Light-emitting devices with improved extraction

Abstract

The present invention relates to a light emitting device comprising a light collector (CL) made of a solid fluorescent or scintillating material, having at least seven faces, namely two parallel faces called large faces (FE1, FE2), a first side face (FL1) and a second side face (FL2) having a larger surface than the surfaces of the other sides, a third side face (FS) adjacent to the first and second side faces and called the exit face, a side face called the first facet (FT1) adjacent to the first side face, and a side face called the second facet (FT2) adjacent to the second side face, and at least five faces called side faces (FL1, FL2, FS, FT1, FT2) in which the first and second facets form an angle a smaller than 175° and larger than 0° with each other, and a first mirror (M1) arranged to cover the first facet (FT1), and a second mirror (M2) arranged to cover the second facet (FT2).

Description

[Technical Field]

[0001] The present invention relates to the field of optical concentrators excited by external radiation, and more particularly to improving the extraction of light emitted within such concentrators. [Background technology]

[0002] Light emitting diodes (LEDs) have many lighting applications, however LED brightness is limited to values ​​that make them unsuitable for some applications.

[0003] One solution to increasing LED brightness is to use LED-excited luminescent concentrators (e.g., Non-Patent Document 1). The concentrators are crystals that fluoresce in the visible (red-orange), such as Ce:YAG, which absorbs blue light at wavelengths where LEDs perform very well (around 450 nm). The crystals are cut into flat shapes, and hundreds (if not thousands) of LEDs are aligned on two large surfaces, emitting light from the edge. These concentrators achieve brightness values ​​10 to 20 times higher than those of LEDs.

[0004] 1A shows an example of a light-emitting module ME0 known from the prior art, based on a collector crystal CL in the form of a parallelepiped with length L, width w and thickness e. The ME0 light-emitting module comprises a set of LEDs designed to emit in a first spectral band and a collector CL. The collector CL collects the electroluminescent radiation L emitted by the LEDs. d The illumination surfaces of FE1 and FE2 have at least one illumination surface FE1, FE2 with dimensions L×w, which is illuminated with incident excitation radiation (L dIt is also known as the "large pump face" because its surface area is larger than that of the other faces of the concentrator to maximize exposure to the light. The exit face FS is selected from the two smallest faces (here e x w). Isotropic emission means that the same amount of light is emitted from all faces. Therefore, the smallest face has the highest illuminance. The concentrator effect is used to increase the illuminance and brightness. Therefore, the structure has two large pump faces (FE1, FE2), two large side faces (FL1, FL2) and two small side faces, one of which is selected as the exit face FS.

[0005] The light-harvesting crystal emits electroluminescent radiation L d The luminous flux emitted by the LED and directed towards the illumination surface is absorbed by the luminophores Lum of the fluorescent crystal, which are distributed throughout the volume of the crystal, before emitting fluorescent radiation inside the crystal. Inside the collector, the emitted light rays can be divided into two main categories: -Captured ray L p : These rays are trapped in the crystal as a result of total internal reflection (TIR) ​​at the various faces of the crystal. For example, these rays exist if the collector is placed in air and its shape is a parallelepiped with six faces that are parallel in pairs and perpendicular to each other, and if the refractive index of the collector is greater than √2. The trapped rays never leave the crystal except in the case of defects. - Untrapped rays are those that ultimately leave the crystal. They are divided into two subcategories: guided rays L that are guided by TIR and emerge at one of the faces of the collector; g and the unguided light ray L that emerges directly from the concentrator without being reflected by the surface. out and

[0006] FIG. 1B shows an angular diagram of the emitted and captured rays in the collector (a parallelepiped with six parallel faces divided into pairs). The dark caps—also known as the "exit cone" or "escape cone"—represent the angles corresponding to the uncaptured rays (both guided and unguided) for each face of the collector, while the light areas represent the angles corresponding to the rays captured by total internal reflection within the collector. In this example, the medium chosen for the collector crystal CL is a Ce:YAG crystal (refractive index n = 1.82), which has a critical angle of 33° when the surrounding medium is air. This angle corresponds to the angle at the apex of the exit cone at the collector face. The ratio of radiation captured by TIR to uncaptured radiation is determined by the Snell-Descartes law, which is the refractive index of the crystal and the refractive index of the surrounding medium.

[0007] For the collector shown in Figure 1A, assuming the output face is in contact with air (refractive index n = 1) and the collector refractive index is n = 1.82 (e.g., YAG), only 8% of the fluorescent radiation passes through the output face FS to form the output beam L s The remaining fluorescence radiation is either trapped within the collector due to total internal emission (52%) or leaves the collector by emitting through other faces (5 × 8%) (see Figure 1B). In the case of a parallelepiped collector in air (n = 2.4), the fraction of trapped rays reaches 73%.

