Optical coupler

• US 7,221,825 B2
• Filed: 12/23/2003
• Issued: 05/22/2007
• Est. Priority Date: 12/23/2002
• Status: Expired due to Fees

• Current Assignee: University of Surrey
• Original Assignee: University of Surrey
• Inventors: Reed, Graham, Passaro, Vittorio, Masanovic, Goran
• Primary Examiner(s): Font; Frank G.
• Assistant Examiner(s): LEPISTO, RYAN A
• Application Number:
  US10/540,618
• Publication Number:
  US 20060120667A1
• Time in Patent Office: 1,246 Days
• Field of Search: 385/37
• US Class Current: 385/37
• CPC Class Codes: G02B 2006/12147 Coupler
• CPC Class Codes: G02B 6/12002 Three-dimensional structures
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: G02B 6/124 Geodesic lenses or integrated gratings
• CPC Class Codes: G02B 6/125 Bends, branchings or intersections

Abstract

An optical coupler comprises an input waveguide, an intermediate waveguide, an output waveguide, a first grating situated between the input and intermediate waveguides, and a second grating situated between the intermediate and output waveguides such that, in use, light propagating in the input waveguide is coupled into the intermediate waveguide with the assistance of the first grating, and thence is coupled into the output waveguide with the assistance of the second grating. The coupler is a directional coupler, in particular a dual grating-assisted directional coupler, and may be used to couple light between an optical fibre and an integrated semiconductor device, or between dissimilar waveguides.

Claims

1. An optical coupler comprising an input waveguide, an intermediate waveguide, an output waveguide, a first grating situated between the input and intermediate waveguides, and a second grating situated between the intermediate and output waveguides such that, in use, light propagating in the input waveguide is coupled into the intermediate waveguide wit the assistance of the first grating, and then is coupled into the output waveguide with the assistance of the second grating, wherein the intermediate waveguide has a higher refractive index than the input waveguide and a lower refractive index than the output waveguide.

2. A coupler according to claim 1, further comprising only two said ratings.

3. A coupler according to claim 1, which is a directional coupler.

4. A coupler according to claim 1, wherein the input and output waveguides have differing refractive indices.

5. A coupler according to claim 1, wherein the input and output waveguides have at least one differing transverse dimension.

6. A coupler according to claim 1, wherein the intermediate waveguide has at least one different transverse dimension to that of the input waveguide, or the output waveguide, or both.

7. A coupler according to claim 1, further comprising a first transitional layer situated between the input waveguide and the intermediate waveguide.

8. A coupler according to claim 1, further comprising a transitional layer situated between the output waveguide and the intermediate waveguide.

9. A coupler according to claim 8, further comprising a second transitional layer disposed between the output waveguide and the intermediate waveguide.

10. A coupler according to claim 1, wherein the first and second gratings have differing periods, or lengths, or depths, or profiles, or duty cycles, or any combination thereof.

11. A coupler according to claim 1, comprising a layered structure, in which each waveguide, grating or transitional layer comprises a respective layer or part thereof, of the structure.

12. A coupler according to claim 11, the layered structure comprises one or more layers of semiconductor material or dielectric material, or both.

14. A coupler according to claim 12, wherein the layered structure comprises one or more layers of dielectric material, wherein to dielectric material is glass.

15. A coupler according to claim 1, wherein the waveguides comprise rib waveguides, or planar waveguides, or strip waveguides, or embedded waveguides, or any combination thereof.

16. An integrated optical device comprising an optical coupler according to claim 1, wherein the input waveguide or the output waveguide of the coupler comprises a semiconductor waveguide of the device.

17. A device according to claim 16, wherein the semiconductor waveguide of the device comprises a semiconductor laser of the device.

18. A device according to claim 16, wherein the semiconductor waveguide of the device comprises a photodiode of the device.

19. The use of an optical coupler or device according to claim 1, to couple light between an external first waveguide and the output waveguide of the coupler, via the input waveguide of the coupler.

20. The use according to claim 19, wherein the external first waveguide comprises an optical fibre.

13. A coupler according to claim l2, wherein the layered structure comprises one or more layers of semiconductor material, wherein the semiconductor material comprises one or more of:

silicon or related compounds;

gallium arsenide or related compounds;

indium phosphide or related compounds;

or lithium niobate or related compounds.