Light source having solid-state laser irradiating single-crystal phosphor with specific composition

Abstract

The light source includes a high-efficiency solid-state laser source emitting excitation coherent radiation, and a single crystal phosphor forming an optic element for receiving the excitation coherent radiation and emitting light with desired parameters. The single crystal phosphor is made of garnets conforming to the general formula (A.sub.x,Lu.sub.1-x).sub.aAl.sub.bO.sub.12:Ce.sub.c formula, or from a single crystal material of perovskite structure conforming to the general formula B.sub.1-gAlO.sub.3:D.sub.q.

Claims

1. A light source comprising: at least one solid-state laser source for emitting coherent excitation radiation, and at least one single crystal phosphor containing at least one doping element for at least partial conversion of the excitation radiation into extracted light with wavelengths in the visible spectrum, wherein the single crystal phosphor is formed with oxide-type compound meeting the general formula
(A.sub.x,Lu.sub.1-x).sub.aAl.sub.bO.sub.12:Ce.sub.c where: A is at least one of the chemical elements from the Y, Gd, Tb group, a is a number from the value interval from 0.5 to 20, b is a number from the value interval from 0.5 to 20, c is a positive number from the value interval from 0.0005 to 0.2, x is a positive number from the value interval from 0 to 1, and the value of the stoichiometric ratio a:b ranges between 0.5 to 0.7.

2. A light source according to claim 1, wherein the values of c and x numbers are defined by the intervals: 0.0005<c<0.03 0.0005<x<0.9999.

3. A light source according to claim 1, wherein the single crystal phosphor contains induced color centers connected with oxygen vacancies.

4. A light source according to claim 1, wherein the single crystal phosphor is made from a single crystal ingot.

5. A light source according to claim 1, wherein the solid-state laser source has a maximum emission of light wavelengths in the range of 340 nm to 480 nm, and where the extracted light is white light with a correlated color temperature ranging from 2700 K to 10000 K.

6. A light source according to claim 1, wherein the single crystal phosphor forms an optic element with a shape selected from the group consisting of a rectangular cuboid, hemisphere, spherical cap, right circular cone, pyramid, polyhedron, and symmetrical shape, for protecting the extracted light in a desired direction.

7. A light source according to claim 1, wherein at least a portion of the single crystal phosphor volume is structured to at least one of create color-homogenized scattered extracted light, and to maximize projection of the extracted light in a desired direction.

8. A light source according to claim 1, further comprising a secondary phosphor connected to the single crystal phosphor, the secondary phosphor having a maximum emission of light wavelengths in the range of 560 nm to 680 nm, for changing the correlated color temperature of the resulting extracted light.

9. A light source according to claim 1, further comprising a cooler connected to the single crystal phosphor.

10. A light source according to claim 1, further comprising at least one of a light-guiding optic fiber or a light guiding planar optic waveguide, the single crystal phosphor connected to the at least one of a light-guiding optic fiber or a light guiding planar optic waveguide with an optical bonding.

11. A light source according to claim 1, further comprising an optic lens between the solid-state laser source and the single crystal phosphor, to direct the excitation radiation to the excitation surface of the single crystal phosphor.

12. A light source according to claim 1, further comprising at least one carrier carrying the single crystal phosphor, and at least one element to direct the extracted light from the single crystal phosphor.

13. A light source according to claim 1, wherein the single crystal phosphor has the shape of an elongated rectangular cuboid or cylinder, the sides of the single crystal phosphor are polished and the face of the single crystal phosphor from which the emitted light is emitted is ground, provided with an anti-reflex layer, or provided with structuring to make the extraction of the emitted light easier.

14. A light source according to claim 1, wherein the excitation surface of the single crystal phosphor is also the emission surface too.

15. A light source according to claim 1, wherein the single crystal phosphor is provided with at least one surface treatment selected from the group consisting of: ground surface, polished surface, surface provided with an anti-reflex layer, structured surface, and a surface provided with a layer of crushed single crystal phosphor material.