[0008] A luminous concentrator is an isotropic light source that emits light from all faces and in all directions. From the user's point of view, it is important to be able to collect light that is emitting from only one face: the exit face FS. The extraction efficiency of a concentrator is the light power (exit beam power L) emitting from FS. s ) to the total light output emitted by the collector.

[0009] The extraction efficiency of luminescent media has been a major topic in the scintillation field for over 50 years (see, for example, Non-Patent Document 2). This subject is particularly important due to the high refractive index of the scintillators (n=1.83 for Ce:YAG, n=2.15 for BGO), which results in a high proportion of light captured by total internal reflection (52% for Ce:YAG and 65% for BGO in a parallelepiped geometry) and therefore a low extraction efficiency.

[0010] The problem of extraction efficiency is also of interest in the field of quantum optics for single-photon emission using diamonds with nitrogen-vacancy centers (NV centers). In fact, diamond has a high fraction of light captured by total internal reflection (73% for parallelepiped geometry) given its high refractive index (n = 2.4). This property limits the performance of NV center transmitters.

[0011] To increase the extraction efficiency, it is known to those skilled in the art to place a mirror on the opposite side of the exit surface, as shown in Figure 1C, which is referred to as the standard configuration. In this case, by using a mirror to combine the exit cones 1 and 2, it is possible to double the extraction efficiency compared to the conventional value (2 x 8% = 16% for Ce:YAG and 2 x 4.5% = 9% for diamond in a parallelepiped geometry). However, this extraction efficiency remains very limited compared to the potential.

[0012] Another solution, detailed in the patent application WO 2007 / 024990 and shown in FIG. 2A, is to define an exit surface and emit an exit beam L sThe objective of this study is to modify the collector of FIG. 1A by introducing a new surface in the form of a chamfered edge SA between the two side surfaces, through which the ray crosses. By carefully adapting the normal of the edge SA, it is possible to "recycle" most of the rays that would otherwise be captured by the collector CL and direct them to the exit surface. By imagining the side surfaces as plane mirrors, the coupling between the cones is ensured. Thus, the image of cone No. 1 through a vertical (or horizontal) surface in FIG. 2B is cone No. 4 (or No. 2). Therefore, FIG. 2B shows that the exit cone has previously been reflected three times by the side surfaces of the structure (cones 1, 2, and 3). Therefore, it is theoretically possible to obtain an extraction efficiency four times higher than that shown in FIG. 1A. This configuration leads to an extraction efficiency of 4 × 8% = 32% for Ce:YAG and 4 × 4.5% = 18% for diamond in a parallelepiped geometry.

[0013] However, further improvements in extraction efficiency are still desirable.

[0014] The principle of the invention is to increase the number of cones coupled to the exit surface by taking into account the reflections that take place before the exit cone through multiple images of the side surfaces.

[0015] With this goal in mind, the object of the present invention is to a light collector made of solid fluorescent or scintillating material, having at least seven faces, namely, two large parallel faces, a first side face and a second side face each having a larger surface than the other side faces, an exit face adjacent to the first side face and the second side face, and at least five faces called side faces, including a first facet adjacent to the first side face and a facet adjacent to the second side face, the first facet and the second facet forming an angle α greater than 0 and less than 175°; a first mirror disposed to cover the first facet; a second mirror disposed to cover the second facet; A light-emitting device comprising:

[0016] By carefully selecting the angle α between the first and second facets, the collector makes it possible to combine the exit cone associated with the exit facet with other cones present in the reflecting structure so as to achieve higher extraction efficiencies than prior art solutions. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] European Patent Application Publication No. 21305827 [Non-patent literature]

[0018] [Non-Patent Document 1] Barbet Adrien, et al., "Light-emitting diode pumped luminescent concentrators: a new opportunity for low-cost solid-state lasers." Optica 3.5 (2016): 465-458 [Non-patent document 2] M. Ankenbrandt and E.M. Lent, "Increasing the light collection efficiency of scintillation counters," RSI, Vol. 34, No. 6, p. 647 (1963). Summary of the Invention [Problem to be solved by the invention]

[0019] With this goal in mind, the object of the present invention is to Refractive index n ca collector of solid fluorescent or scintillating material adapted to absorb incident light and then emit luminescent radiation within the collector, the collector having at least seven faces, namely two parallel faces called major faces; a first side and a second side having a surface area larger than the surface area of ​​the other side; a third side adjacent to the first and second sides, referred to as the exit surface, through which a portion of the light beam of luminescent radiation, referred to as the exit portion, is guided by total internal reflection within the collector; and a side surface adjacent to the first side surface, referred to as a first facet, and a side surface adjacent to the second side surface, referred to as a second facet; At least five faces, referred to as sides, including: a collector comprising: a first mirror disposed to cover the first facet; a second mirror disposed to cover the second facet; Equipped with the first facet and the second facet form an angle α greater than 0 and less than 175°, such that after at least one reflection off the first or second facet or off the first or second mirror, a portion of the luminescent radiation, referred to as the recycled portion, passes through the exit surface, the exit portion and the recycled portion forming an exit beam, It is a light-emitting device. [Means for solving the problem]

[0020] According to one embodiment, the angle α is adapted according to the size and arrangement of the facets in order to maximize the extraction efficiency of the output beam.

