The invention relates to a light generating system and to a light generating device comprising such light generating system.
Conversion devices are known in the art. US2017/0219171, for instance, describes a conversion device, comprising: a phosphor element made of a phosphor element material for converting pump radiation into conversion radiation; and a scattering element embodied as a volume scatterer; wherein the scattering element is arranged in direct optical contact with the phosphor element in order to be transilluminated by the conversion radiation; and wherein the phosphor element material is present in monocrystalline form in the phosphor element over a volume of at least 1×10−2 mm3. The scattering element is provided to be made of a scattering element material which has a refractive index deviating by no more than 20% from a refractive index of the phosphor element material.
While white LED sources can give an intensity of e.g. up to about 300 lm/mm2; static phosphor converted laser white sources can give an intensity even up to about 20.000 lm/mm2. Ce doped garnets (e.g. YAG, LuAG) may be the most suitable luminescent convertors which can be used for pumping with blue laser light as the garnet matrix has a very high chemical stability. Further, at low Ce concentrations (e.g. below 0.5%) temperature quenching may only occur above about 200° C. Furthermore, emission from Ce has a very short decay time so that optical saturation can essentially be avoided. Assuming e.g. a reflective mode operation, blue laser light may be incident on a phosphor. This may in embodiments realize almost full conversion of blue light, leading to emission of converted light. It is for this reason that the use of garnet phosphors with relatively high stability and thermal conductivity is suggested. However, also other phosphors may be applied. Heat management may remain an issue when extremely high-power densities are used.
High brightness light sources can be used in applications such as projection, stage-lighting, spot-lighting and automotive lighting. For this purpose, laser-phosphor technology can be used wherein a laser provides laser light and e.g. a (remote) phosphor converts laser light into converted light. There appears to be a desire for high brightness sources.
Hence, it is an aspect of the invention to provide an alternative light generating system, which preferably further at least partly obviates one or more of above-described drawbacks. The present invention may have as object to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.
In a first aspect, the invention provides a light generating system which may especially comprise (a) first light generating device, (b) a first laser, (c) a second laser and a (d) second light generating device. In embodiments, the first light generating device may be configured to generate first device light having a first device centroid wavelength (λcd,1) (in specific embodiments in the visible). In embodiments, the first light generating device may comprise one or more of a solid state material laser and a super luminescent diode. In embodiments, the first laser may especially comprise a first lanthanide based luminescent material configured to convert at least part of the first device light having the first device centroid wavelength (λcd,1) into first luminescent material light. Especially, the first laser may be configured downstream of the first light generating device. Further, the first laser may especially be configured to provide first laser light comprising at least part of the first luminescent material light. The first laser light may have a first centroid laser wavelength (λcl,1). The first centroid laser wavelength (λcl,1) may especially be in the visible. In embodiments, the second laser may comprise a second lanthanide based luminescent material configured to convert at least part of the first device light having the first device centroid wavelength (λcd,1) into second luminescent material light. Especially, the second laser may be configured downstream of the first light generating device. Further, the second laser may be configured to provide second laser light comprising at least part of the second luminescent material light. The second laser light may have a second centroid laser wavelength (λcl,2). The second centroid laser wavelength (λcl,2) may especially be in the visible. In specific embodiments, |λcl,2−λcl,1|≥25 nm. Especially, in embodiments the first centroid laser wavelength (λcl,1) and the second centroid laser wavelength (λcl,2) may be selected from different wavelength ranges. Further, especially these different wavelength ranges may be selected from the group of (i) 495-570 nm, (ii) 570-590 nm, (iii) 590-620 nm, and (iv) 620-780 nm. The second light generating device is configured to generate second device light having a second device centroid wavelength λcd,2 in the visible, wherein |λcd,2−λcd,1|≥10 nm, wherein the second light generating device comprises one or more of a solid state material laser and a super luminescent diode. In embodiments, in a first operational mode of the light generating system the light generating system may be configured to provide system light comprising one or more of the first laser light, the second laser light and the second device light, especially all three. Further, the system light in the first operational mode is white light having a correlated color temperature CCT selected from the range of 2000-6500 K and a color rendering index CRI≥80. The first device centroid wavelength λcd,1 is selected from the range of 440-495 nm, and the second device centroid wavelength λcd,2 is selected from the range of 430-475 nm,
Hence, especially the invention provides in embodiments a light generating system comprising (a) first light generating device, (b) a first laser, and (c) a second laser, wherein: (A) the first light generating device is configured to generate first device light having a first device centroid wavelength (λcd,1) (in the visible), wherein the first light generating device comprises one or more of a solid state material laser and a super luminescent diode; (B) the first laser comprises a first lanthanide based luminescent material configured to convert at least part of the first device light having the first device centroid wavelength (λcd,1) into first luminescent material light, wherein the first laser is configured downstream of the first light generating device and is configured to provide first laser light comprising at least part of the first luminescent material light, wherein the first laser light has a first centroid laser wavelength (λcl,1) in the visible; (C) the second laser comprises a second lanthanide based luminescent material configured to convert at least part of the first device light having the first device centroid wavelength (λcd,1) into second luminescent material light, wherein the second laser is configured downstream of the first light generating device and is configured to provide second laser light comprising at least part of the second luminescent material light, wherein the second laser light has a second centroid laser wavelength (λcl,2) in the visible, wherein |λcl,2−λcl,1|≥25 nm; (D) the first centroid laser wavelength (λcl,1) and the second centroid laser wavelength (λcl,2) are selected from different wavelength ranges from the group of (i) 495-570 nm, (ii) 570-590 nm, (iii) 590-620 nm, and (iv) 620-780 nm, and (E) in a first operational mode of the light generating system the light generating system is configured to provide system light comprising the first laser light and the second laser light, and wherein in the first operational mode the system light is white light.