16. A light source according to claim 15, wherein the single crystal phosphor is provided with the surface provided with the layer of the crushed material, such layer composed of at least two materials of single crystal phosphors with different properties.

17. A light source according to claim 1, wherein the single crystal phosphor is composed of at least two thin plates, arranged in a sandwich structure.

18. A light source according to claim 17, wherein the thin plates are formed from a single crystal phosphor having different characteristics.

Description

DESCRIPTION OF THE DRAWINGS

(1) The stated invention shall be more closely clarified in enclosed drawings, where:

(2) FIG. 1 illustrates a light source in which the location of the single crystal phosphor is right next to the excitation radiation source and, furthermore, a light source in which the location of the single crystal phosphor is remote from the excitation radiation source,

(3) FIG. 2 depicts a light source where the excitation coherent radiation is conducted to the single crystal phosphor via an optic fiber,

(4) FIG. 3 illustrates a light source with several laser diodes,

(5) FIG. 4 illustrates a light source with two different phosphors,

(6) FIG. 5 depicts a light source whose single crystal phosphor is fitted on a carrier in the cooler,

(7) FIG. 6 represents a light source with an optic lens for the modification of the light beam of the excitation radiation,

(8) FIG. 7 represents a light source with a single crystal phosphor which has a rounded shape of the emission surface,

(9) FIG. 8 represents other possible arrangement of light sources where the single crystal phosphor is firmly fixed to the optic fiber,

(10) FIG. 9 depicts a light source in which the single crystal phosphor is used to conduct the light,

(11) FIG. 10 depicts a light source with a reflective arrangement of the single crystal phosphor,

(12) FIG. 11 represents a light source with a phosphor created with a sandwich structure,

(13) FIG. 12 represents a light source with a single crystal phosphor provided with a crushed material layer.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(14) It is understood that the below stated and depicted specific embodiments of the invention are represented for illustration and not as the limitation of the embodiments of the invention to the stated embodiments. Experts familiar with the state of the art will find or will be able to ensure, when performing routine experimentation, larger or smaller amount of equivalents to the specific embodiments of the invention which are described here. These equivalents shall be included in the extent of the following claims too.

(15) The light source 1 is depicted in a simplified manner in FIG. 1 where we can see it in cross-section. The basic parts of the light source 1 are the solid-state laser source 2 of the excitation coherent radiation 3 to which a single crystal phosphor 4 is fixed, or, possibly, the single crystal phosphor 4 is located in a more remote position from the source of the excitation coherent radiation 3. The single crystal phosphor 4 emits extracted light 5 which is directed by the element 13, created with an alumina cone whose internal wall has reflex treatment. The single crystal phosphor 4 is located at the top of the cone of the element 13. The internal space of the element 13 created by the cone is protected from the influence of the environment by a protective element 16 created with a transparent layer. The protective transparent layer representing the element 16 can be made of glass or clear heat resistant polymer. The element 13 for directing the extracted light 5 and the protective element 16 can be variably shaped for various applications of the light source 1.

(16) The source of the excitation coherent radiation 3 is a solid-state laser source 2, created with an edge-emitting laser diode. The laser diode emits a coherent light beam with the wavelength in the area of 450 nm. The light beam created by the excitation radiation 3 incidences onto the excitation surface 17 of the single crystal phosphor 4, into the volume of which it penetrates. It is possible, for example, to use a laser diode based on the InGaN technology which emits from the edge.

(17) The single crystal phosphor 4 is a luminescent material with a single crystal matrix (Y.sub.0.15Lu.sub.0.85).sub.3Al.sub.5O.sub.12, which is doped with Ce or contains induced color centers connected with oxygen vacancies. In another embodiment of the light source 1 is YAlO.sub.3:Ti.sub.0.5 utilized.

