Optical waveguide element, optical waveguide device, and optical transmission apparatus

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

[0001] The present invention relates to an optical waveguide element, an optical waveguide device, and an optical transmitter.

[0002] 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 LiNbO ３ LN optical modulation elements using a substrate made of LN (hereinafter also referred to as LN) have been put to practical use.

[0003] Optical waveguide elements that are built into driver-integrated LN modulators (CDMs, Coherent Driver Modulators), which have been developed in recent years, or that are directly mounted on optical transceivers, are increasingly being required to achieve higher performance, such as lower power consumption, higher speeds, and wider bandwidths, as well as smaller size. To meet these requirements, 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 waveguiding direction in the optical waveguide, and the high-density arrangement of accompanying functional elements such as high-frequency electrodes, DC electrodes, and light-receiving elements for optical monitoring (e.g., photodiodes (PDs)) achieves both high functionality and compact size.

[0004] The ridge-type or rib-type optical waveguides used in the optical waveguide elements have a mode field diameter (MFD) for propagating light of 3 μm or less. However, optical components such as optical fibers joined to the end faces of the optical waveguides have an MFD of about 10 μm. Therefore, a spot size converter (SSC) is provided at the output end of the optical waveguide element to increase the MFD.

[0005] Furthermore, in order to ensure the bonding strength between the end face of the optical waveguide element and an optical component such as an optical fiber bonded to the end face and to prevent chipping or scratches on the optical waveguide when the end face is polished, a rectangular parallelepiped glass block (reinforcement block) is placed across the entire width of the substrate of the optical waveguide element so as to cover the optical waveguide including the SSC. This reinforcement block is usually fixed to the substrate with an adhesive. This adhesive also functions as a cladding layer for the SSC, so the reinforcement block plays an important role in constructing the optical waveguide element.

[0006] Patent Document 1 discloses an optical waveguide element that includes a reinforcing block at the end of the substrate of the optical waveguide element and a light-receiving element for monitoring light on the surface of the substrate. In this optical waveguide element, the waveguiding direction of the optical waveguide that guides light to the light-receiving element is folded back, so that the light-receiving element is mounted on a portion of the substrate surface where no reinforcing block is provided.

[0007] The above configuration can achieve high functionality without increasing the substrate size, and can therefore be suitably used for modulators such as the above-mentioned CDM, whose device size is standardized. However, from the perspective of further increasing functionality and reducing the substrate size, it would be advantageous if functional components such as photodetectors could also be arranged between the reinforcing block and the substrate.

[0008] The functional elements arranged on the substrate of the 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 signals or low frequency signals.

[0009] However, when thick functional elements such as a light receiving element, electrode pad, or thick film electrode 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 a thickness equivalent to that of 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.

[0010] Japanese Patent Application Laid-Open No. 2021-162642

[0011] An object of the present invention is to improve the degree of freedom in arranging functional elements on a substrate, thereby enabling a highly functional optical waveguide element to be realized without increasing the size of the substrate.

[0012] 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 reinforcement block arranged on the one main surface of the substrate so as to follow the one end surface of the substrate, which is a light input / output surface through which light is input to the optical waveguide and output from the optical waveguide, the reinforcement block being composed of multiple rectangular parallelepiped blocks or a single block having a shape obtained by removing at least a portion of a single rectangular parallelepiped from the single rectangular parallelepiped. According to another aspect of the present invention, the reinforcement block is a single block having a shape obtained by removing at least a portion of the single rectangular parallelepiped from the single rectangular parallelepiped, and the removed portion of the reinforcement block, which is the portion 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 input / output surface of the substrate. According to another aspect of the present invention, the removed portion is at least one notch formed on at least one surface of the reinforcement block. According to another aspect of the present invention, the removed portion, which is at least one cutout portion, is formed on a surface of the reinforcement block facing a surface along the light incident / exit surface of the substrate. According to another aspect of the present invention, the removed portion, which is at least one cutout portion, is formed on a surface of the reinforcement block facing a main surface of the substrate. According to another aspect of the present invention, the removed portion is a through hole provided in the reinforcement block, opening in a direction perpendicular to the main surface of the substrate. According to another aspect of the present invention, the surface of the reinforcement block facing the surface along the light incident / exit surface of the substrate forms a concave curved surface. According to another aspect of the present invention, the reinforcement block has a pentagonal shape in a plan view when viewed from the normal direction of the main surface of the substrate. According to another aspect of the present invention, the reinforcement block has a trapezoidal shape in a plan view when viewed from the normal direction of 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 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 including a spot size conversion portion in which the cross-sectional size of the optical waveguide changes toward an end of the optical waveguide, and the removed portion is formed at a position other than directly above the spot size conversion portion. According to another aspect of the present invention, an adhesive layer is provided between the reinforcement block and one main surface of the substrate. According to another aspect of the present invention, the reinforcement block has a refractive index lower than that of the optical waveguide. According to another aspect of the present invention, in the substrate on which the reinforcing blocks composed of a plurality of rectangular parallelepiped blocks are arranged, an electric circuit element, an optical element, or a mechanical element is arranged in the space between the plurality of rectangular parallelepiped blocks, or in the space in the removed portion, which is the portion removed from the single rectangular parallelepiped, in the substrate on which the reinforcing block composed of a single block shaped by removing at least a portion of the single rectangular parallelepiped 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 of the optical waveguide elements described above, a housing that accommodates the optical waveguide element, an input optical fiber that introduces light into 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 comprising 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 device 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.

