveguide changes toward an end of the optical waveguide, and the removal section is formed at a position other than directly above the spot size conversion section.
According to another aspect of the present invention, an adhesive layer is provided between the reinforcing block and one main surface of the substrate.
According to another aspect of the invention, the reinforcing block has a refractive index lower than that of the optical waveguide.
According to another aspect of the present invention, in a substrate on which a reinforcing block composed of a plurality of rectangular blocks is arranged, an electrical circuit element, an optical element, or a mechanical element is arranged in the space between the plurality of rectangular blocks, or in the space of the removed portion, which is the portion removed from the single rectangular block, in a substrate on which a reinforcing block composed of a single block having a shape obtained by removing at least a portion of the single rectangular block is arranged.
According to another aspect of the present invention, an optical component is fixed to a surface of the reinforcing block along the light incident/exit surface.
Another aspect of the present invention is an optical waveguide device comprising: any one of the optical waveguide elements described above; a housing that houses the optical waveguide element; an input optical fiber that inputs light to the optical waveguide element; and an output optical fiber that guides output light emitted by the optical waveguide element to the outside of the housing.
According to another aspect of the present invention, the optical waveguide element is an optical waveguide device that includes electrodes on the substrate that control light waves propagating through the optical waveguide, and a drive circuit inside the housing that drives the optical waveguide element.
Another aspect of the present invention is an optical transmission apparatus comprising any one of the optical waveguide devices described above and an electronic circuit that generates an electrical signal for causing the optical waveguide element to operate.

The present invention improves the degree of freedom in arranging functional elements on a substrate, making it possible to realize a highly functional optical waveguide element without increasing the substrate size.

FIG. 1 is a plan view of an optical waveguide element according to a first embodiment of the present invention. FIG. 2 is a side view of the optical waveguide element shown in FIG. FIG. 3 is a cross-sectional view of the optical waveguide element shown in FIG. 1 taken along line III-III. FIG. 4 is a cross-sectional view of the optical waveguide element shown in FIG. 1 taken along line IV-IV. FIG. 5 is a plan view of an optical waveguide element according to a second embodiment of the present invention. FIG. 6 is a plan view of an optical waveguide element according to a third embodiment of the present invention. FIG. 7 is a plan view of an optical waveguide element according to a fourth embodiment of the present invention. FIG. 8 is a plan view of an optical waveguide element according to a fifth embodiment of the present invention. FIG. 9 is a plan view of an optical waveguide element according to a sixth embodiment of the present invention. FIG. 10 is a plan view of an optical waveguide element according to a seventh embodiment of the present invention. FIG. 11 is a plan view of an optical waveguide element according to an eighth embodiment of the present invention. FIG. 12 is a cross-sectional view of the optical waveguide element shown in FIG. 11 taken along line XII-XII. FIG. 13 is a plan view of an optical waveguide element according to a ninth embodiment of the present invention. FIG. 14 is a cross-sectional view of the optical waveguide element shown in FIG. 13 taken along line XIV-XIV. FIG. 15 is a diagram showing the configuration of an optical waveguide device according to a tenth embodiment of the present invention. FIG. 16 is a diagram showing the configuration of an optical transmitting apparatus according to the eleventh embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
1. First embodiment
1 is a plan view showing the configuration of an optical waveguide element 1a according to a first embodiment of the present invention. The optical waveguide element 1a includes a substrate 10 having an electro-optic effect, an optical waveguide 14 formed on one main surface 12 (the surface shown in FIG. 1) of the substrate 10, and electrodes 16 for controlling light waves propagating through the optical waveguide 14.

Substrate 10 is, for example, an LN substrate. However, substrate 10 is not limited to an LN substrate and may be a substrate made of lithium tantalate (LT), PLZT (lead lanthanum zirconate titanate), or other materials, or may be a substrate made of various materials such as semiconductor materials or organic materials.

As shown in FIG. 1, the electrodes 16 are arranged, for example, on the main surface of the substrate 10 at positions sandwiching the optical waveguide 14. However, the arrangement of the electrodes 16 shown in FIG. 1 is only one example, and the electrodes 16 can be arranged in any appropriate position in the design, depending on the material and/or crystal orientation used in the substrate 10. For example, the electrodes 16 may be arranged on the optical waveguide 14. This is also true in other embodiments.

The substrate 10 is rectangular in plan view, for example, and has two opposing left and right end faces 18a and 18b that extend in the vertical direction as shown, and two opposing upper and lower end faces 18c and 18d that extend in the horizontal direction as shown.

The optical waveguide 14 is, for example, a convex optical waveguide (e.g., a rib-type optical waveguide or a ridge-type optical waveguide) formed on the main surface 12 of the substrate 10 and consisting of a convex portion extending in a strip shape. In this embodiment, the convex waveguide is implemented by forming grooves on both sides of the optical waveguide 14 on the main surface 12. As an example, the optical waveguide 14 includes two Mach-Zehnder optical waveguides. This allows the optical waveguide element 1a to function as an optical modulator.

Figure 2 is a side view of the optical waveguide element 1a shown in Figure 1, viewed from the direction of the end surface 18d of the substrate 10. The other main surface opposite to the one main surface 12 of the substrate 10 is bonded to a support plate 20 for reinforcement.

Referring to FIG. 1, the end surface 18b of the substrate 10 constitutes a light input/output surface 22 through which light is input to the optical waveguide 14 and through which light is output from the optical waveguide 14.
The optical waveguide 14 includes an optical input waveguide 24a that propagates input light input through the optical input/output surface 22 of the substrate 10, and optical output waveguides 24b and 24c that propagate output light output through the optical input/output surface 22 of the substrate 10 toward the optical input/output surface 22.

The optical input waveguide 24a and the optical output waveguides 24b, 24c each include spot size conversion sections 26a, 26b, 26c (shown as black triangular sections) where the cross-sectional size of the optical waveguide 14 changes toward the end of the optical waveguide 14. Hereinafter, the optical input waveguide 24a and the optical output waveguides 24b, 24c will be collectively referred to as the optical input/output waveguides 24. Furthermore, the spot size conversion sections 26a, 26b, 26c will be collectively referred to as the spot size conversion section 26.

Specifically, the spot size conversion sections 26 are tapered so that the length in the thickness direction and the length in the principal surface direction of the substrate 10 in a cross section perpendicular to the extension direction of the optical input/output waveguides 24 decrease toward the respective ends of the optical input/output waveguides 24.