[0021] According to one embodiment, the angle α is between 95° and 160°.

[0022] According to one embodiment, the angle α is between 100° and 140°.

[0023] According to one embodiment, the angle α is between 100° and 120°.

[0024] According to one embodiment, the angle α is equal to 110° within ±1°.

[0025] According to one embodiment, the concentrator comprises a number of sides equal to five, and the first and second facets are adjacent.

[0026] According to one embodiment, the concentrator comprises a number of sides equal to six, including additional facets adjacent to the first and second facets.

[0027] According to one embodiment, the concentrator has more than six sides including a plurality of additional facets, each additional facet being adjacent to two other additional facets, or adjacent to another additional facet and the first facet, or adjacent to another additional facet and the second facet.

[0028] According to one embodiment, the large surface has a surface area that is greater than the surface area of ​​the other surfaces.

[0029] According to one embodiment, the device comprises a first additional mirror arranged to cover the first side and a second additional mirror arranged to cover the second side, preferably the first and second sides being non-parallel.

[0030] According to one embodiment, the refractive index of the concentrator n c is greater than 1.5, and in contact with the exit surface, n c >n s Refractive index n > 1 s Preferably, the device comprises an optical system mounted on the output medium, the optical system being adapted to collimate the rays of the output beam.

[0031] According to one embodiment, the device comprises a third additional mirror positioned to cover the exit surface, and the collector has a chamfered edge between the exit surface and the first side so that a portion of the captured portion, referred to as the additional recycled portion, passes through the chamfered edge to form what is referred to as the additional exit beam.

[0032] Further features, details and advantages of the invention will become apparent on reading the description given with reference to the attached drawings, which are given by way of example and in which: [Brief explanation of the drawings]

[0033] [Figure 1A] 1 is a schematic diagram of an example of a light emitting module known from the prior art; [Figure 1B] 1B is a representation of the angle diagram of light rays emitted and captured by the collector shown in FIG. 1A. [Figure 1C] 1 is a schematic diagram of an example of a light emitting module known from the prior art; [Figure 2A] 1 is a schematic diagram of an example of a light emitting module known from the prior art; [Figure 2B] 2B is a schematic representation of spatial recycling in the concentrator shown in FIG. 2A. [Figure 3A] 1 is a schematic perspective view of a light-emitting device according to the present invention; [Figure 3B] 1 is a top view of a light emitting device according to the present invention; [Figure 4] 1 is a graphical representation of the angular orientation of the preceding shape of the exit cone generated by reflection at the structure for three different angles between FT1 and FT2: α=169° (left graph), α=135° (middle graph), and α=99° (right graph). [Figure 5] 1 is a graphical representation of extraction efficiency as a function of angle α for a concentrator of the present invention for three different values ​​of concentrator refractive index nc (nc=1.5, nc=1.83, nc=2.4). [Figure 6]1 is a graphical representation of the extraction efficiency as a function of angle α for an inventive concentrator for three different values ​​of the linear loss coefficient: 2×10 cm (upper curve), 2×10 cm (middle curve), and 2×10 cm (lower curve). [Figure 7] 10 is a planar projection representation of the exit cone of a collector of the present invention for α=120°. [Figure 8] 1 is a planar projection representation of the exit cone of a collector of the present invention for α=157.5°. [Figure 9] 1 is a schematic top view of a light-emitting device according to the present invention, in which first and second facets are adjacent and have different dimensions; [Figure 10] 1 is a schematic top view of a light-emitting device according to the present invention, in which the concentrator has a number of sides equal to six, including additional facets adjacent to the first and second facets. [Figure 11] 1 is a schematic diagram of a preferred embodiment of the present invention, the device comprising an output medium in contact with the output surface, the output medium having a refractive index ns such that nc>ns>1, and comprising a collimating optical system. [Figure 12] 1 is a schematic diagram of one embodiment of the present invention; [Figure 13] 1 is a schematic diagram of one embodiment of the present invention;

[0034] In the drawings, unless otherwise indicated, elements are not to scale and like reference numbers refer to like elements. DETAILED DESCRIPTION OF THE INVENTION

[0035] Figure 3A shows a schematic perspective view of a light emitting device 1 according to the present invention, and Figure 3B shows a schematic top view in the xy plane of a light emitting device 1 according to the present invention.