[0013] According to the present invention, it is possible to improve the degree of freedom in arranging functional elements on a substrate, and to realize a highly functional optical waveguide element without increasing the size of the substrate.

[0014] 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. 1. FIG. 3 is a cross-sectional view taken along III-III of the optical waveguide element shown in FIG. 1. FIG. 4 is a cross-sectional view taken along IV-IV of the optical waveguide element shown in FIG. 1. 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 taken along XII-XII of the optical waveguide element shown in FIG. 11. 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 taken along line XIV-XIV of the optical waveguide element shown in Fig. 13. 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 an eleventh embodiment of the present invention.

[0015]

[0023] Hereinafter, embodiments of the present invention will be described with reference to the drawings. [1. First Embodiment] Fig. 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 of the substrate 10 (the surface shown in Fig. 1), and an electrode 16 that controls light waves propagating through the optical waveguide 14.

[0016] The substrate 10 is, for example, an LN substrate. However, the substrate 10 is not limited to an LN substrate and may be a substrate made of lithium tantalate (LT), lead lanthanum zirconate titanate (PLZT), or the like, or may be a substrate made of various materials such as semiconductor materials or organic materials.

[0017] 1, the electrodes 16 are disposed, for example, at positions on the main surface of the substrate 10, sandwiching the optical waveguide 14. However, the arrangement of the electrodes 16 shown in FIG. 1 is merely an example, and the electrodes 16 may be disposed at any appropriate design position depending on the material and / or crystal orientation used for the substrate 10. For example, the electrodes 16 may be disposed on the optical waveguide 14. This is also true for other embodiments.

[0018] The substrate 10 has, for example, a rectangular shape in plan view, and has two opposite end faces 18a and 18b extending in the vertical direction as shown, and two opposite end faces 18c and 18d extending in the horizontal direction as shown.

[0019] 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 configured with 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.

[0020] 2 is a side view of the optical waveguide element 1a shown in Fig. 1 as viewed from the direction of the end surface 18d of the substrate 10. The other main surface of the substrate 10 opposite to the one main surface 12 is bonded to a support plate 20 for reinforcement.

[0021] 1 , the end face 18b of the substrate 10 constitutes a light incident / exit surface 22 that inputs light to the optical waveguide 14 and outputs light from the optical waveguide 14. The optical waveguide 14 includes an optical input waveguide 24a that propagates input light input via the light incident / exit surface 22 of the substrate 10, and optical output waveguides 24b and 24c that propagate output light output via the light incident / exit surface 22 of the substrate 10 toward the light incident / exit surface 22.

[0022] The optical input waveguide 24a and the optical output waveguides 24b, 24c each include spot size conversion sections 26a, 26b, 26c (black triangular sections in the figure) in which 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 also be collectively referred to as optical input / output waveguides 24. Furthermore, the spot size conversion sections 26a, 26b, 26c will also be collectively referred to as spot size conversion sections 26.

[0023] Specifically, the spot size conversion section 26 is tapered so that the length in the thickness direction and the length in the main surface direction of the substrate 10 in a cross section perpendicular to the extension direction of the optical input / output waveguide 24 decrease toward each end of the optical input / output waveguide 24.

[0024] 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 surface 18b, which is the light incident / emitting surface 22 of the substrate 10. Here, "the reinforcing block 28a being arranged "along the end surface 18b" means that one surface of the reinforcing block 28a is flush or nearly flush with the end surface 18b, or is flush or nearly flush with the end surface 18b. In the optical waveguide element 1a shown in FIG. 1, the reinforcing block 28a is arranged so that a surface 36a on the right side of the reinforcing block 28a in the drawing is flush with the end surface 18b, which is the light incident / emitting surface 22 of the substrate 10.

[0025] 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. 1. 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.

[0026] 1 and 2 , optical components are fixed to the surface 36 a of the reinforcement block 28 a (i.e., the surface along the light incident / exit surface 22) and the light incident / exit surface 22 of the substrate 10, which are arranged so as to be flush with each other. In this embodiment, the optical components are, for example, a lens array 32. The optical components may include any optical components such as lenses, wave plates, and prisms. This makes it possible to easily fabricate an assembly including the optical waveguide element 1 a and the optical components by using the reinforcement block 28 a as a structure for fixing the optical components.

[0027] In this embodiment, in particular, the reinforcing block 28a is configured as 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 single block. Note that the phrase "a shape obtained by removing at least one portion of a single rectangular parallelepiped from the single block" expresses the shape of the reinforcing block 28a, and does not necessarily mean that the reinforcing block 28a is actually produced by removing a portion of a single rectangular parallelepiped.