The optical waveguide element 1a also includes a reinforcing block 28a arranged on the main surface 12 of the substrate 10 so as to align with the end face 18b, which is the light incident/emitting surface 22 of the substrate 10. Here, "the reinforcing block 28a being arranged "along the end face 18b" means that one face of the reinforcing block 28a is arranged flush or nearly flush with the end face 18b, or is arranged so as to be on the same plane as or nearly flush with the end face 18b. In the optical waveguide element 1a shown in Figure 1, the reinforcing block 28a is arranged so that the face 36a on the right side of the reinforcing block 28a is flush with the end face 18b, which is the light incident/emitting surface 22 of the substrate 10.

3 and 4 are cross-sectional views taken along the lines III-III and IV-IV, respectively, of the optical waveguide element 1a shown in FIG.
The optical waveguide element 1a has an adhesive layer 30 between the reinforcement block 28a and the main surface 12 of the substrate 10. The adhesive layer 30 also functions as a cladding layer for the spot size conversion section 26 located thereunder. To ensure light confinement in the spot size conversion section 26, the reinforcement block 28a and the adhesive layer 30 are made of a material with a refractive index lower than that of the optical waveguide 14. For example, the adhesive layer 30 is made of a transparent resin. The reinforcement block 28a is preferably made of a material with good processability, such as alkali-free glass that is less susceptible to thermal deformation.

Referring to Figures 1 and 2, optical components are fixed to the surface 36a (i.e., the surface along the light incident/exit surface 22) of the reinforcement block 28a, which is arranged flush with the light incident/exit surface 22 of the substrate 10. In this embodiment, the optical component is, for example, a lens array 32. The optical component may include any optical component such as a lens, a wave plate, or a prism. This makes it possible to easily fabricate an assembly including the optical waveguide element 1a and the optical component by using the reinforcement block 28a as a structure for fixing the optical component.

In this embodiment, in particular, reinforcing block 28a is composed of a single block having a shape obtained by removing at least one portion (i.e., one or more portions) of a single rectangular parallelepiped from the rectangular parallelepiped. Note that "a shape obtained by removing at least one portion of a single rectangular parallelepiped from the rectangular parallelepiped" describes the shape of reinforcing block 28a, and does not necessarily mean that reinforcing block 28a is actually made by removing a portion of a single rectangular parallelepiped.

Here, it is desirable that the removed portion 34a, which is the portion of the reinforcing block 28a that has been removed from the single rectangular parallelepiped, does not include the position directly above the end of the optical waveguide 14 where light enters and exits via the light incident and exit surface 22 of the substrate 10. In other words, it is desirable that the removed portion 34a be formed in a position other than directly above the end of the optical waveguide 14. Here, the end of the optical waveguide 14 where light enters and exits via the light incident and exit surface 22, in this embodiment, is the end of the optical input/output waveguide 24 on the light incident and exit surface 22 side.

As a result, in the optical waveguide element 1a, the reinforcing block 28a is located directly above the end of the optical waveguide 14 where light enters and exits, allowing the reinforcing block 28a and adhesive layer 30 to function as cladding at the end. This achieves good optical confinement at the end of the optical waveguide 14 where light enters and exits, resulting in an optical waveguide element 1a with high functionality and low optical loss.

In more detail, in this embodiment, the removed portion 34a does not include the position directly above the spot size conversion portion 26 formed by the end of the optical input/output waveguide 24. In other words, the removed portion 34a is formed in a position other than directly above the spot size conversion portion 26. As a result, a reinforcing block 28a exists directly above the spot size conversion portion 26 via the adhesive layer 30, thereby achieving good light confinement in the spot size conversion portion 26.

In this embodiment, the removed portion 34a may be, for example, at least one notch formed on at least one surface of the reinforcing block 28a. More specifically, in this embodiment, the removed portion 34a is formed on the surface 36b of the reinforcing block 28a that faces the surface 36a that is aligned with the light incident/exit surface 22 (end surface 18b) of the substrate 10. The shape of this removed portion 34a can be easily formed, for example, using a laser-based cutting device or an NC milling machine.

This makes it possible to arrange electrical circuit elements, optical elements, or mechanical elements in the space on the main surface 12 of the substrate 10 secured by the cutout portion, or removed portion 34a, thereby improving the degree of freedom in arranging these functional elements on the substrate 10. As a result, it is possible to realize a highly functional optical waveguide element 1a without increasing the size of the substrate 10 compared to conventional methods, or using a substrate 10 that is smaller than conventional methods. Furthermore, as a result of the above, there is no need to impose restrictions on the pattern of the optical waveguide 14 or the pattern of the electrodes 16 in order to arrange the functional elements, making it possible to realize better optical characteristics and operating characteristics (in this embodiment, the operating characteristics of optical modulation operation) of the optical waveguide element 1a.

For example, in this embodiment, a space is created above the optical output waveguides 24b and 24c, excluding their respective ends, by the cutout portion, the removed portion 34a. Light-receiving elements 38a and 38b, which serve as electrical circuit elements, are arranged in this space to monitor the light waves propagating through the respective waveguide portions. These light-receiving elements 38a and 38b can be fixed to the top of the optical output waveguides 24b and 24c via a thin adhesive layer so as to evanescently couple with the optical output waveguides 24b and 24c, respectively (see Figure 3).

In the optical waveguide element 1a, the reinforcing block 28a can be configured with cutouts for only the portions where electrical circuit elements, optical elements, or mechanical elements are to be placed, so the area of the adhesive surface with the substrate 10 is not significantly reduced. This ensures sufficient fixing strength between the reinforcing block 28a and the substrate 10.

Furthermore, in the optical waveguide element 1a, the reinforcing block 28a does not have a notch on the surface 36a that is aligned with the light input/output surface 22 of the substrate 10, so the reinforcing block 28a can function as a cladding regardless of where the end of the light input/output waveguide 24 is located on the light input/output surface 22. Therefore, in the optical waveguide element 1a, the degree of freedom in the placement of the end of the light input/output waveguide 24, which is part of the optical waveguide 14, is maintained, while the degree of freedom in the placement of functional elements on the substrate 10 can be increased.

From the standpoint of mechanical strength, it is preferable that the external size of the reinforcement block 28a is such that the lengths of all three sides of the external shape of the reinforcement block 28a are 0.2 mm or more, more preferably 0.4 mm or more, and even more preferably 0.6 mm or more.
Furthermore, from the viewpoint of adhesive strength, the adhesive area between the reinforcing block 28a and the substrate 10 is preferably 1.0 mm ² or more.