[0036] The light emitting device according to the present invention d absorbs and emits luminescent radiation L L The light source includes a light collector CL made of a solid fluorescent or scintillating material adapted to emit a light beam.

[0037] The collector CL of the present invention is L It has an optimized geometry that optimizes the extraction of

[0038] The concentrator preferably has a refractive index n greater than 1.5, since the geometry of the present invention is particularly advantageous for high refractive indices. c (See FIG. 4 described below).

[0039] The collector CL has at least seven surfaces, including two parallel surfaces referred to as "large surfaces" or "illumination surfaces" FE1 and FE2. Here, and in the remainder of the specification, "parallel surfaces" means that the surfaces are parallel to within ±5°. By way of example, in Figures 3A and 3B, the large surfaces FE1 and FE2 have two major dimensions: length L and width w.

[0040] Preferably, the large surface is d ), which maximizes the exposure of the high power output beam L s This results in:

[0041] The light collector CL further comprises at least five so-called side surfaces, including a first side surface FL1 and a second side surface FL2. As explained above, the side surfaces FL1 and FL2 have a larger surface area than the other side surfaces to ensure a light collection effect at the exit surface. By way of example, in Figures 2A and 2B, the side surfaces FL1 and FL2 are rectangular and have dimensions e x L, where e is the thickness of the light collector.

[0042] The collector CL has a third side FS, known as the exit surface, adjacent to the first and second sides FL1 and FL2. By way of example, in Figures 2A and 2B, the surface FS is rectangular and has dimensions e x w.

[0043] Finally, the collector CL comprises two further side faces, one adjacent to the first side face known as the first facet FT1 and one adjacent to the second side face known as the second facet FT2. Normals n1, n2 to the planes of the two facets FT1 and FT2 form an angle A between them (see FIG. 3B). The angle α between the facets is defined as 180°-A. In the present invention, this angle α is greater than 0° and less than 175°.

[0044] Note that α=180° (see, eg, FIG. 5) corresponds to the prior art configuration shown in FIG. 1C (the "standard" configuration), not to an embodiment of the present invention.

[0045] The device 1 further comprises a first mirror M1 arranged to cover the first facet FT1 and a second mirror M2 arranged to cover the second facet FT2.

[0046] Captured part L p Luminous emission known as L L A portion of the light is trapped within the collector by total internal reflection. A second portion consists of light that leaves the collector, and a portion of the light is trapped within the collector by total internal reflection. g is guided to the edge, and some L out The light exits the collector directly without being reflected by any surface. s is the luminous radiation L guided through the exit face FS by total internal reflection within the collector L refers to the rays of light.

[0047] In addition, the luminescent radiation portion that passes through the exit surface FS after at least one reflection at the first or second facet or the first or second mirror is referred to as a recycled portion L r It is called the exit part L s and recycled parts L r and the output beam L tot Form.

[0048] Compared to the previous configurations (FIGS. 1A and 2B), the exit cone can be reflected by four faces (FL1, FL2, FT1, FT2) instead of one (FIG. 1A) or three (FIG. 2B). The exit cone therefore has more side reflections. In this way, more cones are coupled into the exit section, resulting in an increase in extraction efficiency.

[0049] Preferably, the angle α is adapted according to the dimensions and arrangement of the facets in order to maximize the extraction efficiency of the output beam. Indeed, it is understood that the value of the angle α that maximizes the extraction efficiency depends directly on the geometry of the structure. As will be explained in more detail below, for a given geometry, it is possible to calculate by simulation the value of the angle α that allows this optimization.

[0050] Figure 4 is a graphical representation of the angular orientation of the precursory form of the exit cone generated by reflection at the structure for three different angles between FT1 and FT2: α = 169° (left graph), α = 135° (middle graph), and α = 99° (right graph). To make the graph easier to interpret, Figure 4 shows only the angular orientation of the central axis of the cone under consideration, which is determined by a line passing through the center of the circle and a point placed on the circle. Thus, each point on the graph represents the axis of the cone, the precursory form of the exit cone.

[0051] As a non-limiting example, in the embodiment shown in Figures 3A and 3B, each of the side surfaces has a normal in a plane parallel to the large surface. Also, the cones considered in Figure 4 all have their central axes in the xy plane of the large surface. In fact, the image of the large surface is the cone itself, since reflection by the mirror does not change the axis of the cone, which lies in the plane of the mirror.

[0052] 3A and 3B, the dimensions of facets FT1 and FT2 are identical. It has been shown that for the case where α=π-π / p, where p is an integer, the number of possible precursors for the exit cone FS is finite and equal to 2p-1. For example, for α=168.75°, p=16, and therefore the number of precursors for the exit cone is 2p=32. Depending on the value of the angle α, the number of images is very large (as in the case of α=99° shown in FIG. 4).

[0053] More generally, in geometries different from those of the embodiment shown in Figures 3A and 3B, the number of precursors is said to depend on the value of the angle α.