[0028] Here, it is desirable that the removed portion 34a of the reinforcement block 28a, which is the portion removed from the single rectangular parallelepiped, does not include a 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 at 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 refers, in this embodiment, to the end of the optical input / output waveguide 24 on the light incident and exit surface 22 side.

[0029] As a result, in the optical waveguide element 1a, the reinforcing block 28a is present directly above the end of the optical waveguide 14 where light enters and exits, and the reinforcing block 28a and the adhesive layer 30 can function as cladding at the end. This achieves good light confinement at the end of the optical waveguide 14 where light enters and exits, making it possible to realize an optical waveguide element 1a with high functionality and low optical loss.

[0030] More specifically, in this embodiment, the removed portion 34a does not include a position directly above the spot size converter 26 formed by the end of the optical input / output waveguide 24. That is, the removed portion 34a is formed at a position excluding the position directly above the spot size converter 26. This means that the reinforcement block 28a is present directly above the spot size converter 26 via the adhesive layer 30, and therefore good light confinement in the spot size converter 26 can be achieved.

[0031] 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 a surface 36b of the reinforcing block 28a that faces the surface 36a along the light incident / exit surface 22 (end surface 18b) of the substrate 10. The shape of the removed portion 34a can be easily formed using, for example, a laser-based cutting device or an NC milling machine.

[0032] 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, i.e., the removed portion 34a, thereby improving the degree of freedom in arranging these functional elements on the substrate 10. As a result, it becomes possible to realize a highly functional optical waveguide element 1a without increasing the size of the substrate 10 compared to conventional cases, or by using a substrate 10 that is smaller than conventional cases. Furthermore, as a result of the above, it is not necessary 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, and therefore, it is possible to realize better optical characteristics and operating characteristics (in this embodiment, operating characteristics of optical modulation operation) of the optical waveguide element 1a.

[0033] For example, in this embodiment, a space is provided above each of the optical output waveguides 24b and 24c, excluding their respective ends, by a cutout-like removed portion 34a. Light-receiving elements 38a and 38b, which serve as electrical circuit elements, are disposed 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 upper portions of the optical output waveguides 24b and 24c via a thin adhesive layer so as to be evanescently coupled to the optical output waveguides 24b and 24c, respectively (see FIG. 3).

[0034] In the optical waveguide element 1a, the reinforcing block 28a can be configured with a shape in which only the portions where the electric circuit elements, optical elements, or mechanical elements are to be arranged are cut out, so that the area of ​​the adhesive surface with the substrate 10 is not significantly reduced. Therefore, the fixing strength between the reinforcing block 28a and the substrate 10 can be sufficiently ensured.

[0035] Furthermore, in the optical waveguide element 1a, the reinforcing block 28a does not have a notch on the surface 36a along the light incident / exit surface 22 of the substrate 10, and therefore the reinforcing block 28a can function as a cladding regardless of the position of the end of the light input / output waveguide 24 on the light incident / exit 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 ensured, while the degree of freedom in the placement of functional elements on the substrate 10 can be increased.

[0036] From the viewpoint of mechanical strength, the external size of the reinforcing block 28a is preferably such that the lengths of all three sides of the external shape of the reinforcing block 28a are 0.2 mm or more, more preferably 0.4 mm or more, and even more preferably 0.6 mm or more. Also, from the viewpoint of adhesive strength, the adhesive area between the reinforcing block 28a and the substrate 10 is 1.0 mm or more. ２ It is preferable that this is equal to or greater than this.

[0037] Furthermore, 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 normal to the main plane of the reinforcement block 28a) may 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 viewpoint of more effective utilization of the upper surface of the substrate. On the other hand, from the viewpoint 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, more preferably 60% or less. For the same reason, the ratio R is more preferably 50% or less. The same applies to other embodiments.

[0038] Although the planar shape of the removal portion 34 a, which is the cutout portion shown in FIG. 1, is rectangular, the planar shape of the removal portion 34 a as the cutout portion is not limited to a rectangle and may be any shape such as a polygon, a circle, an ellipse, or the like.

[0039] 2. Second Embodiment In the first embodiment described above, the removed portion 34a of the reinforcement 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 reinforcement block may have multiple removed portions formed thereon.

[0040] Fig. 5 is a plan view showing the configuration of an optical waveguide element 1b according to a second embodiment of the present invention. In Fig. 5, 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.

[0041] 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, except that it has a reinforcing block 28b instead of the reinforcing block 28a. The reinforcing block 28b has a configuration similar to that of the reinforcing block 28a, except that it has a removed portion 34b formed in addition to the removed portion 34a, which is a cutout portion.

[0042] The removed portion 34b is a cutout portion similar to the removed portion 34a, and is formed, for example, at the corner of the reinforcing block 28b between the surface 36b and the surface 36c adjacent to the surface 36b.

[0043] 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, for example, electrode pads connected to electrodes (not shown) of the light-receiving elements 38a, 38b via a wiring pattern (not shown) formed on the substrate 10, for connecting these electrodes to an electrical circuit external to the substrate 10.