Furthermore, in a plan view viewed from the normal direction of the main plane of the reinforcement block 28a, the ratio R of the area of the removed portion 34a to the total area (i.e., the area of the rectangular area formed by the area of the reinforcement block 28a and the area of the removed portion 34a in the plan view) can be at least 1% or more. The ratio R is preferably 10% or more, more preferably 30% or more, and even more preferably 50% or more from the perspective of more effectively utilizing the upper surface of the substrate. On the other hand, from the perspective of ensuring the adhesive strength between the reinforcement block 28a and the substrate 10, particularly when the reinforcement block 28a is attached in a position covering three spot size conversion portions 26, it is necessary to form an adhesive layer on these spot size conversion portions 26. Therefore, the ratio R is preferably 70% or less, and more preferably 60% or less. For the same reason, the ratio R is more preferably 50% or less. The same applies to other embodiments.

Note that while the planar shape of the removal portion 34a, which is the cutout portion shown in Figure 1, is rectangular, the planar shape of the removal portion 34a as a cutout portion is not limited to a rectangle and can be any shape, such as a polygon, circle, or ellipse.

[2. Second embodiment]
In the first embodiment described above, the removed portion 34a of the reinforcing block 28a is a single notch provided on the surface 36b opposite the surface 36a along the light incident/exit surface 22 of the substrate 10. However, this is just one example, and the reinforcing block may have multiple removed portions formed thereon.

FIG. 5 is a plan view showing the configuration of an optical waveguide element 1b according to a second embodiment of the present invention. Note that in FIG. 5, the same components as those in FIG. 1 are designated by the same reference numerals, and the explanation for FIG. 1 above is applicable.

The optical waveguide element 1b has a configuration similar to that of the optical waveguide element 1a according to the first embodiment shown in FIG. 1, but differs in that it has a reinforcing block 28b instead of the reinforcing block 28a.
The reinforcing block 28b has the same configuration as the reinforcing block 28a, but differs in that a removed portion 34b is formed in addition to the removed portion 34a which is a cutout portion.

The removed portion 34b is a cutout portion similar to the removed portion 34a. The removed portion 34b is formed, for example, at the corner of the reinforcement block 28b between the surface 36b and the surface 36c adjacent to the surface 36b.

Furthermore, in the optical waveguide element 1b, a plurality of electrode pads 40 serving as electrical circuit elements are arranged in the space on the main surface 12 of the substrate 10 secured by the removed portion 34b. The electrode pads 40 may be connected to the electrodes (not shown) of the light-receiving elements 38a, 38b via a wiring pattern (not shown) formed on the substrate 10, for example, and may serve as electrode pads for connecting these electrodes to an electrical circuit external to the substrate 10.

In this embodiment, the reinforcing block 28b has two cutout portions 34a and 34b formed therein, but any number of cutout portions, three or more, may be provided. These cutout portions do not necessarily have to have the same shape in plan view as shown in Figure 5, and cutout portions with different shapes in plan view may be mixed.

3. Third embodiment
In the first embodiment described above, the removed portion 34 a in the reinforcement block 28 a is a notch, but the removed portion does not necessarily have to be a notch. The removed portion may be, for example, a through hole provided in the reinforcement block that opens in the normal direction to the main surface 12 of the substrate 10.

FIG. 6 is a plan view showing the configuration of an optical waveguide element 1c according to a third embodiment of the present invention. Note that in FIG. 6, the same components as those in FIG. 1 are designated by the same reference numerals, and the explanation for FIG. 1 above is applicable.

The optical waveguide element 1c has a similar configuration to the optical waveguide element 1a according to the first embodiment shown in FIG. 1, but differs in that it has a reinforcing block 28c instead of the reinforcing block 28a.
The reinforcing block 28c has the same configuration as the reinforcing block 28a, but differs in that a through-hole 34c is formed in place of the one removed portion 34a which is a notch portion.

The removed portion 34c is a through-hole provided in the reinforcing block 28c that opens in the normal direction to the main surface 12 of the substrate 10. In this embodiment, the removed portion 34c, which is a through-hole, is provided above the portions of the optical output waveguides 24b and 24c other than their ends. In the space above the main surface 12 of the substrate 10 secured by the removed portion 34c, light-receiving elements 38a and 38b are arranged as electrical circuit elements for monitoring the light waves propagating through the optical output waveguides 24b and 24c, respectively.

In the optical waveguide element 1c, the reinforcement block 28c has a removed portion 34c as a through-hole in the area where functional elements such as light-receiving elements 38a and 38b are located. In other words, in the optical waveguide element 1c, a through-hole of the required size (e.g., the minimum size) for arranging a functional element can be provided at any desired position on the substrate 10 where the reinforcement block 28c is located, thereby securing space for arranging the functional element. Therefore, in the optical waveguide element 1c, the adhesive area between the reinforcement block 28c and the substrate 10 is not excessively narrowed, thereby improving the fixing strength between the reinforcement block 28c and the substrate 10 while increasing the degree of freedom in arranging functional elements on the substrate 10.

In this embodiment, the planar shape of the removed portion 34c as a through hole provided in the reinforcement block 28c shown in Figure 6 is rectangular, but it can be any shape, such as polygonal, circular, or elliptical. Furthermore, while the reinforcement block 28c is provided with one removed portion 34c as a through hole, the number of removed portions as through holes is not limited to one and can be any number of two or more. These removed portions do not necessarily have to have the same shape in the planar view shown in Figure 6, and removed portions of different planar shapes may be mixed.

4. Fourth embodiment
The reinforcing block placed on the main surface 12 of the substrate 10 need only be composed of a single block having a shape obtained by removing at least one portion of a single rectangular parallelepiped, and the removed portion does not necessarily have to be a notch or a through hole.

FIG. 7 is a plan view showing the configuration of an optical waveguide element 1d according to a fourth embodiment of the present invention. Note that in FIG. 7, the same components as those in FIG. 1 are designated by the same reference numerals, and the explanation for FIG. 1 above is applicable.

Optical waveguide element 1d has a configuration similar to that of optical waveguide element 1a according to the first embodiment shown in Figure 1, but differs in that it has reinforcing block 28d instead of reinforcing block 28a.

Reinforcement block 28d has a configuration similar to reinforcement block 28a, but does not have the cutout portion 34a, and the cutout portion 34d forms a concave curved surface 36b1 opposite to surface 36a along the light incident/exit surface 22 of the substrate 10.
That is, the reinforcing block 28d has a shape in which one portion of one surface of a single rectangular parallelepiped is removed in a concave shape, and the one surface is formed into a curved surface.

In the space created by the recessed removed portion 34d, electrical circuit elements, optical elements, or mechanical elements can be placed, similar to removed portion 34a, etc. In the optical waveguide element 1d, for example, light receiving elements 38a and 38b are placed in the space created by removed portion 34d.

