Merging optical waveguides having branch angle within a specific range

• US 6,243,516 B1
• Filed: 02/09/1999
• Issued: 06/05/2001
• Est. Priority Date: 02/23/1998
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Seino, Minoru
• Primary Examiner(s): Lee, John D.
• Assistant Examiner(s): CONNELLY, MICHELLE R
• Application Number:
  US09/246,965
• Time in Patent Office: 847 Days
• Field of Search: 385/39, 385/42, 385/45, 385/47, 385/50, 385/31, 385/27, 385/24, 385/15, 385/14, 385/43
• US Class Current: 385/47
• CPC Class Codes: G02B 2006/12104 Mirror; Reflectors or the like
• CPC Class Codes: G02B 2006/12107 Grating
• CPC Class Codes: G02B 2006/12109 Filter
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/125 Bends, branchings or intersections
• CPC Class Codes: G02B 6/29361 Interference filters, e.g. multilayer coatings, thin film filters, dichroic splitters or mirrors based on multilayers, WDM filters
• CPC Class Codes: G02B 6/29368 Light guide comprising the filter, e.g. filter deposited on a fibre end G02B6/29359 takes precedence

Abstract

An optical waveguide device having a folded waveguide structure on a semiconductor substrate. The optical waveguide device includes first and second single mode optical waveguides formed on a semiconductor substrate. The first and second optical waveguides merge together into a merging optical waveguide. A reflector is positioned so that light travelling through the first optical waveguide into the merging optical waveguide is reflected by the reflector to travel through the second optical waveguide. A total reflection complementary angle for the light traveling through the first optical waveguide is θ_c, and a branch angle θ_b of the first and second optical waveguides is less than or equal to 0.55θ_c.

Claims

1. An apparatus comprising:

first and second optical waveguides merging together into a merging optical waveguide; and

a reflector positioned so that light travelling through the first optical waveguide into the merging optical waveguide is reflected by the reflector to travel through the second optical waveguide, wherein a total reflection complementary angle for the light traveling through the first optical waveguide is θ

_c, and a branch angle θ

_b of the first and second optical waveguides is less than or equal to 0.55θ

_c.

2. An apparatus as in claim 1, wherein the first and second optical waveguides, and the merging optical waveguide, are formed on a substrate.

3. An apparatus as in claim 2, wherein the first and second optical waveguides are single mode optical waveguides.

4. An apparatus as in claim 2, wherein the total reflection complementary angle θ

_c is based on a difference in refractive indexes between the first and second optical waveguides and the substrate.

5. An apparatus as in claim 2, wherein the width, shape and refractive-index distribution of the merging optical waveguide, and an incident angle of the first and second optical waveguides relative to the merging optical waveguide, together cause less than −

15 dB of the light reflected by the reflector to be reflected back to the first optical waveguide.

6. An apparatus as in claim 2, wherein the substrate is one of the group consisting of LiNbO₃ and Si.

7. An apparatus as in claim 1, wherein the reflector is positioned at an end of the merging optical waveguide.

8. An apparatus as in claim 1, wherein less than −

15 dB of the light reflected by the reflector is reflected back to the first optical waveguide.

9. An apparatus as in claim 1, wherein a construction of the merging optical waveguide and an incident angle of the first and second optical waveguides relative to the merging optical waveguide together cause less than −

15 dB of the light reflected by the reflector to be reflected back to the first optical waveguide.

10. An apparatus as in claim 1, wherein the width, shape and refractive-index distribution of the merging optical waveguide, and an incident angle of the first and second optical waveguides relative to the merging optical waveguide, together cause less than −

15 dB of the light reflected by the reflector to be reflected back to the first optical waveguide.

11. An apparatus as in claim 1, wherein the first and second optical waveguides are birefringence type optical waveguides, and less than −

15 dB of the light reflected by the reflector is reflected back to the first optical waveguide for both TE polarized light and TM polarized light.

12. An apparatus as in claim 1, wherein

the first and second optical waveguides are birefringence type optical waveguides, and

the width, shape and refractive-index distribution of the merging optical waveguide, and an incident angle of the first and second optical waveguides relative to the merging optical waveguide, together cause less than − 15 dB of the light reflected by the reflector to be reflected back to the first optical waveguide for both TE polarized light and TM polarized light.

