RESONANT CAVITY STRUCTURES CONTAINING WAVELENGTH CONVERSION MATERIALS - Patent application

Abstract

The present invention provides a resonant cavity structure including an upper layer in which first and second dielectric layers having different refractive indices are alternately stacked, a lower layer in which the first and second dielectric layers are alternately stacked, and a cavity formed between the upper and lower layers, wherein the cavity includes a wavelength conversion material that absorbs light having a first wavelength and emits light having a second wavelength different from the first wavelength, and the resonant cavity structure is designed to resonate in the cavity at the first wavelength, and configured so that excitation light of the first wavelength is incident from below the lower layer.

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE Embodiments of the present invention relate to resonant cavity structures that include a wavelength converting material, such as a phosphor. [Background technology]

[0002] Recently, the LED market size is continuing to grow in various fields such as lighting and displays. In particular, phosphors are essential for white LEDs to convert color. Phosphors are materials that absorb high-energy (i.e., short-wavelength) light and emit low-energy (i.e., long-wavelength) light. Until now, the focus has been mainly on the development of phosphor materials.

[0003] Therefore, if an optical structure that can increase the color conversion efficiency of any fluorescent material, without being limited to a specific material, is developed, it is expected that there will be active demand in various fields that require color conversion, such as lighting and displays. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been devised to improve the above-mentioned problems, and aims to provide an optical structure capable of improving the color conversion efficiency of various wavelength converting materials. Specifically, the present invention aims to provide a resonant cavity structure including a wavelength converting material.

[0005] However, such challenges are illustrative and are not intended to limit the scope of the invention. [Means for solving the problem]

[0006] According to an embodiment of the present invention, there is provided a resonant cavity structure including an upper layer in which first and second dielectric layers having different refractive indices are alternately stacked, a lower layer in which the first and second dielectric layers are alternately stacked, and a cavity formed between the upper layer and the lower layer, the cavity including a wavelength conversion material that absorbs light having a first wavelength and emits light having a second wavelength different from the first wavelength, the cavity being designed to resonate at the first wavelength, and configured such that excitation light of the first wavelength is incident on a lower portion of the lower layer. Effect of the Invention

[0007] According to an embodiment of the present invention configured as described above, the color conversion efficiency of the wavelength conversion material can be improved through the optical structure.

[0008] The resonant cavity structure including the wavelength conversion material (e.g., phosphor) according to an embodiment of the present invention has a simple structure in which thin films are stacked on a plane, and can be easily fabricated and applied to devices. For example, the resonant cavity structure can be fabricated by repeatedly coating thin films of a dielectric material, which is an easy process and allows for mass production.

[0009] Of course, the scope of the present invention is not limited to these effects. [Brief description of the drawings]

[0010] [Figure 1] 1A and 1B are diagrams for explaining excitation light, transmitted light, and color-converted light for a general wavelength converting material. [Diagram 2] 3A and 3B are diagrams illustrating excitation light, transmitted light, and color-converted light for a resonant cavity structure according to an embodiment of the present invention. [Figure 3A] 11A and 11B are diagrams illustrating a resonant cavity structure according to another embodiment of the present invention. [Figure 3B] 11A and 11B are diagrams illustrating a resonant cavity structure according to another embodiment of the present invention. [Figure 4]1 is a diagram showing a schematic structure of a distributed Bragg reflector and an example of its reflectance spectrum S1. [Diagram 5] FIG. 2 shows an example of a schematic structure of a resonant cavity structure and its reflectance spectrum in accordance with an embodiment of the present invention; [Figure 6] FIG. 2 illustrates an environment for simulating the transmittance, absorptance, and reflectance of a resonant cavity structure in accordance with an embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing the results of a simulation of the transmittance, absorptance, and reflectance of a resonant cavity structure in an environment such as that of FIG. 6. [Figure 8] 5A-5C show simulation results of the transmittance, absorptance, and reflectance of resonant cavity structures according to various embodiments of the present invention. [Figure 9] FIG. 2 shows a schematic structure of a resonant cavity structure according to another embodiment of the present invention. [Figure 10] FIG. 2 shows a schematic structure of a resonant cavity structure according to another embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENT

[0011] According to an embodiment of the present invention, there is provided a resonant cavity structure including an upper layer in which first and second dielectric layers having different refractive indices are alternately stacked, a lower layer in which the first and second dielectric layers are alternately stacked, and a cavity formed between the upper layer and the lower layer, the cavity including a wavelength conversion material that absorbs light having a first wavelength and emits light having a second wavelength different from the first wavelength, the cavity being designed to resonate at the first wavelength, and configured such that excitation light of the first wavelength is incident on a lower portion of the lower layer.

[0012] According to an embodiment, the second wavelength may be outside a stopband of the resonant cavity structure.

[0013] According to one embodiment, the second wavelength may be longer than the first wavelength.

[0014] According to one embodiment, a stop band of the resonant cavity structure may be formed in a band of wavelengths shorter than the second wavelength.

[0015] According to one embodiment, the refractive index of the first dielectric layer may be smaller than the refractive index of the cavity containing the wavelength converting material, and the refractive index of the second dielectric layer may be larger than the refractive index of the cavity containing the wavelength converting material.

[0016] According to one embodiment, the layer located at the bottom of the lower layer may be the first dielectric layer.

[0017] According to one embodiment, the layer located on top of the upper layer may be the second dielectric layer.

[0018] According to one embodiment, the dielectric layer in contact with the cavity in the upper layer and the dielectric layer in contact with the cavity in the lower layer are the same dielectric layer, and the thickness of the cavity is n / (2n c ) times (n is a natural number, n c is the refractive index of the cavity).

[0019] According to one embodiment, the dielectric layer in contact with the cavity in the upper layer and the dielectric layer in contact with the cavity in the lower layer are different dielectric layers, and the thickness of the cavity is n / (4n c ) times (n is an odd number, n c is the refractive index of the cavity).

