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 (i) top and bottom opposed surfaces, (ii) an in-coupling region for receiving light, (iii) an out-coupling region for emitting light from the waveguide, and (iv) a depression in the top surface thereof;
a discrete light source disposed proximate the bottom surface of the waveguide in the in-coupling region;
at least partially filling at least a portion of the depression, a conical mirror for reflecting light from the discrete light source into the out-coupling region; and
a phosphor layer for converting a wavelength of light emitted by the discrete light source to a different wavelength.
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 2 , wherein a thickness of the air gap is selected from the range of approximately 10 μm to approximately 200 μm.
4. The illumination structure of claim 2 , wherein a thickness of the air gap is less than approximately 10 μm.
5. The illumination structure of claim 2 , wherein at least a portion of the air gap is filled with a filler material.
6. The illumination structure of claim 5 , wherein the filler material is adhesive.
7. The illumination structure of claim 5 , wherein an index of refraction of the filler material is less than an index of refraction of the waveguide.
8. The illumination structure of claim 5 , wherein the filler material comprises silicone.
9. The illumination structure of claim 1 , further comprising a substantially flat mirror disposed over at least a portion of the depression.
10. The illumination structure of claim 9 , wherein the substantially flat mirror comprises at least one of a specular mirror, a diffusive reflector, a Fresnel reflector, or a diffractive optical element.
11. The illumination structure of claim 1 , wherein the phosphor layer is disposed in the in-coupling region.
12. The illumination structure of claim 1 , wherein the bottom surface of the waveguide defines a notch therewithin.
13. The illumination structure of claim 12 , wherein the phosphor layer is disposed proximate a surface of the notch.
14. The illumination structure of claim 12 , wherein the discrete light source is disposed at least partially within the notch.
15. The illumination structure of claim 1 , wherein a surface of the conical mirror proximate the waveguide comprises a reflective coating thereon.
16. The illumination structure of claim 1 , wherein substantially no light reflected by the conical mirror or the depression into the out-coupling region reflects back to the discrete light source.
17. The illumination structure of claim 1 , further comprising an index-matching material disposed between the waveguide and the conical mirror.
18. The illumination structure of claim 17 , wherein an index of refraction of the index-matching material is substantially equal to an index of refraction of the waveguide.
19. The illumination structure of claim 1 , wherein a shape of the conical mirror is at least one of conical, parabolic, pyramidal, or prismatic.
20. The illumination structure of claim 1 , wherein the conical mirror comprises a reflective metal.
21. The illumination structure of claim 1 , wherein the conical mirror is disposed over the discrete light source.