Optical module

Abstract

An optical module (1) comprises a waveguide (3), a substrate (2), a light-receiving element (5), and a mirror (4). The waveguide (3) includes a core part (31) and a cladding part (32). The core part (31) has an input section (31a) and an output section (31b). The substrate (2) has a first groove (21). The first groove (21) has an opening (21a) on the upper side and extends in a first axial direction (T1). In the substrate (2), the waveguide (3) is disposed in the first groove (21). The light-receiving element (5) has a light-receiving part. The light-receiving part is disposed above the output section (31b) of the core part (31). The mirror (4) is located below the light-receiving part and faces the output section (31b) of the core part (31). A bottom part (31d) of the waveguide (3) includes an inclined section (31dT) that is inclined upward from the input section (31a) toward the output section (31b). A bottom part (21b) of the first groove (21) includes an inclined section (21bT) that is inclined upward from a second end (21t) at which the input section (31a) is disposed toward a first end (21s).

Description

Optical Module

[0001] The present disclosure relates generally to optical modules, and more particularly to optical modules comprising waveguides.

[0002] The optical module disclosed in Patent Document 1 includes a substrate, a mirror portion for optical path conversion, an internal waveguide, and an optical element. The substrate has a first groove and a second groove on its surface. The first groove has an internal waveguide. An optical fiber is disposed in the second groove. The mirror portion is provided at the tip of the first groove. The optical element is mounted on the surface of the substrate so as to face the mirror portion, and emits an optical signal to the core portion of the internal waveguide via the mirror portion, or receives an optical signal from the core portion of the internal waveguide via the mirror portion. The width of the core portion of the internal waveguide gradually narrows from the end portion connected to the core portion of the optical fiber toward the mirror portion.

[0003] In the optical module of Patent Document 1, when the optical element is a light receiving element, the width between both side surfaces of the core portion of the internal waveguide gradually narrows from the connection end of the internal waveguide with the optical fiber toward the mirror portion.

[0004] Similarly, when the optical element is a light-emitting element, the width between both side surfaces of the core portion of the internal waveguide gradually narrows from the mirror portion toward the end portion of the internal waveguide connected to the optical fiber.

[0005] International Publication No. 2011 / 105078

[0006] In the optical module described in Patent Document 1, the height of the core portion of the internal waveguide is constant between the mirror portion and the end of the internal waveguide where it is connected to the optical fiber. Therefore, in the height direction of the core portion of the internal waveguide, the optical coupling loss between the core portion of the internal waveguide and the optical element cannot be reduced, and the optical coupling efficiency decreases.

[0007] An optical module according to one aspect of the present disclosure includes a waveguide, a substrate, a light-receiving element, and a mirror. The waveguide includes a core portion and a cladding portion. The core portion has an input portion and an output portion. The input portion and the output portion are located at both ends in a first axis direction, which is the longitudinal direction. The cladding portion covers the core portion. The substrate has a first groove. The first groove has an opening at the top and extends in the first axis direction. The substrate has the waveguide located in the first groove. The light-receiving element has a light-receiving portion. The light-receiving portion is located above the output portion of the core portion. The mirror is located below the light-receiving portion and faces the output portion of the core portion. The bottom of the waveguide includes an inclined portion that slopes upward from the input portion to the output portion. The bottom of the first groove includes an inclined portion that slopes upward from the second end to the first end. The input portion is located at the second end.

[0008] An optical module according to another aspect of the present disclosure includes a waveguide, a substrate, a light-emitting element, and a mirror. The waveguide includes a core portion and a cladding portion. The core portion has an input portion and an output portion. The input portion and the output portion are located at both ends in a first axis direction, which is the longitudinal direction. The cladding portion covers the core portion. The substrate has a first groove. The first groove has an opening at the top and extends in the first axis direction. The substrate has the waveguide located in the first groove. The light-emitting element has a light-emitting portion. The light-emitting portion is located above the input portion of the core portion. The mirror is located below the light-emitting portion and faces the input portion of the core portion. The bottom of the waveguide includes an inclined portion that slopes upward from the input portion to the output portion. The bottom of the first groove includes an inclined portion that slopes upward from a first end to a second end. The input portion is located at the first end.

[0009] The optical module according to the present disclosure has an advantage of being able to improve the optical coupling efficiency in a direction intersecting the height direction of the core portion of the waveguide.

[0010] FIG. 1 is a perspective view of an optical module according to a first embodiment. FIG. 2 is a perspective view of a substrate of the optical module. FIG. 3 is a perspective view of a substrate on which a core portion of a waveguide of the optical module is arranged. FIG. 4 is an X0-X0 cross-sectional view of FIG. 1. FIG. 5 is a cross-sectional view of a first section of a first groove of the optical module according to the first embodiment. FIG. 6 is a cross-sectional view of a second section of a first groove of the optical module according to the first embodiment. FIG. 7 is a cross-sectional view of a third section of a first groove of the optical module according to the first embodiment. FIG. 8 is an explanatory diagram illustrating the positional relationship between a light receiving unit and an output unit of the optical module according to the first embodiment. FIG. 9 is an X1-X1 cross-sectional view of FIG. 8. FIG. 10 is a plan view illustrating one step of a manufacturing method of the optical module according to the first embodiment. FIG. 11A is a plan view illustrating another step of a manufacturing method of the optical module according to the first embodiment. FIG. 11B is an X2-X2 cross-sectional view of FIG. 11A. FIG. 12 is a perspective view of an optical module according to a first modification. FIG. 13A is a plan view of an optical module according to a second embodiment. FIG. 13B is a cross-sectional view taken along the line X3-X3 of FIG. 13A.

[0011] An optical module according to an embodiment will be described with reference to the drawings.

[0012] (1) First Embodiment (1-1) Overview As shown in FIG. 4, the optical module 1 according to the first embodiment includes a waveguide 3, a substrate 2, a light-receiving element 5, and a mirror 4. The waveguide 3 includes a core 31 and a clad 32. The core 31 has an input portion 31a and an output portion 31b. The input portion 31a and the output portion 31b are arranged at both ends of the core 31 in a first axis direction T1, which is the longitudinal direction of the core 31. The clad 32 covers the core 31. The substrate 2 has a first groove 21. The first groove 21 has an opening 21a at its upper end and extends in the first axis direction T1. The substrate 2 has a waveguide 3 arranged in the first groove 21. The light-receiving element 5 has a light-receiving portion 5a (see FIGS. 8 and 9). The light-receiving portion 5a (see FIG. 9) is arranged above the output portion 31b of the core 31. The mirror 4 is located below the light-receiving portion 5a and faces the output portion 31b of the core portion 31. The bottom 31d of the waveguide 3 includes a slope 31dT that slopes upward (i.e., toward the major surface 2a) from the input portion 31a toward the output portion 31b (see FIG. 4). The bottom 21b of the first groove 21 includes a slope 21bT that slopes upward from the second end 21t, where the input portion 31a is located, toward the first end 21s (see FIG. 4). The slope 31dT of the bottom 31d of the waveguide 3 and the slope 21bT of the bottom 21b of the first groove 21 are located in the first section L1 (see FIG. 3).

[0013] According to this configuration, the bottom 31d of the waveguide 3 includes an inclined portion 31dT that slopes upward from the input portion 31a toward the output portion 31b. This allows the size (size in the first axis direction T1) of the output portion 31b of the waveguide 3, which is in a direction intersecting the height direction (second axis direction T2) of the waveguide 3, to be further reduced. As a result, even if the size of the light-receiving portion 5a is smaller than the diameter of the optical fiber core portion 6a of the optical fiber 6 or the position of the light-receiving portion 5a is misaligned in the direction (first axis direction T1) intersecting the height direction (second axis direction T2) of the waveguide 3, the optical coupling efficiency between the output portion 31b of the waveguide 3 and the light-receiving portion 5a can be improved. As a result, in the optical module 1, the optical coupling efficiency can be improved in the direction (here, the first axis direction T1) intersecting the height direction (second axis direction T2) of the waveguide 3.

[0014] (1-2) Detailed Description As shown in Fig. 1, the optical module 1 according to the first embodiment relays an optical signal propagating between an optical fiber 6 and a light-receiving element 5. The optical module 1 includes a substrate 2, a waveguide 3, a mirror 4 (see Fig. 2), a light-receiving element 5, and an optical fiber 6. In the first embodiment, the optical fiber 6 is included in the configuration of the optical module 1, but it does not have to be included in the configuration of the optical module 1.