[0020] According to one embodiment, the resonant cavity structure may further include a reflective layer disposed below the lower layer, the reflective layer passing light of the first wavelength and reflecting light of the second wavelength.

[0021] According to one embodiment, the cavity may further include a first wavelength converting material that absorbs light of the first wavelength and emits light of the second wavelength, and a second wavelength converting material that absorbs light of the first wavelength and emits light of a third wavelength.

[0022] According to one embodiment, the cavity may include a first layer having the first wavelength converting material distributed therein, a second layer having the second wavelength converting material distributed therein, and a third dielectric layer disposed between the first layer and the second layer.

[0023] According to one embodiment, the thickness of the cavity may be gradually changed along a direction intersecting the thickness direction of the cavity.

[0024] According to one embodiment, the thickness of the cavity may vary periodically along a direction intersecting the thickness direction of the cavity.

[0025] According to one embodiment, the thickness of the first dielectric layer or the thickness of the second dielectric layer may vary gradually as the number of alternations of the upper layer or the lower layer increases.

[0026] According to one embodiment, the refractive index of the first dielectric layer or the refractive index of the second dielectric layer may vary gradually as the number of alternations of the upper layer or the lower layer increases.

[0027] According to one embodiment, the upper or lower surface of the resonant cavity structure may include a concave or convex portion.

[0028] According to one embodiment, the upper or lower surface of the resonant cavity structure may include a plurality of recesses or a plurality of protrusions, and the plurality of recesses or the plurality of protrusions may be regularly arranged.

[0029] According to an embodiment of the present invention, there is provided a light emitting structure including an upper layer in which a first dielectric layer and a second dielectric layer having different refractive indexes are alternately stacked, a lower layer in which the first dielectric layer and the second dielectric layer are alternately stacked, and a resonant cavity structure including a cavity formed between the upper layer and the lower layer, and a light emitting structure or light emitting element disposed below the lower layer and generating excitation light of a first wavelength, the cavity including a wavelength conversion material that absorbs light having the first wavelength and emits light having a second wavelength different from the first wavelength, and the resonant cavity structure can be designed to resonate in the cavity at the first wavelength.

[0030] According to an embodiment, the second wavelength may be located outside a stopband of the resonant cavity structure.

[0031] According to one embodiment, the second wavelength may be longer than the first wavelength.

[0032] According to one embodiment, a stop band of the resonant cavity structure may be formed in a band of wavelengths shorter than the second wavelength.

[0033] According to one embodiment, the refractive index of the first dielectric layer is smaller than the refractive index of the cavity, the refractive index of the second dielectric layer is larger than the refractive index of the cavity, and the layer located at the bottom of the lower layer may be the first dielectric layer.

[0034] According to one embodiment, the refractive index of the first dielectric layer is smaller than the refractive index of the cavity, the refractive index of the second dielectric layer is larger than the refractive index of the cavity, and the layer located on top of the upper layer may be the second dielectric layer.

[0035] According to one embodiment, the cavity may further include a first wavelength converting material that absorbs light of the first wavelength and emits light of the second wavelength, and a second wavelength converting material that absorbs light of the first wavelength and emits light of a third wavelength.

[0036] According to one embodiment, the cavity may include a first layer having the first wavelength converting material distributed therein, a second layer having the second wavelength converting material distributed therein, and a third dielectric layer disposed between the first layer and the second layer.

[0037] Other aspects, features, and advantages beyond those described above will become apparent from the following drawings, claims, and detailed description of the invention.

[0038] Since the present invention can be modified in various ways and can have various embodiments, a specific embodiment will be shown in the drawings and described in detail. The effects and features of the present invention, as well as the methods for achieving them, will become apparent by referring to the embodiments described in detail below with the drawings. However, the present invention is not limited to the embodiments disclosed below, and can be implemented in various forms.

[0039] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. When describing with reference to the drawings, the same or corresponding components are given the same reference numerals, and duplicate descriptions thereof will be omitted.

[0040] In the following embodiments, the terms "first", "second" and the like are not used in a limiting sense but are used for the purpose of distinguishing one component from another component.

[0041] In the following embodiments, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0042] In the following embodiments, terms such as "include" or "have" mean the presence of features or components described in this specification, and do not preclude the possibility that one or more other features or components may be added.

[0043] In the drawings, the size of components may be exaggerated or reduced for the convenience of explanation. For example, the size and thickness of each component shown in the drawings are arbitrarily shown for the convenience of explanation, and the present invention is not necessarily limited to those shown in the drawings.

[0044] In the following embodiments, when a region, component, layer, or other part is said to be on or above another part, this includes not only when it is directly on top of the other part, but also when there is another region, component, layer, etc. in between.

[0045] FIG. 1 is a diagram for explaining excitation light EL, transmitted light TL′, and color-converted light CL′ for a general wavelength conversion material P, and FIG. 2 is a diagram for explaining excitation light EL, transmitted light TL, and color-converted light CL for a resonant cavity structure 100 according to an embodiment of the present invention.

[0046] First, referring to FIG. 1, when excitation light (EL) is irradiated onto a general wavelength conversion material P, the wavelength conversion material P can absorb a portion of the excitation light EL and emit color-converted light (CL'). The wavelength conversion material P can be, for example, a phosphor that absorbs high-energy (i.e., short-wavelength) excitation light EL and emits low-energy (i.e., long-wavelength) color-converted light CL'. However, without being limited thereto, the wavelength conversion material P can be nanoparticles that convert long-wavelength excitation light EL into short-wavelength color-converted light CL' by photon upconversion.

[0047] The color-converted light CL' may be emitted in all directions, while the remaining light of the excitation light EL that is absorbed by the wavelength-converting material P can be transmitted as transmitted light (TL').