[0054] Figure 5 shows the concentrator refractive index, n c (n c =1.5,n c =1.83,n c 5 is a graphical representation of the extraction efficiency as a function of angle α for a concentrator of the present invention for a ray coupling cone of 2.4 λ / 2.4 (α=2.4). FIG. 5 shows the results of a Monte Carlo ray tracing simulation estimating the extraction efficiency of coupling rays into this exit cone.

[0055] The results shown in Figure 5 were obtained for a collector with the geometry of the embodiment shown in Figures 3A and 3B modified to include a first additional mirror positioned to cover the first side surface FL1 and a second additional mirror positioned to cover the second side surface FL2 (the "optimized" configuration). These additional mirrors improve the extraction efficiency.

[0056] As a non-limiting example, a collector with a total reflective mirror and linear loss may have a coefficient of 2×10 for the central wavelength of the luminescent radiation. -3 cm -1 These results are presented assuming that is equal to .

[0057] Figure 5 shows that the extraction efficiency is significantly improved compared to the standard configuration for low linear loss conditions and total reflection mirrors. These conditions are achieved by using a very low loss crystal, Ce:YAG concentrator (refractive index n c =1.83) is close to reality.

[0058] Additionally, the extraction efficiency of the configuration shown in Figure 5 is significantly improved over that of the prior art configuration shown in Figures 2A and 2B. As a reminder, the prior art configuration shown in Figures 2A and 2B achieves the highest extraction efficiencies of 4 x 8% = 32% for Ce:YAG and 4 x 4.5% = 18% for diamond. The configuration shown in Figure 5 achieves extraction efficiencies of 40% for Ce:YAG and 28% for diamond (refractive index 2.4). We note that the improvement is relatively more significant when the concentrator refractive index is high. This can be explained by the higher refractive index as the cone size decreases.

[0059] The "bell shape" of the curve can be interpreted as follows. For angles close to -180°, "spoke rotation" and coupling many spokes to the output requires many round trips through the structure. There are two possible reasons for this. The first is related to the rotation angle of the ray at the output from reflections by facets FT1 and FT2, all of which are smaller the closer angle α is to 180°. The second is that, since it is rare for a ray to hit facet FT2 after reflection from facet FT1, facets FT1 and FT2 cannot combine these effects at angles α close to 180° (and vice versa). Therefore, angles α close to 180° imply a longer ray propagation distance before exiting surface FS, and therefore relatively higher losses. For an angle α=90°, the roof reflects the incident beam in a single direction, i.e. in the opposite direction, so the effect of the image on the exit cone is not significant.

[0060] Figure 6 shows three different values ​​of the linear loss factor, i.e., 2 × 10 -3 cm-1 (upper curve), 2×10 -2 cm -1 (center curve), 2×10 -1 cm -1 1 is a graphical representation of the extraction efficiency as a function of angle α for a concentrator of the present invention for (lower curve).

[0061] Figure 6 shows the same configuration as in Figure 5 (the "optimized configuration") and the diamond concentrator (refractive index n c = 2.4), and the extraction efficiency values ​​have been normalized to the standard configuration.

[0062] Figure 6 shows the fact that there is a very significant drop in extraction efficiency for an angle of 90°, and some localized dips in configurations where only a small number of images are coupled into the exit cone (angles of 120° or 130°). It can be seen that the best performance is obtained for angles close to 110°, when losses in the structure are low. For large losses (lower curves), the effect of the localized dips decreases. Configurations requiring a large number of reflections (and therefore long propagation distances) will result in less efficient extraction, as the average ray propagation distance is limited by losses.

[0063] Preferably, to optimize extraction efficiency, angle α is between 95° and 160°. To further improve extraction efficiency, angle α is between 100° and 140°. To further improve extraction efficiency, angle α is between 100° and 120°. For maximum extraction efficiency, angle α is preferably equal to 110° within ±1°. Through simulations, the inventors have determined that these values ​​of angle α are advantageous whatever the relative sizes of the facets or whatever the number of facets.

[0064] Simulations suggest that the criteria for choosing the angle α are quite broad, as long as there is a sufficient number of multiple images of the exit cone associated with the surface FS, which depends on the refractive index of the medium and the value of the angle α.

[0065] To illustrate this, Figures 7 and 8 show a planar projection representation of the emission cone using angular coordinates (ψ, β), where β is the angle relative to the z-axis and ψ is the angle in the xy plane relative to the y-axis. The white areas between the cones represent the captured rays L p Just to be clear, the angle part L out corresponds to the escape cone at the large faces FE1 and FE2. The angular part L s corresponds to the exit cone associated with the surface FS. Finally, the part L r corresponds to a cone that is recycled by reflections at facets FT1, FT2, FL1, and FL2 and exits through surface FS. Without surfaces FT1 and FT2, this light L r never reaches the exit face, but exits through the side or remains trapped in the collector. Therefore, the exit beam L tot is part L s +L r It consists of:

[0066] As a non-limiting example, Figures 7 and 8 are shown for an "optimized" configuration with a diamond concentrator (refractive index 2.4), where Figure 7 corresponds to an embodiment where α=120° and Figure 8 corresponds to an embodiment where α=157.5°.

[0067] In the embodiment shown in FIG. 7, for an angle α=120°, the exit cone L s is reflected only five times in advance. Considering the high refractive index of the concentrator, the critical angle associated with this exit cone is low, and the cone L s In this case, the recycled part L r The exit cone images forming L will not overlap and the extraction efficiency will be low. To select the angle to maximize the extraction efficiency, one criterion is that the adjacent exit cone images L s and the angle between two adjacent cone axes corresponds to the angle α at the apex of the exit cone.

[0068] As shown in Figure 8, light can be extracted from a "corona" corresponding to the overlap between the exit cone associated with the surface FS and its image. In fact, in the embodiment of Figure 8, the exit beam L totIn this case, 16 escape cones are combined. Figure 8 shows that in this case, virtually the entire corona is extracted.

[0069] It is also possible to maximize extraction efficiency by using a narrow angle α, ensuring rapid beam doubling so that it is not limited by propagation losses. In fact, an angle of approximately 110° provides the best extraction efficiency, as shown in Figures 5 and 6. This solution covers the entire corona with only a few round trips. At such an angle, depending on its position in the collector, the beam has four possibilities before returning to the exit surface: it can be reflected only by FT1, only by FT2, or by a combination of FT1-FT2 or FT2-FT1.

[0070] PMMA concentrators CL(n) doped with orange dye (Lumogen, Evonik) with optimized geometry c An experimental proof of concept was carried out using a 1000 .0001 .0001 .0001 .0001 .0001 .0001 .0002 .0003 .0004 .0005 .0006 .0007 .0008 .0009 .0009 .0009 .0001 .0001 .0002 .0003 .0004 .0005 .0006 .0007 .0008 .0009 .0009 .0001 .0001 .0002 .0003 .0004 .0005 .0006 .0007 .0008 .0009 .0009 .0001 .0001 .0002 .0003 .0004 .0005 .0006 .0007 .0008 .0009 .0001 .0001 .0001 .0002 .0003 .0004 .0005 .0001 .0002 .0003 .0004 .0005 .0005 .0006 .0007 .0008 .0009 ... -2 cm -1 is.

[0071] Although the experimental setup is far from optimal because the chosen medium is lossy (dye-doped PMMA), the concept of the present invention has thus been verified. -3 cm -1 In this case, the performance is even better, reaching the values ​​shown in Figure 5, tripling the extraction compared to the standard configuration.

[0072] As a non-limiting example, in the embodiment shown in Figures 3A and 3B, the collector has a number of sides equal to 5, and the first facet FT1 and the second facet FT2 are adjacent and have the same dimensions. Alternatively, according to another embodiment shown in Figure 9, the first and second facets are adjacent and have different dimensions. This has the advantage of providing a less symmetrical structure, limiting the captured rays that can propagate within the collector without striking the exit surface at angles that belong to the exit cone.

[0073] According to another embodiment shown in Figure 10, the light collector CL has a number of sides equal to six, including an additional facet FTA adjacent to the first facet FT1 and the second facet FT2. For clarity, the mirrors M1, M2 are not shown in Figure 10, but are included in the device 1. The facet FTA is r The facet FTA facilitates multiple reflections of the light beam from the part and therefore a fast average exit of the light beam through the face FS. out 10)。Since the angles α1 and α2 (defined in Figure 10) are related to α by the relationship α + π = α1 + α2, it can be seen that it is always the angle α that controls the extraction efficiency of the structure of the embodiment shown in Figure 10.

[0074] According to another embodiment, the collector has more than six sides, including a plurality of additional facets, each of which is adjacent to two other additional facets, or adjacent to another additional facet and a first facet FT1, or adjacent to another additional facet and a second facet FT2. Like the additional facet FTA in the embodiment of FIG. 10, these additional facets direct the beam L out This can potentially increase extraction efficiency by reducing the propagation losses associated with the

[0075] According to an embodiment compatible with all of the most recently considered embodiments, the first flank FL1 and the second flank FL2 are not parallel. Depending on the angle α selected, this non-parallelism makes it possible to increase the number of images of the exit cone resulting from reflections at the flanks. In cases where the angle α is not maximized, this potential increases the extraction efficiency.

[0076] optical radiation L d In a structure pumped by , the large pump faces FE1 and FE2 must remain freely accessible. Moreover, in practice, it is difficult to equip these large faces FE1 and FE2 with dichroic mirrors, since the pump radiation must be transmitted while reflecting a large number of incident beams and a broad spectrum with an excellent reflection coefficient (R>99.9%). In addition, the escape cone L of the large faces is small. out are not recoverable. The losses in these cones are related to the refractive index. Table 1 below shows that for high refractive indices (e.g., n=1.83, or n=2.4), the corona extracted from the air is only partially recovered from the entire potential (i.e., from the total emitted light) within two cones L out In fact, the corona thickness is far from the total internal reflection (θ TIR ) angle of the exit cone.

[0077] [Table 1]

[0078] This critical angle θ TIR To increase , when the concentrator refractive index is high, it is preferable to use an exit medium with a refractive index higher than air.

[0079] Figure 11 shows the state of contact with the exit surface, n c >n s Refractive index n > 1 s11 shows a preferred embodiment of the invention, in which the device comprises an output medium MS having a first side surface FL1 and a second side surface FL2. According to the embodiment shown in Fig. 11, the device comprises a first additional mirror M1' arranged to cover the first side surface FL1 and a second additional mirror M2' arranged to cover the second side surface FL2. These mirrors M1', M2' are optional and increase the extraction efficiency by preventing the luminescent radiation from traversing the surfaces FL1, FL2 before emitting through the output surface FS (referred to as optimized configuration).

[0080] The exit medium MS increases extraction efficiency by increasing the critical angle associated with the face exit cone FS, creating a wider exit cone. This is particularly beneficial when the collector refractive index is high. This effect is shown in the "Adhesive Corona Extraction" column of Table 1, which shows the extraction efficiency for the configuration shown in Figure 11. Compare this to the "Air Corona Extraction" line, which shows the extraction efficiency for the configuration shown in Figures 3A and 3B, where air is the exit medium. For example, using an MS exit medium with a refractive index of 1.7, and an index of refraction n c For a concentrator with λ = 2.4, the extraction efficiency can increase from 42% to 71%.

[0081] Preferably, as shown in FIG. 11, the device is mounted in an output medium to direct the output beam L tot The optical system SO is adapted to collimate the light beams of the light collector CL. The optical system SO is a non-imaging optical system capable of conditioning the light beams exiting the output medium MS and outputting them into air. In this embodiment, the output medium MS is, for example, an adhesive material that provides a mechanical and optical coupling between the collector CL and the optical system SO.

[0082] The refractive index of the adhesive between the structure and the non-imaging optics limits extraction. Ideally, an adhesive with the same refractive index as the optical system SO would be ideal, but high-index adhesives (n>1.7) are difficult to find today.

[0083] FIG. 12 shows a device a first additional mirror M1′ disposed to cover the first side surface FL1; a second additional mirror M2′ disposed to cover the second side surface FL2; a third additional mirror M3 arranged to cover the exit surface FS; 1 shows a schematic representation of an embodiment of the present invention comprising:

[0084] In addition, the collector CL has a capture section L p 1 part L r’ The portion L has a chamfered edge AB between the light exit surface FS and the first side surface FL1 (or the second side surface FL2) so that the light passes through the chamfered edge AB. r’ The ray of light from the additional output beam L tot’ In the configuration shown in Figure 12, passing through edge AB is the only way for light rays to exit the structure (except for the pump surface). Thus, light rays must undergo multiple reflections before reaching the correct position and angle. This effect imposes a strong internal superposition of light rays, which can be described as both angular and spatial recycling. The use of edge AB increases the propagation distance, potentially reducing overall extraction, but increasing brightness.

[0085] Preferably, the perpendicular to the chamfered edge is parallel to the sum of the perpendiculars to the two side surfaces FL1, FS adjacent to the chamfered edge at an angle of ±5°.

[0086] 11 and 12 may be combined, i.e., according to one embodiment of the present invention, the exit medium MS is tot’ The edge AB is adjacent to the chamfered edge AB to maximize the brightness and maximize the extraction efficiency.

[0087] FIG. 13 shows a device a first additional mirror M1′ disposed to cover the first side surface FL1; a second additional mirror M2′ disposed to cover the second side surface FL2; at least one additional mirror M3 arranged to partially cover the exit surface FS and to define a surface SFS that is not covered by the mirror M3; 1 shows a schematic representation of an embodiment of the present invention comprising:

[0088] As already explained, mirrors M1', M2' increase the extraction efficiency by preventing the luminescent radiation from traversing faces FL1, FL2 before emerging from surface SFS.

[0089] The mirror M3, which partially covers the exit surface, increases the illuminance at the surface SFS. The luminous radiation rays reflect off M3 and travel an average distance L within the collector CL before passing through the surface SFS. moy The ratio R between the uncoated surface SFS and the surface FS in such a way that it propagates over L = SFS / S SF The dimensions of the light emitting module are adapted so that the luminous light beam leaving the collector is an output beam L tot Forming L moy ≫L is L moy is greater than 7 times, preferably 15 times, L.

[0090] Condition L moy The ratio R adapted to verify ≫L ensures the effect of confining the light rays in a three-dimensional space, i.e. that the luminescent radiation, instead of passing directly through the SFS surface after its generation, is mainly reflected within the collector CL and makes several round trips within the collector CL on average before emitting from the SFS surface. The smaller the ratio R, the greater the average distance L that the luminescent light rays travel within the collector CL before emitting. moy Thus, the luminous radiation takes time to "fill" the collector CL before exiting, increasing the illuminance at the exit surface. When the ratio R is less than or equal to 1 / 4, or preferably less than or equal to 1 / 8, the average distance L moy The inventors have realized that the ratio R is sufficient to achieve a consistent concentrator effect. Also, according to a preferred embodiment of the present invention, the ratio R is less than or equal to 1 / 4, or preferably less than or equal to 1 / 8.

[0091] The device structures detailed in this specification and in the figures are given by way of example and are intended to illustrate the invention. They should not be considered to limit the scope of the invention in any way. Various modifications and variations in the described structures, methods of manufacture, and their application and use will be apparent to those skilled in the art without departing from the scope and spirit of the invention.

Claims

1. Refractive index n ｃ and the incident light (L ｄ ) and then emits luminescent radiation (L Ｌ a light collector (CL) of solid fluorescent or scintillating material adapted to emit a light beam (F) having at least seven faces, namely two parallel faces called large faces (FE1, FE2); a first side (FL1) and a second side (FL2) having a surface larger than the surface of the other side; a third side surface (FS) adjacent to the first and second sides, called the exit surface, Ｌ ) of the light beam, the part called the exit part (L ｓ a third side, on which the light beams are guided through an exit surface (FS) by total internal reflection within the collector; a side surface adjacent to the first side surface and referred to as a first facet (FT1), and a side surface adjacent to the second side surface and referred to as a second facet (FT2); At least five faces, referred to as sides (FL1, FL2, FS, FT1, FT2), including: a collector comprising: a first mirror (M1) arranged to cover the first facet (FT1); a second mirror (M2) arranged to cover the second facet (FT2); Equipped with After at least one reflection on the first or second facet or the first or second mirror, a portion of the luminescent radiation, called the recycled portion (L ｒ The first facet and the second facet form an angle α that is greater than 0 and less than 175° so that the exit portion (L ｓ ) and the recycled portion (L ｒ ) and the output beam (L ｔｏｔ ) to form Light-emitting device.

2. The device of claim 1 , wherein the angle α is adapted according to the size and arrangement of the facets to maximize extraction efficiency of the output beam.

3. 3. The device of claim 1, wherein the angle α is between 95° and 160°.

4. The device according to any one of claims 1 to 3, wherein the angle α is between 100° and 140°.

5. The device according to any one of claims 1 to 4, wherein the angle α is between 100° and 120°.

6. The device according to any one of claims 1 to 5, wherein the angle α is equal to 110° within ±1°.

7. The device of any one of claims 1 to 6, wherein the concentrator has a number of sides equal to five, and the first and second facets are adjacent.

8. The device according to any one of claims 1 to 6, wherein the concentrator has a number of sides equal to six, including additional facets (FTA) adjacent to the first and second facets.

9. 7. The device of claim 1, wherein the concentrator has more than six sides including a plurality of additional facets, each additional facet being adjacent to two other additional facets, or adjacent to another additional facet and the first facet, or adjacent to another additional facet and the second facet.

10. A device according to any preceding claim, wherein the large face has a surface area that is greater than the surface area of ​​the other faces.

11. 11. The device according to claim 1, comprising a first additional mirror (M1') arranged to cover the first side and a second additional mirror (M2') arranged to cover the second side.

12. The device of any one of claims 1 to 11, wherein the first side and the second side are not parallel.

13. The refractive index of the concentrator, n ｃ is greater than 1.5, and in contact with the exit surface, n ｃ >n ｓ Refractive index n > 1 ｓ 13. The device according to claim 1, which is a device comprising an emission medium having:

14. The outgoing beam (L ｔｏｔ 14. The device according to claim 13, comprising an optical system (SO) adapted to collimate the light beams of the light source (10) and mounted on said exit medium.

15. a device comprising a third additional mirror arranged to cover the exit surface, the third additional mirror having a capture portion (L ｐ ) of the additional recycled portion (L ｒ’ ) passes through the chamfered edge (AB) to form the so-called additional exit beam (L ｔｏｔ’ 15. The device of any one of claims 1 to 10, 12 to 14 in combination with claim 11, wherein the concentrator has a chamfered edge (AB) between the exit surface and the first side surface so as to form a

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