Furthermore, in the optical waveguide element 1d, the surface 36b1 is configured as a curved surface, which has the following advantages.
That is, generally, stress occurs in the portion of the substrate 10 to which the reinforcing block is adhered as the operating temperature changes due to the difference in the linear expansion coefficient between the reinforcing block and the substrate 10. This stress tends to concentrate and become unevenly distributed at positions on the main surface 12 of the substrate 10 where the corners of the reinforcing block are located (for example, the corners of the removed portion 34a, which is the notch portion in the configuration of FIG. 1 ).

In contrast, in the optical waveguide element 1d, the reinforcement block 28d has a rectangular parallelepiped shape in which a portion has been removed in a concave shape by the removal portion 34d, and the remaining surface 36b1 is a curved surface without corners. This suppresses uneven distribution of stress at the adhesive portion between the reinforcement block 28d and the substrate 10 in the optical waveguide element 1d, preventing the stress from causing the reinforcement block 28d to peel off from the substrate 10 or adversely affecting the optical and operating characteristics of the optical waveguide element 1d.

5. Fifth embodiment
Fig. 8 is a plan view showing the configuration of an optical waveguide element 1e according to a fifth embodiment of the present invention. In Fig. 8, the same components as those in Fig. 1 are designated by the same reference numerals as those in Fig. 1, and the above description of Fig. 1 is incorporated herein.

Optical waveguide element 1e has a configuration similar to that of optical waveguide element 1a according to the first embodiment shown in Figure 1, but differs in that it has reinforcing block 28e instead of reinforcing block 28a.

Reinforcement block 28e has the same configuration as reinforcement block 28a, but does not have the cutout portion 34a, and is configured so that its planar shape when viewed from the normal direction of main surface 12 of substrate 10 is pentagonal. This shape can be formed by forming two triangular cutout portions 34e1 and 34e2 in a planar view in the portion facing surface 36a along the light incident/exit surface 22 of substrate 10.

As with removed portion 34a, etc., electrical circuit elements, optical elements, or mechanical elements can be placed in the space secured by removed portions 34e1 and 34e2. In optical waveguide element 1e, light-receiving elements 38a and 38b are placed in the space secured by removed portion 34e1. In Figure 8, nothing is placed in the space secured by removed portion 34e2, but elements such as electrode pads 40 may also be placed there.

The reinforcing block 28e can be easily fabricated by linear machining using a general-purpose dicing saw.

6. Sixth Embodiment
Fig. 9 is a plan view showing the configuration of an optical waveguide element 1f according to a sixth embodiment of the present invention. In Fig. 9, the same components as those in Fig. 8 are designated by the same reference numerals as those in Fig. 8, and the description of Fig. 8 above is used.

The optical waveguide element 1f has a similar configuration to the optical waveguide element 1e according to the fifth embodiment shown in Figure 8, but differs in that it has a reinforcing block 28f instead of reinforcing block 28e. This shape can be formed by forming a single removed portion 34f that is triangular in plan view in the portion facing the surface 36a along the light incident/exit surface 22 of the substrate 10.

Electrical circuit elements, optical elements, or mechanical elements can be placed in the space secured by the removed portion 34f. In the optical waveguide element 1f, light receiving elements 38a and 38b are placed in the space secured by the removed portion 34f.

Reinforcement block 28f has fewer sides (or faces) than reinforcement block 28e, so it can be manufactured more easily than reinforcement block 28e by linear processing using a dicing saw.

[7. Seventh embodiment]
Fig. 10 is a plan view showing the configuration of an optical waveguide element 1g according to a seventh embodiment of the present invention. In Fig. 10, the same components as those in Fig. 1 are designated by the same reference numerals as those in Fig. 1, and the above description of Fig. 1 is used.

Optical waveguide element 1g has a similar configuration to optical waveguide element 1a according to the first embodiment shown in FIG. 1, but instead of reinforcement block 28a, it has reinforcement block 28g composed of two sub-blocks 28g1 and 28g2. Sub-blocks 28g1 and 28g2 have a similar configuration to reinforcement block 28a, but do not have removed portion 34a, and each is configured as a block having a rectangular parallelepiped shape. In other words, reinforcement block 28g is composed of sub-blocks 28g1 and 28g2, which are two rectangular parallelepiped blocks.

The sub-blocks 28g1 and 28g2 that make up the reinforcing block 28g are each arranged so that one surface is aligned with the light incident/exit surface 22 of the substrate 10 (e.g., flush or nearly flush).

Furthermore, sub-block 28g1 is arranged directly above the end of optical input waveguide 24a that includes spot size conversion section 26a, and sub-block 28g2 is arranged directly above the end of optical output waveguides 24b and 24c that include spot size conversion sections 26b and 26c. As a result, sub-block 28g1 and the adhesive layer 30 below it function as cladding for spot size conversion section 26a of optical input waveguide 24a, and sub-block 28g2 and the adhesive layer 30 below it function as cladding for spot size conversion sections 26b and 26c of optical output waveguides 24b and 24c.

Here, the sum of lengths Lg1 and Lg2 of the sub-blocks 28g1 and 28g2 constituting the reinforcement block 28g along the respective sides is assumed to be smaller than the length Lb of the side along the light incident/exit surface 22 in the plan view of the main surface 12 of the substrate 10 shown in Figure 10. In other words, the following formula (1) is satisfied.
Lg1+Lg2<Lb (1)

This allows a space to be secured on the main surface 12 of the substrate 10 along the light incident/exit surface 22 between the sub-blocks 28 g 1 and 28 g 2 , which are two rectangular parallelepiped blocks.
In this space, functional elements such as electrical circuit elements, optical elements, or mechanical elements can be placed on the main surface 12 of the substrate 10, similar to the space secured by the removed portion 34a in Figure 1 (the functional elements placed in the space are not shown in Figure 10).

In this embodiment, the reinforcing block 28g includes two rectangular parallelepiped sub-blocks 28g1 and 28g2, but the number of rectangular parallelepiped sub-blocks included in the reinforcing block 28g can be any number greater than or equal to three. In this case, each sub-block can be arranged so that one face is aligned with the light incident/exit surface 22 of the substrate 10. Furthermore, the sum of the lengths of the sub-blocks along the light incident/exit surface 22 of the substrate 10 can be set to be shorter than the length Lb of the side of the substrate 10 along the light incident/exit surface 22.