[0044] In the present embodiment, the reinforcement block 28b has two cutouts 34a and 34b, but any number of cutouts greater than three may be provided. The cutouts do not necessarily have to be identical in shape in plan view as shown in FIG. 5, and cutouts of different shapes in plan view may be mixed.

[0045] 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.

[0046] Fig. 6 is a plan view showing the configuration of an optical waveguide element 1c according to a third embodiment of the present invention. In Fig. 6, 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.

[0047] 1, the optical waveguide element 1c has a similar configuration to the optical waveguide element 1a according to the first embodiment shown in FIG. 1, except that the optical waveguide element 1c has a reinforcing block 28c instead of the reinforcing block 28a. The reinforcing block 28c has a similar configuration to the reinforcing block 28a, except that the reinforcing block 28c has a through-hole reinforcing block 34c instead of the one reinforcing block 34a that is a notch.

[0048] 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 the 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.

[0049] In the optical waveguide element 1c, the reinforcement block 28c has a removed portion 34c as a through-hole in a portion where functional elements such as light-receiving elements 38a and 38b are arranged. That is, in the optical waveguide element 1c, a through-hole of the required size (e.g., the minimum size) for arranging the functional element can be provided at any desired position on the substrate 10 where the reinforcement block 28c is arranged, 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 increasing the degree of freedom in arranging the functional element on the substrate 10 while maintaining a good fixation strength between the reinforcement block 28c and the substrate 10.

[0050] In this embodiment, the shape of the removed portion 34c as a through hole provided in the reinforcement block 28c shown in Figure 6 is rectangular in plan view, but it may 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 may be any number of two or more. The removed portions do not necessarily have to have the same shape in plan view shown in Figure 6, and removed portions of different shapes in plan view may be mixed.

[0051] [4. Fourth Embodiment] The reinforcing block arranged on the main surface 12 of the substrate 10 may be formed from a single block having a shape obtained by removing at least a portion of a single rectangular parallelepiped, and the removed portion does not necessarily have to be a notch or a through-hole.

[0052] Fig. 7 is a plan view showing the configuration of an optical waveguide element 1d according to a fourth embodiment of the present invention. In Fig. 7, 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.

[0053] The optical waveguide element 1d 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 28d instead of the reinforcing block 28a.

[0054] Reinforcement block 28d has the same configuration as reinforcement block 28a, but does not have removed portion 34a, which is a cutout portion, and instead has removed portion 34d, which forms surface 36b1, which faces surface 36a along light incident / exit surface 22 of substrate 10, as a concave curved surface. In other words, reinforcement block 28d has a shape in which one portion of a single rectangular parallelepiped is removed in a concave shape from one surface of the rectangular parallelepiped, forming the one surface into a curved surface.

[0055] In the space secured by the recessed removed portion 34d, an electric circuit element, an optical element, or a mechanical element can be disposed, similar to the removed portion 34a, etc. In the optical waveguide element 1d, for example, light receiving elements 38a and 38b are disposed in the space secured by the removed portion 34d.

[0056] Furthermore, in the optical waveguide element 1d, the surface 36b1 is configured as a curved surface, which has the following advantage: 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 in the configuration of FIG. 1 ).

[0057] In contrast, in the optical waveguide element 1d, the reinforcement block 28d has a rectangular parallelepiped shape in which a portion thereof has been removed by the removal portion 34d to form a concave shape, 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, thereby preventing the stress from causing the reinforcement block 28d to peel off from the substrate 10 or adversely affecting the optical characteristics and operating characteristics of the optical waveguide element 1d.

[0058] 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 description of Fig. 1 above is incorporated herein.

[0059] The optical waveguide element 1e 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 28e instead of the reinforcing block 28a.

[0060] Reinforcement block 28e has a configuration similar to that of reinforcement block 28a, but does not have removed portion 34a, which is a cutout portion, and is configured so that its shape in plan view is pentagonal when viewed from the normal direction of main surface 12 of substrate 10. This shape can be formed by forming two removed portions 34e1 and 34e2 that are triangular in plan view in a portion of substrate 10 that faces surface 36a along light incident / exit surface 22.

[0061] As with the removed portion 34a, etc., the space secured by the removed portions 34e1 and 34e2 can accommodate electrical circuit elements, optical elements, or mechanical elements. In the optical waveguide element 1e, the light-receiving elements 38a and 38b are disposed in the space secured by the removed portion 34e1. Although nothing is disposed in the space secured by the removed portion 34e2 in FIG. 8, an element such as an electrode pad 40 may be disposed therein.

[0062] The reinforcing block 28e can be easily produced by linear processing using a general-purpose dicing saw.

[0063] 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.

[0064] The optical waveguide element 1f has a configuration similar to that of the optical waveguide element 1e according to the fifth embodiment shown in Fig. 8, but differs in that it has a reinforcing block 28f instead of the reinforcing block 28e. Such a shape can be formed by forming one removed portion 34f that is triangular in plan view in a portion of the substrate 10 that faces the surface 36a along the light incident / exit surface 22.

[0065] An electric circuit element, an optical element, or a mechanical element can be disposed in the space secured by the removed portion 34f. In the optical waveguide element 1f, the light receiving elements 38a and 38b are disposed in the space secured by the removed portion 34f.