With such system, it is possible to provide in a relatively simple way a light source, especially a high intensity light source, having an acceptable CRI. In embodiments, it is possible to generate with a single pump laser a laser light source essentially based on only laser light at different frequencies. Further, the invention allows a simplified architecture without the need of an additional red laser diode and/or an additional green laser diode, though these are not excluded herein in embodiments.
As indicated above, the light generating system may comprise (a) first light generating device, (b) a first laser, and (c) a second laser.
The first light generating device may comprise one or more light sources. The first laser may comprise one or more solid state material lasers. The second laser may (also) comprise one or more solid state material lasers.
The term “light source” may in principle relate to any light source known in the art. It may be a conventional (tungsten) light bulb, a low-pressure mercury lamp, a high-pressure mercury lamp, a fluorescent lamp, a LED (light emissive diode). In a specific embodiment, the light source comprises a solid-state LED light source (such as a LED or laser diode (or “diode laser”)). The term “light source” may also relate to a plurality of light sources, such as 2-200 (solid state) LED light sources. Hence, the term LED may also refer to a plurality of LEDs. Further, the term “light source” may in embodiments also refer to a so-called chips-on-board (COB) light source. The term “COB” especially refers to LED chips in the form of a semiconductor chip that is neither encased nor connected but directly mounted onto a substrate, such as a PCB. Hence, a plurality of light emitting semiconductor light source may be configured on the same substrate. In embodiments, a COB is a multi-LED chip configured together as a single lighting module.
The light source may have a light escape surface. Referring to conventional light sources such as light bulbs or fluorescent lamps, it may be outer surface of the glass or quartz envelope. For LED's it may for instance be the LED die, or when a resin is applied to the LED die, the outer surface of the resin. In principle, it may also be the terminal end of a fiber. The term escape surface especially relates to that part of the light source, where the light actually leaves or escapes from the light source. The light source is configured to provide a beam of light. This beam of light (thus) escapes from the light exit surface of the light source.
Likewise, a light generating device may comprise a light escape surface, such as an end window. Further, likewise a light generating system may comprise a light escape surface, such as an end window.
The term “light source” may refer to a semiconductor light-emitting device, such as a light emitting diode (LEDs), a resonant cavity light emitting diode (RCLED), a vertical cavity laser diode (VCSELs), an edge emitting laser, etc. The term “light source” may also refer to an organic light-emitting diode (OLED), such as a passive-matrix (PMOLED) or an active-matrix (AMOLED). In a specific embodiment, the light source comprises a solid-state light source (such as a LED or laser diode). In an embodiment, the light source comprises a LED (light emitting diode). The terms “light source” or “solid state light source” may also refer to a superluminescent diode (SLED).
The term LED may also refer to a plurality of LEDs. Further, the term “light source” may in embodiments also refer to a so-called chips-on-board (COB) light source. The term “COB” especially refers to LED chips in the form of a semiconductor chip that is neither encased nor connected but directly mounted onto a substrate, such as a PCB. Hence, a plurality of semiconductor light sources may be configured on the same substrate. In embodiments, a COB is a multi-LED chip configured together as a single lighting module.
The term “light source” may also relate to a plurality of (essentially identical (or different)) light sources, such as 2-2000 solid state light sources. In embodiments, the light source may comprise one or more micro-optical elements (array of micro lenses) downstream of a single solid-state light source, such as a LED, or downstream of a plurality of solid-state light sources (i.e. e.g. shared by multiple LEDs). In embodiments, the light source may comprise a LED with on-chip optics. In embodiments, the light source comprises a pixelated single LEDs (with or without optics) (offering in embodiments on-chip beam steering).
In embodiments, the light source may be configured to provide primary radiation, which is used as such, such as e.g. a blue light source, like a blue LED, or a green light source, such as a green LED, and a red light source, such as a red LED. Such LEDs, which may not comprise a luminescent material (“phosphor”) may be indicated as direct color LEDs.
In other embodiments, however, the light source may be configured to provide primary radiation and part of the primary radiation is converted into secondary radiation. Secondary radiation may be based on conversion by a luminescent material. The secondary radiation may therefore also be indicated as luminescent material radiation. The luminescent material may in embodiments be comprised by the light source, such as a LED with a luminescent material layer or dome comprising luminescent material. Such LEDs may be indicated as phosphor converted LEDs or PC LEDs (phosphor converted LEDs). In other embodiments, the luminescent material may be configured at some distance (“remote”) from the light source, such as a LED with a luminescent material layer not in physical contact with a die of the LED. Hence, in specific embodiments the light source may be a light source that during operation emits at least light at wavelength selected from the range of 380-470 nm. However, other wavelengths may also be possible. This light may partially be used by the luminescent material.