[0048] In comparison, and referring to FIG. 2, a resonant cavity structure 100 according to an embodiment of the present invention includes an upper layer 10, a lower layer 30, and a cavity 20 formed between the upper layer 10 and the lower layer 30 and containing a wavelength converting material P.

[0049] The wavelength converting material P can absorb light having a first wavelength and emit light having a second wavelength longer or shorter than the first wavelength. If the wavelength converting material P is a general phosphor, the second wavelength may be longer than the first wavelength. If the wavelength converting material P is an upconverting nanoparticle, the second wavelength may be shorter than the first wavelength.

[0050] Hereinafter, the wavelength of the excitation light that excites the wavelength converting material P will be referred to as a first wavelength, and the wavelength of the color converted light emitted from the wavelength converting material will be referred to as a second wavelength.

[0051] The resonant cavity structure 100 according to the embodiment of the present invention can be designed to resonate at a first wavelength. For example, each of the upper layer 10 and the lower layer 30 can be a reflector that reflects light in a predetermined range including the first wavelength, and the thickness of the cavity 20 can satisfy a predetermined condition. When the resonant cavity structure 100 satisfies the predetermined condition, resonance of light of the first wavelength can occur in the cavity 20.

[0052] When the resonant cavity structure 100 is irradiated with excitation light EL, the wavelength converting material P contained in the cavity 20 can absorb a portion of the excitation light EL and emit color converted light CL. The color converted light CL may be emitted in all directions. The remaining light of the excitation light EL that is absorbed by the wavelength converting material P can be transmitted to the outside of the resonant cavity structure 100 as transmitted light TL. The excitation light EL and the transmitted light TL may have the above-mentioned first wavelength, and the color converted light CL may have a second wavelength.

[0053] 1 and 2 , when a common wavelength converting material P is compared with the resonant cavity structure 100 according to the embodiment of the present invention in a case where the same excitation light EL is irradiated, the resonant cavity structure 100 including the wavelength converting material P can absorb more excitation light EL than the common wavelength converting material P. In other words, the absorptivity of the resonant cavity structure 100 including the wavelength converting material P for the first wavelength can be higher than the absorptivity of the common wavelength converting material P for the first wavelength.

[0054] Therefore, the intensity of the color-converted light CL emitted from the resonant cavity structure 100 containing the wavelength converting material P can be greater than the intensity of the color-converted light CL′ emitted from a general wavelength converting material P. Furthermore, the intensity of the transmitted light TL in the resonant cavity structure 100 containing the wavelength converting material P can be smaller than the intensity of the transmitted light TL′ in a general wavelength converting material P.

[0055] Therefore, according to one embodiment of the present invention, if the excitation light EL is blue light and the wavelength conversion material P is a phosphor that absorbs the blue light and emits yellow or red light, the resonant cavity structure 100 can be used for a white light LED. In this case, a part of the blue light can exit the resonant cavity structure 100 as transmitted light TL, and another part can be absorbed by the phosphor and exit the resonant cavity structure 100 as color-converted light CL of yellow or red light.

[0056] Meanwhile, according to an embodiment of the present invention, each of the upper layer 10 and the lower layer 30 may be a Distributed Bragg Reflector (DBR).

[0057] 2 shows that the surface of the resonant cavity structure 100, specifically the upper or lower surface, is a planar structure, but the present invention is not limited thereto, and in another embodiment, the upper or lower surface of the resonant cavity structure 100 may have a shape including a concave or convex portion. For example, the upper or lower surface of the resonant cavity structure 100 may have a shape including a plurality of concave or convex portions, in which the plurality of concave or convex portions are regularly arranged.

[0058] 3A and 3B are diagrams illustrating a resonant cavity structure 100 according to another embodiment of the present invention.

[0059] 3A and 3B, a resonant cavity structure 100 according to another embodiment includes an upper layer 10, a lower layer 30, and a cavity 20 formed between the upper layer 10 and the lower layer 30 and containing a wavelength converting material P, similar to the resonant cavity structure 100 of FIG. 2, and may further include a substrate 1 provided on the upper layer 10 or the lower layer 30.

[0060] The substrate 1 may be made of a transparent material and may be disposed between another device, such as a light-emitting device, and the resonant cavity structure 100. In one embodiment, the substrate 1 may be made of a glass material. In this case, the resonant cavity structure 100 according to another embodiment may have different thicknesses between the upper layer 10 and the lower layer 30, unlike the resonant cavity structure of FIG. 2.

[0061] More specifically, the thickness of the lower layer 30 closer to the excitation light EL may be thinner than the thickness of the upper layer 10. In this case, the substrate 1 may be disposed adjacent to the lower layer 30 as shown in Fig. 3A, or may be disposed adjacent to the upper layer 10 as shown in Fig. 3B.

[0062] 4 is a diagram showing a schematic structure of a distributed Bragg reflector (DBR) and an example of its reflectance spectrum S1. The distributed Bragg reflector may have a structure in which a first dielectric layer 11 and a second dielectric layer 12 having mutually different refractive indices are alternately laminated.

[0063] 4, each of the upper layer 10 and the lower layer 30 according to an embodiment of the present invention may be formed of a distributed Bragg reflector. Each of the upper layer 10 and the lower layer 30 may have a structure in which a first dielectric layer 11 and a second dielectric layer 12 having different refractive indices are alternately stacked. In other words, each of the upper layer 10 and the lower layer 30 may have a structure in which the refractive index changes periodically.

[0064] Distributed Bragg reflectors can be designed to reflect light within a specific wavelength range. The wavelength range (or frequency range) that is reflected is called the stopband. Light with wavelengths within the stopband is prohibited from propagating through the distributed Bragg reflector.

[0065] In one embodiment of the present invention, the upper layer 10 and the lower layer 30 can be designed to have a stop band including a first wavelength. For example, in the upper layer 10 and the lower layer 30, the refractive index and thickness of the first dielectric layer 11 and the refractive index and thickness of the second dielectric layer 12 can be adjusted to design the upper layer 10 and the lower layer 30 so that a stop band is formed at the first wavelength.