[0015] (1-2-1) Substrate 2 As shown in FIG. 2, the substrate 2 is a member for fixing one end of the light receiving element 5 (see FIG. 1), the waveguide 3 (see FIG. 1), and the optical fiber 6 (see FIG. 1). The substrate 2 is, for example, a rectangular flat plate. The substrate 2 is, for example, a silicon substrate. The substrate 2 has a main surface 2a on one side in the thickness direction (second axis direction T2). A first groove 21 and a second groove 22 are provided on the main surface 2a of the substrate 2.

[0016] The first groove 21 is a groove in which the waveguide 3 and the mirror 4 are disposed. The first groove 21 is recessed into the main surface 2a of the substrate 2 along the longitudinal direction (first axis direction T1) of the main surface 2a. The first groove 21 has a first end 21s and a second end 21t on both sides in the longitudinal direction. The first end 21s is closed. The first end 21s forms an inclined surface on which the mirror 4 is disposed. The inclined first end 21s is inclined toward an opening 21a (described below) of the first groove 21 with respect to the longitudinal direction of the first groove 21. The second end 21t is connected to a first end 22s of the second groove 22. In other words, the internal space of the first groove 21 and the internal space of the second groove 22 are connected.

[0017] The width W1 of the first groove 21 gradually decreases in the depth direction (second axis direction T2) of the first groove 21 from an opening 21a side (described later) of the first groove 21 toward a bottom 21b side (described later) of the first groove 21. The depth D1 of the first groove 21 has a portion that gradually becomes shallower from the second end 21t side toward the first end 21s side of the first groove 21. That is, at least a portion of the bottom 21b of the first groove 21 is inclined upward (toward the main surface 2a of the substrate 2) from the second end 21t side toward the first end 21s side (see FIG. 4).

[0018] More specifically, the first groove 21 has an opening 21a, a bottom 21b, and side surfaces 21c on both sides. The opening 21a is an opening formed in the main surface 2a of the substrate 2. The side surfaces 21c on both sides are inclined inward of the first groove 21 in the direction of the depth D1 of the first groove 21, from the opening 21a side toward the bottom 21b side. In the first section L1 between the first end 21s and the intermediate position M1, the lower edges (edges on the bottom 21b side) of the side surfaces 21c on both sides are connected to each other. That is, in the first section L1, the bottom 21b is formed by the connected lower edges of the side surfaces 21c on both sides. That is, in the first section L1, the first groove 21 is a V-groove portion 211. The V-groove portion 211 is a groove portion having a V-shaped cross section perpendicular to the longitudinal direction (first axial direction T1) of the first groove 21. The intermediate position M1 is a position between the first end 21s and the second end 21t. More specifically, the intermediate position M1 is a position in the first axial direction T1 where the first groove 21 changes from the V-groove portion 211 to the inverted trapezoidal groove portion 212 described below. In the first section L1, the width W1 of the first groove 21 gradually decreases from the intermediate position M1 toward the first end 21s. In addition, in the first section L1, the depth D1 of the first groove 21 gradually decreases from the intermediate position M1 toward the first end 21s.

[0019] In the second section L2 between the intermediate position M1 and the second end 21t, the lower edges (edges on the bottom 21b side) of both side surfaces 21c are connected to the hypotenuses of the isosceles triangle's bottom surface 21d. That is, in the second section L2, the bottom 21b is defined by the isosceles triangle's bottom surface 21d. That is, in the second section L2, the first groove 21 is an inverted trapezoidal groove 212. The inverted trapezoidal groove 212 is a groove whose cross section perpendicular to the longitudinal direction of the first groove 21 (first axial direction T1) has an inverted trapezoidal shape. In the second section L2, the width W1 of the first groove 21 gradually decreases from the second end 21t side of the first groove 21 toward the intermediate position M1. The depth D1 of the first groove 21 is constant from the second end 21t to the intermediate position M1. The depth D1 of the first groove 21 may gradually become shallower from the second end 21t toward the intermediate position M1 of the first groove 21. The depth D1 of the first groove 21 gradually becomes shallower from the intermediate position M1 toward the first end 21s.

[0020] As described above, the first groove 21 has the V-groove portion 211 and the inverted trapezoidal groove portion 212. That is, the first groove 21 has the V-groove portion 211 in at least a portion of the first groove 21 (e.g., the first section L1) in the longitudinal direction of the first groove 21 (the first axial direction T1).

[0021] The second groove 22 is a groove in which one end of the optical fiber 6 is disposed. The second groove 22 is concavely formed in the main surface 2a of the substrate 2 along the longitudinal direction (first axis direction T1) of the main surface 2a. The second groove 22 is, for example, a V-shaped groove. More specifically, the second groove 22 has side surfaces 221a on both sides. The side surfaces 221a on both sides are inclined inward from the opening 22a of the second groove 22 toward the bottom 22b. The lower edges (i.e., edges on the bottom 22b side) of the side surfaces 221a on both sides are connected to each other to form the bottom 22b. The second groove 22 has a first end 22s and a second end 22t on both sides in the longitudinal direction (first axis direction T1). The first end 22s is connected to the second end 21t of the first groove 21. As a result, the internal spaces of the first groove 21 and the second groove 22 are connected to each other. The second end 22t opens at an end surface 2c of the substrate 2. The end surface 2c is a side surface on one side in the longitudinal direction of the substrate 2. The width W2 of the second groove 22 is constant along the longitudinal direction of the second groove 22 (first axis direction T1). The depth D2 of the second groove 22 is constant along the longitudinal direction of the second groove 22. That is, the bottom 22b of the second groove 22 is parallel to the opening surface of the opening 22a in the longitudinal direction of the second groove 22. The depth D2 of the second groove 22 is deeper than the depth D1 of the first groove 21. The opening surface of the opening 22a is a plane whose edge is the opening 22a.

[0022] 3, the waveguide 3 is a member that relays an optical signal propagating between one end of the optical fiber 6 and the light-receiving element 5. The waveguide 3 is disposed inside the first groove 21 and along the first groove 21.

[0023] The waveguide 3 has a core portion 31 and a clad portion 32 .

[0024] The core portion 31 is a portion through which an optical signal propagates. The core portion 31 is formed of a light-transmitting material (e.g., resin). The core portion 31 is disposed inside the first groove 21. More specifically, the core portion 31 is provided at the bottom portion 21b of the first groove 21 along the first groove 21 (i.e., along the first axis direction T1). More specifically, the core portion 31 is provided from the first end 21s to the second end 21t of the first groove 21. The core portion 31 is provided so as to cover a mirror 4 (described below) provided at the first end 21s of the first groove 21.

[0025] The core portion 31 has an input portion 31a and an output portion 31b. The input portion 31a and the output portion 31b are arranged at both ends of the core portion 31 in the longitudinal direction (first axis direction T1). The input portion 31a is a portion that inputs an optical signal output from one end of the optical fiber 6. The input portion 31a is arranged inside the first groove 21 near the second end 21t. The input portion 31a is formed by the end face of the core portion 31 on the second end 21t side. The output portion 31b is a portion that outputs an optical signal that has propagated through the core portion 31 to the outside (light receiving element 5). The output portion 31b is arranged inside the first groove 21 near the first end 21s. More specifically, the output portion 31b is formed by a region of a top surface 31u (described below) of the core portion 31 onto which a light spot R1 (described below) is projected.

[0026] The width W3 of the core portion 31 is smaller than the width W1 at the opening 21a of the first groove 21 (i.e., the width at the main surface 2a of the substrate 2). The width W3 of the core portion 31 gradually decreases from the input portion 31a side toward the output portion 31b side. The height D3 of the core portion 31 gradually decreases from the input portion 31a side toward the output portion 31b side. In other words, at least a portion of the bottom 31d of the core portion 31 is inclined upward (toward the opening 21a of the first groove 21, i.e., toward the main surface 2a of the substrate 2) from the input portion 31a side toward the output portion 31b side (see FIG. 4 ). More specifically, in the first section L1, the height of the core portion 31 gradually decreases from the intermediate position M1 toward the first end 21s. The height of the core portion 31 is constant from the second end 21t of the first groove 21 to the intermediate position M1.

[0027] As described above, the core portion 31 has a top surface 31u and a bottom portion 31d (see FIG. 4). The top surface 31u is the main surface of the core portion 31 on the side of the opening 21a of the first groove 21 in the direction of the height D3. The bottom portion 31d is the portion of the core portion 31 on the side of the bottom portion 21b of the first groove 21 in the direction of the height D3.