[0066] The reinforcing block 28f has fewer sides (or faces) than the reinforcing block 28e, and can therefore be manufactured more easily than the reinforcing block 28e by linear processing using a dicing saw.

[0067] 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 description of Fig. 1 above is incorporated herein.

[0068] The optical waveguide element 1g has a configuration similar to that of the optical waveguide element 1a according to the first embodiment shown in Fig. 1, but includes a reinforcement block 28g composed of two sub-blocks 28g1 and 28g2 instead of the reinforcement block 28a. The sub-blocks 28g1 and 28g2 have a configuration similar to that of the reinforcement block 28a, but do not have the removed portion 34a, and each is configured as a block having a rectangular parallelepiped shape. That is, the reinforcement block 28g is composed of the two sub-blocks 28g1 and 28g2, which are rectangular parallelepiped blocks.

[0069] The sub-blocks 28g1 and 28g2 constituting the reinforcing block 28g are each arranged so that one surface thereof is aligned with the light incident / emitting surface 22 of the substrate 10 (for example, so as to be flush or approximately flush with the surface).

[0070] Furthermore, the sub-block 28g1 is disposed immediately above the end of the optical input waveguide 24a that includes the spot size conversion portion 26a, and the sub-block 28g2 is disposed immediately above the end of the optical output waveguides 24b, 24c that include the spot size conversion portions 26b, 26c. As a result, the sub-block 28g1 and the adhesive layer 30 below it function as cladding for the spot size conversion portion 26a of the optical input waveguide 24a, and the sub-block 28g2 and the adhesive layer 30 below it function as cladding for the spot size conversion portions 26b, 26c of the optical output waveguides 24b, 24c.

[0071] Here, the sum of the lengths Lg1 and Lg2 of the sub-blocks 28g1 and 28g2 constituting the reinforcing 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)

[0072] As a result, a space can be secured between the two rectangular parallelepiped blocks, sub-blocks 28g1 and 28g2, along the light incident / exit surface 22 on the main surface 12 of the substrate 10. In this space, functional elements such as electrical circuit elements, optical elements, or mechanical elements can be arranged on the main surface 12 of the substrate 10, similar to the space secured by the removed portion 34a in FIG. 1 (the functional elements arranged in the space are not shown in FIG. 10).

[0073] In the present embodiment, the reinforcement block 28g includes two rectangular parallelepiped sub-blocks 28g1 and 28g2, but the number of rectangular parallelepiped sub-blocks included in the reinforcement block 28g may be any number equal to or greater than three. In this case, each sub-block may be arranged such that one face thereof is aligned with the light incident / exit surface 22 of the substrate 10. The sum of the lengths of the sub-blocks along the light incident / exit surface 22 of the substrate 10 may be set to be shorter than the length Lb of the side of the substrate 10 along the light incident / exit surface 22.

[0074] [8. Eighth Embodiment] Figure 11 is a plan view showing the configuration of an optical waveguide element 1h according to an eighth embodiment of the present invention. Figure 12 is a cross-sectional view of the optical waveguide element 1h shown in Figure 11 taken along the line XII-XII. In Figures 11 and 12, the same components as those in Figures 1 and 4 are designated by the same reference numerals as those in Figures 1 and 4, and the above-mentioned explanations for Figures 1 and 4 are incorporated herein.

[0075] 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, except that it has a reinforcing block 28h instead of the reinforcing block 28a. The reinforcing block 28h has a configuration similar to that of the reinforcing block 28a, except that it has a reinforcing block 34h (Fig. 12) formed therein in addition to the one reinforcing block 34a, which is a cutout portion.

[0076] The removed portion 34h is a notch like the removed portion 34a, but is formed on the surface 36d (FIG. 12) of the reinforcing block 28h that faces the main surface 12 of the substrate 10.

[0077] As a result, in the optical waveguide element 1h, a space for arranging functional elements can be secured between the reinforcement block 28h and the substrate 10, thereby increasing the degree of freedom in arranging functional elements on the substrate 10. Furthermore, in the optical waveguide element 1h, the reinforcement block 28h is formed as a single block, and therefore the strength of the reinforcement block 28h can be improved compared to the reinforcement block 28g of the seventh embodiment, which is composed of multiple sub-blocks.

[0078] Furthermore, since the reinforcement block 28h is formed as a single block, it is easier to align it when placing it on the main surface 12 of the substrate 10 than the reinforcement block 28g of the seventh embodiment, which is composed of multiple rectangular parallelepiped sub-blocks.

[0079] 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.

[0080] Figure 13 is a plan view showing the configuration of an optical waveguide element 1i according to a ninth embodiment of the present invention. Also, Figure 14 is a cross-sectional view taken along the line XIV-XIV of the optical waveguide element 1i shown in Figure 13. In Figures 13 and 14, the same components as those in Figures 11 and 12 are designated by the same reference numerals as those in Figures 11 and 12, and the above-mentioned explanations for Figures 11 and 12 are incorporated herein.