In embodiments, the light generating device may comprise a luminescent material. In embodiments, the light generating device may comprise a PC LED. In other embodiments, the light generating device may comprise a direct LED (i.e. no phosphor). In embodiments, the light generating device may comprise a laser device, like a laser diode. In embodiments, the light generating device may comprise a superluminescent diode. Hence, in specific embodiments, the light source may be selected from the group of laser diodes and superluminescent diodes. In other embodiments, the light source may comprise an LED.
The light source may especially be configured to generate light source light having an optical axis (O), (a beam shape,) and a spectral power distribution. The light source light may in embodiments comprise one or more bands, having band widths as known for lasers.
The term “light source” may (thus) refer to a light generating element as such, like e.g. a solid state light source, or e.g. to a package of the light generating element, such as a solid state light source, and one or more of a luminescent material comprising element and (other) optics, like a lens, a collimator. A light converter element (“converter element” or “converter”) may comprise a luminescent material comprising element. For instance, a solid-state light source as such, like a blue LED, is a light source. A combination of a solid-state light source (as light generating element) and a light converter element, such as a blue LED and a light converter element, optically coupled to the solid state light source, may also be a light source (but may also be indicated as light generating device). Hence, a white LED is a light source (but may e.g. also be indicated as (white) light generating device).
The term “light source” herein may also refer to a light source comprising a solid-state light source, such as an LED or a laser diode or a superluminescent diode.
The “term light source” may (thus) in embodiments also refer to a light source that is (also) based on conversion of light, such as a light source in combination with a luminescent converter material. Hence, the term “light source” may also refer to a combination of a LED with a luminescent material configured to convert at least part of the LED radiation, or to a combination of a (diode) laser with a luminescent material configured to convert at least part of the (diode) laser radiation.
In embodiments, the term “light source” may also refer to a combination of a light source, like a LED, and an optical filter, which may change the spectral power distribution of the light generated by the light source. Especially, the “term light generating device” may be used to address a light source and further (optical components), like an optical filter and/or a beam shaping element, etc.
The phrases “different light sources” or “a plurality of different light sources”, and similar phrases, may in embodiments refer to a plurality of solid-state light sources selected from at least two different bins. Likewise, the phrases “identical light sources” or “a plurality of same light sources”, and similar phrases, may in embodiments refer to a plurality of solid-state light sources selected from the same bin.
The term “solid state light source”, or “solid state material light source”, and similar terms, may especially refer to semiconductor light sources, such as a light emitting diode (LED), a diode laser, or a superluminescent diode.
The term “laser light source” especially refers to a laser. Such laser may especially be configured to generate laser light source light having one or more wavelengths in the UV, visible, or infrared, especially having a wavelength selected from the spectral wavelength range of 200-2000 nm, such as 300-1500 nm. The term “laser” especially refers to a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.
Especially, in embodiments the term “laser” may refer to a solid-state laser. In specific embodiments, the terms “laser” or “laser light source”, or similar terms, refer to a laser diode (or diode laser).
Hence, in embodiments the light source comprises a laser light source. In embodiments, the terms “laser” or “solid state laser” or “solid state material laser” may refer to one or more of cerium doped lithium strontium (or calcium) aluminum fluoride (Ce:LiSAF, Ce:LiCAF), chromium doped chrysoberyl (alexandrite) laser, chromium ZnSe (Cr:ZnSe) laser, divalent samarium doped calcium fluoride (Sm:CaF2) laser, Er:YAG laser, erbium doped and erbium-ytterbium codoped glass lasers, F-Center laser, holmium YAG (Ho:YAG) laser, Nd:YAG laser, NdCrYAG laser, neodymium doped yttrium calcium oxoborate Nd:YCa4O(BO3)3 or Nd:YCOB, neodymium doped yttrium orthovanadate (Nd:YVO4) laser, neodymium glass (Nd:glass) laser, neodymium YLF (Nd:YLF) solid-state laser, promethium 147 doped phosphate glass (147Pm3+:glass) solid-state laser, ruby laser (Al2O3:Cr3+), thulium YAG (Tm:YAG) laser, titanium sapphire (Ti:sapphire; Al2O3:Ti3+) laser, trivalent uranium doped calcium fluoride (U:CaF2) solid-state laser, Ytterbium doped glass laser (rod, plate/chip, and fiber), Ytterbium YAG (Yb:YAG) laser, Yb2O3 (glass or ceramics) laser, etc.
For instance, including second and third harmonic generation embodiments, the light source may comprise one or more of an F center laser, an yttrium orthovanadate (Nd:YVO4) laser, a promethium 147 doped phosphate glass (147Pm3+:glass), and a titanium sapphire (Ti:sapphire; Al2O3:Ti3+) laser. For instance, considering second and third harmonic generation, such light sources may be used to generated blue light.
In embodiments, the terms “laser” or “solid state laser” or “solid state material laser” may refer to one or more of a semiconductor laser diode, such as GaN, InGaN, AlGaInP, AlGaAs, InGaAsP, lead salt, vertical cavity surface emitting laser (VCSEL), quantum cascade laser, hybrid silicon laser, etc.
A laser may be combined with an upconverter in order to arrive at shorter (laser) wavelengths. For instance, with some (trivalent) rare earth ions upconversion may be obtained or with non-linear crystals upconversion can be obtained. Alternatively, a laser can be combined with a downconverter, such as a dye laser, to arrive at longer (laser) wavelengths.
