Slim waveguide coupling apparatus and method
In various embodiments, an illumination structure includes a discrete light source disposed proximate a bottom surface of a waveguide and below a depression in a top surface thereof. A top mirror may be disposed above the discrete light source to convert modes of light emitted from the discrete light source into trapped modes, thereby increasing the coupling efficiency of the illumination structure.
1. An illumination structure comprising:
a waveguide having a depression in a top surface thereof;
a discrete light source disposed proximate a bottom surface of the waveguide and below the depression; and
a top mirror disposed above the discrete light source, the top mirror comprising a conical mirror disposed over and at least substantially filling the depression.
2. The illumination structure of claim 1 , further comprising an air gap disposed between the conical mirror and the depression.
3. The illumination structure of claim 1 , further comprising a substantially flat mirror disposed over substantially all of the depression.
4. The illumination structure of claim 3 , wherein the substantially flat mirror comprises at least one of a specular mirror, a diffusive reflector, a Fresnel reflector, or a diffractive optical element.
5. The illumination structure of claim 1 , wherein a surface of the conical mirror proximate the waveguide comprises a reflective coating thereon.
6. The illumination structure of claim 1 , further comprising an index-matching material disposed between the waveguide and the conical mirror.
7. The illumination structure of claim 6 , wherein an index of refraction of the index-matching material is substantially equal to an index of refraction of the waveguide.
8. The illumination structure of claim 1 , wherein a shape of the conical mirror is at least one of conical, parabolic, pyramidal, or prismatic.
9. The illumination structure of claim 1 , wherein the conical mirror comprises a reflective metal.
10. The illumination structure of claim 9 , wherein the reflective metal comprises at least one of aluminum or silver.
11. The illumination structure of claim 1 , wherein the conical mirror comprises topaz or a polymer.
12. The illumination structure of claim 11 , wherein the conical mirror comprises polymethyl methacrylate.
13. A method for coupling light emitted from a discrete light source to a waveguide, the method comprising:
emitting light from a discrete light source disposed within a waveguide; and
reflecting a portion of the emitted light from a top mirror disposed above a depression in a top surface of the waveguide, the depression being disposed above the discrete light source, so as to confine the reflected portion of the emitted light within the waveguide,
wherein the top mirror comprises a conical mirror substantially filling the depression, and the portion of the emitted light traverses an air gap between the depression and the top mirror before being reflected.
14. The illumination structure of claim 2 , wherein a thickness of the air gap is selected from the range of approximately 10 μm to approximately 50 μm.
15. The illumination structure of claim 2 , wherein a thickness of the air gap is less than approximately 10 μm.
16. The illumination structure of claim 2 , wherein at least a portion of the air gap is filled with a filler material.
17. The illumination structure of claim 16 , wherein the filler material is adhesive.
18. The illumination structure of claim 16 , wherein an index of refraction of the filler material is less than an index of refraction of the waveguide.
19. The illumination structure of claim 16 , wherein the filler material comprises silicone.