[0028] More specifically, the core portion 31 has a first core portion 311 (lower portion) and a second core portion 312 (upper portion) (see FIG. 5).

[0029] The first core portion 311 is disposed on the bottom 21b side of the first groove 21 and tapers downward (i.e., from the opening 21a side of the first groove 21 toward the bottom 21b) (see FIGS. 5 and 6). The first core portion 311 is a portion that contacts both side surfaces 21c of the first groove 21 and is disposed between the both side surfaces 21c. The second core portion 312 is disposed on the opening 21a side of the first groove 21 and is located above the first core portion 311 (see FIGS. 5 to 7). The first core portion 311 and the second core portion 312 are aligned in the height D3 direction of the core portion 31 and connected to each other.

[0030] In the first section L1 (see FIG. 1 ) between the first end 21 s and the intermediate position M1, as shown in FIG. 5 , the cross-sectional shape of the first core portion 311 (i.e., the cross-sectional shape perpendicular to the longitudinal direction (first axial direction T1) of the core portion 31) is an inverted triangle, and the cross-sectional shape of the second core portion 312 is a rectangle. The width of the cross-sectional shape of the second core portion 312 is the same as the width of the cross-sectional shape of the first core portion 311 (the length of the upper side of the inverted triangle). That is, in the first section L1, the side surfaces 311 c on both sides of the first core portion 311 have the same inclination angle as the side surfaces 21 c on both sides of the first groove 21 adjacent to the side surfaces 311 c on both sides of the first core portion 311. The inclination angles of the side surfaces 311 c, 21 c are angles between the side surfaces 311 c and the main surface 2 a of the substrate 2 when viewed in a cross section perpendicular to the first axial direction T1. That is, the side surfaces 311c on both sides of the first core portion 311 are parallel to the side surfaces 21c on both sides of the first groove 21 adjacent to the side surfaces 311c on both sides of the first core portion 311. Furthermore, in the first section L1, the side surfaces 312c on both sides of the second core portion 312 have a different inclination angle from the side surfaces 21c on both sides of the first groove 21 adjacent to the side surfaces 312c on both sides of the second core portion 312. That is, the side surfaces 312c on both sides of the second core portion 312 are not parallel to the side surfaces 21c on both sides of the first groove 21 adjacent to the side surfaces 312c on both sides of the second core portion 312. In the example of FIG. 5 , the side surfaces 312c on both sides of the second core portion 312 are perpendicular to the main surface 2a of the substrate 2. Note that this perpendicularity is not limited to being strictly perpendicular and may include an error of, for example, 1 to 3 degrees. In the first section L1, the bottom 31d of the core portion 31 is defined by the vertex Q1 of the inverted triangle (the portion where both side surfaces 311c are connected).

[0031] In addition, in a third section L21 (see FIG. 1 ) between the intermediate positions M1 and M2, as shown in FIG. 6 , the cross-sectional shape of the first core portion 311 is an inverted trapezoid, and the cross-sectional shape of the second core portion 312 is a rectangle. The width of the cross-sectional shape of the second core portion 312 is the same as the width of the cross-sectional shape of the first core portion 311 (the length of the upper side of the inverted trapezoid). In the third section L21, the side surfaces 311c on both sides of the first core portion 311 have the same inclination angle as the side surfaces 21c on the same side of the first groove 21. That is, the side surfaces 311c on both sides of the first core portion 311 are parallel to the side surfaces 21c on the same side of the first groove 21. In addition, in the third section L21, the side surfaces 312c on both sides of the second core portion 312 have an inclination angle different from the side surfaces 21c on the same side of the first groove 21. That is, the side surfaces 312c on both sides of the second core portion 312 are not parallel to the side surfaces 21c on the same side of the first groove 21. In the example of FIG. 6, the side surfaces 312c on both sides of the second core portion 312 are perpendicular to the main surface 2a of the substrate 2. Note that this perpendicularity does not have to be strictly perpendicular and may include an error of, for example, 1 to 3 degrees. In the third section L21, the bottom 31d of the core portion 31 is formed by the bottom surface 311d of the first core portion 311 (i.e., the main surface corresponding to the bottom side of the inverted trapezoid). In the third section L21, the width W4 of the bottom 31d of the core portion 31 (i.e., the bottom surface 311d) is the same size as the width W5 of the bottom surface 21d of the first groove 21. The intermediate position M2 is a position between the intermediate position M1 and the second end 21t, and is a position where the width W6 of the second core portion 312 is the same as the width W5 of the bottom surface 21d of the first groove 21.

[0032] Furthermore, in the fourth section L22 (see FIG. 1 ) between the intermediate position M2 and the second end 21t, as shown in FIG. 7 , the core portion 31 does not contact the side surfaces 21c of the first groove 21. Therefore, the core portion 31 does not have a first core portion 311, which is a portion that contacts the side surfaces 21c, and is composed only of the second core portion 312. The side surfaces 312c of the second core portion 312 have a different inclination angle from the side surfaces 21c on the same side of the first groove 21. In other words, the side surfaces 312c of the second core portion 312 are not parallel to the side surfaces 21c on the same side of the first groove 21. In the example shown in FIG. 7 , the side surfaces 312c of the second core portion 312 are perpendicular to the main surface 2a of the substrate 2. Note that this perpendicularity is not limited to being strictly perpendicular and may include an error of, for example, 1 to 3 degrees. In the fourth section L22, the bottom 31d of the core portion 31 is formed by the bottom surface 312b of the second core portion 312. In the fourth section L22, the width W4 of the bottom 31d of the core portion 31 (i.e., the width W6 of the core portion 31) is the same as or smaller than the width W5 of the bottom surface 21d of the first groove 21.

[0033] The cladding portion 32 is a member that prevents an optical signal propagating through the core portion 31 from leaking outside the core portion 31. The cladding portion 32 is formed of a light-transmitting member (e.g., resin). The refractive index of the cladding portion 32 is smaller than the refractive index of the core portion 31. The cladding portion 32 is provided inside the first groove 21 so as to cover at least a portion of the outer circumferential surface of the core portion 31 (e.g., the top surface 31u and both side surfaces 312c of the second core portion 312). In the example of FIG. 1 , the cladding portion 32 is also provided around the first groove 21 on the main surface 2a of the substrate 2.

[0034] (1-2-3) Mirror 4 The mirror 4 (see FIGS. 2 to 4) is a reflective member (e.g., a metal member) for optical path conversion. The mirror 4 is located below the light-receiving portion 5a (described later) and is disposed inside the first groove 21 so as to face the output portion 31b of the core portion 31 of the waveguide 3. The mirror 4 reflects the optical signal propagating through the core portion 31 of the waveguide 3 toward the output portion 31b of the waveguide 3. The mirror 4 is disposed at the first end 21s (inclined surface) of the first groove 21. The mirror 4 is disposed so as to overlap the light-receiving portion 5a (described later) in the thickness direction (second axis direction T2) of the substrate 2 (see FIGS. 8 and 9). The mirror 4 is disposed so as to be inclined toward the light-receiving portion 5a from the direction facing the input portion 31a of the waveguide 3 (first axis direction T1). As described above, the mirror 4 is covered by the core portion 31.

[0035] In the first embodiment, as described above, the bottom 31d of the waveguide 3 is inclined toward the main surface 2a of the substrate 2 from the input portion 31a toward the output portion 31b. Therefore, the cross-sectional area of ​​the core portion 31 of the waveguide 3 (the cross-sectional area of ​​a cross section perpendicular to the longitudinal direction (first axis direction T1) of the waveguide 3) is smallest at a position (minimum position P2) just before the first end 21s of the first groove 21 (see FIG. 9 ). The cross section of the core portion 31 at the minimum position P2 is referred to as the minimum cross section S1. In the first embodiment, the minimum cross section S1 (e.g., a pentagonal cross section) of the core portion 31 at the minimum position P2 is reflected by the mirror 4 toward the light receiving portion 5a (top surface 31u). At this time, a light spot R1 having the shape of the reflected minimum cross section S1 is projected onto the top surface 31u of the waveguide 3. The region of the top surface 31u where the light spot R1 is located becomes the output portion 31b of the waveguide 3. The mirror 4 is disposed so as to be inclined at, for example, 45 degrees with respect to the top surface 31 u of the waveguide 3 .