[0081] 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. The reinforcing block 28i has a configuration similar to that of the reinforcing block 28h, but differs in that two cutout portions 34i1 and 34i2 are provided on the surface 36d facing the main surface 12 of the substrate 10 instead of the cutout portion 34h (see Fig. 14).

[0082] 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.

[0083] 13 and 14, two parallel waveguides 42a, 42b and 44a, 44b of two Mach-Zehnder optical waveguides included in the optical waveguide 14 are bent in a zigzag pattern. The bent portions of the parallel waveguides 42a, 42b and 44a, 44b as optical elements are arranged together with electrodes 16 as electrical elements in the spaces on the main surface 12 of the substrate 10 secured by the removed portions 34i1, 34i2.

[0084] As a result, in the optical waveguide element 1i, longer parallel waveguides 42a, 42b and 44a, 44b can be formed over a wider area, including the removed portions 34i1, 34i2, on the main surface 12 of the substrate 10. As a result, in the optical waveguide element 1i, a longer acting 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, thereby making it possible to reduce the operating voltage.

[0085] [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.

[0086] 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, and 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.

[0087] 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, and the interior thereof is hermetically sealed.

[0088] The optical waveguide element 62 may be any one 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 the 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 incident / exit surface 22 of the substrate 10, which are arranged flush with each other.

[0089] The optical waveguide device 60 includes an input optical fiber 66 that inputs light to the optical waveguide element 62, and an output optical fiber 68 that guides output light emitted by the optical waveguide element 62 to the outside 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.

[0090] Light input from the input optical fiber 66 is collimated by a lens 74 arranged in the support 70, and then input to the optical input waveguide 24a of the optical waveguide element 62 via a corresponding lens of the lens array 32 fixed to the optical waveguide element 62.

[0091] The light beams output from the two optical output waveguides 24b, 24c of the optical waveguide element 62 are collimated through corresponding lenses of the lens array 32 fixed to the optical waveguide element 62, and are combined into one beam by an optical unit 76 including a polarization combiner etc. The combined beam is coupled to the output optical fiber 68 through a lens 78 disposed on the support 72.

[0092] A plurality of pins 80 are arranged on the outer surface of the housing 64 for transmitting and receiving electrical signals, etc., necessary 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., necessary for the operation of the optical waveguide element 62, to and from an external device. As the electrical interface, an electrical interface other than pins having any shape and electrical characteristics can be selected and used depending on the electrical characteristics required of the optical waveguide device 60 and constraints on mounting on other devices. Such an electrical interface may be, in addition to the pins 80, a flexible printed circuit (FPC) or the like connected to the housing 64.

[0093] A relay board 82 may be provided inside the housing 64 to relay 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 board 82 includes a drive circuit 84 that drives the optical waveguide element 62. The drive circuit 84 receives electrical signals from the pins 80 as input and outputs high-frequency signals to the electrodes 16 of the optical waveguide element 62.

[0094] Each of the optical waveguide elements 1 includes two Mach-Zehnder optical waveguides as the optical waveguide 14, similar to the optical waveguide element 1a, and functions as an optical modulator. That is, an optical waveguide device 60 including any of the optical waveguide elements 1 as an optical waveguide element 62 can function as an optical modulation device.

[0095] The optical waveguide device 60 having the above-described configuration uses, as the optical waveguide element 62, a high-performance optical waveguide element 1 that can be constructed without increasing the size of the substrate 10 or by using a smaller sized substrate 10, and 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.

[0096] In the present embodiment, the relay substrate 82 includes the drive circuit 84, but the relay substrate 82 does not necessarily have to include the drive circuit 84. For example, the relay substrate 82 may not include the drive circuit 84, and may include only a wiring pattern that connects the pins 80 to electrodes such as the electrode 16 provided on the optical waveguide element 62 and the light-receiving elements 38 a, 38 b, and passive circuit components such as capacitors.

[0097] 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 device 90 that incorporates 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 device 90 according to this embodiment. This optical transmitting device 90 includes an optical waveguide device 60 that is 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 the drive circuit 84, the optical transmitting device 90 may include a modulator driving unit having the same function as the drive circuit 84.

[0098] The modulation signal generation unit 94 is an electronic circuit that generates an electrical signal for causing the optical waveguide device 60 to perform a modulation operation, and based on transmission data provided from the outside, generates a modulation signal, which is a high-frequency signal for causing 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 substrate 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 transmitting apparatus 90.

[0099] The optical transmitter 90 having the above configuration is configured by the optical waveguide device 60 using any of the optical waveguide elements 1 described above as the optical waveguide element 62, and therefore can realize a highly functional or high performance optical transmitter.

[0100] [12. Other Embodiments] In the above-described embodiment, the optical waveguide element 1 functions as an optical modulator, but it may also have any other function, such as an optical switch, polarization rotation, or wavelength conversion.

[0101] In the above-described embodiment, the optical waveguide 14 constituting the optical waveguide element 1 includes a Mach-Zehnder optical waveguide, but may include a waveguide pattern of a type other than a Mach-Zehnder optical waveguide depending on the function required of the optical waveguide element 1. For example, the optical waveguide 14 may be one constituting a directional coupler or a multi-port optical branch.