[8. Eighth embodiment]
Fig. 11 is a plan view showing the configuration of an optical waveguide element 1h according to an eighth embodiment of the present invention. Fig. 12 is a cross-sectional view taken along the line XII-XII of the optical waveguide element 1h shown in Fig. 11. In Figs. 11 and 12, the same components as those in Figs. 1 and 4 are designated by the same reference numerals as those in Figs. 1 and 4, and the above-mentioned explanations for Figs. 1 and 4 are incorporated herein by reference.

The optical waveguide element 1h has a configuration similar to that of the optical waveguide element 1a according to the first embodiment shown in FIG. 1, but differs in that it has a reinforcing block 28h instead of the reinforcing block 28a.
The reinforcing block 28h has the same configuration as the reinforcing block 28a, but differs in that in addition to the one removed portion 34a which is a cutout portion, a removed portion 34h (FIG. 12) is formed.

The removed portion 34h is a notch like the removed portion 34a, but is located on the surface 36d (Figure 12) of the reinforcement block 28h that faces the main surface 12 of the substrate 10.

As a result, in the optical waveguide element 1h, space can be secured between the reinforcing block 28h and the substrate 10 for arranging functional elements, thereby increasing the degree of freedom in arranging functional elements on the substrate 10. Furthermore, in the optical waveguide element 1h, the reinforcing block 28h is formed as a single block, so the strength of the reinforcing block 28h can be improved compared to the reinforcing block 28g of the seventh embodiment, which is composed of multiple sub-blocks.

Furthermore, since the reinforcing block 28h is formed as a single block, it is easier to align when placing it on the main surface 12 of the substrate 10 compared to the reinforcing block 28g according to the seventh embodiment, which is composed of multiple rectangular parallelepiped sub-blocks.

[9. Ninth embodiment]
In the above-described eighth embodiment, the reinforcement block 28h is provided with one removed portion 34h that is a notch portion on the surface 36d that faces the main surface 12 of the substrate 10. However, this is just one example, and the number of removed portions provided on the surface 36d that faces the main surface 12 of the substrate 10 may be two or more.

FIG. 13 is a plan view showing the configuration of an optical waveguide element 1i according to a ninth embodiment of the present invention. Furthermore, FIG. 14 is a cross-sectional view of the optical waveguide element 1i shown in FIG. 13, taken along the line XIV-XIV. Note that in FIGS. 13 and 14, the same components as those in FIGS. 11 and 12 are designated by the same reference numerals, and the explanations for FIGS. 11 and 12 above are incorporated herein.

The optical waveguide element 1i has a configuration similar to that of the optical waveguide element 1h according to the eighth embodiment shown in FIG. 11, but includes a reinforcing block 28i instead of the reinforcing block 28h.
Reinforcement block 28i has a configuration similar to reinforcement block 28h, but differs in that instead of removal portion 34h, two removal portions 34i1 and 34i2 as cutout portions are provided on surface 36d opposite main surface 12 of substrate 10 (see Figure 14).

In the optical waveguide element 1i, similar to the optical waveguide element 1a, it is possible to arrange electrical circuit elements, optical elements, or mechanical elements in the space on the main surface 12 of the substrate 10 secured by the two cutout portions 34i1 and 34i2, thereby improving the degree of freedom in arranging these functional elements on the substrate 10.

As an example, in the optical waveguide element 1i shown in Figures 13 and 14, the two parallel waveguides 42a, 42b and 44a, 44b of the two Mach-Zehnder optical waveguides included in the optical waveguide 14 are formed in a zigzag bent shape. The bent portions of the parallel waveguides 42a, 42b and 44a, 44b, which serve as optical elements, are arranged together with electrodes 16, which serve as electrical elements, in the space on the main surface 12 of the substrate 10 secured by the removed portions 34i1, 34i2.

As a result, in the optical waveguide element 1i, longer parallel waveguides 42a, 42b and 44a, 44b can be formed over a wider area on the main surface 12 of the substrate 10, including the removed portions 34i1, 34i2. As a result, in the optical waveguide element 1i, a longer interaction distance can be ensured between the light propagating through the parallel waveguides 42a, 42b and 44a, 44b and the high-frequency electrical signal propagating through the electrode 16, making it possible to reduce the operating voltage.

[10. Tenth embodiment]
Next, a tenth embodiment of the present invention will be described. This embodiment is an optical waveguide device incorporating any one of the optical waveguide elements 1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, and 1i according to the first to ninth embodiments described above.

Hereinafter, optical waveguide elements 1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, and 1i will be collectively referred to as optical waveguide element 1. Furthermore, reinforcement blocks 28a, 28b, 28c, 28d, 28e, 28f, 28g, 28h, and 28i provided in optical waveguide elements 1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, and 1i will be collectively referred to as reinforcement blocks 28. Furthermore, removed portions 34a, 34b, 34c, 34d, 34e, 34f, 34g, 34h, and 34i of reinforcement blocks 28a, 28b, 28c, 28d, 28e, 28f, 28g, 28h, and 28i will be collectively referred to as removed portions 34.

Figure 15 is a diagram showing the configuration of an optical waveguide device 60 according to the tenth embodiment. The optical waveguide device 60 has an optical waveguide element 62 and a housing 64 that houses the optical waveguide element 62. A plate-shaped cover (not shown) is ultimately fixed to the opening of the housing 64, hermetically sealing the interior.

The optical waveguide element 62 may be any of the optical waveguide elements 1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, and 1i described above. That is, the optical waveguide element 62 includes common components such as the optical input waveguide 24a and optical output waveguides 24b and 24c provided in the optical waveguide element 1 described above. In addition, a lens array 32 is fixed to the surface 36a of the reinforcement block 28 of the optical waveguide element 62 and the light input/output surface 22 of the substrate 10, which are arranged flush with each other.

The optical waveguide device 60 comprises an input optical fiber 66 that inputs light into the optical waveguide element 62, and an output optical fiber 68 that guides the output light emitted by the optical waveguide element 62 out of the housing 64. The input optical fiber 66 and the output optical fiber 68 are fixed to the housing 64 via supports 70 and 72, which are fixing members, respectively.

Light input from the input optical fiber 66 is collimated by a lens 74 arranged within the support 70, and then input to the optical input waveguide 24a of the optical waveguide element 62 via a corresponding lens in the lens array 32 fixed to the optical waveguide element 62.

The light output from the two optical output waveguides 24b, 24c of the optical waveguide element 62 is collimated via corresponding lenses in the lens array 32 fixed to the optical waveguide element 62 and combined into a single beam by an optical unit 76 that includes a polarization combiner and other components. The combined beam is coupled to the output optical fiber 68 via a lens 78 arranged on the support 72.