[0036] (1-2-4) Light-Receiving Element 5 The light-receiving element 5 (see FIG. 1) is an element (e.g., a photodiode) that receives an optical signal output from the output portion 31b of the core portion 31 of the waveguide 3. The light-receiving element 5 is disposed above the output portion 31b of the core portion 31 of the waveguide 3. More specifically, the light-receiving element 5 is disposed on the main surface 2a of the substrate 2 so as to overlap with the output portion 31b of the waveguide 3 in the thickness direction (second axis direction T2) of the substrate 2 (see FIGS. 8 and 9).

[0037] As shown in FIGS. 8 and 9 , the light-receiving element 5 has a light-receiving portion 5a. The light-receiving portion 5a is arranged to overlap the output portion 31b of the waveguide 3 in the thickness direction (second axis direction T2) of the substrate 2 (see FIG. 9 ). The area of ​​the light-receiving portion 5a is the same as or larger than the area of ​​the output portion 31b of the waveguide 3. In a plan view in the thickness direction of the substrate 2, the range of the light-receiving portion 5a includes the range of the output portion 31b of the waveguide 3 (see FIG. 8 ). In this way, by overlapping the light-receiving portion 5a with the output portion 31b in the thickness direction of the substrate 2, even if the position of the light-receiving element 5 is misaligned, the optical signal output from the output portion 31b can be received by the light-receiving portion with reduced optical loss. Note that the area of ​​the light-receiving portion 5a is preferably larger than the area of ​​the output portion 31b of the waveguide 3. The area of ​​the light receiving portion 5a is the same as or smaller than the area of ​​the input portion 31a of the waveguide 3. This makes it possible to accommodate the light receiving portion 5a becoming smaller than the input portion 31a of the waveguide 3 as communication speeds increase.

[0038] (1-2-5) Optical Fiber 6 The optical fiber 6 is a member that propagates an optical signal. As shown in FIG. 1, the optical fiber 6 has a core 6a (optical fiber core) and a cladding 6b. The core 6a is the portion through which the optical signal propagates, and is, for example, a core with a circular cross section. The core 6a is made of a light-transmitting material (for example, resin or glass fiber). The cladding 6b is a material that prevents the optical signal propagating through the core 6a from leaking outside the core 6a. The cladding 6b is made of a light-transmitting material (for example, resin). The refractive index of the cladding 6b is smaller than the refractive index of the core 6a. The cladding 6b is provided so as to cover the outer periphery of the core 6a.

[0039] One end of the optical fiber 6 is, for example, an output portion that outputs an optical signal that has propagated through the core portion 6a. One end side of the optical fiber 6 is arranged inside the second groove 22 and along the second groove 22. One end side of the optical fiber 6 is fixed to the second groove 22 by, for example, an adhesive 10. In this fixed state, one end of the optical fiber 6 faces the input portion 31a of the waveguide 3 that is arranged in the first groove 21. More specifically, the core portion 6a exposed from one end of the optical fiber 6 faces the input portion 31a of the waveguide 3.

[0040] The cross-sectional area of ​​the core 6a is the same as or smaller than the area of ​​the input portion 31a of the core 31 of the waveguide 3. When viewed in the longitudinal direction of the waveguide 3, the range of the input portion 31a includes the range of the core 6a. This allows an optical signal output from one end of the optical fiber 6 to be input to the input portion 31a of the core 31 with reduced optical loss. It is desirable that the area of ​​the surface of the core 6a facing the input portion 31a be smaller than the area of ​​the input portion 31a of the waveguide 3.

[0041] (1-3) Description of Operation The operation of the optical module 1 according to the first embodiment (that is, the propagation of an optical signal) will be described with reference to FIG.

[0042] An optical signal C1 output from one end of the optical fiber 6 is input to the input portion 31a of the core portion 31 of the waveguide 3. At this time, the area of ​​the core portion 6a of the optical fiber 6 is equal to or smaller than the area of ​​the input portion 31a of the waveguide 3 (the area of ​​the input portion 31a of the waveguide 3), so optical loss is suppressed when input from one end of the optical fiber 6 to the input portion 31a of the waveguide 3. The optical signal C1 input to the waveguide 3 propagates through the waveguide 3, is reflected by the mirror 4, is output from the output portion 31b, and is received by the light-receiving portion 5a. At this time, the width W3 (see FIG. 3) of the waveguide 3 gradually decreases from the input portion 31a side toward the output portion 31b side, so that the optical coupling efficiency between the output portion 31b of the waveguide 3 and the light-receiving portion 5a is improved in the width direction of the waveguide 3. Furthermore, the height D3 (see FIG. 4) of the waveguide 3 gradually decreases from the input portion 31a side toward the output portion 31b side, which improves the optical coupling efficiency between the output portion 31b of the waveguide 3 and the light-receiving portion 5a in the height direction of the waveguide 3. Furthermore, the area of ​​the light-receiving portion 5a is the same as or larger than the area of ​​the output portion 31b of the waveguide 3 (the area of ​​the output portion 31b of the waveguide 3) (see FIGS. 8 and 9), which further improves the optical coupling efficiency between the light-receiving portion 5a and the output portion 31b of the waveguide 3.

[0043] (1-4) Manufacturing Method A manufacturing method for the optical module 1 according to the first embodiment will be described with reference to FIGS.

[0044] As shown in FIG. 10 , an etching mask 7 having a first opening 7a for forming the first groove 21 and a second opening 7b for forming the second groove 22 is first formed on the main surface 2a of the substrate 2. The first opening 7a and the second opening 7b may be formed simultaneously or separately. FIG. 10 is a top view of the etching mask 7. The first opening 7a has a tapered rectangular shape that is slightly smaller than the opening 21a of the first groove 21. The tip of the first opening 7a is T-shaped. This ensures that when the first groove 21 is formed by anisotropic etching, as described below, an inclined surface for positioning the mirror 4 is formed at the first end 21s of the first groove 21. The second opening 7b has a rectangular shape that is slightly smaller than the opening of the second groove 22. The second opening 7b is connected to the base end of the first opening 7a.

[0045] In the first embodiment, the tip of the first groove 21 on the first end 21s side is thin. To form an inclined surface at such a thin end, the tip of the first opening 7a needs to be T-shaped. However, if the tip of the first groove 21 on the first end 21s side is not so thin, the tip of the first opening 7a does not need to be T-shaped.

[0046] Next, anisotropic etching is performed on the etching mask 7. This etching removes the portions of the main surface 2a of the substrate 2 exposed through the first opening 7a and the second opening 7b and their surrounding areas. As a result, a first groove 21 and a second groove 22 are formed in the main surface 2a of the substrate 2. The first groove 21 and the second groove 22 may be formed separately or simultaneously. In this manner, the first groove 21 is formed so that the width W3 of the first groove 21 gradually decreases from the second end 21t toward the first end 21s and the bottom 31d of the first groove 21 slopes toward the main surface 2a of the substrate 2 from the second end 21t toward the first end 21s (see FIG. 11 ). The second groove 22 is formed to have a V-shaped cross section. An etching mask 7 for forming the first groove 21 may be formed, and after the first groove 21 is formed by etching, a mask for etching the second groove 22 may be formed.

[0047] After the first groove 21 is formed, the first groove 21 is covered with a film. The film is preferably made of a material having a lower refractive index than the waveguide 3.

[0048] Next, as shown in FIG. 11, a mirror 4 is provided at the first end 21s of the first groove 21.

[0049] Then, the first groove 21 of the substrate 2 is filled with a first photocurable resin (e.g., ultraviolet curable resin) containing a material for forming the core portion 31. The surface of the filled first photocurable resin is then planarized. The planarized first photocurable resin is then partially irradiated with light (e.g., ultraviolet light) to harden necessary portions of the planarized first photocurable resin, thereby forming the core portion 31 from the first photocurable resin. The unhardened portions of the first photocurable resin are then removed. In this manner, the core portion 31 of the waveguide 3 (see FIG. 11 ) is formed from the first photocurable resin.

[0050] Next, a second photocurable resin (e.g., ultraviolet curable resin) containing a material for forming the cladding portion 32 is filled into the first groove 21 of the substrate 2 from above the core portion 31. The surface of the filled second photocurable resin is then planarized, and light (e.g., ultraviolet light) is irradiated onto necessary portions of the planarized second photocurable resin to harden the necessary portions of the planarized second photocurable resin, thereby forming the cladding portion 32 from the second photocurable resin. The unhardened portions of the second photocurable resin are then removed. Note that a thermosetting resin may be used as the first photocurable resin and the second photocurable resin.

