High luminance light converting device
The invention describes a light converting device comprising: a bonded layer stack comprising a light converter and a diamond layer, wherein the diamond layer is bonded to a bonding surface of the light converter, wherein the light converter is adapted to convert laser light to converted light, wherein a peak emission wavelength of the converted light is in a longer wavelength range than a laser peak emission wavelength of the laser light, wherein a refractive index of the diamond layer is bigger than a refractive index of the light converter, and a light outcoupling structure attached to a first surface of the bonded layer stack, wherein a second surface of the bonded layer stack is a light-entrance surface arranged to receive the laser light, wherein the bonding surface is arranged between the first surface and the second surface of the bonded layer stack, wherein a refractive index of the light outcoupling structure is at least 90% of the refractive index of the light converter, and wherein the light outcoupling structure is optically coupled to the first surface of the bonded layer stack such that total internal reflection of light traversing an emission path from the light-entrance surface to the light outcoupling structure is reduced. The invention further describes a laser-based light source comprising such a light converting device and a vehicle headlight comprising such a laser-based light source.
1. Alight converting device comprising:
a light converter being adapted to convert laser light to converted light, a peak emission wavelength of the converted light being in a longer wavelength range than a peak emission wavelength of the laser light, the light converter having a first surface and an oppositely positioned second surface,
a diamond layer with a refractive index bigger than a refractive index of the light converter, the diamond layer bonded to and covering the entire second surface of the light converter, the light converter and the diamond layer forming by such bonding a bonded layer stack, and
a light outcoupling structure attached to a first surface of the bonded layer stack, a second surface of the bonded layer stack arranged to receive the laser light, the second surface of the light converter arranged between the first surface and the second surface of the bonded layer stack, a refractive index of the light outcoupling structure being at least 90% of the refractive index of the light converter, the light outcoupling structure optically coupled to the first surface of the bonded layer stack such that total internal reflection of light traversing the bonded layer stack from the second surface of the bonded layer stack to the light outcoupling structure is reduced.
2. The light converting device according to claim 1 , wherein the first surface of the bonded layer stack is a surface of the diamond layer opposite to another surface of the diamond layer bonded to the second surface of the light converter.
3. The light converting device according to claim 1 , wherein the first surface of the bonded layer stack is the first surface of the light converter.
4. The light converting device according to claim 1 wherein the light outcoupling structure is attached to the first surface of the bonded layer stack by means of an optical coupling layer, wherein a refractive index of the optical coupling layer is at least 90% of the refractive index of the light converter.
5. The light converting device according to claim 1 wherein the diamond layer is of elongated shape, wherein a length of the diamond layer is at least two times a width of the diamond layer.
6. The light converting device according to claim 5 , wherein the light converter is arranged symmetrically with respect to an optical axis of the light outcoupling structure.
7. The light converting device according to claim 6 , wherein the first surface of the bonded layer stack is a surface of the diamond layer opposite to another surface of the diamond layer bonded to the second surface of the light converter, and wherein an extension of the light converter parallel to the length direction of the diamond layer is smaller than the length of the diamond layer.
8. The light converting device according to claim 1 , wherein the bonded layer stack is thermally coupled to a heat sink.
9. The light converting device according to claim 8 , wherein the bonded layer stack is coupled to the heat sink by means of a thermal coupling layer.
10. The light converting device according to claim 9 , wherein the diamond layer faces a surface of the heat sink.
11. The light converting device according to claim 10 , wherein a part of the light converter is removed from the diamond layer, and wherein a surface of the diamond layer pointing away from the second surface of the light converter faces the light outcoupling structure.
12. The light converting device according to claim 1 , wherein the bonded layer stack comprises an antireflective coating attached to the second surface of the bonded layer stack, wherein the antireflective coating is arranged to reduce reflection of the laser light.
13. A laser-based light source comprising:
a light converting device according to claim 1 , and
at least one laser, the at least one laser being adapted to emit the laser
light to the second surface of the bonded layer stack.
14. A vehicle headlight comprising at least one laser-based light source according to claim 13 .