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 plurality of discrete light sources disposed proximate the waveguide and positioned to emit light into the in-coupling region, wherein the depression reflects a first portion of light emitted by the discrete light sources into the waveguide and transmits a second portion of light emitted by the discrete light sources through the depression;
disposed over the depression, an absorber for preventing transmission of at least a portion of the second portion of light therethrough; and
disposed between the absorber and the discrete light sources, a phosphor layer for converting a wavelength of light emitted by at least one of the discrete light sources to a different wavelength.
2. The illumination structure of claim 1 , wherein the plurality of discrete light sources comprises at least three discrete light sources.
3. The illumination structure of claim 1 , wherein the plurality of discrete light sources comprises at least four discrete light sources.
4. The illumination structure of claim 1 , wherein at least two of the discrete light sources emit light of substantially the same wavelength.
5. The illumination structure of claim 1 , wherein at least two of the discrete light sources emit light of different wavelengths.
6. The illumination structure of claim 1 , wherein a thickness of the waveguide spanning the top and bottom surfaces is greater than a width of at least one of the discrete light sources.
7. The illumination structure of claim 6 , wherein the thickness of the waveguide is at least as thick as a sum of the width of at least one of the discrete light sources and a thickness of at least one of the discrete light sources.
8. The illumination structure of claim 1 , wherein the absorber is diffusive.
9. The illumination structure of claim 1 , further comprising an index-matching material disposed between the waveguide and the absorber.
10. The illumination structure of claim 9 , wherein an index of refraction of the index-matching material is substantially equal to an index of refraction of the waveguide.
11. The illumination structure of claim 9 , wherein the index-matching material is adhesive.
12. The illumination structure of claim 9 , wherein an index of refraction of the index-matching material is less than an index of refraction of the waveguide.
13. The illumination structure of claim 9 , wherein the index-matching material comprises silicone.
14. The illumination structure of claim 9 , further comprising, disposed over and/or at least partially within the depression, a mirror for reflecting light from the discrete light sources into the waveguide.
15. The illumination structure of claim 1 , further comprising, disposed over and/or at least partially within the depression, a mirror for reflecting light from the discrete light sources into the waveguide.
16. The illumination structure of claim 15 , further comprising an air gap disposed between the mirror and the depression.
17. The illumination structure of claim 16 , wherein a thickness of the air gap is selected from the range of approximately 10 μm to approximately 200 μm.
18. The illumination structure of claim 16 , wherein a thickness of the air gap is less than approximately 10 μm.
19. The illumination structure of claim 15 , further comprising a filler material disposed between the mirror and the depression.
20. The illumination structure of claim 15 , wherein the mirror comprises at least one of a specular mirror, a diffusive reflector, a Fresnel reflector, or a diffractive optical element.
21. The illumination structure of claim 15 , wherein the mirror comprises a mirror having a shape that is at least one of conical, parabolic, pyramidal, or prismatic.
22. The illumination structure of claim 1 , wherein the phosphor layer is disposed in the in-coupling region.
23. The illumination structure of claim 1 , wherein the bottom surface of the waveguide defines a notch therewithin.
24. The illumination structure of claim 23 , wherein the phosphor layer is disposed proximate a surface of the notch.
25. The illumination structure of claim 23 , wherein at least one of the discrete light sources is disposed at least partially within the notch.
26. The illumination structure of claim 1 , wherein a surface of the waveguide proximate the discrete light sources comprises a reflective coating thereon.
27. The illumination structure of claim 1 , wherein at least a portion of the bottom surface of the waveguide comprises a reflective coating thereon.
28. The illumination structure of claim 1 , wherein substantially no light reflected by the depression into the waveguide reflects back to the discrete light sources.