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Emitting device with improved extraction

  • US 9,142,741 B2
  • Filed: 06/14/2012
  • Issued: 09/22/2015
  • Est. Priority Date: 06/15/2011
  • Status: Active Grant
First Claim
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1. A device comprising:

  • an at least partially transparent layer having a first side and a second side, wherein radiation enters the at least partially transparent layer through the first side and exits the at least partially transparent layer through the second side, and wherein at least one of the first side or the second side comprises a profiled surface, the profiled surface including;

    a set of large roughness components providing a first variation of the profiled surface having a characteristic scale approximately an order of magnitude larger than a target wavelength of the radiation; and

    a set of small roughness components providing a second variation of the profiled surface having a characteristic scale on the order of the target wavelength of the radiation, wherein the set of small roughness components are superimposed on the set of large roughness components, and wherein a graded refractive index along a height of each small roughness component in the set of small roughness components decreases substantially linearly along the height, and wherein a refractive index at a particular height of a small roughness component corresponds to an average of a refractive index of a material forming the small roughness component and a refractive index of a material adjacent to the profiled surface of the at least partially transparent layer, weighted by a fractional cross-sectional area of the small roughness component at the particular height.

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