Wavelength conversion element with convective cooling

1. A phosphor wheel comprising:

a disk;

a wavelength conversion layer comprising phosphor disposed on a first side of the disk; and

an impeller disposed on the first side of the disk, the impeller comprising vanes which are shaped as airfoils with each vane oriented to drive outward airflow across the disk and across the wavelength conversion layer when the disk is rotated in a rotation direction.

2. The phosphor wheel of claim 1 wherein the vanes are shaped as airfoils with each airfoil having its leading edge disposed radially inward of its trailing edge on the disk and with each vane oriented to drive outward airflow across the disk and across the wavelength conversion layer when the disk is rotated in the rotation direction.

3. The phosphor wheel of claim 2 wherein the leading edge of each airfoil is a rounded leading edge and the trailing edge of each airfoil is a sharp trailing edge.

4. The phosphor wheel of claim 3 wherein the airfoils further have a widest cross-section located between the rounded leading edge and the sharp trailing edge.

5. The phosphor wheel claim 4 wherein the wavelength conversion layer is disposed at a larger radial position than the impeller on the disk.

6. The phosphor wheel of claim 5 wherein the wavelength conversion layer comprises an annular wavelength conversion layer.

7. The phosphor wheel of claim 6 wherein the wavelength conversion layer is disposed on a single side of the disk and the impeller comprises vanes with all vanes of the impeller disposed on the same side of the disk as the wavelength conversion layer.

8. The phosphor wheel of claim 6 wherein the vanes include a first set of vanes disposed on a first side of the disk and a second set of vanes disposed on a second side of the disk opposite from the first side of the disk.

9. The phosphor wheel of claim 8 wherein the vanes are adhered onto the disk by an adhesive.

10. The phosphor wheel of claim 8 wherein the disk comprises sheet metal and the vanes protrude from the disk and are formed by sheet metal stamping.

11. The phosphor wheel of claim 8 wherein the vanes are formed by deposition of vane material onto the disk.

12. The phosphor wheel of claim 11 wherein the impeller protrudes from a surface of the disk on which the impeller is disposed by 2.0 mm or less.

13. The phosphor wheel of claim 12 further comprising:

an electric motor operatively coupled with the disk to rotate the disk in the rotation direction.

14. The phosphor wheel of claim 13 further comprising:

a light source arranged to output a pump beam impinging on the wavelength conversion layer.

15. The phosphor wheel of claim 14 wherein the light source is a laser or a light emitting diode (LED).

16. The phosphor wheel of claim 14 wherein the wavelength conversion layer comprises a yellow phosphor including one or more of cerium-substituted yttrium aluminum garnet (YAG:Ce), cerium-substituted terbium aluminum garnet (TAG:Ce), or europium-substituted barium orthosilicate (BOS) and a binder comprising a ceramic, a silicone, an epoxy, or a plastic.

17. A method of cooling the phosphor wheel of claim 1 , the method comprising:

rotating the disk in the rotation direction using an electric motor;

while rotating the disk in the rotation direction, optically pumping the wavelength conversion layer comprising phosphor disposed on the disk to generate wavelength converted light; and

while rotating the disk in the rotation direction, driving airflow across the wavelength conversion layer disposed on the disk using the impeller comprising airfoil-shaped vanes disposed on the disk wherein the impeller is operated by the rotating of the disk in the rotation direction.

18. The method of claim 17 wherein each airfoil-shaped vane has a rounded leading edge and a sharp trailing edge.

19. The method of claim 18 wherein the airfoil-shaped vanes further have a widest cross-section located between the rounded leading edge and the sharp trailing edge.

20. The method of claim 19 wherein the wavelength conversion layer is disposed at a larger radial position than the impeller on the disk, and the impeller comprises vanes shaped as airfoils to accelerate the airflow outwardly over the disk and across the wavelength conversion layer.

21. The method of claim 20 wherein the optical pumping uses blue or ultraviolet light having a largest spectral peak at or below 500 nm and the wavelength converted light has one or more spectral peaks at or above 500 nm.

22. A method of manufacturing a phosphor wheel, the method comprising:

disposing a wavelength conversion layer comprising phosphor on a first side of a disk; and

disposing or forming an impeller on the first side of the disk, wherein the impeller comprises airfoil-shaped vanes that are oriented to drive outward airflow across the disk and across the wavelength conversion layer when the disk is rotated in a rotation direction.

23. The method of manufacturing of claim 22 wherein the airfoil-shaped vanes have rounded leading edges and sharp trailing edges with each airfoil-shaped vane having its rounded leading edge disposed radially inward of its sharp trailing edge on the first side of the disk.

24. The method of manufacturing of claim 23 wherein the airfoil-shaped vanes further have a widest cross-section located between the rounded leading edge and the sharp trailing edge.

25. The method of manufacturing of claim 24 wherein the disposing or forming of the impeller on the disk comprises one of:

adhering vanes of the impeller onto the disk using an adhesive;

depositing vane material forming vanes of the impeller onto the disk; or

forming vanes of the impeller by sheet metal stamping.

26. The method of manufacturing of claim 25 wherein the disposing of the wavelength conversion layer on the disk consists of one of:

(i) depositing material forming the wavelength conversion layer on the disk; or

(ii) adhering the wavelength conversion layer onto the disk.

27. A phosphor wheel comprising:

a disk;

a wavelength conversion layer comprising phosphor disposed on the disk; and

an impeller disposed on the disk, the impeller comprising vanes which are shaped as airfoils with each vane oriented to drive outward airflow across the disk and across the wavelength conversion layer when the disk is rotated in a rotation direction, wherein the vanes are shaped as airfoils with each airfoil having its leading edge disposed radially inward of its trailing edge on the disk, and wherein the leading edge of each airfoil is a rounded leading edge and the trailing edge of each airfoil is a sharp trailing edge.