[0066] In one embodiment, the thickness of the first dielectric layer 11 or the thickness of the second dielectric layer 12 may gradually change as the number of alternations increases for the upper layer 10 or the lower layer 30. In other words, the first dielectric layer 11 and the second dielectric layer 12 are alternately stacked, but the alternating layers are not stacked to the same thickness, but may be designed so that the thickness of each layer becomes thinner or thicker along the direction in which the number of alternations increases. Alternatively, the refractive index of the first dielectric layer 11 or the refractive index of the second dielectric layer 12 may gradually change as the number of alternations increases for the upper layer 10 or the lower layer 30.

[0067] When excitation light EL of a first wavelength is irradiated onto a distributed Bragg reflector (DBR) 10, 30 designed in this manner, almost no light may be transmitted to the opposite side. Figure 4 shows a situation in which, when excitation light EL is irradiated toward the DBR 10, 30 from the bottom thereof, no light is transmitted to the top of the DBR 10, 30.

[0068] The reflectance spectrum S1 of the DBRs 10 and 30 is a graph simulating the spectrum of light intensity at a plane P1 below the DBRs 10 and 30 when excitation light EL is irradiated toward the DBRs 10 and 30 from below.

[0069] FIG. 5 shows a schematic structure of a resonant cavity structure 100 according to an embodiment of the present invention and an example of its reflectance spectrum S2.

[0070] Referring to FIG. 5, a resonant cavity structure 100 according to an embodiment of the present invention includes an upper layer 10 in which a first dielectric layer 11 and a second dielectric layer 12 having different refractive indices are alternately stacked, a lower layer 30 in which the first dielectric layer 11 and the second dielectric layer 12 are alternately stacked, and a cavity 20 formed between the upper layer 10 and the lower layer 30, and the cavity 20 contains a wavelength conversion material.

[0071] According to an embodiment of the present invention, the wavelength converting material P can absorb light having a first wavelength and emit light having a second wavelength, which is longer or shorter than the first wavelength, and the resonant cavity structure 100 can be designed such that a resonance occurs in the cavity 20 at the first wavelength.

[0072] The resonant cavity structure 100 according to the embodiment of the present invention can improve the color conversion efficiency of the wavelength conversion material P from a first wavelength to a second wavelength. In various embodiments, the resonant cavity structure 100 can be applied to various light emitting devices by setting the first wavelength and the second wavelength as necessary and using the excitation light EL and the wavelength conversion material P that match the first and second wavelengths. For example, the resonant cavity structure 100 including the wavelength conversion material (e.g., phosphor) that absorbs the blue excitation light EL and emits yellow light or red light can be applied to a white LED. However, the present invention is not limited thereto.

[0073] The resonant cavity structure 100 can induce strong resonance at a specific wavelength by including the cavity 20 between the upper layer 10 and the lower layer 30. Specifically, optical resonance can occur at a specific wavelength determined based on the thickness T and refractive index of the cavity 20. A detailed description of the condition of the thickness T of the cavity 20 for optical resonance at a first wavelength will be described later.

[0074] In the embodiment of the present invention, the thickness T of the cavity 20 can be determined so that the cavity 20 resonates at a first wavelength, which is an absorption wavelength of the wavelength converting material P. When the cavity 20 resonates at the first wavelength, at least a part of the light of the first wavelength can be trapped in the cavity 20. Therefore, the absorptance of the resonant cavity structure 100 at the first wavelength can be increased, and the color conversion efficiency of the wavelength converting material P can be improved.

[0075] In other embodiments, the thickness T of the cavity 20 may vary along a direction intersecting the thickness direction of the cavity 20, for example, along the planar direction of the resonant cavity structure 100. Specifically, the thickness of the cavity 20 may vary gradually along the planar direction of the resonant cavity structure 100. Alternatively, the thickness of the cavity 20 may vary periodically along the planar direction of the resonant cavity structure 100.

[0076] The reflectance spectrum S2 of the resonant cavity structure 100 is a graph obtained by simulating the spectrum of light intensity at a plane P2 below the resonant cavity structure 100 when excitation light is generated from the bottom of the resonant cavity structure 100 toward the resonant cavity structure 100.

[0077] Compared to the reflectance spectrum S1 of only the DBRs 10, 30 without a cavity, the reflectance spectrum S2 of the resonant cavity structure 100 in which the cavity 20 is formed between the upper layer 10 and the lower layer 30 may have a dip at a first wavelength.

[0078] Therefore, when the excitation light EL of the first wavelength is irradiated to the resonant cavity structure 100, a part of the light of the first wavelength is confined in the cavity 20 and resonates, and another part of the light can escape from the resonant cavity structure 100 as transmitted light TL. Of course, the remaining part may be reflected. Therefore, the absorptance of the resonant cavity structure 100 at the first wavelength is increased, and the color conversion efficiency of the wavelength converting material P can be improved.

[0079] Fig. 6 is a diagram showing an environment for simulating the transmittance, absorptance, and reflectance of a resonant cavity structure 100 according to an embodiment of the present invention, and Fig. 7 is a diagram showing the simulation results of the transmittance T, absorptance A, and reflectance R of the resonant cavity structure 100 in the environment as shown in Fig. 6.

[0080] The simulation environment shown in Fig. 6 assumes that excitation light EL is irradiated from the bottom of the resonant cavity structure 100 toward the resonant cavity structure 100. It is assumed that the excitation light EL is a plane wave. It is assumed that the bottom surface and the top surface of the resonant cavity structure 100 are PML (Perfectly Matched Layer) in the simulation environment. It is assumed that the side surface of the resonant cavity structure 100 is under a periodic boundary condition (PBC) in the simulation environment.