[0102] In the above-described embodiment, the substrate 10 constituting the optical waveguide element 1 is a substrate such as LN having an electro-optic effect, but it may be made of a material that does not have an electro-optic effect depending on the function required of the optical waveguide element 1.

[0103] In the fifth and sixth embodiments described above, reinforcement blocks 28e and 28f having a pentagonal and trapezoidal planar shape are illustrated in Figures 8 and 9, respectively, but the planar shape of reinforcement block 28 may be any polygon other than a pentagon or a trapezoid.

[0104] 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 formed with any two or more of the removed portions 34a, 34b, 34c, 34d, 34e, 34f, 34h, and 34i shown in the above-mentioned embodiments. Furthermore, in a reinforcing block configured from multiple rectangular parallelepiped sub-blocks, at least one of the sub-blocks may have a shape formed with one or more of the removed portions 34a, 34b, 34c, 34d, 34e, 34f, 34h, and 34i.

[0105] The present invention is not limited to the configurations of the above-described embodiments, and can be implemented in various forms without departing from the spirit of the present invention.

[0106] 13. Configurations Supported by the Above-described Embodiments The above-described embodiments support the following configurations.

[0107] (Configuration 1) An optical waveguide element comprising a substrate, an optical waveguide formed on one principal surface of the substrate, and a reinforcing block arranged on the one principal surface of the substrate so as to align with the one end face of the substrate, the end face being a light input / output surface through which light is input to the optical waveguide and output from the optical waveguide, wherein the reinforcing block is composed of a plurality of rectangular parallelepiped blocks or 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 between the rectangular parallelepipeds constituting the reinforcing block on the substrate or in the space created by the removed portion of the single rectangular parallelepiped. Therefore, the optical waveguide element of Configuration 1 improves the degree of freedom in arranging functional elements on the substrate, thereby enabling a high-performance optical waveguide element to be realized without increasing the size of the substrate.

[0108] (Configuration 2) The optical waveguide element according to Configuration 1, wherein the reinforcement 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 of the reinforcement block, which is the portion 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 incident and exit surface of the substrate. In the optical waveguide element of Configuration 2, the reinforcement block is present directly above the end of the optical waveguide where light enters and exits, so that the reinforcement block and an adhesive layer that may be interposed between the reinforcement 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.

[0109] (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 a space for arranging a functional element can be easily formed in the reinforcing block.

[0110] (Configuration 4) 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 a surface along the light incident / exit surface of the substrate. According to the optical waveguide element of Configuration 4, the reinforcing block does not need to be provided with a cutout portion on a surface along one end face of the substrate that constitutes the light incident / exit surface, for example, and it is possible to increase the degree of freedom in the placement of functional elements on the substrate while ensuring the degree of freedom in the placement of the end portion of the optical waveguide.

[0111] (Configuration 5) The optical waveguide element according to Configuration 3, wherein the removed portion, which is at least one cutout portion, is formed on the surface of the reinforcement 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 reinforcement 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 reinforcement block is formed as a single block, thereby improving the strength of the reinforcement block compared to a reinforcement block composed of multiple sub-blocks.

[0112] (Configuration 6) The optical waveguide element according to Configuration 2, wherein the removed portion is a through hole provided in the reinforcement block that opens 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 reinforcement block is disposed, thereby securing space for arranging the functional element. Therefore, with the optical waveguide element of Configuration 6, for example, the adhesive area between the reinforcement block and the substrate is not excessively narrowed, thereby increasing the degree of freedom in arranging the functional element on the substrate while maintaining good fixing strength between the reinforcement block and the substrate.

[0113] (Configuration 7) The optical waveguide element according to Configuration 2, wherein the surface of the reinforcing block facing the surface of the substrate along the light incident / exit surface forms a concave curved surface. According to the optical waveguide element of Configuration 7, the surface of the reinforcing block facing the surface of the substrate along the light incident / exit surface is configured as a concave curved surface without corners, thereby suppressing uneven distribution of stress in the portion of the substrate to which the reinforcing block is fixed, and making it possible to achieve more stable optical characteristics and / or operating characteristics as an optical waveguide element.

[0114] (Configuration 8) The optical waveguide element according to Configuration 2, wherein the reinforcing block has a pentagonal 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 8, the reinforcing block capable of securing a space for arranging a functional element can be easily fabricated by linear processing using a general-purpose dicing saw.

[0115] (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 a functional element can be easily fabricated by linear processing using a general-purpose dicing saw.

[0116] (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 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 each include a spot size conversion section whose cross-sectional size changes toward an end of the optical waveguide, and the removed section is formed at a position other than directly above the spot size conversion section. In the optical waveguide element of Configuration 10, an adhesive layer and a reinforcement block are present directly above the spot size conversion section, allowing the reinforcement block and the adhesive layer to function as cladding in the spot size conversion section. This allows the optical waveguide element of Configuration 10 to achieve good light confinement in the spot size conversion section, resulting in a highly functional optical waveguide element with low optical loss.

