Optical waveguide and manufacturing method of optical waveguide

1. An optical waveguide having a first rib and a second rib being provided on a slab layer along one direction from one side to the other side, and a barrier layer being connected between said first rib and said second rib, comprising:

said first rib including a first taper part having a width widening from a first end in said one side to a second end connected with said barrier layer;

said second rib including a first layer and a second layer laminated on a face of said slab layer in turn;

said first layer having an approximately same width as said second end and being of a shape having one of a same width and a width widening from a third end being connected with said barrier layer to a fourth end in said other side;

said second layer having a second taper part having a width widening from a fifth end in said one side to a sixth end; and

both of one end and the other end of said barrier layer in said one direction having a width wider than said second end and said third end.

2. The optical waveguide according to claim 1 , wherein said fifth end touches a step existing in an upper surface of said barrier layer in a height direction.

3. The optical waveguide according to claim 1 , wherein said sixth end is formed in a manner being aligned with said fourth end.

4. The optical waveguide according to claim 1 , wherein upper surfaces of said first rib and said first layer in a height direction are in nearly a same surface.

5. The optical waveguide according to claim 1 , further comprising a first joint being extended from said first end with an approximately same width.

6. The optical waveguide according to claim 5 connected with an optical functional device by said first joint.

7. The optical waveguide according to claim 1 , wherein said sixth end has an approximately same width as said fourth end.

8. The optical waveguide according to claim 7 , further comprising a second joint being extended from said sixth end and said fourth end with an approximately same width.

9. The optical waveguide according to claim 8 connected with an optical fiber by said second joint.

10. The optical waveguide according to claim 1 , wherein a cross section of said first end in a laminated part of said first rib and said slab layer is approximately 1 μm square.

11. The optical waveguide according to claim 1 , wherein a cross section of said first end has approximately a same shape as a cross section of an optical waveguide of an optical functional device to be connected.

12. The optical waveguide according to claim 1 , wherein width and height of a cross section in a laminating direction in said fourth end and said sixth end in a laminated part of said first layer, said second layer and said slab layer is 4-7 μm.

13. The optical waveguide according to any one of claim 1 , wherein a width of said third end is 10-20 times as large as a width of said fifth end.

14. The optical waveguide according to claim 1 , wherein said first rib, said second rib and said slab layer are silicon.

15. The optical waveguide according to claim 1 , wherein a width of said third end is made to be wide relative to a thickness of said barrier layer.

16. A manufacturing method of an optical waveguide, comprising the steps of:

forming a first rib in a core layer of a substrate, said substrate having said core layer arranged on a cladding layer;

forming a protection layer for covering said first rib and an area neighboring said first rib among areas of said core layer not including said first ribs;

forming an additional core layer onto said core layer not covered by said protection layer; and

forming a second rib having a first layer and a second layer by applying multiple-stage etching to said additional core.

17. The manufacturing method of the optical waveguide according to claim 16 , wherein said additional core layer is formed in contact with said protection layer.