[0081] 6 and 7, under the above-mentioned simulation conditions, the transmittance spectrum T of the resonant cavity structure 100 can be obtained based on the optical spectrum in the upper region A1 of the resonant cavity structure 100. Under the above simulation conditions, the reflectance spectrum R of the resonant cavity structure 100 can be obtained based on the optical spectrum in the lower region A3 of the resonant cavity structure 100. In addition, the absorptance spectrum A in the cavity region A2 can be obtained by subtracting the transmittance spectrum T and the reflectance spectrum R from the excitation light EL spectrum.

[0082] 7 shows a simulation result of the transmittance spectrum T, the absorptance spectrum A, and the reflectance spectrum R of the resonant cavity structure 100 under the above-mentioned conditions. The simulation may be, for example, a finite-difference time-domain (FDTD) simulation.

[0083] Here, the wavelength conversion material P contained in the cavity 20 is assumed to be red quantum dots (red colloidal quantum dots, red CQDs) (refractive index: 1.82). The material of the first dielectric layer 11 is SiO 2 (refractive index 1.46), and the material of the second dielectric layer 12 is SiN 4(refractive index 2.04) was assumed. The resonant cavity structure 100 was designed so that resonance occurs in the cavity 20 at a set first wavelength. The first wavelength can be set to, for example, 450 nm, but is not limited thereto. The first wavelength is set to an absorption wavelength of the wavelength converting material P according to the characteristics of the wavelength converting material P.

[0084] Specifically, the thickness of the first dielectric layer 11, the thickness of the second dielectric layer 12, and the thickness of the cavity 20 are set so as to resonate at the first wavelength and form a stop band around the first wavelength. For example, when the two dielectric layers in contact with the upper and lower parts of the cavity 20 are the same type of dielectric layers, the thickness T of the cavity 20 is n / (2n-1) of the first wavelength (e.g., 450 nm). c ) times (n is a natural number, n- c In another example, when the refractive index of one of the two dielectric layers in contact with the upper and lower parts of the cavity 20 is smaller than that of the cavity 20 and the refractive index of the other dielectric layer is larger than that of the cavity 20, the thickness T of the cavity 20 can be set to n / (4n-1) of the first wavelength (e.g., 450 nm). c ) times (n is an odd number, n- c can be set to the refractive index of the cavity 20).

[0085] Referring to graph G100, a dip in reflectance spectrum R may be formed at a set first wavelength. Thus, a peak in absorptance spectrum A may be formed at the first wavelength due to resonance at the first wavelength. Also, referring to transmittance spectrum T, it can be seen that a portion of light at the first wavelength is transmitted.

[0086] Based on this, when excitation light EL of a first wavelength is irradiated onto a resonant cavity structure 100 containing a wavelength converting material P, some of the light of the first wavelength can exit the resonant cavity structure 100 as is, and some of the light can be color converted to a second wavelength by the wavelength converting material P and then exit the resonant cavity structure 100.

[0087] In one embodiment of the present invention, the color-converted light of the second wavelength must successfully exit a distributed Bragg reflector (DBR) corresponding to the upper layer 10. Therefore, in one embodiment of the present invention, the stopband (i.e., the band with reflectivity close to 1) of the resonant cavity structure 100 can be formed to exclude the second wavelength.

[0088] In the following, the conditions necessary to design the resonant cavity structure 100 such that the stopband of the resonant cavity structure 100 does not include the second wavelength are described.

[0089] The following formula 1 represents the stopband width.

[0090]

number

[0091] In formula 1, Δλ max represents the stopband width, λ represents the central wavelength of the stopband, and n L is the refractive index of the first dielectric layer 11 at the wavelength λ, and n H denotes the refractive index of the second dielectric layer 12 at a wavelength λ. In the embodiment of the present invention, the central wavelength of the stop band is designed to match the first wavelength, which is the absorption wavelength of the wavelength converting material P, so that λ is the first wavelength.

[0092] Referring to Equation 1, the refractive index n of the first dielectric layer 11 L and the refractive index n of the second dielectric layer 12 H The larger the difference between the first wavelength and the second wavelength, the larger the stopband width can be. However, if the stopband width is too large, the stopband will include the second wavelength. If the stopband includes the second wavelength, the structure 100 will prohibit the propagation of the light of the second wavelength, causing a problem that the color-converted light cannot exit the structure 100 well.

[0093] Therefore, according to an embodiment of the present invention, the difference between the refractive index of the first dielectric layer 11 and the refractive index of the second dielectric layer 12 can be set so that the stop band of the resonant cavity structure 100 does not include the second wavelength. In other words, the difference between the refractive index of the first dielectric layer 11 and the refractive index of the second dielectric layer 12 can be set so that the stop band of the resonant cavity structure 100 is formed in a band of shorter or longer wavelengths than the second wavelength.

[0094] According to one embodiment, the difference between the refractive index of the first dielectric layer 11 and the refractive index of the second dielectric layer 12 may be set to be less than a specified value.

[0095] According to one embodiment of the present invention, the number of pairs of the first dielectric layer 11 and the second dielectric layer 12 in the upper layer 10 and the number of pairs of the first dielectric layer 11 and the second dielectric layer 12 in the lower layer 30 may be 4 or more and 6 or less, respectively.

[0096] For example, the more pairs between the first dielectric layer 11 and the second dielectric layer 12 in the upper layer 10 and the lower layer 30, the more clearly the stop band can be defined. For example, the more pairs between the first dielectric layer 11 and the second dielectric layer 12, the more abruptly the reflectance can change at the boundary of the stop band. However, the more pairs, the more the reflectance of the structure 100 at the first wavelength increases, and the transmittance of the structure 100 at the first wavelength may decrease. Therefore, the absorptance of the structure 100 at the first wavelength may be highest when the number of pairs in the upper layer 10 is 4 to 6, and the number of pairs in the lower layer 30 is 4 to 6. However, this is merely an embodiment, and the present invention is not limited thereto.