13. An apparatus as in claim 1, wherein the reflector allows light to pass partially therethrough.

14. An apparatus as in claim 13, wherein the reflector is formed by one of the group consisting of an optical waveguide filter, a half-mirror and a polarization mirror.

15. An apparatus as in claim 13, further comprising an optical waveguide which guides light passing through the reflector.

16. An apparatus as in claim 13, further comprising:

a third optical waveguide on an opposite side of the reflector as the first and second optical waveguides so that light travelling through the third optical waveguide passes through the reflector and travels to either the first or second optical waveguide.

17. An apparatus as in claim 13, further comprising:

third and fourth optical waveguides on an opposite side of the reflector as the first and second optical waveguides so that light travelling through the third optical waveguide passes through the reflector and travels to one of the first and second optical waveguides and light travelling through the fourth optical waveguide passes through the reflector and travels to the other of the first and second optical waveguides.

18. An apparatus as in claim 13, further comprising:

third and fourth optical waveguides on an opposite side of the reflector as the first and second optical waveguides, wherein the width, shape and refractive-index distribution of the third and fourth optical waveguides, and a branching angle between the third and fourth optical waveguides, together cause light travelling through the third optical waveguide to pass through the reflector and travel to one of the first and second optical waveguides and cause light travelling through the fourth optical waveguide to pass through the reflector and travel to the other of the first and second optical waveguides.

19. An apparatus as in claim 1, wherein the apparatus is a folded optical waveguide structure provided as an optical waveguide in one of the group consisting of an optical switch, an optical modulator and an optical filter.

20. An apparatus as in claim 1, wherein the branch angle θ

_b is less than or equal to 0.3θ

_c.

21. An apparatus as in claim 1, wherein the branch angle θ

_b is in the range of 0.1°

≦

θ

_b ≦

1.5°

.

22. An apparatus as in claim 1, wherein the branch angle θ

_b is in the range of 0.3°

≦

θ

_b≦

0.8°

.

23. An apparatus as in claim 1, wherein the reflector is positioned beyond an intersection point of a center line of the first optical waveguide and a center line of the second optical waveguide.

24. An apparatus as in claim 1, wherein the length of the merging optical waveguide travelled by the light from the first optical waveguide causes substantially all of the light travelling through the first optical waveguide and reflected by the reflector to travel to the second optical waveguide.

25. An apparatus comprising:

first and second optical waveguides merging together into a merging optical waveguide, the first and second optical waveguides and the merging optical waveguide being formed on a substrate; and

a reflector positioned so that light travelling through the first optical waveguide and into the merging optical waveguide is reflected by the reflector to travel through the second optical waveguide, wherein a total reflection complementary angle based on a difference in refractive indexes between the first and second optical waveguides and the substrate is θ

_c, and a branch angle θ

_b of the first and second optical waveguides is less than or equal to 0.55θ

_c.

26. An apparatus as in claim 25, wherein the reflector is positioned at an end of the merging optical waveguide.

27. An apparatus as in claim 25, wherein the first and second optical waveguides are single mode optical waveguides.

28. An apparatus as in claim 25, wherein less than −

15 dB of the light reflected by the reflector is reflected back to the first optical waveguide.

29. An apparatus as in claim 25, wherein a construction of the merging optical waveguide and an incident angle of the first and second optical waveguides relative to the merging optical waveguide together cause less than −

15 dB of the light reflected by the reflector to be reflected back to the first optical waveguide.

30. An apparatus as in claim 25, wherein the first and second optical waveguides are birefringence type optical waveguides, and less than −

15 dB of the light reflected by the reflector is reflected back to the first optical waveguide for both TE polarized light and TM polarized light.

31. An apparatus as in claim 25, wherein

the first and second optical waveguides are birefringence type optical waveguides, and

the width, shape and refractive-index distribution of the merging optical waveguide, and an incident angle of the first and second optical waveguides relative to the merging optical waveguide, together cause less than − 15 dB of the light reflected by the reflector to be reflected back to the first optical waveguide for both TE polarized light and TM polarized light.

32. An apparatus as in claim 25, wherein the reflector allows light to pass partially therethrough.

33. An apparatus as in claim 32, further comprising:

a third optical waveguide on an opposite side of the reflector as the first and second optical waveguides so that light travelling through the third optical waveguide passes through the reflector and travels to either the first or second optical waveguide.

