FILTER FOR A LIGHT EMITTING DEVICE
Embodiments of the invention include a semiconductor light emitting device capable of emitting first light having a first peak wavelength and a wavelength converting element capable of absorbing the first light and emitting second light having a second peak wavelength. In some embodiments, the structure further includes a metal nanoparticle array configured to pass a majority of light in a first wavelength range and reflect or absorb a majority of light in a second wavelength range. In some embodiments, the structure further includes a filter configured to pass a majority of light in a first wavelength range and reflect or absorb a majority of light in a second wavelength range, wherein the filter is configured such that a wavelength at which a minimum amount of light is passed by the filter shifts no more than 30 nm for light incident on the filter at angles between 0° and 60° relative to a normal to a major surface of the filter.
1 . A structure comprising:
a semiconductor light emitting device capable of emitting first light having a first peak wavelength;
a wavelength converting element capable of absorbing the first light and emitting second light having a second peak wavelength; and
a filter comprising a metal nanoparticle array, the metal nanoparticle array comprising an array of areas of a first material separated by a second material, wherein the first material and the second material have different indices of refraction and one of the first material and the second material is metal; wherein
the metal nanoparticle array is configured to pass a majority of light in a first wavelength range and reflect or absorb a majority of light in a second wavelength range.
2 . The structure of claim 1 wherein the metal nanoparticle array is disposed between the semiconductor light emitting device and the wavelength converting element.
3 . The structure of claim 2 wherein the first wavelength range includes the first light and the second wavelength range includes the second light.
4 . The structure of claim 1 wherein the wavelength converting element is disposed between the semiconductor light emitting device and the metal nanoparticle array.
5 . The structure of claim 4 wherein the first wavelength range includes the second light and the second wavelength range includes the first light.
6 . The structure of claim 1 wherein the first material is metal and the second material is air.
7 . The structure of claim 1 wherein the first material is air and the second material is metal.
8 . The structure of claim 1 wherein metal comprises at least one of silver and gold.
9 . The structure of claim 1 wherein the metal nanoparticle array is configured to pass at least 70% of the light in the first wavelength range regardless of angle of incidence on the metal nanoparticle array.
10 . The structure of claim 1 wherein the filter is configured such that a wavelength at which a minimum amount of light is passed by the filter shifts no more than 30 nm for light incident on the filter at angles between 0° and 60° relative to a normal to a major surface of the filter.
11 . The structure of claim 1 wherein the areas of first material are metal elements, wherein each metal element has a width between 5 and 500 nm and a height between 5 and 500 nm, and wherein nearest neighbor metal elements are spaced between 10 and 1000 nm apart.
12 . A structure comprising:
a semiconductor light emitting device capable of emitting first light having a first peak wavelength;
a wavelength converting element capable of absorbing the first light and emitting second light having a second peak wavelength; and
a filter configured to pass a majority of light in a first wavelength range and reflect or absorb a majority of light in a second wavelength range, wherein the filter is configured such that a wavelength at which a minimum amount of light is passed by the filter shifts no more than 30 nm for light incident on the filter at angles between 0° and 60° relative to a normal to a major surface of the filter.
13 . The structure of claim 12 wherein the filter comprises a multilayer stack of materials with different indices of refraction.
14 . The structure of claim 13 wherein the multilayer stack comprises titania and a material having an index of refraction of at least 1.4 and no more than 2.
15 . The structure of claim 12 wherein the filter is disposed between the semiconductor light emitting device and the wavelength converting element.
16 . The structure of claim 15 wherein the first wavelength range includes the first light and the second wavelength range includes the second light.
17 . The structure of claim 12 wherein the wavelength converting element is disposed between the semiconductor light emitting device and the filter.
18 . The structure of claim 17 wherein the first wavelength range includes the second light and the second wavelength range includes the first light.
19 . The structure of claim 12 wherein:
the filter is a metal nanoparticle array;
the wavelength converting element is a ceramic phosphor; and
the filter is disposed between the semiconductor light emitting device and the phosphor.
20 . The structure of claim 19 wherein:
the metal nanoparticle array comprises an array of metal elements;
each metal element has a width between 5 and 500 nm and a height between 5 and 500 nm; and
nearest neighbor metal elements are spaced between 10 and 1000 nm apart.