[0097] According to one embodiment of the present invention, the number of pairs of the first dielectric layer 11 and the second dielectric layer 12 in the upper layer 10 may be different from the number of pairs of the first dielectric layer 11 and the second dielectric layer 12 in the lower layer 30. Also, according to one embodiment of the present invention, the number of pairs of the first dielectric layer 11 and the second dielectric layer 12 in the upper layer 10 or the lower layer 30 does not necessarily have to be an integer. For example, when the upper layer 10 has five pairs of the first dielectric layer 11 and the second dielectric layer 12, five first dielectric layers 11 and five second dielectric layers 12 may be alternately stacked in the upper layer 10. For example, when the lower layer 30 has 4.5 pairs of the first dielectric layer 11 and the second dielectric layer 12, five first dielectric layers 11 and four second dielectric layers 12 may be alternately stacked in the lower layer 30. However, this is merely an example, and the present invention is not limited thereto.

[0098] According to one embodiment of the present invention, the layer in contact with the cavity 20 in the upper layer 10 (i.e., the bottom layer of the upper layer 10) may be the first dielectric layer 11 or the second dielectric layer 12. Also, the layer in contact with the cavity 20 in the lower layer 30 (i.e., the top layer of the lower layer 30) may be the first dielectric layer 11 or the second dielectric layer 12.

[0099] In the following, it is assumed that the refractive index of the first dielectric layer 11 is smaller than that of the cavity 20 , and the refractive index of the second dielectric layer 12 is larger than that of the cavity 20 .

[0100] In one embodiment, when the layer adjacent to the cavity 20 is the second dielectric layer 12, the boundary between the cavity 20 and the second dielectric layer 12 is a fixed end and a node may be formed. In one embodiment, when the layer adjacent to the cavity 20 is the first dielectric layer 11, the boundary between the cavity 20 and the first dielectric layer 11 is a free end and an antinode may be formed.

[0101] According to one embodiment, both the dielectric layer in contact with the cavity 20 in the upper layer 10 and the dielectric layer in contact with the cavity 20 in the lower layer 30 may be the second dielectric layer 12. In this case, both the upper and lower ends of the cavity 20 become fixed ends, and a strong field can be formed in the center of the cavity 20.

[0102] According to another embodiment, both the dielectric layer in contact with the cavity 20 in the upper layer 10 and the dielectric layer in contact with the cavity 20 in the lower layer 30 may be the first dielectric layer 11. In this case, both the upper and lower ends of the cavity 20 become free ends, and a strong field can be formed at the upper and lower ends of the cavity 20.

[0103] When the dielectric layer in contact with the cavity 20 in the upper layer 10 and the dielectric layer in contact with the cavity 20 in the lower layer 30 are the same type of dielectric layer, the thickness T of the cavity 20 is n / (2n c ) times (n is a natural number, n c is the refractive index of the cavity 20).

[0104] According to yet another embodiment, the dielectric layer bordering the cavity 20 at the upper layer 10 and the dielectric layer bordering the cavity 20 at the lower layer 30 can be different types of dielectric layers. In this case, to resonate at the first wavelength, the thickness T of the cavity 20 is n / (4n c ) times (n is an odd number, n c is the refractive index of the cavity 20).

[0105] FIG. 8 illustrates simulated transmittance T, absorptance A, and reflectance R of a resonant cavity structure 100 according to various embodiments of the present invention.

[0106] In various embodiments of the present invention, it is assumed that the refractive index of the second dielectric layer 12 is greater than the refractive index of the first dielectric layer 11 .

[0107] 8, in the resonant cavity structures 100 according to various embodiments of the present invention, the top layer of the upper layer 10 (layer 1 in FIG. 8), the bottom layer of the upper layer 10 (layer 2 in FIG. 8), the top layer of the lower layer 30 (layer 3 in FIG. 8), and the bottom layer of the lower layer 30 (layer 4 in FIG. 8) may be the first dielectric layer 11 or the second dielectric layer 12. Graphs G1 to G16 shown in FIG. 8 are graphs of the transmittance T, the absorptance A, and the optical reflectance R versus the number for all these cases.

[0108] In the notation of FIG. 8, L represents a low refractive index, ie, the first dielectric layer 11, and H represents a high refractive index, ie, the second dielectric layer 12.

[0109] For example, G1 is written as LHHL, and is a simulation graph of a resonant cavity structure in which layer 1 is the first dielectric layer 11, layers 2 and 3 are the second dielectric layer 12, and layer 4 is the first dielectric layer 11.

[0110] G2, denoted as LHHH, is a simulation graph of a resonant cavity structure in which the first layer is the first dielectric layer 11, and the second, third and fourth layers are all second dielectric layers 12.

[0111] G3 is a simulation graph of a resonant cavity structure, denoted as HHHL, in which the first, second and third layers are all second dielectric layers 12 and the fourth layer is the first dielectric layer 11.

[0112] Moreover, G1 to G4 in the first row are simulation graphs in which the second and third layers are both second dielectric layers 12.

[0113] G5 to G8 in the second row are simulation graphs in which the second layer is the second dielectric layer 12 and the third layer is the first dielectric layer 11.

[0114] G9 to G12 in the third row are simulation graphs in which the second layer is the first dielectric layer 11 and the third layer is the second dielectric layer 12.

[0115] G13 to G16 in the fourth row are simulation graphs in which the second and third layers are both first dielectric layers 11.

[0116] According to an embodiment of the present invention, the layer (layer 4) located at the bottom of the lower layer 30 is preferably the first dielectric layer 11. This is because, if the refractive index of the layer (layer 4) located at the bottom of the lower layer 30 is low, it may reflect less excitation light. Referring to graphs G1 to G16, it can be seen that when the layer 4 is the first dielectric layer 11 (G1, G3, G6, G8, G9, G11, G14, and G16), a deep dip in the reflectance spectrum at the first wavelength is formed. Therefore, in order to minimize the reflection of the excitation light and to allow the excitation light to enter the inside of the structure 100 as much as possible and resonate in the cavity 20, it is preferable that the layer (layer 4) located at the bottom of the lower layer 30 is the first dielectric layer 11. However, the present invention is not limited thereto. In the resonant cavity structure 100 according to any embodiment, a second dielectric layer 12 may be disposed at the bottom of the lower layer 30.