As can be derived from the below, the term “laser light source” may also refer to a plurality of (different or identical) laser light sources. In specific embodiments, the term “laser light source” may refer to a plurality N of (identical) laser light sources. In embodiments, N=2, or more. In specific embodiments, N may be at least 5, such as especially at least 8. In this way, a higher brightness may be obtained. In embodiments, laser light sources may be arranged in a laser bank (see also above). The laser bank may in embodiments comprise heat sinking and/or optics e.g. a lens to collimate the laser light.
The laser light source is configured to generate laser light source light (or “laser light”). The light source light may essentially consist of the laser light source light. The light source light may also comprise laser light source light of two or more (different or identical) laser light sources. For instance, the laser light source light of two or more (different or identical) laser light sources may be coupled into a light guide, to provide a single beam of light comprising the laser light source light of the two or more (different or identical) laser light sources. In specific embodiments, the light source light is thus especially collimated light source light. In yet further embodiments, the light source light is especially (collimated) laser light source light.
The laser light source light may in embodiments comprise one or more bands, having band widths as known for lasers. In specific embodiments, the band(s) may be relatively sharp line(s), such as having full width half maximum (FWHM) in the range of less than 20 nm at RT, such as equal to or less than 10 nm. Hence, the light source light has a spectral power distribution (intensity on an energy scale as function of the wavelength) which may comprise one or more (narrow) bands.
The beams (of light source light) may be focused or collimated beams of (laser) light source light. The term “focused” may especially refer to converging to a small spot. This small spot may be at the discrete converter region, or (slightly) upstream thereof or (slightly) downstream thereof. Especially, focusing and/or collimation may be such that the cross-sectional shape (perpendicular to the optical axis) of the beam at the discrete converter region (at the side face) is essentially not larger than the cross-section shape (perpendicular to the optical axis) of the discrete converter region (where the light source light irradiates the discrete converter region). Focusing may be executed with one or more optics, like (focusing) lenses. Especially, two lenses may be applied to focus the laser light source light. Collimation may be executed with one or more (other) optics, like collimation elements, such as lenses and/or parabolic mirrors. In embodiments, the beam of (laser) light source light may be relatively highly collimated, such as in embodiments≤2° (FWHM), more especially 1° (FWHM), most especially 0.5° (FWHM). Hence, ≤2° (FWHM) may be considered (highly) collimated light source light. Optics may be used to provide (high) collimation (see also above).
The term “solid state material laser”, and similar terms, may refer to a solid-state laser like based on a crystalline or glass body dopes with ions, like transition metal ions and/or lanthanide ions, to a fiber laser, to a photonic crystal laser, to a semiconductor laser, such as e.g. a vertical cavity surface-emitting laser (VCSEL), etc.
The term “solid state light source”, and similar terms, may especially refer to semiconductor light sources, such as a light emitting diode (LED), a diode laser, or a superluminescent diode.
As indicated above, especially the first light generating device is configured to generate first device light having a first device centroid wavelength (λcd,1). The first device centroid wavelength (λcd,1) is especially in the visible.
The term “centroid wavelength”, also indicated as λc, is known in the art, and refers to the wavelength value where half of the light energy is at shorter and half the energy is at longer wavelengths; the value is stated in nanometers (nm). It is the wavelength that divides the integral of a spectral power distribution into two equal parts as expressed by the formula λc=Σλ*I(λ)/(ΣI(λ), where the summation is over the wavelength range of interest, and I(λ) is the spectral energy density (i.e. the integration of the product of the wavelength and the intensity over the emission band normalized to the integrated intensity). The centroid wavelength may e.g. be determined at operation conditions.
The terms “visible”, “visible light” or “visible emission” and similar terms refer to light having one or more wavelengths in the range of about 380-780 nm. Herein, UV may especially refer to a wavelength selected from the range of 200-380 nm. The terms “light” and “radiation” are herein interchangeably used, unless clear from the context that the term “light” only refers to visible light. The terms “light” and “radiation” may thus refer to UV radiation, visible light, and IR radiation. In specific embodiments, especially for lighting applications, the terms “light” and “radiation” refer to (at least) visible light.
In embodiment, the first light generating device comprises one or more of a solid state material laser and a super luminescent diode. The solid state material laser may, as indicated above, comprise e.g. (i) a laser diode or (ii) a laser based on a luminescent material, especially a ceramic or single crystal, of which some examples are provided above (and below). In embodiments, the first light generating device comprises a diode laser.
