Waveguide device incorporating a light pipe

1. A waveguide apparatus comprising:

a light guide device comprising a light pipe having a set of one or more reflecting surfaces disposed around an optical axis configured to guide light from a first end along a spiral-like total internal reflection path therethrough to a second end such that the light is expanded along a first direction parallel to said optical axis;

a fold grating in optical contact with an elongate portion of at least one reflecting surface of the set of said reflecting surfaces;

an optical waveguide defining a plane in optical contact with said fold grating; and

a coupling grating in optical contact with said light pipe to couple incident light into said light pipe, said coupling grating having a non zero degree grating vector angle with respect to said optical axis such that incident light is coupled into said light pipe along a spiral-like total internal reflection path around said optical axis by said coupling grating,

wherein said coupling grating is configured such that said light spiraling within said light pipe is on-Bragg with said fold grating, and

wherein said fold grating is tilted around an axis perpendicular to the plane of said optical waveguide such that it is configured to extract at least a portion of said light guided through said light pipe along the at least one reflecting surface in optical contact with said folding grating such that the extracted light is coupled into said optical waveguide and directs said extracted light principally in a direction orthogonal to the first direction along a path of total internal reflection within said optical waveguide.

2. The apparatus of claim 1 , wherein said fold grating is configured to extract light uniformly along an output edge of said fold grating while limiting the amount of light emerging from a side edge of said fold grating.

3. The apparatus of claim 1 , wherein said reflecting surfaces comprises abutting elongate elements mutually inclined at a common angle, wherein at least one said elongate element in optical contact with said fold grating such that the elongated reflecting surfaces remain equidistant from the optical axis of the light pipe.

4. The apparatus of claim 1 further comprising, disposed along the optical path between said light pipe and optical waveguide, at least one element selected from the group of a beam splitter, an evanescent coupling optical medium and a gradient index optical medium.

5. The apparatus of claim 1 , wherein said fold grating is a surface relief grating.

6. The apparatus of claim 1 , wherein said fold grating couples light characterized by at least one optical characteristic selected from the group of angular range, wavelength range or polarization state.

7. The apparatus of claim 1 , wherein said fold grating is selected from the group consisting of a Bragg grating, a switchable Bragg grating or an array of selectively switchable elements, and is recorded to provide a grating selected from the group consisting of a HPDLC grating, uniform modulation grating or reverse mode HPDLC grating.

8. The apparatus of claim 1 , wherein said fold grating has at least one characteristic selected from the group of spatially-varying thickness, spatially-varying diffraction efficiency, or spatially-varying k-vector directions.

9. The apparatus of claim 1 , wherein the optical medium of said light pipe is at least one material selected from the group of air, optical refractive material or a gradient index material.

10. The apparatus of claim 1 , wherein said optical waveguide contains a grating operative to one of either extract light propagating therethrough out of the optical waveguide or couple-in light from outside the optical waveguide.

11. The apparatus of claim 1 , wherein said optical waveguide contains a grating having a reciprocal diffractive relationship with said coupling grating.

12. The apparatus of claim 1 , wherein said light pipe coupling grating couples light modulated with temporally varying angularly distributed information content into said light pipe.

13. The apparatus of claim 1 , wherein said light guide device further comprises a light pipe outcoupling grating in optical contact with said light pipe, wherein said outcoupling grating couples data modulated light out of said light pipe.

14. The apparatus of claim 1 , wherein said light pipe is divided into two elongate portions by a light coupling element, and wherein said light coupling element is a beamsplitter layer.

15. The apparatus of claim 1 , wherein said light pipe is curved.

16. A waveguide apparatus comprising:

a light guide device comprising a light pipe having a set of one or more reflecting surfaces disposed around an optical axis configured to guide light from a first end along a spiral-like total internal reflection path therethrough to a second end such that the light is expanded along a first direction parallel to said optical axis;

a fold grating in optical contact with an elongate portion of at least one reflecting surface of the set of said reflecting surfaces; and

an optical waveguide defining a plane in optical contact with said fold grating,

wherein said fold grating is tilted around an axis perpendicular to the plane of said optical waveguide such that it is configured to extract at least a portion of said light guided through said light pipe along the at least one reflecting surface in optical contact with said folding grating such that the extracted light is coupled into said optical waveguide and directs said extracted light principally in a direction orthogonal to the first direction along a path of total internal reflection within said optical waveguide, and

wherein said reflecting surface comprises abutting mutually inclined elongate elements, at least one said elongate element in optical contact with said fold grating.

17. A waveguide apparatus comprising:

a light guide device comprising a light pipe having a set of one or more reflecting surfaces disposed around an optical axis configured to guide light from a first end along a spiral-like total internal reflection path therethrough to a second end such that the light is expanded along a first direction parallel to said optical axis;

a fold grating in optical contact with an elongate portion of at least one reflecting surface of the set of said reflecting surfaces; and

an optical waveguide defining a plane in optical contact with said fold grating,

wherein said fold grating is tilted around an axis perpendicular to the plane of said optical waveguide such that it is configured to extract at least a portion of said light guided through said light pipe along the at least one reflecting surface in optical contact with said folding grating such that the extracted light is coupled into said optical waveguide and directs said extracted light principally in a direction orthogonal to the first direction along a path of total internal reflection within said optical waveguide, and

wherein said fold grating comprises at least two multiplexed gratings.