34. An apparatus as in claim 32, further comprising:

third and fourth optical waveguides on an opposite side of the reflector as the first and second optical waveguides so that light travelling through the third optical waveguide passes through the reflector and travels to one of the first and second optical waveguides and light travelling through the fourth optical waveguide passes through the reflector and travels to the other of the first and second optical waveguides.

35. An apparatus as in claim 25, wherein the reflector is one of the group consisting of an optical waveguide filter, a half-mirror and a polarization mirror.

36. An apparatus as in claim 25, wherein the apparatus is a folded optical waveguide structure provided as an optical waveguide in one of the group consisting of an optical switch, an optical modulator and an optical filter.

37. An apparatus as in claim 25, wherein the branch angle θ

_b is less than or equal to 0.3θ

_c.

38. An apparatus as in claim 25, wherein the branch angle θ

_b in the range of 0.1°

≦

θ

_b≦

1.5°

.

39. An apparatus as in claim 25, wherein the branch angle θ

_b is in the range of 0.3°

≦

θ

_b≦

0.8°

.

40. An apparatus as in claim 25, wherein the substrate is one of the group consisting of LiNbO₃ and Si.

41. An apparatus as in claim 25, wherein the reflector is positioned beyond an intersection point of a center line of the first optical waveguide and a center line of the second optical waveguide.

42. An apparatus as in claim 25, wherein the length of the merging optical waveguide travelled by the light from the first optical waveguide causes substantially all of the light travelling through the first optical waveguide and reflected by the reflector to travel to the second optical waveguide.

43. An apparatus comprising:

first and second optical waveguides merging together into a merging optical waveguide;

a reflector positioned so that light travelling through the first optical waveguide into the merging optical waveguide is reflected by the reflector to travel through the second optical waveguide, a branch angle θ

_b of the first and second optical waveguides being less than or equal to 0.55θ

_c, where θ

_c is a total reflection complementary angle for the light traveling through the first optical waveguide; and

third and fourth optical waveguides on an opposite side of the reflector as the first and second optical waveguides, the reflector having transmission characteristics and positioned so that light travelling through the third optical waveguide passes through the reflector and travels to one of the first and second optical waveguides and light travelling through the fourth optical waveguide passes through the reflector and travels to the other of the first and second optical waveguides.

44. An apparatus as in claim 43, wherein the reflector is formed by one of the group consisting of an optical waveguide filter, a half-mirror and a polarization mirror.

45. An apparatus as in claim 43, wherein the first, second, third and fourth optical waveguides, and the merging optical waveguide, are formed on a substrate.

46. An apparatus as in claim 45, wherein the substrate is one of the group consisting of LiNbO₃ and Si.

47. An apparatus as in claim 43, wherein the first and second optical waveguides are single mode optical waveguides.

48. An apparatus as in claim 43, wherein the branch angle θ

_b is less than or equal to 0.3θ

_c.

49. An apparatus as in claim 43, wherein the branch angle θ

_b is in the range of 0.1°

≦

θ

_b23 1.5°

.

50. An apparatus as in claim 43, wherein the branch angle θ

_b is in the range 0.3°

≦

θ

_b≦

0.8°

.

51. An apparatus comprising:

a substrate;

first and second optical waveguides merging together into a merging optical waveguide, the first and second optical waveguides and the merging optical waveguide being on the substrate; and

a reflector positioned so that light travels through the first optical waveguide into the merging optical waveguide, then through the merging optical waveguide to the reflector, and is then reflected by the reflector to travel through the second optical waveguide, wherein the reflector is positioned beyond an intersection point of a center line of the first optical waveguide and a center line of the second optical waveguide, a total reflection complementary angle for the light traveling through the first optical waveguide is Θ

_c, and a branch angle Θ

_b of the first and second optical waveguides is less than or equal to 0.55Θ

_c.

52. An apparatus comprising:

a substrate;

first and second optical waveguides merging together into a merging optical waveguide, the first and second optical waveguides and the merging optical waveguide being on the substrate; and

a reflector positioned so that light travels through the first optical waveguide into the merging optical waveguide, then through the merging optical waveguide to the reflector, and is then reflected by the reflector to travel through the second optical waveguide, wherein the reflector is positioned beyond an intersection point of a center line of the first optical waveguide and a center line of the second optical waveguide, and the branch angle Θ

_b is less than or equal to 0.3Θ

_c, wherein Θ

_c is a total reflection complementary angle for the light traveling through the first optical waveguide.