[0117] (Configuration 11) The optical waveguide element according to any one of Configurations 1 to 10, further comprising an adhesive layer between the reinforcement block and one main surface of the substrate. According to the optical waveguide element of Configuration 11, the reinforcement block and the adhesive layer between the reinforcement block and the substrate can function as a cladding for the optical waveguide formed below the reinforcement block and on the main surface of the substrate. This allows the optical waveguide element of Configuration 11 to achieve good optical confinement in the optical waveguide.

[0118] (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 that of the optical waveguide. According to the optical waveguide element of Configuration 12, the reinforcing block can be made to effectively function as a cladding for the optical waveguide element.

[0119] (Configuration 13) The optical waveguide element according to any one of Configurations 1 to 12, wherein, in the substrate on which the reinforcement blocks composed of a plurality of rectangular parallelepiped blocks are arranged, an electrical circuit element, an optical element, or a mechanical element is arranged in the space between the plurality of rectangular parallelepiped blocks, or in the space of the removed portion, which is the portion removed from the single rectangular parallelepiped, in the substrate on which the reinforcement blocks composed of a single block having a shape obtained by removing at least a portion of the single rectangular parallelepiped are arranged. In the optical waveguide element of Configuration 13, the space between the plurality of rectangular parallelepiped blocks formed on the substrate by the reinforcement blocks, or the space of the removed portion of the single block, is used as the arrangement space for the electrical circuit element, the optical element, or the mechanical element. Therefore, the optical waveguide element of Configuration 13 makes it possible to realize a high-performance optical waveguide element without increasing the size of the substrate.

[0120] (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, making it possible to easily fabricate a subassembly including the optical waveguide element and the optical component.

[0121] (Configuration 15) An optical waveguide device comprising: the optical waveguide element according to any one of configurations 1 to 14; a housing for accommodating the optical waveguide element; an input optical fiber for inputting light into the optical waveguide element; and an output optical fiber for guiding output light emitted by the optical waveguide element to the outside of the housing. The optical waveguide device of configuration 15 uses a high-performance optical waveguide element that can be realized without increasing the size of the substrate or by using a smaller-sized 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.

[0122] (Configuration 16) The optical waveguide device according to Configuration 15, wherein the optical waveguide element includes electrodes on the substrate that control light waves propagating through the optical waveguide, and a drive circuit for driving the optical waveguide element is provided inside the housing. According to the optical waveguide device of Configuration 16, a drive circuit is provided inside the housing that houses the optical waveguide element, thereby realizing an optical waveguide device with higher functionality.

[0123] (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 high-performance or high-performance optical transmitter can be realized by using a high-performance or high-performance optical waveguide device without increasing the housing size or using a smaller housing.

[0124] 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 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

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 align with the one end surface of the substrate, which 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.

2. The optical waveguide element according to claim 1, wherein 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 via the light incident and exit surface of the substrate.

3. The optical waveguide element according to claim 2, wherein the removed portion is at least one notch formed in at least one surface of the reinforcing block.

4. The optical waveguide element according to claim 3, wherein the removed portion, which is at least one notch, is formed on a surface of the reinforcing block opposite to a surface of the substrate that is aligned with the light incident / emitting surface.

5. The optical waveguide element according to claim 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.

6. The optical waveguide element according to claim 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.

7. The optical waveguide element according to claim 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.

8. The optical waveguide element according to claim 2, wherein the reinforcing block has a pentagonal shape in plan view when viewed from the normal direction to the main surface of the substrate.

9. The optical waveguide element according to claim 2, wherein the reinforcing block has a trapezoidal shape in plan view when viewed from the normal direction of the main surface of the substrate.

10. The optical waveguide element according to claim 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.

11. The optical waveguide element according to any one of claims 1 to 10, further comprising an adhesive layer between the reinforcing block and one main surface of the substrate.

12. The optical waveguide element according to any one of claims 1 to 11, wherein the reinforcing block has a refractive index lower than that of the optical waveguide.

13. An optical waveguide element according to any one of claims 1 to 12, wherein, in the substrate on which the reinforcing block composed of a plurality of rectangular parallelepiped blocks is arranged, an electrical circuit element, an optical element, or a mechanical element is arranged in the space between the plurality of rectangular parallelepiped blocks, or in the space of the removed portion, which is the portion removed from the single rectangular parallelepiped, in the substrate on which the reinforcing block composed of a single block having a shape obtained by removing at least a portion of the single rectangular parallelepiped is arranged.

14. The optical waveguide element according to any one of claims 1 to 13, wherein an optical component is fixed to a surface of the reinforcing block that is aligned with the light incident / exit surface.

15. An optical waveguide device comprising: an optical waveguide element according to any one of claims 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.

16. The optical waveguide device according to claim 15, wherein the optical waveguide element comprises electrodes on the substrate for controlling light waves propagating through the optical waveguide, and a drive circuit for driving the optical waveguide element is provided inside the housing.

17. An optical transmitter comprising: an optical waveguide device according to claim 15 or 16; and an electronic circuit that generates an electrical signal for causing the optical waveguide element to operate.

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