[0117] According to one embodiment of the present invention, the layer (first layer) located at the top of the upper layer 10 is preferably the second dielectric layer 12. This is because if the refractive index of the layer (first layer) located at the top of the upper layer 10 is high, there is a possibility that the transmission is reduced and the absorption is increased. Also referring to graphs G1 to G16, it can be seen that the transmittance is small at the first wavelength when the first layer is the second dielectric layer 12 (G3, G4, G7, G8, G9, G10, G13, and G14). Therefore, in order to minimize the transmission of the excitation light and to confine the excitation light as much as possible inside the structure 100 so that it resonates in the cavity 20, it is preferable that the layer (first layer) located at the top of the upper layer 10 is the second dielectric layer 12. However, the present invention is not limited thereto.

[0118] FIG. 9 is a diagram showing a schematic structure of a resonant cavity structure 101 according to another embodiment of the present invention.

[0119] 9, a resonant cavity structure 101 according to another embodiment of the present invention may further include a reflective layer 40 disposed on a side where excitation light is irradiated, compared to the above-described resonant cavity structure 100. Assuming that excitation light is irradiated from the lower portion of the resonant cavity structures 100 and 101 as described above, the resonant cavity structure 101 may further include a reflective layer 40 below the lower layer 30, compared to the above-described resonant cavity structure 100.

[0120] Specifically, the resonant cavity structure 101 according to another embodiment of the present invention may include an upper layer 10, a lower layer 30, a cavity 20 formed between the upper layer 10 and the lower layer 30 and including a wavelength conversion material P, and a reflective layer 40 disposed under the lower layer 30. The wavelength conversion material P may absorb light of a first wavelength and emit light of a second wavelength. The upper layer 10 and the lower layer 30 may each have a structure that reflects light of the first wavelength. The cavity 20 between the upper layer 10 and the lower layer 30 may be formed so that light of the first wavelength resonates. In addition, the reflective layer 40 disposed under the lower layer 30 may have a structure that reflects light of a second wavelength. An excitation light may be irradiated from the lower part of the reflective layer 40 toward the resonant cavity structure 101.

[0121] According to an embodiment, each of the upper layer 10 and the lower layer 30 may be a distributed Bragg reflector (DBR) that reflects light of a first wavelength. Also, the reflective layer 40 may be a distributed Bragg reflector (DBR) that reflects light of a second wavelength. The stop band of the reflective layer 40 may be formed so as not to include the first wavelength. That is, the stop band of the reflective layer 40 may be formed in a band of longer or shorter wavelengths than the first wavelength. As a result, the optical spectrum around the first wavelength of the resonant cavity structure 101 to which the reflective layer 40 is added may be similar to the optical spectrum around the first wavelength of the resonant cavity structure 100 described above. That is, the reflective layer 40 may be designed so that the transmittance, absorptance, and reflectance at the first wavelength are hardly decreased even when the reflective layer 40 is added. Meanwhile, the intensity of the color-converted light of the second wavelength that escapes to the upper part may be further improved due to the presence of the reflective layer 40 that reflects light of the second wavelength.

[0122] FIG. 10 is a diagram showing a schematic structure of a resonant cavity structure 102 according to another embodiment of the present invention.

[0123] Referring to FIG. 10, a cavity 20' of a resonant cavity structure 102 according to another embodiment of the present invention may include a first wavelength converting material P1 and a second wavelength converting material P2.

[0124] According to one embodiment, the cavity 20' may include a first layer having a first wavelength converting material P1 distributed therein, a second layer having a second wavelength converting material P2 distributed therein, and a third dielectric layer 21 disposed between the first and second layers.

[0125] According to one embodiment, the first wavelength-converting material P1 can absorb light of a first wavelength, which is the wavelength of the excitation light EL, and emit light of a second wavelength, and the second wavelength-converting material P2 can absorb light of the first wavelength and emit light of a third wavelength.

[0126] According to an embodiment, the first wavelength conversion material P1 may be a first phosphor that absorbs light of a first wavelength and emits light of a second wavelength that is longer than the first wavelength, and the second wavelength conversion material P2 may be a second phosphor that absorbs light of the first wavelength and emits light of a third wavelength that is longer than the first wavelength. In this case, when the excitation light EL is irradiated from the lower part of the resonant cavity structure 102 and the first layer including the first phosphor is disposed below the second layer including the second phosphor, the second wavelength that is the emission wavelength of the first phosphor may be longer than the third wavelength that is the emission wavelength of the second phosphor. Only then can the light of the second wavelength that has been color-converted by the first phosphor be reabsorbed by the second phosphor.

[0127] The upper layer 10 and the lower layer 30 of the resonant cavity structure 102 according to the embodiment shown in FIG. 10 may correspond to the upper layer 10 and the lower layer 30 described above.

[0128] The present invention may further include a light emitting structure including a light emitting layer disposed below the resonant cavity structures 100, 101, 102 according to various embodiments and the resonant cavity structures 100, 101, 102 and emitting excitation light (not shown). The light emitting layer may be, for example, a light emitting structure or a light emitting element (e.g., LED, etc.). Thus, a light emitting structure according to an embodiment of the present invention may include the resonant cavity structures 100, 101, 102 and the light emitting structure or a light emitting element (e.g., LED, etc.) disposed below the resonant cavity structures 100, 101, 102 and generating excitation light of a first wavelength.