53. An apparatus comprising:

a substrate;

first and second optical waveguides merging together into a merging optical waveguide, the first and second optical waveguides and the merging optical waveguide being on the substrate; and

a reflector positioned so that light travels through the first optical waveguide into the merging optical waveguide, then through the merging optical waveguide to the reflector, and is then reflected by the reflector to travel through the second optical waveguide, wherein the reflector is positioned beyond an intersection point of a center line of the first optical waveguide and a center line of the second optical waveguide, and the branch angle Θ

_b is in the range of 0.1°

≦

Θ

_b≦

1.5°

.

54. An apparatus comprising:

a substrate;

first and second optical waveguides merging together into a merging optical waveguide, the first and second optical waveguides and the merging optical waveguide being on the substrate; and

a reflector positioned so that light travels through the first optical waveguide into the merging optical waveguide, then through the merging optical waveguide to the reflector, and is then reflected by the reflector to travel through the second optical waveguide, wherein the reflector is positioned beyond an intersection point of a center line of the first optical waveguide and a center line of the second optical waveguide, and the branch angle Θ

_b is in the range of 0.3°

≦

Θ

_b≦

0.8°

.

55. An apparatus comprising:

a substrate;

first and second optical waveguides merging together into a merging optical waveguide, the first and second optical waveguides and the merging optical waveguide being formed on the substrate; and

a reflector positioned so that light travels through the first optical waveguide and into the merging optical waveguide, then through the merging optical waveguide to the reflector, and is then reflected by the reflector to travel through the second optical waveguide, wherein the length of the merging optical waveguide travelled by the light from the first optical waveguide to the reflector causes substantially all of the light travelling through the first optical waveguide and reflected by the reflector to travel to the second optical waveguide, a total reflection complementary angle for the light traveling through the first optical waveguide is Θ

_c, and a branch angle Θ

_b of the first and second optical waveguides is less than or equal to 0.55Θ

_c.

56. An apparatus comprising:

a substrate;

first and second optical waveguides merging together into a merging optical waveguide, the first and second optical waveguides and the merging optical waveguide being formed on the substrate; and

a reflector positioned so that light travels through the first optical waveguide and into the merging optical waveguide, then through the merging optical waveguide to the reflector, and is then reflected by the reflector to travel through the second optical waveguide, wherein the length of the merging optical waveguide travelled by the light from the first optical waveguide to the reflector causes substantially all of the light travelling through the first optical waveguide and reflected by the reflector to travel to the second optical waveguide, and the branch angle Θ

_b is less than or equal to 0.3Θ

_c, wherein Θ

_c is a total reflection complementary angle for light traveling through the first optical waveguide.

57. An apparatus comprising:

a substrate;

first and second optical waveguides merging together into a merging optical waveguide, the first and second optical waveguides and the merging optical waveguide being formed on the substrate; and

a reflector positioned so that light travels through the first optical waveguide and into the merging optical waveguide, then through the merging optical waveguide to the reflector, and is then reflected by the reflector to travel through the second optical waveguide, wherein the length of the merging optical waveguide travelled by the light from the first optical waveguide to the reflector causes substantially all of the light travelling through the first optical waveguide and reflected by the reflector to travel to the second optical waveguide, and the branch angle Θ

_b is in the range of 0.1°

≦

Θ

_b≦

1.5°

.

58. An apparatus comprising:

a substrate;

first and second optical waveguides merging together into a merging optical waveguide, the first and second optical waveguides and the merging optical waveguide being formed on the substrate; and

a reflector positioned so that light travels through the first optical waveguide and into the merging optical waveguide, then through the merging optical waveguide to the reflector, and is then reflected by the reflector to travel through the second optical waveguide, wherein the length of the merging optical waveguide travelled by the light from the first optical waveguide to the reflector causes substantially all of the light travelling through the first optical waveguide and reflected by the reflector to travel to the second optical waveguide, and the branch angle Θ

_b is in the range of 0.3°

≦

Θ

_b≦

0.8°

.