(18) The induced color centers are connected with oxygen vacancies which are present in the material due to the lack of oxygen during the single crystal growth. The adjustment of conditions during the single crystal growth is controlled. The induced color centers are connected with certain anomalies in the crystalline lattice which generate light of different wavelengths after incidence of the excitation radiation.

(19) The resulting shape of the single crystal phosphor 4 corresponds to the specific application. For the sake of simplicity, it is created in the light sources 1 depicted in drawings as a low cylinder with wide faces which appears as a rectangle in section. The laser light beam is converted from its major part and the single crystal phosphor 4 starts to emit the emitted light 5 in all directions from the emission surface 18. A part of the excitation radiation 3 in the form of a laser light beam passes through the single crystal phosphor 4 and due to the passage through the single crystal phosphor 4 it loses its arranged character and mixes up with the extracted light 5 into the resulting light color which is suitable with its correlated color temperature and intensity for usage in household applications too.

(20) The surface of the single crystal phosphor 4 may be treated in such a manner that parameters are changed for the creation or elimination of total reflection. The surface may be polished, provided with an anti-reflex layer 7 or with structuring 8 which makes light extraction easier.

(21) The single crystal phosphor 4 shaped into an optic member defines with its shape the direction of the emission of emitted light. In some cases, the optic member volume is structured in such a manner that there is an easy light extraction from the single crystal phosphor 4.

(22) FIG. 2 depicts the example of embodiment the light source 1, which is adjusted for lower heat transfer from the single crystal phosphor 4 back to the laser diode of the source 2 of the excitation radiation 3. The laser diode is in a remote position from the phosphor 4 and the excitation radiation 3 is conducted to the phosphor 4 via an optic fiber 10. To decrease the light energy losses, the excitation light beam is collimated with a collimation lens 19 in the optic fiber 10. The center of the light beam, the center of the collimation lens 19 and the center of the entrance into the optic fiber 10 lie in one common axis. The light beam extracted from the optic fiber 10 is scattered onto the excitation surface 17 of the single crystal phosphor 4 by projection apparatus optic lens 11. An optic waveguide can be used instead of the optic fiber 10.

(23) FIG. 3 depicts the example of embodiment the light source 1, which is of similar construction as in the example from FIG. 2. The difference is in the multiplication of the solid-state laser sources 2 of the excitation radiation 3 for the increase in luminance of the light source 1. The laser diodes may be spatially moved from each other, so that there is again the decrease in the heating up of the laser diodes with the heat from the single crystal phosphor 4.

(24) FIG. 4 depicts the example of the light source 1, which is provided with a single crystal phosphor 4 and a secondary phosphor 6. The secondary phosphor 6 is created with for example single crystal material described with the (Gd, Lu, Eu).sub.3Al.sub.5O.sub.12 formula or with a single crystal material described with (Y, Ti)AlO.sub.3. The secondary phosphor 6 radiates extracted light 5 of a different color, here it is e.g. orange-red, so that its mixing with the extracted light 5 of the single crystal phosphor 4 changes the resulting color of the light of the light sources 1. Any known luminescent material may be used for the production of the secondary phosphor 6 too.

(25) FIG. 5 depicts the example of the light source 1, which is provided with a cooler 9 to take away the generated heat. The cooler 9 protrudes out of the internal space of the element 13 for directing the extracted light 5, and inside the element 13 it is formed in the shape of a carrier 12 onto which the single crystal phosphor 4 is fixed. The supply of the excitation radiation 3 is similar as in the example of FIG. 3.

(26) FIG. 6 depicts the example of embodiment the light source 1 which uses only one laser diode as the source of the excitation radiation 3. The laser diode has sufficient output so that it is not necessary to conduct the excitation light beam to the single crystal phosphor 4 from distance with e.g. an optic fiber 10. The surface of single crystal phosphor 4 is provided with an anti-reflex layer 7. An optic lens 11 is used to scatter the excitation light beam onto as large as possible part of the excitation surface 17.