Superluminescent diodes are known in the art. A superluminescent diode may be indicated as a semiconductor device which may be able to emit low-coherence light of a broad spectrum like a LED, while having a brightness in the order of a laser diode. US2020192017 indicates for instance that “With current technology, a single SLED is capable of emitting over a bandwidth of, for example, at most 50-70 nm in the 800-900 nm wavelength range with sufficient spectral flatness and sufficient output power. In the visible range used for display applications, i.e. in the 450-650 nm wavelength range, a single SLED is capable of emitting over bandwidth of at most 10-30 nm with current technology. Those emission bandwidths are too small for a display or projector application which requires red (640 nm), green (520 nm) and blue (450 nm), i.e. RGB, emission”. Further, superluminescent diodes are amongst others described, in “Edge Emitting Laser Diodes and Superluminescent Diodes”, Szymon Stanczyk, Anna Kafar, Dario Schiavon, Stephen Najda, Thomas Slight, Piotr Perlin, Book Editor(s): Fabrizio Roccaforte, Mike Leszczynski, First published: 3 Aug. 2020 https://doi.org/10.1002/9783527825264.ch9 in chapter 9.3 superluminescent diodes. This book, and especially chapter 9.3, are herein incorporated by reference. Amongst others, it is indicated therein that the superluminescent diode (SLD) is an emitter, which combines the features of laser diodes and light-emitting diodes. SLD emitters utilize the stimulated emission, which means that these devices operate at current densities similar to those of laser diodes. The main difference between LDs and SLDs is that in the latter case, the device waveguide may be designed in a special way preventing the formation of a standing wave and lasing. Still, the presence of the waveguide ensures the emission of a high-quality light beam with high spatial coherence of the light, but the light is characterized by low time coherence at the same time” and “Currently, the most successful designs ofnitride SLD are bent, curved, or tilted waveguide geometries as well as tiltedfacet geometries, whereas in all cases, the front end of the waveguide meets the device facet in an inclined way, as shown in
The first light generating device may also be indicated as “pump”, or “pump light source”, for instance a “pump laser”. The first light generating device is especially used to pump the first laser and the second laser.
Especially, both the first laser and the second laser comprise a luminescent material. The term “luminescent material” especially refers to a material that can convert first radiation, especially one or more of UV radiation and blue radiation, into second radiation. In general, the first radiation and second radiation have different spectral power distributions. Hence, instead of the term “luminescent material”, also the terms “luminescent converter” or “converter” may be applied. In general, the second radiation has a spectral power distribution at larger wavelengths than the first radiation, which is the case in the so-called down-conversion. In specific embodiments, however the second radiation has a spectral power distribution with intensity at smaller wavelengths than the first radiation, which is the case in the so-called up-conversion. In embodiments, the “luminescent material” may especially refer to a material that can convert radiation into e.g. visible and/or infrared light. For instance, in embodiments the luminescent material may be able to convert one or more of UV radiation and blue radiation, into visible light. The luminescent material may in specific embodiments also convert radiation into infrared radiation (IR). Hence, upon excitation with radiation, the luminescent material emits radiation. In general, the luminescent material will be a down converter, i.e. radiation of a smaller wavelength is converted into radiation with a larger wavelength (λex<λem), though in specific embodiments the luminescent material may comprise up-converter luminescent material, i.e. radiation of a larger wavelength is converted into radiation with a smaller wavelength (λex>λem).
In embodiments, the term “luminescence” may refer to phosphorescence. In embodiments, the term “luminescence” may also refer to fluorescence. Instead of the term “luminescence”, also the term “emission” may be applied. Hence, the terms “first radiation” and “second radiation” may refer to excitation radiation and emission (radiation), respectively. Likewise, the term “luminescent material” may in embodiments refer to phosphorescence and/or fluorescence. The term “luminescent material” may also refer to a plurality of different luminescent materials. Examples of possible luminescent materials are indicated below. Hence, the term “luminescent material” may in specific embodiments also refer to a luminescent material composition. In embodiments, luminescent materials are selected from garnets and nitrides, especially doped with trivalent cerium or divalent europium, respectively. The term “nitride” may also refer to oxynitride or nitridosilicate, etc.
In specific embodiments the luminescent material comprises a luminescent material of the type A3B5O12:Ce, wherein A in embodiments comprises one or more of Y, La, Gd, Tb and Lu, especially (at least) one or more of Y, Gd, Tb and Lu, and wherein B in embodiments comprises one or more of Al, Ga, In and Sc. Especially, A may comprise one or more of Y, Gd and Lu, such as especially one or more of Y and Lu. Especially, B may comprise one or more of Al and Ga, more especially at least Al, such as essentially entirely Al. Hence, especially suitable luminescent materials are cerium comprising garnet materials. Embodiments of garnets especially include A3B5O12 garnets, wherein A comprises at least yttrium or lutetium and wherein B comprises at least aluminum. Such garnets may be doped with cerium (Ce), with praseodymium (Pr) or a combination of cerium and praseodymium; especially however with Ce. Especially, B comprises aluminum (Al), however, B may also partly comprise gallium (Ga) and/or scandium (Sc) and/or indium (In), especially up to about 20% of Al, more especially up to about 10% of Al (i.e. the B ions essentially consist of 90 or more mole % of Al and 10 or less mole % of one or more of Ga, Sc, and In); B may especially comprise up to about 10% gallium. In another variant, B and O may at least partly be replaced by Si and N. The element A may especially be selected from the group consisting of yttrium (Y), gadolinium (Gd), terbium (Tb) and lutetium (Lu). Further, Gd and/or Tb are especially only present up to an amount of about 20% of A. In a specific embodiment, the garnet luminescent material comprises (Y1-xLux)3B5O12:Ce, wherein x is equal to or larger than 0 and equal to or smaller than 1. The term “:Ce”, indicates that part of the metal ions (i.e. in the garnets: part of the “A” ions) in the luminescent material is replaced by Ce. For instance, in the case of (Y1-xLux)3Al5O12:Ce, part of Y and/or Lu is replaced by Ce. This is known to the person skilled in the art. Ce will replace A in general for not more than 10%; in general, the Ce concentration will be in the range of 0.1 to 4%, especially 0.1 to 2% (relative to A). Assuming 1% Ce and 10% Y, the full correct formula could be (Y0.1Lu0.89Ce0.01)3Al5O12. Ce in garnets is substantially or only in the trivalent state, as is known to the person skilled in the art.
