Waveguide and optical coupling device

1. A waveguide comprising:

first and second transmission areas which transmit an input optical signal; and

a coupling area provided between the first transmission area and the second transmission area;

wherein a width of the coupling area is less than a width of the first and second transmission areas; and

wherein each of the first transmission area, the second transmission area, and the coupling area comprises:

a core through which an optical signal is transmitted; and

a cladding layer provided on an upper portion, a lower portion, and a side surface of the core, the cladding layer having a refractive index lower than a refractive index of the core; and

wherein the coupling area weakens a mode confinement of the optical signal and at least part of the optical signal transmitted through the transmission areas is branched to a neighboring optical member;

wherein a gap between the coupling area and the neighboring optical member is approximately equal to or greater than a width of the coupling area; and

wherein a difference between the refractive index of the core and the refractive index of the cladding layer is 2 or more.

2. The waveguide as claimed in claim 1 , further comprising:

a first taper area provided between the first transmission area and the coupling area; and

a second taper area provided between the coupling area and the second transmission area;

wherein a width of the first taper area and a width of the second taper area gradually decreases from a width corresponding to a width of the first and second transmission areas to a width corresponding to a width of the coupling area.

3. The waveguide as claimed in claim 2 , wherein each of the first and second taper areas comprises:

a core through which an optical signal is transmitted; and

a cladding layer provided on a lower portion of the core and having a refractive index lower than a refractive index of the core.

4. The waveguide as claimed in claim 1 , wherein:

the core is an Si material, the cladding layer is an SiO 2 material, and the upper portion and the side surface of the core are air.

5. An optical coupling device comprising:

a first waveguide comprising at least two first transmission areas, which transmits an input optical signal, and a first coupling area disposed between the at least two first transmission areas; wherein a width of the first coupling area is less than a width of the at least two first transmission areas; and

a second waveguide disposed adjacent to the first waveguide and comprising at least two second transmission areas which transmit an input optical signal and a second coupling area disposed between the at least two second transmission areas;

wherein each of the first and second waveguides comprises:

a core through which an optical signal is transmitted; and

a cladding layer provided on a lower portion of the core and having a refractive index lower than a refractive index of the core;

wherein a difference between the refractive index of the core and the refractive index of the cladding layer is 2 or more; and

wherein the first coupling area weakens a mode confinement of the optical signal and at least part of the optical signal transmitted through the first waveguide is branched to the second waveguide, and a gap between the first coupling area and the second waveguide is approximately equal to or greater than a width of the first coupling area.

6. The optical coupling device as claimed in claim 5 , wherein the first waveguide further comprises:

at least two first taper areas disposed between the first coupling area and the at least two first transmission areas;

wherein a width of the at least two taper areas gradually decreases from a width corresponding to a width of the first transmission areas to a width corresponding to a width of the first coupling area.

7. The optical coupling device as claimed in claim 5 , wherein a width of the second coupling area is less than a width of the at least two second transmission areas.

8. The optical coupling device as claimed in claim 7 , wherein the second waveguide further comprises:

at least two second taper areas disposed between the second coupling area and the at least two second transmission areas;

wherein a width of the at least two second taper areas gradually decreases from a width corresponding to a width of the at least two second transmission areas to a width corresponding to a width of the second coupling area.

9. The optical coupling device as claimed in claim 5 , wherein the core of the first and second waveguides is formed of an Si material, the cladding layer is an SiO 2 material, and the upper portion and the side surface of the core are air.

10. The optical coupling device as claimed in claim 5 , further comprising:

a resonator, disposed between the first and second coupling areas, which transmits at least part of an optical signal transmitted through the first waveguide to the second waveguide.

11. The optical coupling device as claimed in claim 10 , wherein a spacing between the first waveguide and the ring resonator is about 0.2 μm -0.4 μm.

12. The optical coupling device as claimed in claim 10 , wherein the first waveguide further comprises:

at least two first taper areas disposed between the first coupling area and the at least two first transmission areas;

wherein a width of the at least two taper areas gradually decreases from a width corresponding to a width of the at least two first transmission areas to a width corresponding to a width of the first coupling area.

13. The optical coupling device as claimed in claim 10 , wherein a width of the second coupling area is less than a width of the at least two second transmission areas.

14. The optical coupling device as claimed in claim 13 , wherein the second waveguide further comprises:

at least two second taper areas disposed between the second coupling area and the at least two second transmission areas;

wherein a width of the at least two second taper areas gradually decreases from a width corresponding to a width of the at least two second transmission areas to a width corresponding to a width of the second coupling area.

15. The optical coupling device as claimed in claim 5 , wherein the second waveguide further comprises a Bragg grating type filter, disposed in the second coupling area, which transmits only an optical signal having a predetermined wavelength.

16. The optical coupling device as claimed in claim 15 , wherein the first waveguide further comprises:

at least two first taper areas disposed between the first coupling area and the at least two first transmission areas;

wherein a width of the at least two first taper areas gradually decreases from a width corresponding to a width of the at least two first transmission areas to a width corresponding to a width of the first coupling area.

17. The optical coupling device as claimed in claim 15 , wherein a width of the second coupling area is less than a width of the at least two second transmission areas.

18. The optical coupling device as claimed in claim 17 , wherein the second waveguide further comprises:

at least two second taper areas disposed between the second coupling area and the at least two second transmission areas;

wherein a width of the at least two second taper areas gradually decreases from a width corresponding to a width of the at least two second transmission areas to a width corresponding to a width of the second coupling area.

19. The optical coupling device as claimed in claim 5 , further comprising a modulator, disposed in the vicinity of the second waveguide, which varies a refractive index of the second wave guide by application of an electric signal.

20. The optical coupling device as claimed in claim 19 , wherein the first waveguide further comprises:

at least two first taper areas disposed between the first coupling area and the at least two first transmission areas;

wherein a width of the at least two first taper areas gradually decreases from a width corresponding to a width of the at least two first transmission areas to a width corresponding to a width of the first coupling area.

21. The optical coupling device as claimed in claim 19 , wherein a width of the second coupling area is less than a width of the at least two second transmission areas.

22. The optical coupling device as claimed in claim 21 , wherein the second waveguide further comprises:

at least two second taper areas disposed between the second coupling area and the at least two second transmission areas;

wherein a width of the at least two second taper areas gradually decreases from a width corresponding to a width of the at least two second transmission areas to a width corresponding to a width of the second coupling area.