Light-emitting device having photoluminescent layer
View Patent ↗A light-emitting device comprises a layered structure between a first layer and a second layer. The first layer has a refractive index n1 for first light having a wavelength λ a in air. The second layer has a refractive index n2 for the first light. The layered structure comprises: a photoluminescent layer having a first surface facing the first layer and a second surface facing the second layer; and a surface structure disposed on at least one selected from the group consisting of the first surface and the second surface of the photoluminescent layer. The refractive index n1 and the refractive index n2 are lower than a refractive index n wav-a of the photoluminescent layer for the first light. The layered structure has an effective thickness to more strongly emit TE polarized light than TM polarized light.
1. A light-emitting device comprising a layered structure between a first layer and a second layer, the first layer having a refractive index n1 for first light having a wavelength λ a in air, the second layer having a refractive index n2 for the first light,
the layered structure comprising:
a photoluminescent layer having a first surface facing the first layer and a second surface facing the second layer; and
a surface structure disposed on at least one selected from the group consisting of the first surface and the second surface of the photoluminescent layer, the surface structure having projections and recesses,
wherein the photoluminescent layer emits the first light upon receiving excitation light,
the refractive index n1 and the refractive index n2 are lower than a refractive index n wav-a of the photoluminescent layer for the first light and satisfy a relationship n1>n2, and
the layered structure has an effective thickness to more strongly emit TE polarized light than TM polarized light.
2. The light-emitting device according to claim 1 , wherein
at least one selected from the group consisting of a portion of the first layer and a portion of the second layer is disposed in the recesses of the surface structure, and
an effective thickness t eff satisfies the following relational expressions (1) and (2), wherein t wav denotes a thickness of the photoluminescent layer, h denotes a thickness of the surface structure, n p denotes a refractive index of the surface structure for the first light, R v denotes a ratio of a volume of the recesses to a volume of the projections and the recesses, and m is an integer.
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3. The light-emitting device according to claim 1 , wherein
the photoluminescent layer includes discrete belt-like portions,
the surface structure is disposed on the belt-like portions,
at least one selected from the group consisting of a portion of the first layer and a portion of the second layer is disposed in the recesses of the surface structure, and
an effective thickness t eff satisfies the following relational expressions (3) and (4), wherein t wav denotes a thickness of the belt-like portions, h denotes a thickness of the surface structure, n p denotes a refractive index of the surface structure for the first light, R v denotes a ratio of a volume of the recesses to a volume of the projections and the recesses, and m is an integer.
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4. A light-emitting device comprising a layered structure between a first layer and a second layer, the first layer having a refractive index n1 for first light having a wavelength λ a in air, the second layer having a refractive index n2 for the first light,
the layered structure comprising:
a light guiding layer having a first surface facing the first layer and a second surface facing the second layer; and
a surface structure disposed on at least one selected from the group consisting of the first surface and the second surface of the light guiding layer, the surface structure having projections and recesses,
wherein the light guiding layer includes
a photoluminescent layer that emits the first light upon receiving excitation light and that has a refractive index n wav-a for the first light, and
an intermediate layer disposed between the surface structure and the photoluminescent layer, the intermediate layer having a refractive index n m for the first light,
the refractive index n1 and the refractive index n2 are lower than a refractive index of the light guiding layer for the first light and satisfy a relationship n1>n2, and
the layered structure has an effective thickness to more strongly emit TE polarized light than TM polarized light.
5. The light-emitting device according to claim 4 , wherein
at least one selected from the group consisting of a portion of the first layer and a portion of the second layer is disposed in the recesses of the surface structure, and
an effective thickness t eff satisfies the following relational expressions (5) and (6), wherein t wav denotes a thickness of the photoluminescent layer, h denotes a thickness of the surface structure, t m denotes a thickness of the intermediate layer, n p denotes a refractive index of the surface structure for the first light, R v denotes a ratio of a volume of the recesses to a volume of the projections and the recesses, and m is an integer.
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6. The light-emitting device according to claim 4 , wherein
the photoluminescent layer includes discrete belt-like portions,
the surface structure is disposed on the belt-like portions,
at least one selected from the group consisting of a portion of the first layer and a portion of the second layer is disposed in the recesses of the surface structure, and
the effective thickness t eff satisfies the following relational expressions (7) and (8), wherein t wav denotes a thickness of the belt-like portions, h denotes a thickness of the surface structure, t m denotes a thickness of the intermediate layer, n p denotes a refractive index of the surface structure for the first light, R v denotes a ratio of a volume of the recesses to a volume of the projections and the recesses, and m is an integer.
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7. The light-emitting device according to claim 3 , wherein
the belt-like portions are separately arranged in a first direction, and
the projections and the recesses extend in the first direction.
8. The light-emitting device according to claim 7 , wherein the projections and the recesses are arranged perpendicularly to the first direction.
9. The light-emitting device according to claim 7 , wherein a length of the belt-like portions in the first direction is not more than four times a distance D int between two adjacent projections or between two adjacent recesses.
10. The light-emitting device according to claim 7 , wherein a length of the belt-like portions in the first direction is 2 μm or less.
11. The light-emitting device according to claim 1 , wherein the first layer or the second layer is a substrate that supports the photoluminescent layer.
12. The light-emitting device according to claim 11 , wherein the photoluminescent layer is in direct contact with the substrate.
13. The light-emitting device according to claim 1 , wherein the first layer or the second layer is air.
14. The light-emitting device according to claim 1 , wherein a distance D int between two adjacent projections or between two adjacent recesses in the surface structure satisfies a relationship (λ a /n wav-a )<D int <λ a .
15. The light-emitting device according to claim 1 , wherein
the projections or the recesses constitute at least one periodic structure, and
the at least one periodic structure has a period p that satisfies a relationship (λ a /n wav-a )<p<λ a .
16. The light-emitting device according to claim 6 , wherein
the belt-like portions are separately arranged in a first direction, and
the projections and the recesses extend in the first direction.
17. The light-emitting device according to claim 16 , wherein the projections and the recesses are arranged perpendicularly to the first direction.
18. The light-emitting device according to claim 16 , wherein a length of the belt-like portions in the first direction is not more than four times a distance D int between adjacent projections or between adjacent recesses.
19. The light-emitting device according to claim 1 , wherein the photoluminescent layer and the surface structure are integrated.
20. The light-emitting device according to claim 4 , wherein the photoluminescent layer and the surface structure are integrated.
21. The light-emitting device according to claim 3 , wherein the belt-like portions include the first surface and the second surface.
22. The light-emitting device according to claim 6 , wherein the belt-like portions include the first surface and the second surface.