A plurality of pins 80 are arranged on the outer surface of the housing 64 for transmitting and receiving electrical signals, etc., required for the operation of the optical waveguide element 62, to and from an external device. The pins 80 may include power pins for receiving power from an external device in addition to transmitting and receiving electrical signals. Note that the pins 80 are an example of an electrical interface for transmitting and receiving electrical signals, etc., required for the operation of the optical waveguide element 62, to and from an external device. The above electrical interface can be an electrical interface other than pins that has any shape and electrical characteristics, depending on the electrical characteristics required of the optical waveguide device 60 and mounting constraints on other devices. Such an electrical interface can be pins 80, a flexible printed circuit (FPC), or other device connected to the housing 64.

The housing 64 may include a relay board 82 inside that relays electrical signals transmitted and received via the pins 80 and/or power lines input via the pins 80 to the optical waveguide element 62 .
The relay substrate 82 includes a drive circuit 84 that drives the optical waveguide element 62. The drive circuit 84 receives an electrical signal from the pin 80 as an input and outputs a high-frequency signal to the electrode 16 of the optical waveguide element 62.

Each of the optical waveguide elements 1, like the optical waveguide element 1a, has an optical waveguide 14 that includes two Mach-Zehnder optical waveguides, and functions as an optical modulator. In other words, an optical waveguide device 60 that includes any of the optical waveguide elements 1 as an optical waveguide element 62 can function as an optical modulation device.

The optical waveguide device 60 having the above-described configuration uses a high-performance optical waveguide element 1 as the optical waveguide element 62, which can be constructed without increasing the size of the substrate 10 or by using a smaller-sized substrate 10. Therefore, a high-performance or high-performance optical waveguide device can be realized without increasing the size of the housing 64 or by using a smaller housing 64.

In this embodiment, the relay board 82 is provided with a drive circuit 84, but the relay board 82 does not necessarily have to include a drive circuit 84. For example, the relay board 82 may not include a drive circuit 84, and may include only a wiring pattern and passive circuit components such as capacitors that connect the pins 80 to electrodes such as the electrode 16 and light-receiving elements 38a and 38b provided on the optical waveguide element 62.

However, as in this embodiment, by providing a drive circuit 84 inside the housing 64 that houses the optical waveguide element 62, a more sophisticated optical waveguide device can be realized.
[11. Eleventh embodiment]
Next, an eleventh embodiment of the present invention will be described. This embodiment is an optical transmitting apparatus 90 equipped with an optical waveguide device 60 as the optical modulation device according to the tenth embodiment. FIG. 16 is a diagram showing the configuration of the optical transmitting apparatus 90 according to this embodiment. This optical transmitting apparatus 90 includes the optical waveguide device 60 as an optical modulation device, a light source 92 that inputs light to the optical waveguide device 60, and a modulation signal generating unit 94. Note that when the optical waveguide device 60 does not include a driving circuit 84, the optical transmitting apparatus 90 may include a modulator driving unit having the same function as the driving circuit 84.

The modulation signal generation unit 94 is an electronic circuit that generates an electrical signal to cause the optical waveguide device 60 to perform a modulation operation. Based on externally provided transmission data, it generates a modulation signal, which is a high-frequency signal that causes the optical waveguide device 60 to perform an optical modulation operation in accordance with the modulation data, and outputs it to the optical waveguide device 60. The modulation signal is input to a drive circuit 84 mounted on the relay board 82 of the optical waveguide device 60. The drive circuit 84 amplifies the input modulation signal, and outputs a drive signal, which is a high-frequency signal for driving the optical waveguide element 62, to the electrode 16 of the optical waveguide element 62. As a result, the output light of the light source 92 is modulated by the optical waveguide device 60 and output from the optical transmitter 90.

The optical transmitter 90 having the above configuration is composed of an optical waveguide device 60 that uses any of the optical waveguide elements 1 described above as the optical waveguide element 62, making it possible to realize a highly functional or high-performance optical transmitter.

12. Other Embodiments
In the above-described embodiment, the optical waveguide element 1 functions as an optical modulator, but it may have any other function such as an optical switch, polarization rotation, or wavelength conversion.

In the above-described embodiment, the optical waveguide 14 that constitutes the optical waveguide element 1 includes a Mach-Zehnder optical waveguide, but depending on the functionality required of the optical waveguide element 1, it may also include a waveguide pattern of a type other than a Mach-Zehnder optical waveguide. For example, the optical waveguide 14 may constitute a directional coupler or a multi-port optical branch.

In the above-described embodiment, the substrate 10 constituting the optical waveguide element 1 is a substrate such as LN that has an electro-optic effect, but it may also be made of a material that does not have an electro-optic effect, depending on the functionality required of the optical waveguide element 1.

In the fifth and sixth embodiments described above, Figures 8 and 9 respectively illustrate reinforcing blocks 28e and 28f having a pentagonal and trapezoidal shape in plan view, but the reinforcing block 28 may have any polygonal shape in plan view other than a pentagon or a trapezoid.

The reinforcing block provided on the substrate 10 may be configured by combining two or more characteristic configurations of the reinforcing block 28 shown in the first to ninth embodiments. For example, a reinforcing block configured from a single block may have a shape in which any two or more of the removed portions 34a, 34b, 34c, 34d, 34e, 34f, 34h, and 34i shown in the above-mentioned embodiments are formed. Also, in a reinforcing block configured from multiple rectangular parallelepiped sub-blocks, at least one of the sub-blocks may have a shape in which any one or more of the removed portions 34a, 34b, 34c, 34d, 34e, 34f, 34h, and 34i are formed.

The present invention is not limited to the configuration of the above embodiment, and can be implemented in various forms without departing from the spirit of the invention.

13. Configurations supported by the above embodiments
The above-described embodiment supports the following configurations.

(Configuration 1) An optical waveguide element comprising: a substrate; an optical waveguide formed on one main surface of the substrate; and a reinforcing block arranged on the one main surface of the substrate so as to be aligned with the one end surface of the substrate, which is an end surface that is a light input/output surface that inputs light to the optical waveguide and outputs light from the optical waveguide, wherein the reinforcing block is composed of a plurality of rectangular parallelepiped blocks, or is composed of a single block having a shape obtained by removing at least a portion of a single rectangular parallelepiped from the single rectangular parallelepiped.
In the optical waveguide element of configuration 1, functional elements such as electrical circuit elements, optical elements, or mechanical elements can be arranged in the spaces on the substrate between the multiple rectangular parallelepipeds that make up the reinforcing block, or in the space secured by removing a portion from a single rectangular parallelepiped. Therefore, the optical waveguide element of configuration 1 improves the degree of freedom in arranging functional elements on the substrate, making it possible to realize a highly functional optical waveguide element without increasing the size of the substrate.

