Ceramic Wavelength Converter Having a High Reflectivity Reflector

• US 20160334552A1
• Filed: 01/26/2015
• Published: 11/17/2016
• Est. Priority Date: 01/27/2014
• Status: Active Grant

• Current Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Original Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Inventors: Lenef, Alan, Avallon, James, Scotch, Adam
• Granted Patent: US 10,488,566 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: C04B 2237/062 based on silica or silicates
• CPC Class Codes: C04B 2237/121 based on aluminium
• CPC Class Codes: C04B 2237/125 based on noble metals, e.g. silver
• CPC Class Codes: C04B 2237/343 Alumina or aluminates
• CPC Class Codes: C04B 2237/407 Copper
• CPC Class Codes: C04B 2237/708 of one or more of the interlayers
• CPC Class Codes: C04B 2237/72 Forming laminates or joined articles comprising at least two interlayers directly next to each other
• CPC Class Codes: C04B 37/026 consisting of metals or metal salts
• CPC Class Codes: C09K 11/0883 Arsenides; Nitrides; Phosphides
• CPC Class Codes: C09K 11/7774 Aluminates
• CPC Class Codes: G02B 5/0858 the reflecting layers comprising a single metallic layer with one or more dielectric layers
• CPC Class Codes: G02B 7/1815 with cooling or heating systems cooling arrangements for laser mirrors H01S3/0401
• CPC Class Codes: H01L 33/505 characterised by the shape, e.g. plate or foil
• CPC Class Codes: H01L 33/60 Reflective elements

Abstract

There is herein described a ceramic wavelength converter having a high reflectivity reflector. The ceramic wavelength converter is capable of converting a primary light into a secondary light and the reflector comprises a reflective metal layer and a dielectric buffer layer between the ceramic wavelength converter and the reflective metal layer. The buffer layer is non-absorbing with respect to the secondary light and has an index of refraction that is less than an index of refraction of the ceramic wavelength converter. Preferably the reflectivity of the reflector is at least 80%, more preferably at least 85% and even more preferably at least 95% with respect to the secondary light emitted by the converter.

Claims

1. A ceramic wavelength converter having a high reflectivity reflector, the ceramic wavelength converter being capable of converting a primary light into a secondary light, the reflector comprising a reflective metal layer and a dielectric buffer layer between the ceramic wavelength converter and the reflective metal layer, the buffer layer being non-absorbing with respect to the secondary light and having an index of refraction that is less than an index of refraction of the ceramic wavelength converter.

2. The ceramic wavelength converter of claim 1 wherein the reflectivity of the reflector is at least 80% with respect to the secondary light.

3. The ceramic wavelength converter of claim 1 wherein the reflectivity of the reflector is at least 85% with respect to the secondary light.

4. The ceramic wavelength converter of claim 1 wherein the reflectivity of the reflector is at least 95% with respect to the secondary light.

5. The ceramic wavelength converter of claim 1 where the converter comprises at least one phosphor selected from (Y,Lu,Gd)₃Al₅O₁₂:

Ce and (Ba,Ca,Sr)Si₂O₂N₂;

Eu.

6. The ceramic wavelength converter of claim 1 wherein the converter is in the form of a flat plate having a thickness greater than a scattering length of the secondary light in the converter.

7. The ceramic wavelength converter of claim 1 wherein the reflective metal layer is optically thick with respect to the secondary light.

8. The ceramic wavelength converter of claim 1 wherein the buffer layer has a thickness of at least one secondary light wavelength.

9. The ceramic wavelength converter of claim 1 wherein the refractive index of the buffer layer is at least 10% lower than the refractive index of the ceramic wavelength converter.

10. The ceramic wavelength converter of claim 1 wherein the refractive index of the buffer layer is at least 20% lower than the refractive index of the ceramic wavelength converter.

11. The ceramic wavelength converter of claim 1 wherein the ceramic wavelength converter is comprised of YAG:

Ce and the buffer layer is SiO₂.

12. The ceramic wavelength converter of claim 1 wherein the buffer layer has a thickness of less than 10 μ

m.

13. The ceramic wavelength converter of claim 1 wherein the buffer layer has a thickness of less than 5 μ

m.

14. The ceramic wavelength converter of claim 11 wherein the buffer layer has a thickness of less than 200 W/m divided by an incident power of the primary light per unit area, E, expressed as W/m².

15. The ceramic wavelength converter of claim 11 wherein the buffer layer has a thickness, l_b, defined by

16. The ceramic wavelength converter of claim 1 wherein the reflector has a quenching layer between the buffer layer and the reflective metal layer, the quenching layer having an index of refraction that is greater than the index of refraction of the buffer layer.

17. The ceramic wavelength converter of claim 16 wherein the quenching layer has an index of refraction greater than or equal to 1.8.

18. The ceramic wavelength converter of claim 16 wherein the quenching layer is comprised of a dielectric material selected from Y₂O₃, HfO₂, ZrO₂, Nb₂O₅, and TiO₂ (rutile phase).

19. The ceramic wavelength converter of claim 16 wherein the quenching layer has a thickness such that secondary light reflected by the reflective metal layer is in phase with secondary light reflected at an interface between the buffer layer and the quenching layer.

20. The ceramic wavelength converter of claim 16 wherein the buffer layer is comprised of SiO₂ and the quenching layer is comprised of Y₂O₃.

21. The ceramic wavelength converter of claim 20 wherein the ceramic wavelength converter is comprised of YAG:

Ce.

22. The ceramic wavelength converter of claim 21 wherein the quenching layer has a thickness, l_q, defined by

23. A ceramic wavelength converter having a high reflectivity reflector, the ceramic wavelength converter comprising a (Y,Lu,Gd)₃Al₅O₁₂:

Ce phosphor, the reflector comprising a reflective silver metal layer and a dielectric SiO₂ buffer layer between the ceramic wavelength converter and the reflective silver metal layer, the buffer layer having a thickness of less than 10 μ

m.

24. The ceramic wavelength converter of claim 23 wherein the buffer layer has a thickness of less than 5 μ

m.

25. The ceramic wavelength converter of claim 23 wherein the reflector has a Y₂O₃ quenching layer between the buffer layer and the reflective silver metal layer.

26. The ceramic wavelength converter of claim 25 wherein the quenching layer has a thickness of 50 nm.