(27) FIG. 7 depicts the example of embodiment the light source 1 which uses the single crystal phosphor 4 with a rounded emission surface 18. The excitation surface 17 is enlarged and the excitation radiation 3 is evenly scattered onto it with the optic lens 11. The rounding of the emission surface 18 decreases the occurrence of the light beams total reflection.

(28) FIG. 8 depicts the example of embodiment the light source 1 which includes the single crystal phosphor 4 with connected optic fiber 10. The phosphor 4 is in the shape of a cylinder or a ball and radiates evenly in the all directions. The phosphor 4 is also provided with structuring 8 which makes light extraction easier.

(29) FIG. 9 depicts another example of embodiment the light source 1. The laser diode produces excitation radiation 3 which is guided via the optic lens 11 to the single crystal phosphor 4 that is machined into the shape of an elongated rectangular cuboid or cylinder. The side walls of the phosphor 4 are polished with the exception of the emission face 14, located in the front of the rectangular cuboid or cylinder base. Due to the high refractive index of the material of the phosphor 4 there occurs a total light reflection on the interface of the polished surfaces with the surrounding environment and the waveguiding character of the material of the single crystal phosphor 4 manifests itself. The emission face 14 may be ground or provided with an anti-reflex layer which enables the extraction of light 5 from the single crystal phosphor 4 directly in the place of the emission face 14. To supply the excitation radiation 3 it is also possible to use collimation lenses 19, optic fibers 10, optic lenses 11, similarly as in the preceding embodiments of this invention.

(30) It is also possible to use several diodes for the excitation of the single crystal phosphor 4 which are located along its longer polished side and thus it is possible to utilize maximum surface for the excitation of the single crystal phosphor 4. With the emission from an active center, the extracted light 5 is emitted in all directions and due to the polished surfaces there occurs total reflection until the extracted light reaches the emission surface 18 of the face 14 where it is outcoupled from the single crystal phosphor 4.

(31) FIG. 10 depicts another example of embodiment the light source 1 whose single crystal phosphor 4 has excitation and emission surfaces 17 and 18 simultaneously on one of the walls of the body of the single crystal phosphor 4. The surface of the remaining walls of the body of the single crystal phosphor 4 is treated to induce total light reflection back into the interior of the phosphor 4.

(32) FIG. 11 depicts an example of embodiment the light source 1 where the phosphor is created from thin plates 15 cut out from the single crystal phosphor 4 and 6. Two kinds of material were utilized to produce the plates 15 which differ in the maximum wavelength of emitted light. Therefore the resulting light of the light source is mixed and as a result it has a more pleasant color. The individual plates 15 are put on the carrier 12 alternately one over the other. This sandwich structure absorbs more efficiently the excitation radiation 3 which passes with decreasing intensity into plates 15 of the phosphor located higher in the structure until it is completely absorbed.

(33) FIG. 12 depicts an example of embodiment the light source 1 where a layer 20 of a crushed material for the production of single crystal phosphors 4 is applied onto the excitation surface 17 and emission surface 18 of the single crystal phosphor 4. The layer 20 is applied with the plasma deposition method. Two different materials are mixed in the layer 20 to admix the requested correlated color temperature of the extracted light 5.

INDUSTRIAL APPLICABILITY

(34) The light source according to the invention can be utilized in optic projection devices, for public lighting, in lighting systems for defense and weapons systems, in factory and production premises, halls, warehouses, in automotive industry and everywhere where efficient lighting is required.

OVERVIEW OF THE MARKINGS USED IN THE DRAWINGS

(35) 1 Light source 2 Solid-state laser source 3 Excitation coherent radiation 4 Single crystal phosphor 5 Emitted light 6 Secondary phosphor 7 Anti-reflex layer 8 Structure on the phosphor surface 9 Cooler 10 Optic fiber 11 Optic lens 12 Carrier 13 Element to direct extracted light 14 Single crystal phosphor emission face 15 Thin plate 16 Protective element 17 Excitation surface 18 Emission surface 19 Collimation lens 20 Single crystal phosphor crushed material layer