[0129] The present invention has been described with reference to an embodiment shown in the drawings, but this is merely illustrative, and those skilled in the art will appreciate that various modifications and variations of the embodiment are possible. Therefore, the true technical scope of the present invention should be determined by the technical ideas of the appended claims. Industrial Applicability

[0130] According to an embodiment of the present invention, a resonant cavity structure is provided, which can be used in a variety of fields requiring color conversion, such as lighting and displays.

Claims

1. 1. A resonant cavity structure comprising: an upper layer in which first and second dielectric layers having different refractive indices are alternately stacked; a lower layer in which the first dielectric layer and the second dielectric layer are alternately stacked; and a cavity formed between the upper layer and the lower layer, the dielectric layer in the upper layer in contact with the cavity and the dielectric layer in the lower layer in contact with the cavity are the same dielectric layer; the cavity includes a wavelength converting material that absorbs light having a first wavelength and emits light having a second wavelength different from the first wavelength; the first wavelength is a wavelength of excitation light irradiated to the resonant cavity structure, the second wavelength is a wavelength of color-converted light emitted from the resonant cavity structure; The thickness of the cavity is n / (2n ｃ ) times (n is a natural number, n ｃ is the refractive index of the cavity), the resonant cavity structure is designed to cause resonance in the cavity at the first wavelength; A resonant cavity structure configured so that the excitation light at the first wavelength is incident from a lower portion of the lower layer.

2. The resonant cavity structure of claim 1 , wherein the second wavelength is outside a stopband of the resonant cavity structure.

3. The resonant cavity structure of claim 1 , wherein said second wavelength is longer than said first wavelength.

4. The resonant cavity structure of claim 3 , wherein a stopband of the resonant cavity structure is formed in a band of wavelengths shorter than the second wavelength.

5. 1. A resonant cavity structure comprising: an upper layer in which first and second dielectric layers having different refractive indices are alternately stacked; a lower layer in which the first dielectric layer and the second dielectric layer are alternately stacked; and a cavity formed between the upper layer and the lower layer, the dielectric layer in the upper layer in contact with the cavity and the dielectric layer in the lower layer in contact with the cavity are different dielectric layers from each other, the cavity includes a wavelength converting material that absorbs light having a first wavelength and emits light having a second wavelength different from the first wavelength; the first wavelength is a wavelength of excitation light irradiated to the resonant cavity structure, The second wavelength is the wavelength of the color-converted light emitted from the resonant cavity structure, and the thickness of the cavity is n / (4n ｃ ) times (n is an odd number, n ｃ is the refractive index of the cavity), the resonant cavity structure is designed to cause resonance in the cavity at the first wavelength; The excitation light of the first wavelength is configured to be incident from a lower part of the lower layer. Resonant cavity structure.

6. a reflective layer disposed under the lower layer, the reflective layer passing the light of the first wavelength and reflecting the light of the second wavelength; 2. The resonant cavity structure of claim 1.

7. The cavity is a first wavelength-converting material that absorbs light at the first wavelength and emits light at the second wavelength; and Further comprising a second wavelength converting material that absorbs light of the first wavelength and emits light of a third wavelength.

2. The resonant cavity structure of claim 1.

8. the cavity includes a first layer having the first wavelength converting material distributed therein, a second layer having the second wavelength converting material distributed therein, and a third dielectric layer disposed between the first layer and the second layer.

8. The resonant cavity structure of claim 7.

9. The resonant cavity structure of claim 1 , wherein the thickness of the cavity varies gradually along a direction intersecting the thickness direction of the cavity.

10. The resonant cavity structure of claim 1 , wherein the thickness of the cavity varies periodically along a direction intersecting the thickness direction of the cavity.

11. 2. The resonant cavity structure of claim 1, wherein the thickness of the first dielectric layer or the thickness of the second dielectric layer varies gradually as the number of alternations of the upper layer or the lower layer increases.

12. The resonant cavity structure of claim 1 , wherein a top surface or a bottom surface of the resonant cavity structure includes a concave or convex portion.

13. an upper surface or a lower surface of the resonant cavity structure includes a plurality of recesses or a plurality of protrusions; The plurality of recesses or the plurality of protrusions are regularly arranged.

13. The resonant cavity structure of claim 12.

14. An upper layer in which a first dielectric layer and a second dielectric layer having different refractive indices are alternately stacked, a lower layer in which the first dielectric layer and the second dielectric layer are alternately stacked, and a resonant cavity structure including a cavity formed between the upper layer and the lower layer, a light emitting structure or light emitting element disposed under the lower layer and generating excitation light of a first wavelength; the dielectric layer in the upper layer in contact with the cavity and the dielectric layer in the lower layer in contact with the cavity are the same dielectric layer; the cavity includes a wavelength converting material that absorbs light having the first wavelength and emits light having a second wavelength different from the first wavelength; the first wavelength is a wavelength of excitation light irradiated to the resonant cavity structure, the second wavelength is a wavelength of color-converted light emitted from the resonant cavity structure; The thickness of the cavity is n / (2n ｃ ) times (n is a natural number, n ｃ is the refractive index of the cavity), The resonant cavity structure is designed to provide resonance in the cavity at the first wavelength.

15. 15. The light emitting structure of claim 14, wherein the second wavelength is outside a stopband of the resonant cavity structure.

16. 15. The light emitting structure of claim 14, wherein the second wavelength is longer than the first wavelength.

17. 17. The light emitting structure of claim 16, wherein a stopband of the resonant cavity structure is formed at a band of wavelengths shorter than the second wavelength.

18. The cavity is a first wavelength-converting material that absorbs light at the first wavelength and emits light at the second wavelength; and Further comprising a second wavelength converting material that absorbs light of the first wavelength and emits light of a third wavelength. The light emitting structure of claim 14.

19. the cavity includes a first layer having the first wavelength converting material distributed therein, a second layer having the second wavelength converting material distributed therein, and a third dielectric layer disposed between the first layer and the second layer.

20. The light emitting structure of claim 18.

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