(Configuration 2) The reinforcing block is a single block having a shape obtained by removing at least a portion of a single rectangular parallelepiped from the single rectangular parallelepiped, and the removed portion, which is the portion of the reinforcing block removed from the single rectangular parallelepiped, is formed at a position other than directly above the end of the optical waveguide where light enters and exits through the light entrance and exit surface of the substrate, an optical waveguide element described in Configuration 1.
In the optical waveguide element of configuration 2, since a reinforcing block is present directly above the end of the optical waveguide where light enters and exits, the reinforcing block and the adhesive layer that may be interposed between the reinforcing block and the substrate can function as a cladding at the end. As a result, the optical waveguide element of configuration 2 can achieve good light confinement at the end of the optical waveguide where light enters and exits, thereby realizing an optical waveguide element with high functionality and low optical loss.

(Configuration 3) The optical waveguide element according to Configuration 2, wherein the removed portion is at least one notch formed in at least one surface of the reinforcing block.
According to the optical waveguide element of Configuration 3, the removed portion for securing the space for arranging the functional element can be easily formed in the reinforcing block.

(Configuration 4) An optical waveguide element according to Configuration 3, wherein the removed portion, which is at least one cutout portion, is formed on a surface of the reinforcing block opposite to a surface of the substrate along the light incident/exit surface.
According to the optical waveguide element of configuration 4, in the reinforcing block, for example, no notch is provided on the surface along one end face of the substrate that constitutes the light incident/exit surface, and thus the degree of freedom in the placement of the terminal end of the optical waveguide can be ensured while increasing the degree of freedom in the placement of functional elements on the substrate.

(Configuration 5) The optical waveguide element according to Configuration 3, wherein the removed portion, which is at least one cutout portion, is formed on a surface of the reinforcing block facing the main surface of the substrate.
According to the optical waveguide element of configuration 5, a space for arranging functional elements can be secured between the reinforcing block and the substrate, thereby increasing the degree of freedom in arranging functional elements on the substrate. Furthermore, according to the optical waveguide element of configuration 5, the reinforcing block is formed as a single block, which can improve the strength of the reinforcing block compared to a reinforcing block composed of multiple sub-blocks.

(Configuration 6) The optical waveguide element according to configuration 2, wherein the removed portion is a through hole provided in the reinforcing block and opening in a direction perpendicular to the main surface of the substrate.
In the optical waveguide element of configuration 6, a through hole of a necessary size can be provided at any desired position on the substrate where the reinforcing block is disposed, thereby ensuring space for arranging the functional element. Therefore, with the optical waveguide element of configuration 6, for example, the adhesive area between the reinforcing block and the substrate is not excessively narrowed, and therefore the degree of freedom in arranging the functional element on the substrate can be increased while maintaining a good fixing strength between the reinforcing block and the substrate.

(Configuration 7) The optical waveguide element according to configuration 2, wherein the reinforcing block has a concave curved surface that faces the surface of the substrate that is aligned with the light incident/exit surface.
According to the optical waveguide element of configuration 7, the surface of the reinforcing block that faces the surface along the light input/output surface of the substrate is composed of a concave curved surface without corners, thereby suppressing uneven distribution of stress in the portion of the substrate where the reinforcing block is fixed, thereby achieving more stable optical and/or operating characteristics as an optical waveguide element.

(Configuration 8) The optical waveguide element according to configuration 2, wherein the reinforcing block has a pentagonal shape in plan view when viewed from the normal direction of the main surface of the substrate.
According to the optical waveguide element of configuration 8, the reinforcing block capable of securing a space for arranging the functional element can be easily fabricated by linear processing using a general-purpose dicing saw.

(Configuration 9) The optical waveguide element according to configuration 2, wherein the reinforcing block has a trapezoidal shape in a plan view when viewed from the normal direction of the main surface of the substrate.
According to the optical waveguide element of Configuration 9, the reinforcing block capable of securing a space for arranging the functional element can be easily fabricated by linear processing using a general-purpose dicing saw.

(Configuration 10) The optical waveguide element according to Configuration 2, wherein the optical waveguide includes an optical input waveguide that propagates input light input through the optical incident/exit surface of the substrate, and an optical output waveguide that propagates output light output through the optical incident/exit surface of the substrate toward the optical incident/exit surface, the optical input waveguide and the optical output waveguide each include a spot size conversion section in which the cross-sectional size of the optical waveguide changes toward an end of the optical waveguide, and the removal section is formed at a position other than directly above the spot size conversion section.
In the optical waveguide element of configuration 10, the adhesive layer and the reinforcing block are present directly above the spot size conversion portion, and the reinforcing block and the adhesive layer can function as cladding in the spot size conversion portion. As a result, the optical waveguide element of configuration 10 achieves good light confinement in the spot size conversion portion, making it possible to realize an optical waveguide element with high functionality and low optical loss.

(Configuration 11) The optical waveguide element according to any one of configurations 1 to 10, further comprising an adhesive layer between the reinforcing block and one main surface of the substrate.
In the optical waveguide element of Configuration 11, the reinforcing block and the adhesive layer between the reinforcing block and the substrate can function as a cladding for the optical waveguide formed on the main surface of the substrate below the reinforcing block, thereby achieving good light confinement in the optical waveguide.

(Configuration 12) The optical waveguide element according to any one of configurations 1 to 11, wherein the reinforcing block has a refractive index lower than the refractive index of the optical waveguide.
According to the optical waveguide element of Configuration 12, the reinforcing block can be made to function effectively as a cladding for the optical waveguide element.

(Configuration 13) An optical waveguide element described in any one of configurations 1 to 12, wherein an electrical circuit element, an optical element, or a mechanical element is arranged in the space between the plurality of rectangular blocks on the substrate on which the reinforcing block is arranged, or in the space of the removed portion, which is the portion removed from the single rectangular block on the substrate on which the reinforcing block is arranged and which is composed of a single block having a shape obtained by removing at least a portion of the single rectangular block.
In the optical waveguide element of configuration 13, the spaces between the rectangular parallelepiped blocks formed on the substrate by the reinforcing blocks or the spaces in the removed portions of a single block are utilized as arrangement spaces for electrical circuit elements, optical elements, or mechanical elements. Therefore, the optical waveguide element of configuration 13 can realize a high-performance optical waveguide element without increasing the size of the substrate.