[0051] Then, the light receiving element 5 is attached at a predetermined position on the main surface 2a of the substrate 2. Furthermore, one end of the optical fiber 6 is fixed in the second groove 22 of the substrate 2 with an adhesive.

[0052] (1-5) Effects The optical module 1 according to the first embodiment includes a waveguide 3, a substrate 2, a light-receiving element 5, and a mirror 4. The waveguide 3 includes a core 31 and a cladding 32. The core 31 has an input portion 31a and an output portion 31b. The input portion 31a and the output portion 31b are arranged at both ends in the first axis direction T1, which is the longitudinal direction. The cladding 32 covers the core 31. The substrate 2 has a first groove 21. The first groove 21 has an opening 21a at its upper end and extends in the first axis direction T1. The substrate 2 has a waveguide 3 arranged in the first groove 21. The light-receiving element 5 has a light-receiving portion 5a. The light-receiving portion 5a is arranged above the output portion 31b of the core 31. The mirror 4 is located below the light-receiving portion 5a and faces the output portion 31b of the core 31. The bottom 31d of the waveguide 3 includes a slope 31dT (see FIG. 4) that slopes upward from the input portion 31a toward the output portion 31b. The bottom 21b of the first groove 21 includes a slope 21bT (see FIG. 4) that slopes upward from the second end 21t, where the input portion 31a is located, toward the first end 21s.

[0053] According to this configuration, the bottom 31d of the waveguide 3 slopes upward from the input portion 31a toward the output portion 31b. This allows the size of the output portion 31b of the waveguide 3 in a direction intersecting the height direction of the waveguide 3 (the direction of height D3) to be further reduced. As a result, even if the size of the light-receiving portion 5a is smaller than the diameter of the core portion 6a of the optical fiber 6 or the position of the light-receiving portion 5a is misaligned in the direction intersecting the height direction of the waveguide 3 (here, the first axis direction T1), the optical coupling efficiency between the output portion 31b of the waveguide 3 and the light-receiving portion 5a can be improved. As a result, in the optical module 1, light (optical signal) is more easily transmitted from the output portion 31b of the waveguide 3 to the light-receiving portion 5a in the direction intersecting the height direction of the waveguide 3 (here, the first axis direction T1), thereby improving the optical coupling efficiency.

[0054] In the optical module 1 according to the first embodiment, the area of ​​the light receiving portion 5a is equal to or smaller than the area of ​​the input portion 31a of the core portion 31. This configuration can improve the optical coupling efficiency between the output portion 31b of the core portion 31 of the waveguide 3 and the light receiving portion 5a.

[0055] Furthermore, in the optical module 1 according to the first embodiment, the area of ​​the light receiving portion 5a is equal to or larger than the area of ​​the output portion 31b of the core portion 31. With this configuration, even if the position of the light receiving portion 5a is misaligned, the optical coupling efficiency between the output portion 31b of the waveguide 3 and the light receiving portion 5a can be improved.

[0056] The optical module 1 according to the first embodiment further includes an optical fiber 6 optically coupled to the input portion 31a of the waveguide 3. The substrate 2 further includes a second groove 22. The second groove 22 is connected to the second end 21t of the first groove 21, and one end of the optical fiber 6 is disposed in the second groove 22. The optical fiber 6 has a core 6a (optical fiber core). The core 6a faces the input portion 31a. The area of ​​the surface of the core 6a facing the input portion 31a is the same as or smaller than the area of ​​the input portion 31a (the area of ​​the input portion 31a). This configuration improves the optical coupling efficiency between the optical fiber 6 and the input portion 31a of the core 31 of the waveguide 3.

[0057] Furthermore, in the optical module 1 according to the first embodiment, the first groove 21 has a V-groove portion 211. The V-groove portion 21 is a groove portion having a V-shaped cross section perpendicular to the first axis direction T1. This configuration makes it easy to position the core portion 31 of the waveguide 3 in the width direction of the first groove 21. As a result, it is easy to align the core portion 31 of the waveguide 3 and the light receiving portion 5a in the width direction of the first groove 21.

[0058] Furthermore, in the optical module 1 according to the first embodiment, the width W1 of the first groove 21 decreases from the input portion 31a toward the output portion 31b. The width W3 of the core portion 31 decreases from the input portion 31a toward the output portion 31b. This configuration further reduces the widthwise size of the output portion 31b of the waveguide 3. As a result, even when the size of the light-receiving portion 5a or the light-emitting portion 9a is smaller than the diameter of the core portion 31 of the optical fiber 6 or when the light-receiving portion 5a or the light-emitting portion 9a is misaligned in the widthwise direction of the output portion 31b of the waveguide 3, the optical coupling efficiency between the output portion 31b of the waveguide 3 and the light-receiving portion 5a or the light-emitting portion 9a can be improved. As a result, in the optical module 1, the optical coupling efficiency can be improved in a direction intersecting the widthwise direction (the direction of the width W3) of the waveguide 3.

[0059] In the optical module 1 according to the first embodiment, the first groove 21 is formed in the substrate 2 by anisotropic etching. With this configuration, the bottom of the first groove 21 can be formed with high precision so as to slope upward from the input section 31 a side toward the output section 31 b side.

[0060] Furthermore, in the optical module 1 according to the first embodiment, the width W3 of the core portion 31 is smaller than the width W1 of the opening 21a of the first groove 21. With this configuration, the positional deviation of the core portion 31 of the waveguide 3 in the width direction of the first groove 21 can be limited to within the range of the width W1 of the first groove 21 on the main surface 2a. This makes it possible to suppress the positional deviation of the first groove 21 in the width direction of the core portion 31 of the waveguide 3 relative to the light-receiving element 5.

[0061] Furthermore, in the optical module 1 according to the first embodiment, the core portion 31 of the waveguide 3 has a first core portion 311 (lower portion) and a second core portion 312 (upper portion) in the first axial direction T1. The first core portion 311 is disposed at the bottom 21b of the first groove 21 and tapers toward the bottom 21b of the first groove 21. The second core portion 312 is located above the first core portion 311 in the first groove 21. Side surfaces 311c on both sides of the first core portion 311 have the same inclination angle as the side surfaces 21c on both sides of the first groove 21 adjacent to the side surfaces 311c on both sides of the first core portion 311. Side surfaces 312c on both sides of the second core portion 312 have a different inclination angle than the side surfaces 21c on both sides of the first groove 21 adjacent to the side surfaces 312c on both sides of the second core portion 312.

[0062] According to this configuration, the side surfaces 311c on both sides of the first core portion 311 have the same inclination angle as the side surfaces 21c on both sides of the first groove 21 adjacent to the side surfaces 311c on both sides of the first core portion 311. Therefore, the first core portion 311 can be fitted into the first groove 21 in the width direction of the first groove 21 (direction of width W1). This allows the core portion 31 of the waveguide 3 relative to the first groove 21 to be tapered downward in the width direction of the first groove 21. As a result, it is possible to reduce misalignment of the light-receiving element 5 with respect to the core portion 31 of the waveguide 3 in the width direction of the first groove 21.

[0063] (1-6) Modifications The first embodiment is merely one of various embodiments of the present disclosure. Various modifications of the first embodiment are possible depending on the design, etc., as long as the object of the present disclosure can be achieved. Modifications of the first embodiment are listed below. The modifications described below can be applied in appropriate combinations.

[0064] As shown in Figure 12, the optical module 1 of this modified example is configured in the same way as the optical module 1 of embodiment 1, except that the cross-sectional shape of the second groove 22 (the shape of the cross section perpendicular to the longitudinal direction (first axial direction T1) of the second groove 22) is rectangular, and a positioning member 8 that positions the optical fiber 6 is arranged within the second groove 22.

[0065] More specifically, in this modification, the second groove 22 extends along the longitudinal direction (first axis direction T1) of the first groove 21, as in the first embodiment, and the first end 22s of the second groove 22 is connected to the second end 21t of the first groove 21, and the second end 22t of the second groove 22 opens at the end face 2c of the substrate 2. The cross-sectional shape of the second groove 22 is rectangular. The depth of the second groove 22 is deeper than the depth of the first groove 21. A pair of positioning members 8 are arranged inside the second groove 22. That is, the optical module 1 of this modification includes a pair of positioning members 8.

[0066] The pair of positioning members 8 are arranged inside the second groove 22 so as to fit into the gaps on both sides of the optical fiber 6. The pair of positioning members 8 are formed, for example, from resin in the shape of a rectangular flat plate. One end side of the optical fiber 6 is arranged between the pair of positioning members 8 inside the second groove 22. As a result, the position of the second groove 22 in the width direction is determined by the pair of positioning members 8. In this modification, as in the case of embodiment 1, the optical fiber 6 is fixed in the second groove 22 with an adhesive.

[0067] The pair of positioning members 8 are formed, for example, from the same material as the core portion 31 of the waveguide 3. In this case, the pair of positioning members 8 are formed in the second groove 22 together with the core portion 31 using the same material as the core portion 31 in the same manufacturing process as the manufacturing process for forming the core portion 31 of the waveguide 3.

[0068] According to this modification, the optical fiber 6 can be stably positioned and disposed in the second groove 22 by the pair of positioning members 8 .

[0069] (2) Second Embodiment (2-1) Configuration An optical module 1 according to the second embodiment will be described with reference to FIG.

[0070] The optical module 1 according to the second embodiment has the same configuration as the optical module 1 according to the first embodiment, except that the light receiving element 5 is replaced with a light emitting element 9. The second embodiment will be described in detail below. In the following description, the same components as those in the first embodiment will be assigned the same reference numerals and their description may be omitted.

[0071] In the optical module 1 according to the second embodiment, the light receiving element 5 in the optical module 1 according to the first embodiment is changed to a light emitting element 9 .

[0072] In embodiment 2, the first groove 21 is configured in the same way as the first groove 21 in embodiment 1, except that the direction in which the width W1 of the first groove 21 becomes smaller and the direction in which the depth D1 of the first groove 21 becomes shallower are opposite in the longitudinal direction of the first groove 21 (first axial direction T1).

[0073] More specifically, unlike in the first embodiment, the width W1 of the first groove 21 gradually decreases from the first end 21s toward the second end 21t (see A in FIG. 13 ). Also, unlike in the first embodiment, the depth D1 of the first groove 21 gradually decreases from the first end 21s toward the second end 21t (see B in FIG. 13 ). That is, the bottom 21b of the first groove 21 slopes upward from the first end 21s toward the second end 21t. Also, in the second embodiment, the width W1 of the first groove 21 gradually decreases from the opening 21a of the first groove 21 toward the bottom 21b of the first groove 21, as in the first embodiment.

[0074] In addition, in the second embodiment, the core portion 31 of the waveguide 3 is configured similarly to the core portion 31 of the waveguide 3 of the first embodiment, except that the arrangements of the input portion 31a and the output portion 31b are interchanged. That is, in the second embodiment, the end of the waveguide 3 on the first end 21s side of the first groove 21 is the input portion 31a. Also, the end of the waveguide 3 on the second end 21t side of the first groove 21 is the output portion 31b. In the second embodiment, as in the first embodiment, the width W3 of the core portion 31 of the waveguide 3 gradually decreases from the input portion 31a side toward the output portion 31b side (see A in FIG. 13 ). Also, as in the first embodiment, the height D3 of the core portion 31 of the waveguide 3 gradually decreases from the input portion 31a side toward the output portion 31b side (see B in FIG. 13 ). That is, the bottom 31d of the core portion 31 of the waveguide 3 is inclined upward (toward the main surface 2a of the substrate 2) from the input portion 31a side toward the output portion 31b side.

[0075] The input section 31a of the core section 31 is a region of the top surface 31u of the core section 31 of the waveguide 3 that overlaps with, for example, the trapezoidal mirror 4 in the thickness direction (second axis direction T2) of the substrate 2. More specifically, the input section 31a is a region of the top surface 31u through which light (optical signal) emitted from the light emitting section 9a (described later), reflected by the mirror 4, and propagating through the core section 31 passes. The output section 31b of the core section 31 is the end of the core section 31 on the second end 21t side (i.e., the end facing one end of the optical fiber 6). Note that in A of FIG. 13 , the range of the input section 31a is positioned outside the range of the mirror 4 for convenience of drawing, but in reality, the range of the input section 31a coincides with the range of the mirror 4.

[0076] The cross-sectional area of ​​the core portion 6a of the optical fiber 6 is equal to or larger than the area of ​​the output portion 31b of the core portion 31 of the waveguide 3 (the area of ​​the output portion 31b of the core portion 31 of the waveguide 3). Desirably, the cross-sectional area of ​​the core portion 6a of the optical fiber 6 is larger than the area of ​​the output portion 31b of the core portion 31. Furthermore, when viewed from the longitudinal direction of the waveguide 3, the range of the core portion 6a of the optical fiber 6 includes the range of the output portion 31b of the core portion 31 of the waveguide 3. When the cross-sectional area of ​​the core portion 6a of the optical fiber 6 is equal to or larger than the area of ​​the output portion 31b of the core portion 31 (the area of ​​the output portion 31b of the core portion 31), the optical coupling efficiency between the core portion of the optical fiber 6 and the output portion 31b of the core portion 31 of the waveguide 3 can be improved.

[0077] The light-emitting element 9 is an element (e.g., a light-emitting diode) that emits light (optical signal). The light-emitting element 9 is arranged on the main surface 2a of the substrate 2 so as to overlap with the input portion 31a of the waveguide 3 in the thickness direction of the substrate 2 (second axis direction T2). The light-emitting element 9 has a light-emitting portion 9a. The light-emitting portion 9a is arranged above the output portion 31b of the waveguide 3. More specifically, the light-emitting portion 9a is arranged so as to overlap with the input portion 31a of the waveguide 3 in the thickness direction of the substrate 2. The area of ​​the light-emitting portion 9a is the same as or smaller than the area of ​​the input portion 31a of the waveguide 3 (the area of ​​the input portion 31a of the waveguide 3). In a plan view seen in the thickness direction of the substrate 2, the range of the light-emitting portion 9a includes the range of the input portion 31a of the core portion 31 of the waveguide 3. In this way, by arranging the light emitting portion 9a so that it overlaps with the input portion 31a of the waveguide 3 in the thickness direction of the substrate 2, even if the positioning of the light emitting portion 9a is shifted, the light (optical signal) from the light emitting portion 9a can be input to the input portion 31a with reduced optical loss.

[0078] (2-2) Description of Operation The operation of the optical module 1 according to the second embodiment (that is, the propagation of an optical signal) will be described with reference to FIG. 13B.

[0079] An optical signal C2 output from the light-emitting portion 9a of the light-emitting element 9 is input to the input portion 31a of the core portion 31 of the waveguide 3. At this time, the area of ​​the light-emitting portion 9a is the same as or smaller than the area of ​​the input portion 31a of the waveguide 3 (the area of ​​the input portion 31a of the waveguide 3), so optical loss is suppressed when input from the light-emitting portion 9a to the input portion 31a of the waveguide 3. The optical signal C2 input to the waveguide 3 propagates through the waveguide 3, is output from the output portion 31b, is reflected by the mirror 4, and is received by one end of the core portion 6a of the optical fiber 6. At this time, the width W3 (see A in FIG. 13 ) of the waveguide 3 gradually decreases from the input portion 31a side toward the output portion 31b side, so that the optical coupling efficiency between the output portion 31b of the waveguide 3 and the optical fiber 6 is improved in the width direction of the waveguide 3. Furthermore, since the height D3 of the waveguide 3 gradually decreases from the input portion 31a side toward the output portion 31b side (see B in FIG. 13), the optical coupling efficiency between the output portion 31b of the waveguide 3 and the optical fiber 6 is also improved in the height direction of the waveguide 3. Furthermore, since the area of ​​the light emitting portion 9a is the same as or smaller than the area of ​​the input portion 31a of the waveguide 3 (the area of ​​the input portion 31a of the waveguide 3) (see A in FIG. 13), the optical coupling efficiency between the light emitting portion 9a and the input portion 31a of the waveguide 3 is also improved.

[0080] (2-3) Effects The optical module 1 according to the second embodiment includes a waveguide 3, a substrate 2, a light-emitting element 9, and a mirror 4. The waveguide 3 includes a core 31 and a clad 32. The core 31 has an input portion 31a and an output portion 31b arranged at both ends in the first axis direction T1, which is the longitudinal direction. The clad 32 covers the core 31. The substrate 2 has a first groove 21. The first groove 21 has an opening 21a at its upper end and extends in the first axis direction T1. The substrate 2 has a waveguide 3 arranged in the first groove 21. The light-emitting element 9 has a light-emitting portion 9a. The light-emitting portion 9a is arranged above the input portion 31a of the core 31. The mirror 4 is located below the light-emitting portion 9a and faces the input portion 31a of the core 31. The bottom 31d of the waveguide 3 includes a slope 31dT (see FIG. 13) that slopes upward from the input portion 31a toward the output portion 31b. The bottom 21b of the first groove 21 includes a slope 21bT (see FIG. 13) that slopes upward from the first end 21s where the input portion 31a is located toward the second end 21t.

[0081] According to this configuration, the bottom 31d of the waveguide 3 slopes upward from the input portion 31a toward the output portion 31b. This allows the size of the output portion 31b of the waveguide 3 in a direction (here, the first axis direction T1) intersecting the height direction (direction of height D3) of the waveguide 3 to be further reduced. As a result, even if the size of the light emitting portion 9a is smaller than the diameter of the core portion 31 of the optical fiber 6 or the position of the light emitting portion 9a is misaligned in the direction (here, the first axis direction T1) intersecting the height direction of the waveguide 3, the optical coupling efficiency between the output portion 31b of the waveguide 3 and the optical fiber 6 can be improved. As a result, in the optical module 1, light (optical signal) is more easily transmitted from the light emitting portion 9a to the output portion 31b of the waveguide 3 in the direction (here, the first axis direction T1) intersecting the height direction of the waveguide 3, thereby improving the optical coupling efficiency.

[0082] Furthermore, in the optical module 1 according to the second embodiment, the area of ​​the light emitting portion 9 a is equal to or smaller than the area of ​​the input portion 31 a of the core portion 31. With this configuration, even if the position of the light emitting portion 9 a is misaligned, the optical coupling efficiency between the light emitting portion 9 a and the input portion 31 a of the core portion 31 of the waveguide 3 can be improved.

[0083] The optical module 1 according to the second embodiment further includes an optical fiber 6 optically coupled to the output portion 31b of the waveguide 3. The substrate 2 has a second groove 22. One end of the optical fiber 6 is disposed in the second groove 22, connected to the second end 21t of the first groove 21. The optical fiber 6 has a core 6a (optical fiber core). The core 6a faces the output portion 31b. The area of ​​the surface of the core 6a facing the output portion 31b is the same as or larger than the area of ​​the output portion 31b (the area of ​​the output portion 31b). This configuration further improves the optical coupling efficiency between the optical fiber 6 and the output portion 31b of the core 31 of the waveguide 3.

[0084] (3) Aspects The present disclosure discloses the following aspects.

[0085] The optical module (1) of the first aspect includes a waveguide (3), a substrate (2), a light-receiving element (5), and a mirror (4). The waveguide (3) includes a core portion (31) and a clad portion (32). The core portion (31) has an input portion (31a) and an output portion (31b). The input portion (31a) and the output portion (31b) are arranged at both ends in a first axis direction (T1), which is the longitudinal direction. The clad portion (32) covers the core portion (31). The substrate (2) has a first groove (21). The first groove (21) has an opening (21a) at its upper end and extends in the first axis direction (T1). The substrate (2) has a waveguide (3) arranged in the first groove (21). The light-receiving element (5) has a light-receiving portion (5a). The light receiving section (5a) is disposed above the output section (31b) of the core section (31). The mirror (4) is located below the light receiving section (5a) and faces the output section (31b) of the core section (31). The bottom (31d) of the waveguide (3) includes a sloped section (31dT) that slopes upward from the input section (31a) toward the output section (31b). The bottom (21b) of the first groove (21) includes a sloped section (21bT) that slopes upward from the second end (21t) where the input section (31a) is disposed toward the first end (21s).

[0086] According to this configuration, the bottom portion (31d) of the waveguide (3) slopes upward from the input portion (31a) to the output portion (31b). Therefore, the size (size in the first axis direction (T1)) of the output portion (31b) of the waveguide (3) intersecting the height direction (second axis direction (T2)) of the waveguide (3) can be further reduced. As a result, even if the size of the light receiving portion (5a) is smaller than the diameter of the core portion (6a) of the optical fiber (6) or the position of the light receiving portion (5a) is misaligned in the direction (first axis direction (T1)) intersecting the height direction (second axis direction (T2)) of the waveguide (3), the optical coupling efficiency between the output portion (31b) of the waveguide (3) and the light receiving portion (5a) can be improved. As a result, in the optical module (1), the optical coupling efficiency can be improved in the direction (first axis direction (T1)) intersecting the height direction of the waveguide (3).

[0087] In the optical module (1) of the second embodiment, the area of ​​the light receiving section (5a) in the first embodiment is the same as or smaller than the area of ​​the input section (31a).

[0088] This configuration can improve the optical coupling efficiency between the output portion (31b) of the core portion (31) of the waveguide (3) and the light receiving portion (5a).

[0089] In the optical module (1) of the third aspect, in the first or second aspect, the area of ​​the light receiving section (5a) is the same as or larger than the area of ​​the output section (31b).

[0090] According to this configuration, even if the position of the light receiving portion (5a) is shifted, the optical coupling efficiency between the output portion (31b) of the core portion (31) of the waveguide (3) and the light receiving portion (5a) can be further improved.

[0091] The optical module (1) of a fourth aspect is any one of the first to third aspects, further comprising an optical fiber (6) optically coupled to an input portion (31a) of the core portion (31) of the waveguide (3). The substrate (2) further has a second groove (22). The second groove (22) is connected to a second end (21t) of the first groove (21) and one end of the optical fiber (6) is disposed in the second groove (22). The optical fiber (6) has an optical fiber core portion (6a). The optical fiber core portion (6a) faces the input portion (31a) of the core portion (31) of the waveguide (3). The area of ​​the surface of the optical fiber core portion (6a) facing the input portion (31a) of the core portion (31) is the same as or smaller than the area of ​​the input portion (31a).

[0092] This configuration can improve the efficiency of optical coupling between the optical fiber (6) and the input portion (31a) of the core portion (31) of the waveguide (3).

[0093] The optical module (1) of the fifth aspect includes a waveguide (3), a substrate (2), a light-emitting element (9), and a mirror (4). The waveguide (3) includes a core portion (31) and a clad portion (32). The core portion (31) has an input portion (31a) and an output portion (31b). The input portion (31a) and the output portion (31b) are arranged at both ends in a first axis direction (T1), which is the longitudinal direction. The clad portion (32) covers the core portion (31). The substrate (2) has a first groove (21). The first groove (21) has an opening (21a) at its upper end and extends in the first axis direction (T1). The substrate (2) has a waveguide (3) arranged in the first groove (21). The light-emitting element (9) has a light-emitting portion (9a). The light emitting portion (9a) is disposed above the input portion (31a) of the core portion (31). The mirror (4) is located below the light emitting portion (9a) and faces the input portion (31a) of the core portion (31). The bottom portion (31d) of the waveguide 3 includes a sloped portion (31dT) that slopes upward from the input portion (31a) toward the output portion (31b). The bottom portion (21b) of the first groove (21) includes a sloped portion (21bT) that slopes upward from the first end (21s) where the input portion (31a) is disposed toward the second end (21t).

[0094] According to this configuration, the bottom portion (31d) of the waveguide (3) slopes upward from the input portion (31a) to the output portion (31b). Therefore, the size (size in the first axis direction (T1)) of the output portion (31b) of the waveguide (3) intersecting the height direction (second axis direction (T2)) of the waveguide (3) can be further reduced. As a result, even if the size of the light emitting portion (9a) is smaller than the diameter of the core portion (31) of the optical fiber (6) in the direction intersecting the height direction (first axis direction (T1)) of the waveguide (3), or even if the light emitting portion (9a) is misaligned, the optical coupling efficiency between the output portion (31b) of the waveguide (3) and the optical fiber (6) can be improved. As a result, the optical coupling efficiency in the direction intersecting the height direction of the waveguide (3) in the optical module (1) can be improved.

[0095] In the optical module (1) of the sixth aspect, the area of ​​the light emitting section (9a) in the fifth aspect is the same as or smaller than the area of ​​the input section (31a).

[0096] According to this configuration, even if the light emitting portion (9a) is misaligned, the optical coupling efficiency between the light emitting portion (9a) and the input portion (31a) of the core portion (31) of the waveguide (3) can be improved.

[0097] The optical module (1) of a seventh aspect is the fifth or sixth aspect, further comprising an optical fiber (6) optically coupled to the output portion (31b) of the core portion (31) of the waveguide (3). The substrate (2) has a second groove (22). The second groove (22) is connected to the second end (21t) of the first groove (21) and one end of the optical fiber (6) is disposed in the second groove (22). The optical fiber (6) has an optical fiber core portion (6a). The optical fiber core portion (6a) faces the output portion (31b) of the core portion (31). The area of ​​the surface of the optical fiber core portion (6a) facing the output portion (31b) of the core portion (31) is the same as or larger than the area of ​​the output portion (31b).

[0098] This configuration can further improve the efficiency of optical coupling between the optical fiber (6) and the output portion (31b) of the core portion (31) of the waveguide (3).

[0099] In the optical module (1) of the eighth aspect, in any one of the first to seventh aspects, the first groove (21) has a V-shaped groove portion (211) in a cross section perpendicular to the first axis direction (T1).

[0100] This configuration makes it easy to position the core portion (31) of the waveguide (3) in the width direction of the first groove (21), thereby facilitating alignment between the core portion (31) of the waveguide (3) and the light receiving portion (5 a) in the width direction of the first groove (21).

[0101] In the optical module (1) of the ninth aspect, in any one of the first to eighth aspects, the width (W1) of the first groove (21) decreases from the input section (31a) side toward the output section (31b) side, and the width (W3) of the core section (31) decreases from the input section (31a) side toward the output section (31b) side.

[0102] This configuration allows the widthwise size of the output portion (31b) of the core portion (31) of the waveguide (3) to be further reduced. As a result, even if the size of the light-receiving portion (5a) or the light-emitting portion (9a) is smaller than the diameter of the core portion (31) of the optical fiber (6) in the widthwise direction of the output portion (31b) of the core portion (31) of the waveguide (3), or even if the light-receiving portion (5a) or the light-emitting portion (9a) is misaligned, the optical coupling efficiency between the output portion (31b) of the core portion (31) of the waveguide (3) and the light-receiving portion (5a) or the light-emitting portion (9a) can be improved. As a result, in the optical module (1), the optical coupling efficiency can be improved in a direction intersecting the widthwise direction of the core portion (31) of the waveguide (3).

[0103] In the optical module (1) of the tenth aspect, in any one of the first to ninth aspects, the first groove (21) is formed in the substrate (2) by anisotropic etching.

[0104] According to this configuration, the bottom of the first groove (21) can be formed with high precision so as to be inclined toward the main surface (2a) from the input portion (31a) side toward the output portion (31b) side.

[0105] In the optical module (1) of the eleventh aspect, in any one of the first to tenth aspects, the width (W3) of the core portion (31) is smaller than the width (W1) of the opening (21a) of the first groove (21).

[0106] According to this configuration, the positional deviation of the core portion (31) of the waveguide (3) relative to the width direction of the first groove (21) can be limited to within the range of the width (W1) of the opening (21 a) of the first groove (21), thereby suppressing the positional deviation of the first groove (21) in the width direction of the core portion (31) of the waveguide (3) relative to the light receiving element (5).

[0107] In the optical module (1) of a twelfth aspect, in any one of the first to eleventh aspects, the core portion (31) of the waveguide (3) has a lower portion (311) and an upper portion (312) in the first axis direction (T1). The lower portion (311) is disposed at the bottom portion (21b) of the first groove (21) and tapers toward the bottom portion (21b) of the first groove (21). The upper portion (312) is located above the lower portion (311) in the first groove (21). Side surfaces (311c) on both sides of the lower portion (311) have the same inclination angle as side surfaces (21c) on both sides of the first groove (21) adjacent to the side surfaces (311c) on both sides of the lower portion (311). The side surfaces (312c) on both sides of the upper portion (312) have an inclination angle different from that of the side surfaces (21c) on both sides of the first groove (21) adjacent to the side surfaces (312c) on both sides of the upper portion (312).

[0108] According to this configuration, the side surfaces (311c) on both sides of the lower portion (311) have the same inclination angle as the side surfaces (21c) on both sides of the first groove (21) adjacent to the side surfaces (311c) on both sides of the lower portion (311). Therefore, the first core portion (311) can be fitted into the first groove (21) in the width direction of the first groove (21). This allows the core portion (31) of the waveguide (3) relative to the first groove (21) to be tapered downward in the width direction of the first groove (21). As a result, it is possible to reduce misalignment of the light receiving element (5) or the light emitting element (9) relative to the core portion (31) of the waveguide (3) in the width direction of the first groove (21).

[0109] DESCRIPTION OF SYMBOLS 1 Optical module 2 Substrate 2a Main surface 3 Waveguide 4 Mirror 5 Light receiving element 5a Light receiving section 6 Optical fiber 6a Core section (optical fiber core section) 6b Cladding section 9 Light emitting element 9a Light emitting section 21 First groove 21a Opening 21b Bottom section 21bT Inclined section 21s First end 21t Second end 211 V-groove section 22 Second groove 31 Core section 31a Input section 31b Output section 31d Bottom section 31dT Inclined section 311 First core section (lower section) 311c Side surface 312 Second core section (upper section) 312c Side surface L1 First section L2 Second section T1 Longitudinal direction (first axis direction) T2 Thickness direction (second axis direction) W1 Width of first groove W2 Width of second groove W3 Core width

Claims

1. An optical module comprising: a waveguide including a core portion having an input portion and an output portion located at both ends in a first axis direction which is the longitudinal direction, and a cladding portion covering the core portion; a substrate having a first groove which has an opening at the top and extends in the first axis direction, the waveguide being located in the first groove; a light-receiving element having a light-receiving portion located above the output portion of the core portion; and a mirror located below the light-receiving portion and facing the output portion of the core portion; wherein the bottom of the waveguide includes a sloped portion which slopes upward from the input portion toward the output portion, and the bottom of the first groove includes a sloped portion which slopes upward from the second end where the input portion is located toward the first end.

2. The optical module according to claim 1, wherein the area of ​​the light receiving section is equal to or smaller than the area of ​​the input section.

3. An optical module according to claim 1 or 2, wherein the area of ​​the light receiving section is equal to or larger than the area of ​​the output section.

4. An optical module according to any one of claims 1 to 3, further comprising an optical fiber optically coupled to the input portion of the core portion of the waveguide, wherein the substrate further has a second groove connected to the second end of the first groove and in which one end of the optical fiber is positioned, wherein the optical fiber has an optical fiber core portion facing the input portion of the core portion, and the area of ​​the surface of the optical fiber core portion facing the input portion of the core portion is the same as or smaller than the area of ​​the input portion.

5. An optical module comprising: a core portion having an input portion and an output portion located at both ends of a first axis which is the longitudinal direction, and a waveguide including a cladding portion covering the core portion; a substrate having a first groove which has an opening at the top and extends in the first axial direction, the substrate having the waveguide located in the first groove; a light emitting element having a light emitting portion located above the input portion of the core portion; and a mirror located below the light emitting portion and facing the input portion of the core portion; wherein the bottom of the waveguide includes a sloped portion which slopes upward from the input portion toward the output portion, and the bottom of the first groove includes a sloped portion which slopes upward from the first end where the input portion is located toward the second end.

6. The optical module according to claim 5, wherein the area of ​​the light emitting section is equal to or smaller than the area of ​​the input section.

7. An optical module as claimed in claim 5 or 6, further comprising an optical fiber optically coupled to the output portion of the core portion of the waveguide, wherein the substrate has a second groove in which one end of the optical fiber is positioned, connected to the second end in the first groove, the optical fiber has an optical fiber core portion (6a) facing the output portion of the core portion, and the area of ​​the surface of the optical fiber core portion facing the output portion of the core portion is the same as or larger than the area of ​​the output portion.

8. An optical module according to any one of claims 1 to 7, wherein the first groove has a groove portion whose cross section perpendicular to the first axis direction is V-shaped.

9. An optical module according to any one of claims 1 to 8, wherein the width of the first groove decreases from the input section side toward the output section side, and the width of the core section decreases from the input section side toward the output section side.

10. An optical module according to any one of claims 1 to 9, wherein the first groove is formed in the substrate by anisotropic etching.

11. An optical module according to any one of claims 1 to 10, wherein the width of the core portion is smaller than the width of the opening of the first groove.

12. An optical module according to any one of claims 1 to 11, wherein the core portion of the waveguide has, in the first axial direction, a lower portion disposed at the bottom of the first groove and tapering towards the bottom of the first groove, and an upper portion located above the lower portion in the first groove, wherein both side surfaces of the lower portion have the same inclination angle as both side surfaces of the first groove adjacent to both side surfaces of the lower portion, and both side surfaces of the upper portion have a different inclination angle than both side surfaces of the first groove adjacent to both side surfaces of the upper portion.

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