Enhancement of output of optically pumped phosphor by use of surface nanostructures
Phosphor elements comprising phosphors in a host material having a phosphorescence-emitting surface with surface nanostructures are disclosed. Phosphor wheels having such phosphor elements, methods of making such phosphor elements, and methods of using such phosphor elements are also disclosed.
1. A phosphor element comprising:
a host material defining the shape of the phosphor element; and
one or more phosphors dispersed in the host material that emit phosphorescence in response to an optical pump beam;
wherein the phosphor element has a phosphorescence-emitting surface with surface nanostructures which do not comprise the host material; and
wherein the surface nanostructures have a lateral dimension T x along an x-direction which is a statistical average spacing between adjacent surface nanostructures along the x-direction and a lateral dimension T y along a y-direction which is a statistical average spacing between adjacent surface nanostructures along the y-direction, wherein the x-direction and the y-direction are mutually orthogonal and the lateral dimensions T x and T y are different, and wherein the different lateral dimensions T x and T y are effective to lead to optical emission anisotropy in the phosphorescence.
2. The phosphor element of claim 1 , wherein the surface nanostructures comprise a membrane made of a different material from the host material and attached to the phosphorescence-emitting surface.
3. The phosphor element of claim 1 , wherein the surface nanostructures are laterally periodic in the x- and y-directions over the phosphorescence-emitting surface and the lateral dimensions T x and T y are the periodicity of the surface nanostructures in the x- and y-directions, respectively.
4. The phosphor element of claim 1 , wherein the surface nanostructures are non-periodically distributed in the x- and y-directions over the phosphorescence-emitting surface and the lateral dimensions T x and T y are the statistical average spacing between adjacent surface nanostructures in the x- and y-directions, respectively.
5. The phosphor element of claim 1 , wherein the surface nanostructures are frustoconical surface nanostructures.
6. The phosphor element of claim 1 , wherein the surface nanostructures are rounded bump surface nanostructures.
7. The phosphor element of claim 1 , wherein the surface nanostructures are tapered conical surface nanostructures.
8. The phosphor element of claim 1 , wherein no anti-reflection coating is disposed on the phosphorescence-emitting surface.
9. The phosphor element of claim 1 , wherein the host material is silicone or a transparent or translucent thermoplastic resin.
10. A phosphor wheel device comprising:
a wheel having a central axis via which the wheel is rotatable; and
a phosphor element as set forth in claim 1 disposed along a rim of the wheel and secured to the wheel.
11. A phosphor element comprising:
a host material defining the shape of the phosphor element; and
one or more phosphors dispersed in the host material that emit phosphorescence in response to an optical pump beam;
wherein the phosphor element has a phosphorescence-emitting surface with surface nanostructures having a lateral dimension T x along an x-direction which is a statistical average spacing between adjacent surface nanostructures along the x-direction and a lateral dimension T y along a y-direction which is a statistical average spacing between adjacent surface nanostructures along the y-direction,
wherein the x-direction and the y-direction are mutually orthogonal, the lateral dimensions T x and T y are different and the different lateral dimensions Tx and Ty are effective to lead to optical emission anisotropy in the phosphorescence.
12. The phosphor element of claim 11 , wherein the surface nanostructures are frustoconical surface nanostructures.
13. The phosphor element of claim 11 , wherein the surface nanostructures are rounded bump surface nanostructures.
14. The phosphor element of claim 11 , wherein the surface nanostructures are laterally periodic in the x- and y-directions over the phosphorescence-emitting surface and the lateral dimensions T x and T y are the periodicity of the surface nanostructures in the x- and y-directions, respectively.
15. The phosphor element of claim 11 , wherein the surface nanostructures are non-periodically distributed in the x- and y-directions over the phosphorescence-emitting surface and the lateral dimensions T x and T y are the statistical average spacing between adjacent surface nanostructures in the x- and y-directions, respectively.
16. A phosphor wheel device comprising:
a wheel having a central axis via which the wheel is rotatable; and
a phosphor element as set forth in claim 11 disposed along a rim of the wheel and secured to the wheel.