Optical waveguide device and optical integrated circuit that includes optical waveguide device

1. An optical waveguide device having a function of removing or suppressing a higher-order none component of propagating light, the optical waveguide device comprising:

a curved waveguide having a curved shape where curvature continuously changes, wherein

a first waveguide is coupled to one end of the curved waveguide,

a second waveguide is coupled to the other end of the curved waveguide,

a curvature of the first waveguide and the curvature of the curved waveguide are equal to each other in a coupling point in which the first waveguide is coupled to the curved waveguide, and

a curvature of the second waveguide and the curvature of the curved waveguide are equal to each other in a coupling point in which the second waveguide is coupled to the curved waveguide.

2. The optical waveguide device according to claim 1 , wherein

the curvature of the curved waveguide is zero in the coupling point in which the first waveguide is coupled to the curved waveguide, and

the curvature of the curved waveguide is zero in the coupling point in which the second waveguide is coupled to the curved waveguide.

3. The optical waveguide device according to claim 1 , wherein

the curved waveguide includes a first transition curve waveguide coupled to the first waveguide, a second transition curve waveguide coupled to the second waveguide, and an arc waveguide formed between the first transition curve waveguide and the second transition curve waveguide.

4. The optical waveguide device according to claim 3 , wherein

a curvature of the first transition curve waveguide and a curvature of the arc waveguide are equal to each other in a coupling point in which the first transition curve waveguide is coupled to the arc waveguide, and

a curvature of the second transition curve waveguide and the curvature of the arc waveguide are equal to each other in a coupling point in which the second transition curve waveguide is coupled to the arc waveguide.

5. The optical waveguide device according to claim 1 , wherein

the curved waveguide is a multi-mode waveguide through which basic mode light and higher-order mode light propagate.

6. The optical waveguide device according to claim 1 , wherein

the curved waveguide is a single mode waveguide though which only basic mode light propagates.

7. The optical waveguide device according to claim 1 , further comprising:

a second curved waveguide having a curved shape where a curvature continuously changes, wherein

the second waveguide is coupled to one end of the second curved waveguide,

a third waveguide is coupled to the other end of the second curved waveguide,

the curvature of the second waveguide and the curvature of the second curved waveguide are equal to each other in a coupling point in which the second waveguide is coupled to the second curved waveguide, and

a curvature of the third waveguide and the curvature of the second curved waveguide are equal to each other in a coupling point which the third waveguide coupled to the second curved waveguide.

8. The optical waveguide device according to claim 7 , wherein

a direction in which light propagates via the first waveguide is orthogonal to a direction in which the light propagates via the second waveguide, and

the direction in which the light propagates via the second waveguide is orthogonal to a direction in which the light propagates via the third waveguide.

9. An optical waveguide device having a function of removing or suppressing a higher-order mode component of propagating light, the optical waveguide device comprising:

a curved waveguide having a curved shape where curvature continuously changes, wherein

an input waveguide is coupled to one end of the curved waveguide,

an optical device is coupled to the other end of the curved waveguide, and

a curvature of the input waveguide and the curvature of the curved waveguide are equal to each other in a coupling point in which the input waveguide is coupled to the curved waveguide.

10. An optical waveguide device having a function of removing or suppressing a higher-order mode component of propagating Light, the optical waveguide device comprising:

N curved waveguides coupled in series, N being an integer larger than one, wherein

each of the curve waveguides has a curved shape where a curvature continuous changes,

a first waveguide is coupled to one end of a first curved waveguide among the N curved waveguides,

the curvature of the first curved waveguide and a curvature of the first waveguide are equal to each other the one end of the first curved waveguide,

one end of an ith (1<i≤N) curved waveguide among the N curved waveguides is coupled to the other end of an i-1th curved waveguide among the N curved waveguides, and

the curvature of the i-1th curved waveguide and the curvature of the i-1th curved waveguide are equal to each other in a coupling point in which the ith curved waveguide is coupled to the i-1th curved waveguide.

11. The optical waveguide device according to claim 10 , wherein

a second waveguide is coupled to the other end of an Nth curved waveguide among the N curved waveguides, and

the curvature of the Nth curved waveguide and curvature of the second waveguide are equal to each other at the other end of the Nth curved waveguide.

12. The optical waveguide device according to claim 10 , wherein

an optical device is coupled to the other end of the Nth curved way guide.

13. The optical waveguide device according claim 10 , wherein

the one end of the ith curved waveguide is coupled to the other end of the i-1th curved waveguide via a linear waveguide.

14. An optical integrated circuit comprising:

a first waveguide;

a curved waveguide coupled to the first waveguide and configured to have a function of removing or suppressing a higher-order mode component of propagating light;

a second waveguide coupled to the curved waveguide; and

an optical device coupled to the second waveguide, wherein

a curvature of the first waveguide and a curvature of the curved waveguide are equal to each other in a coupling point in which the first waveguide is coupled to the curved waveguide, and

a curvature of the second waveguide and the curvature of the curved waveguide are equal to each other in a coupling point in which the second waveguide is coupled to the curved waveguide.

15. The optical integrated circuit according to claim 14 , wherein

the optical device is a 1×2 optical coupler or a 2×2 optical coupler.

16. The optical integrated circuit according to claim 14 , wherein

the optical device is a tapered waveguide where a width of a core continuously changes in a propagation direction of the light,

a cross-sectional shape of the tapered waveguide is asymmetry in a direction perpendicular to a substrate with the tapered waveguide formed, and

when a first effective refractive index indicative of an effective refractive index of a TE0 mode is larger than a second effective refractive index indicative of an effective refractive index of a TEm (m≥1) mode in an input end of the tapered waveguide, the first effective refractive index is smaller than the second effective refractive index in an output end of the tapered waveguide, and when the first effective refractive index is smaller than the second effective refractive index the input end, the first effective refractive index is larger than the second effective refractive index in the output end.

17. An optical integrated circuit comprising:

an input waveguide;

a curved waveguide coupled to the input waveguide and configured to have a function of removing or suppressing a higher-order mode component of propagating light; and

an optical device coupled to the curved waveguide, wherein

a curvature of the input waveguide and a curvature of the curved waveguide are equal to each other in a coupling point in which the input waveguide is coupled to the curved waveguide.

18. An optical integrated circuit comprising:

a first optical device;

a second optical device;

a first curved waveguide provided between the first optical device and the second optical device and configured to have a function of removing or suppressing a higher-order mode component of propagating light; and

a second curved waveguide provided between the first optical device and the second optical device and configured to have the function of removing or suppressing the higher-order mode component of propagating light, wherein

the first curved waveguide and the second curved waveguide are coupled in series between the first optical device and the second optical device,

each of the first curved waveguide and the second curved waveguide has a curved shape where a curvature continuously changes,

a first waveguide is coupled to one end of the first curved waveguide,

the curvature of the first curved waveguide and a curvature of the first waveguide are equal to each other in a coupling point in which the first curved waveguide is coupled to the first waveguide,

the curvature of the first curved waveguide and the curvature of the second curved waveguide are equal to each other in a coupling point in which the other end of the first curved waveguide is coupled to one end of the second curved waveguide,

a second waveguide is coupled to the other end of the second curved waveguide, and

the curvature of the second curved waveguide and a curvature of the second waveguide are equal to each other is a coupling point in which the second curved waveguide is coupled to the second waveguide.