In embodiments, the luminescent material (thus) comprises A3B5O12 wherein in specific embodiments at maximum 10% of B—O may be replaced by Si—N.
In specific embodiments the luminescent material comprises (Yx1-x2-x3A′x2Cex3)3(Aly1-y2B′y2)5O12, wherein x1+x2+x3=1, wherein x3>0, wherein 0<x2+x3≤0.2, wherein y1+y2=1, wherein 0≤y2≤0.2, wherein A′ comprises one or more elements selected from the group consisting of lanthanides, and wherein B′ comprises one or more elements selected from the group consisting of Ga, In and Sc. In embodiments, x3 is selected from the range of 0.001-0.1. In the present invention, especially x1>0, such as >0.2, like at least 0.8. Garnets with Y may provide suitable spectral power distributions.
In specific embodiments at maximum 10% of B—O may be replaced by Si—N. Here, B in B—O refers to one or more of Al, Ga, In and Sc (and O refers to oxygen); in specific embodiments B—O may refer to Al—O. As indicated above, in specific embodiments x3 may be selected from the range of 0.001-0.04. Especially, such luminescent materials may have a suitable spectral distribution (see however below), have a relatively high efficiency, have a relatively high thermal stability, and allow a high CRI (in combination with the first light source light and the second light source light (and the optical filter)). Hence, in specific embodiments A may be selected from the group consisting of Lu and Gd. Alternatively or additionally, B may comprise Ga. Hence, in embodiments the luminescent material comprises (Yx1-x2-x3(Lu,Gd)x2Cex3)3(Aly1-y2Gay2)5O12, wherein Lu and/or Gd may be available. Even more especially, x3 is selected from the range of 0.001-0.1, wherein 0<x2+x3≤0 1, and wherein 0≤y2≤0.1. Further, in specific embodiments, at maximum 1% of B—O may be replaced by Si—N. Here, the percentage refers to moles (as known in the art); see e.g. also EP3149108. In yet further specific embodiments, the luminescent material comprises (Yx1-x3Cex3)3Al5O12, wherein x1+x3=1, and wherein 0<x3≤0.2, such as 0.001-0.1.
In specific embodiments, the light generating device may only include luminescent materials selected from the type of cerium comprising garnets. In even further specific embodiments, the light generating device includes a single type of luminescent materials, such as (Yx1-x2-x3A′x2Cex3)3(Aly1-y2B′y2)5O12. Hence, in specific embodiments the light generating device comprises luminescent material, wherein at least 85 weight %, even more especially at least about 90 wt. %, such as yet even more especially at least about 95 weight % of the luminescent material comprises (Yx1-x2-x3A′x2Cex3)3(Aly1-y2B′y2)5O12. Here, wherein A′ comprises one or more elements selected from the group consisting of lanthanides, and wherein B′ comprises one or more elements selected from the group consisting of Ga, In and Sc, wherein x1+x2+x3=1, wherein x3>0, wherein 0<x2+x3≤0.2, wherein y1+y2=1, wherein 0≤y2≤0.2. Especially, x3 is selected from the range of 0.001-0.1. Note that in embodiments x2=0. Alternatively or additionally, in embodiments y2=0.
In specific embodiments, A may especially comprise at least Y, and B may especially comprise at least Al.
Alternatively or additionally, wherein the luminescent material may comprises a luminescent material of the type A3Si6N11:Ce3+, wherein A comprises one or more of Y, La, Gd, Tb and Lu, such as in embodiments one or more of La and Y.
In embodiments, the luminescent material may alternatively or additionally comprise one or more of M2Si5N8:Eu2+ and/or MAlSiN3:Eu2+ and/or Ca2AlSi3O2N5:Eu2+, etc., wherein M comprises one or more of Ba, Sr, and Ca, especially in embodiments at least Sr. Hence, in embodiments, the luminescent may comprise one or more materials selected from the group consisting of (Ba,Sr,Ca)S:Eu, (Ba,Sr,Ca)AlSiN3:Eu and (Ba,Sr,Ca)2Si5N8:Eu. In these compounds, europium (Eu) is substantially or only divalent, and replaces one or more of the indicated divalent cations. In general, Eu will not be present in amounts larger than 10% of the cation; its presence will especially be in the range of about 0.5 to 10%, more especially in the range of about 0.5 to 5% relative to the cation(s) it replaces. The term “:Eu”, indicates that part of the metal ions is replaced by Eu (in these examples by Eu2+). For instance, assuming 2% Eu in CaAlSiN3:Eu, the correct formula could be (Ca0.98Eu0.02)AlSiN3. Divalent europium will in general replace divalent cations, such as the above divalent alkaline earth cations, especially Ca, Sr, or Ba. The material (Ba,Sr,Ca)S:Eu can also be indicated as MS:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca). Further, the material (Ba,Sr,Ca)2Si5N8:Eu can also be indicated as M2Si5N8:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound Sr and/or Ba. In a further specific embodiment, M consists of Sr and/or Ba (not considering the presence of Eu), especially 50 to 100%, more especially 50 to 90% Ba and 50 to 0%, especially 50 to 10% Sr, such as Ba1.5Sr0.5Si5N8:Eu (i.e. 75% Ba; 25% Sr). Here, Eu is introduced and replaces at least part of M, i.e. one or more of Ba, Sr, and Ca). Likewise, the material (Ba,Sr,Ca)AlSiN3:Eu can also be indicated as MAlSiN3:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca). Eu in the above indicated luminescent materials is substantially or only in the divalent state, as is known to the person skilled in the art.
