Light-diffusing elements
A light-diffusing element with high coupling efficiency to LED sources. The light-diffusing element may be a glass monolith that includes a plurality of internal voids. When light propagating through the monolith encounters the internal voids, it is scattered in a transverse direction and exits the lateral surface of the monolith to provide a broad-area illumination effect. The glass monolith has a diameter of at least 0.7 mm and features a numerical aperture of at least 0.6 to facilitate efficient coupling to LED sources. The internal voids have a cross-sectional dimension that ranges from about 100 nm to several microns and a length that ranges from about 1 μm to a few millimeters. The light-diffusing element can be configured as a rod or as a bent or arbitrarily-shaped fixture.
1. A light-diffusing element comprising:
a solidified glass monolith including internal voids, said glass monolith having a cross-section with a dimension between 1 mm and 20 mm and a numerical aperture of at least 0.7, said internal voids having a cross-section with a dimension between 100 nm and 20 μm, said internal voids occupying between 0.5% and 20% of said cross-section of said glass monolith.
2. The light-diffusing element of claim 1 , wherein said glass monolith has a cross-section with a dimension of at least 3 mm.
3. The light-diffusing element of claim 1 , wherein said glass monolith has a length of at least 5 cm.
4. The light-diffusing element of claim 1 , wherein said glass monolith has a length of at least 20 cm.
5. The light-diffusing element of claim 1 , wherein said glass monolith has a length between 1 cm and 100 cm.
6. The light-diffusing element of claim 1 , wherein said glass monolith has a numerical aperture of at least 0.8.
7. The light-diffusing element of claim 1 , wherein said internal voids have a cross-section with a dimension between 500 nm and 10 μm.
8. The light-diffusing element of claim 1 , wherein said internal voids have a length between 1 μm and 5 mm.
9. The light-diffusing element of claim 1 , wherein the volume fraction of said internal voids is between 0.5% and 20%.
10. The light-diffusing element of claim 1 , wherein said internal voids are localized in a first region of said cross-section of said glass monolith, said first region having a width between 5% and 90% of said dimension of said cross-section of said glass monolith.
11. The light-diffusing element of claim 10 , wherein said first region has an annular shape.
12. The light-diffusing element of claim 1 , wherein said internal voids are filled with a gas selected from the group consisting of Ar, Kr, SO 2 , N 2 , CO 2 , O 2 , air, Cl 2 , and CF 4 .
13. The light-diffusing element of claim 1 , wherein said element is configured as a rod.
14. The light-diffusing element of claim 1 , wherein said element is bent.
15. The light-diffusing element of claim 1 , further comprising internal light, said voids scattering said internal light, the efficiency of said scattering varying by less than 50% of the maximum scattering efficiency along the length of said light-diffusing element.
16. The light-diffusing element of claim 15 , wherein the scattering loss of said internal light is at least 100 dB/km.
17. The light-diffusing element of claim 1 , further comprising a surface coating, said surface coating comprising a phosphor, a fluorophore, or a scattering material.
18. The light-diffusing element of claim 1 , further comprising a polymer jacket, said polymer jacket surrounding said light-diffusing element.
19. The light-diffusing element of claim 18 , further comprising a scattering layer, said scattering layer surrounding said light-diffusing element, said polymer jacket surrounding said scattering layer.
20. An illumination system comprising the light-diffusing element of claim 1 and a light-emitting diode, said light-emitting diode being coupled to said light-diffusing element.
21. The illumination system of claim 20 , wherein said light-emitting diode has a cross-sectional area of 1 mm 2 and a numerical aperture of at least 0.6.
22. The illumination system of claim 20 , further comprising an optic comprising glass or polymer, said optic receiving light from said light-emitting diode, said optic delivering said light to said light-diffusing element.
23. The light diffusing element of claim 1 , wherein said internal voids are distributed throughout said cross-section.
24. The light diffusing element of claim 1 , wherein said glass monolith includes a glass surrounding said internal voids, said glass having a uniform composition throughout said cross-section.