(Configuration 14) The optical waveguide element according to any one of configurations 1 to 13, wherein an optical component is fixed to a surface of the reinforcing block along the light incident/exit surface.
According to the optical waveguide element of configuration 14, the reinforcing block can be used as a structure for fixing the optical component, and a subassembly including the optical waveguide element and the optical component can be easily produced.

(Configuration 15) An optical waveguide device comprising: an optical waveguide element according to any one of configurations 1 to 14; a housing that houses the optical waveguide element; an input optical fiber that inputs light to the optical waveguide element; and an output optical fiber that guides output light emitted by the optical waveguide element to the outside of the housing.
According to the optical waveguide device of configuration 15, a high-performance optical waveguide element is used that can be realized without increasing the size of the substrate or by using a smaller size substrate, so that a high-performance or high-performance optical waveguide device can be realized without increasing the size of the housing or by using a smaller housing.

(Configuration 16) The optical waveguide device described in Configuration 15, wherein the optical waveguide element has electrodes on the substrate that control light waves propagating through the optical waveguide, and the housing has a drive circuit inside that drives the optical waveguide element.
According to the optical waveguide device of Configuration 16, a driving circuit is provided in the housing that houses the optical waveguide element, and an optical waveguide device with higher functionality can be realized.

(Configuration 17) An optical transmitter comprising: the optical waveguide device according to configuration 15 or 16; and an electronic circuit that generates an electrical signal for causing the optical waveguide element to operate.
According to the optical transmitter of configuration 17, a highly functional or high performance optical transmitter can be realized by using a highly functional or high performance optical waveguide device without increasing the housing size or using a smaller housing.

1, 1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, 1i, 62...optical waveguide element, 10...substrate, 12...main surface, 14...optical waveguide, 16...electrode, 18a, 18b, 18c, 18d...end surface, 20...support plate, 22...light incident/exit surface, 24...optical input/output waveguide, 24a...optical input waveguide, 24b, 24c...optical output waveguide, 26, 26a, 26b, 26c...spot size conversion section, 28, 28a, 28b, 28c, 28d, 28e, 28f, 28g, 28h, 28i...reinforcement block, 28g1, 28g2...sub-block, 30...adhesive layer, 32...lens array, 34, 34a, 34b, 34c, 34d, 34e, 34f, 34g, 34h, 34i, 34i1, 34i2...removal section, 36a, 36b, 36c, 36d...surface, 38a, 38b...light receiving element, 40...electrode pad, 42a, 42b, 44a, 44b...parallel waveguide, 60...optical waveguide device, 64...housing, 66...input optical fiber, 68...output optical fiber, 70, 72...support, 74, 78...lens, 76...optical unit, 80...pin, 82...relay board, 84...drive circuit, 90...optical transmitter, 92...light source, 94...modulation signal generator.

Claims (17)

A substrate;
an optical waveguide formed on one main surface of the substrate;
a reinforcing block disposed on the one main surface of the substrate so as to be aligned with one end surface of the substrate, the end surface being a light input/output surface through which light is input to the optical waveguide and through which light is output from the optical waveguide;
An optical waveguide element comprising:
The reinforcing block is composed of a plurality of rectangular parallelepiped blocks, or is composed of a single block having a shape obtained by removing at least a portion of a single rectangular parallelepiped from the single rectangular parallelepiped.
Optical waveguide element. the reinforcing block is a single block having a shape obtained by removing at least a portion of a single rectangular parallelepiped from the single rectangular parallelepiped,
a removed portion, which is the portion of the reinforcing block removed from the single rectangular parallelepiped, is formed at a position other than directly above an end of the optical waveguide where light enters and exits through the light incident and exit surface of the substrate.
The optical waveguide element according to claim 1 . The removed portion is at least one notch formed on at least one surface of the reinforcing block.
The optical waveguide element according to claim 2 . the removal portion being at least one notch portion is formed on a surface of the reinforcing block facing a surface along the light incident/exit surface of the substrate;
The optical waveguide element according to claim 3 . the removal portion being at least one notch portion is formed on a surface of the reinforcing block facing a main surface of the substrate;
The optical waveguide element according to claim 3 . the removed portion is a through hole provided in the reinforcing block and opening in a direction perpendicular to the main surface of the substrate.
The optical waveguide element according to claim 2 . the reinforcing block has a concave curved surface facing a surface of the substrate aligned with the light incident/exit surface;
The optical waveguide element according to claim 2 . the reinforcing block has a pentagonal shape in a plan view when viewed from a normal direction of the main surface of the substrate;
The optical waveguide element according to claim 2 . The reinforcing block has a trapezoidal shape in a plan view when viewed from a normal direction of the main surface of the substrate.
The optical waveguide element according to claim 2 . the optical waveguide includes an optical input waveguide that propagates input light input through the light incident/exit surface of the substrate, and an optical output waveguide that propagates output light output through the light incident/exit surface of the substrate toward the light incident/exit surface,
the optical input waveguide and the optical output waveguide each include a spot size conversion section in which a cross-sectional size of the optical waveguide changes toward an end of the optical waveguide;
the removal portion is formed at a position other than directly above the spot size conversion portion.
The optical waveguide element according to claim 2 . an adhesive layer between the reinforcing block and one main surface of the substrate;
The optical waveguide element according to claim 1 . the reinforcing block has a refractive index lower than that of the optical waveguide;
The optical waveguide element according to claim 1 . In the substrate on which the reinforcing blocks made up of a plurality of rectangular parallelepiped blocks are arranged, an electric circuit element, an optical element, or a mechanical element is arranged in a space between the plurality of rectangular parallelepiped blocks, or in a space in a removed portion which is the portion removed from the single rectangular parallelepiped in the substrate on which the reinforcing blocks made up of a single block having a shape obtained by removing at least a portion of the single rectangular parallelepiped are arranged.
The optical waveguide element according to claim 1 . an optical component is fixed to a surface of the reinforcing block along the light incident/exit surface;
The optical waveguide element according to claim 1 . The optical waveguide element according to any one of claims 1 to 14;
a housing that houses the optical waveguide element;
an input optical fiber for inputting light into the optical waveguide element;
an output optical fiber that guides output light emitted by the optical waveguide element to the outside of the housing;
An optical waveguide device comprising: the optical waveguide element includes an electrode on the substrate that controls a light wave propagating through the optical waveguide;
a drive circuit for driving the optical waveguide element is provided inside the housing;
16. The optical waveguide device according to claim 15. The optical waveguide device according to claim 15 or 16;
an electronic circuit for generating an electrical signal for causing the optical waveguide element to operate;
An optical transmitting device comprising: