OPTICAL MODULE

1 . An optical module comprising:

a block attached to an end part of an optical fiber, the block including a front face from which a tip face of the optical fiber is exposed;

a waveguide substrate in which an optical waveguide is embedded, the waveguide substrate including a side face from which a tip face of the optical waveguide is exposed, the side face facing the front face of the block, a top part of the front face protruding upward from the side face, the optical fiber and the optical waveguide aligning on a coinciding optical axis;

a base substrate including a top face to which a bottom face of the waveguide substrate is fixed, the base substrate including a sticking-out part protruding under the block from the waveguide substrate, the top face facing the bottom face of the block; and

an adhesive bonding the block to the waveguide substrate and the base substrate,

the adhesive including a top segment located at a corner section delineated by the top part of the front face of the block and a top face of the waveguide substrate, the adhesive including a middle segment interposed between the front face of the block and the side face of the waveguide substrate, the adhesive including a bottom segment interposed between the bottom face of the block and a top face of the base substrate.

2 . The optical module according to claim 1 , wherein a spacing between the bottom face of the block and the top face of the base substrate is greater than a spacing between the bottom face of the waveguide substrate and the top face of the base substrate.

3 . The optical module according to claim 2 , wherein the bottom face of the block is positioned higher than the bottom face of the waveguide substrate.

4 . The optical module according to claim 3 , wherein the top face of the base substrate is flat under the block and the waveguide substrate.

5 . The optical module according to claim 2 , wherein the bottom face of the block is positioned lower than the bottom face of the waveguide substrate.

6 . The optical module according to claim 5 , wherein the top face of the base substrate is lower under the block than under the waveguide substrate.

7 . The optical module according to claim 1 , further comprising an adhesive layer interposed between the waveguide substrate and the base substrate,

the top face of the base substrate including a groove,

an end part of the adhesive layer being positioned inside the groove.

8 . The optical module according to claim 7 , wherein the groove extends along a bottom edge of the side face of the waveguide substrate.

9 . The optical module according to claim 8 , wherein the groove faces the bottom face of the waveguide substrate.

10 . The optical module according to claim 8 , wherein the groove faces the bottom face of the block.

11 . The optical module according to claim 8 , wherein the groove is directly below the side face of the waveguide substrate.

12 . The optical module according to claim 1 , wherein

the block includes some blocks,

the optical waveguide embedded in the waveguide substrate includes some optical waveguides, and

the optical fiber to which each of the blocks is attached is one or more optical fibers.

13 . The optical module according to claim 12 , wherein the top face of the base substrate includes a projection between an adjacent pair of the blocks.

14 . The optical module according to claim 13 , wherein the adhesive does not reach up to the projection.

15 . The optical module according to claim 12 , wherein the top face of the base substrate includes a recess between an adjacent pair of the blocks.

16 . The optical module according to claim 15 , wherein

the top face of the base substrate includes an edge adjacent to the recess, and

a tip of a bottom face of the adhesive aligns with the edge.

17 . The optical module according to claim 12 , wherein

the base substrate includes a main body to which the waveguide substrate is fixed,

the base substrate includes some protrusions protruding from the main body,

the base substrate includes a cut-out between an adjacent pair of the protrusions, and

the blocks are bonded to the respective protrusions.

18 . The optical module according to claim 17 , wherein

the top face of the base substrate includes an edge adjacent to the cut-out, and

a tip of a bottom face of the adhesive aligns with the edge.

19 . The optical module according to claim 17 , wherein each of the blocks is at a center of a corresponding one of the protrusions in a direction in which the protrusions line up.

20 . The optical module according to claim 1 , wherein

the block includes a lower substrate bonded to the base substrate and an upper substrate on the lower substrate,

the optical fiber is sandwiched between the lower substrate and the upper substrate, and

the lower substrate is thinner than the upper substrate.

21 . The optical module according to claim 20 , wherein the upper substrate includes a V-groove, located on a surface facing the lower substrate, in which the optical fiber is placed.

22 . The optical module according to claim 20 , wherein the lower substrate is shorter, in length from the front face of the block, than the upper substrate.

23 . The optical module according to claim 22 , further comprising a bonding material that bonds the upper substrate and the lower substrate,

the upper substrate including a sticking-out undersurface protruding from the lower substrate,

the lower substrate including a rear end face opposite to the front face,

part of the bonding material being located at a corner section delineated by the sticking-out undersurface and the rear end face.

24 . The optical module according to claim 23 , wherein the base substrate is of a length that prevents overlap with the part of the bonding material.

25 . The optical module according to claim 1 , wherein

the block is made of a light transmissive material, and

the adhesive is a light-curable adhesive.

26 . The optical module according to claim 1 , wherein the adhesive is greater in thermal expansion coefficient than the base substrate.