In embodiments, a red luminescent material may comprise one or more materials selected from the group consisting of (Ba,Sr,Ca)S:Eu, (Ba,Sr,Ca)AlSiN3:Eu and (Ba,Sr,Ca)2Si5N8:Eu. In these compounds, europium (Eu) is substantially or only divalent, and replaces one or more of the indicated divalent cations. In general, Eu will not be present in amounts larger than 10% of the cation; its presence will especially be in the range of about 0.5 to 10%, more especially in the range of about 0.5 to 5% relative to the cation(s) it replaces. The term “:Eu”, indicates that part of the metal ions is replaced by Eu (in these examples by Eu2+). For instance, assuming 2% Eu in CaAlSiN3:Eu, the correct formula could be (Ca0.98Eu0.02)AlSiN3. Divalent europium will in general replace divalent cations, such as the above divalent alkaline earth cations, especially Ca, Sr, or Ba.
The material (Ba,Sr,Ca)S:Eu can also be indicated as MS:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca).
Further, the material (Ba,Sr,Ca)2Si5N8:Eu can also be indicated as M2Si5N8:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound Sr and/or Ba. In a further specific embodiment, M consists of Sr and/or Ba (not considering the presence of Eu), especially 50 to 100%, more especially 50 to 90% Ba and 50 to 0%, especially 50 to 10% Sr, such as Ba1.5Sr0.5Si5N8:Eu (i.e. 75% Ba; 25% Sr). Here, Eu is introduced and replaces at least part of M, i.e. one or more of Ba, Sr, and Ca).
Likewise, the material (Ba,Sr,Ca)AlSiN3:Eu can also be indicated as MAlSiN3:Eu, wherein M is one or more elements selected from the group consisting of barium (Ba), strontium (Sr) and calcium (Ca); especially, M comprises in this compound calcium or strontium, or calcium and strontium, more especially calcium. Here, Eu is introduced and replaces at least part of M (i.e. one or more of Ba, Sr, and Ca).
Eu in the above indicated luminescent materials is substantially or only in the divalent state, as is known to the person skilled in the art.
Blue luminescent materials may comprise YSO(Y2SiO5:Ce3+), or similar compounds, or BAM (BaMgAl10O17:Eu2+), or similar compounds.
The term “luminescent material” herein especially relates to inorganic luminescent materials. Instead of the term “luminescent material” also the term “phosphor”. These terms are known to the person skilled in the art.
Alternatively or additionally, also other luminescent materials may be applied. For instance quantum dots and/or organic dyes may be applied and may optionally be embedded in transmissive matrices like e.g. polymers, like PMMA, or polysiloxanes, etc. etc.
Quantum dots are small crystals of semiconducting material generally having a width or diameter of only a few nanometers. When excited by incident light, a quantum dot emits light of a color determined by the size and material of the crystal. Light of a particular color can therefore be produced by adapting the size of the dots. Most known quantum dots with emission in the visible range are based on cadmium selenide (CdSe) with a shell such as cadmium sulfide (CdS) and zinc sulfide (ZnS). Cadmium free quantum dots such as indium phosphide (InP), and copper indium sulfide (CuInS2) and/or silver indium sulfide (AgInS2) can also be used. Quantum dots show very narrow emission band and thus they show saturated colors. Furthermore the emission color can easily be tuned by adapting the size of the quantum dots. Any type of quantum dot known in the art may be used in the present invention. However, it may be preferred for reasons of environmental safety and concern to use cadmium-free quantum dots or at least quantum dots having a very low cadmium content.
Instead of quantum dots or in addition to quantum dots, also other quantum confinement structures may be used. The term “quantum confinement structures” should, in the context of the present application, be understood as e.g. quantum wells, quantum dots, quantum rods, tripods, tetrapods, or nano-wires, etcetera.
Organic phosphors can be used as well. Examples of suitable organic phosphor materials are organic luminescent materials based on perylene derivatives, for example compounds sold under the name Lumogen® by BASF. Examples of suitable compounds include, but are not limited to, Lumogen® Red F305, Lumogen® Orange F240, Lumogen® Yellow F083, and Lumogen® F170.
Different luminescent materials may have different spectral power distributions of the respective luminescent material light. Alternatively or additionally, such different luminescent materials may especially have different color points (or dominant wavelengths).
As indicated above, other luminescent materials may also be possible. Hence, in specific embodiments the luminescent material is selected from the group of divalent europium containing nitrides, divalent europium containing oxynitrides, divalent europium containing silicates, cerium comprising garnets, and quantum structures. Quantum structures may e.g. comprise quantum dots or quantum rods (or other quantum type particles) (see above). Quantum structures may also comprise quantum wells. Quantum structures may also comprise photonic crystals.
The terms “violet light” or “violet emission” especially relates to light having a wavelength in the range of about 380-440 nm. The terms “blue light” or “blue emission” especially relates to light having a wavelength in the range of about 440-495 nm (including some violet and cyan hues). The terms “green light” or “green emission” especially relate to light having a wavelength in the range of about 495-570 nm. The terms “yellow light” or “yellow emission” especially relate to light having a wavelength in the range of about 570-590 nm. The terms “orange light” or “orange emission” especially relate to light having a wavelength in the range of about 590-620 nm. The terms “red light” or “red emission” especially relate to light having a wavelength in the range of about 620-780 nm. The term “pink light” or “pink emission” refers to light having a blue and a red component. The term “cyan” may refer to one or more wavelengths selected from the range of about 490-520 nm. The term “amber” may refer to one or more wavelengths selected from the range of about 585-605 nm, such as about 590-600 nm. The phrase “light having one or more wavelengths in a wavelength range” and similar phrases may especially indicate that the indicated light (or radiation) has a spectral power distribution with at least intensity or intensities at these one or more wavelengths in the indicate wavelength range. For instance, a blue emitting solid state light source will have a spectral power distribution with intensities at one or more wavelengths in the 440-495 nm wavelength range.
More especially, both the first luminescent material and the second luminescent material are based on lanthanide luminescent materials, more especially based on their narrow f-f-transitions, as well known in the art, such as found for trivalent Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm. For lasing purposes, essentially only trivalent lanthanides are of interest. Also combinations of two (or optionally more) trivalent lanthanides may be of interest.
As indicated above, the first light generating device may especially be configured to pump the first laser. Hence, the first laser may be configured downstream of the first light generating device. Or, in other word, the first laser may be configured in a light receiving relationship with the first light generating device.
The terms “light-receiving relationship” or “light receiving relationship”, and similar terms, may indicate that an item may during operation of a source of light (like a light generating device or light generating element or light generating system) may receive light from that source of light. Hence, the item may be configured downstream of that source of light. Between the source of light and the item, optics may be configured.
The terms “upstream” and “downstream”, such as in the context of propagation of light, may especially relate to an arrangement of items or features relative to the propagation of the light from a light generating element (here the especially the . . . ), wherein relative to a first position within a beam of light from the light generating element, a second position in the beam of light closer to the light generating element (than the first position) is “upstream”, and a third position within the beam of light further away from the light generating element (than the first position) is “downstream”. For instance, instead of the term “light generating element” also the term “light generating means” may be applied.
The terms “radiationally coupled” or “optically coupled” or “radiatively coupled” may especially mean that (i) a light generating element, such as a light source, and (ii) another item or material, are associated with each other so that at least part of the radiation emitted by the light generating element is received by the item or material. In other words, the item or material is configured in a light-receiving relationship with the light generating element. At least part of the radiation of the light generating element will be received by the item or material. This may in embodiments be directly, such as the item or material in physical contact with the (light emitting surface of the) light generating element. This may in embodiments be via a medium, like air, a gas, or a liquid or solid light guiding material. In embodiments, also one or more optics, like a lens, a reflector, an optical filter, may be configured in the optical path between light generating element and item or material. The term “in a light-receiving relationship” does, as indicated above, not exclude the presence of intermediate optical elements, such as lenses, collimators, reflectors, dichroic mirrors, etc. In embodiments, the term “light-receiving relationship” and “downstream” may essentially be synonyms.
Especially, the first laser may comprise a first lanthanide based luminescent material configured to convert at least part of the first device light having the first device centroid wavelength (λcd,1) into first luminescent material light, wherein the first laser is configured to provide first laser light comprising at least part of the first luminescent material light. Hence, the first luminescent material may be brought into a lasing mode upon pumping by the first laser. The generation of the first luminescent material light may especially be a downconversion process. In specific embodiments, the first laser light has a first centroid laser wavelength (λcl,1) in the visible.
As indicated above, the first light generating device may especially be configured to pump the first laser. Hence, the second laser may be configured downstream of the first light generating device; or, the second laser may (also) be configured in a light receiving relationship with the first light generating device.
Especially, the second laser may comprise a second lanthanide based luminescent material configured to convert at least part of the first device light having the first device centroid wavelength (λcd,1) into second luminescent material light, wherein the second laser is configured to provide second laser light comprising at least part of the second luminescent material light. Hence, the second luminescent material may (also) be brought into a lasing mode upon pumping by the first laser. The generation of the second luminescent material light may especially be a downconversion process. In specific embodiments, the second laser light has a second centroid laser wavelength (λcl,2) in the visible.
The first laser and the second laser are especially selected such that the laser light of the first laser and the second laser have different spectral power distributions. This may be achieved by selecting different luminescent materials and/or by choosing different lasing wavelengths for the same luminescent material. Especially, in embodiments |λcl,2−λcl,1|≥20 nm, more especially |λcl,2−λcl,1|≥225 nm. Yet even more especially, |λcl,2−λcl,1|≥40 nm may apply. For instance, in embodiments 20 nm≤|λcl,2−λcl,1|≤100 nm. Different values may be possible when in specific embodiments upconversion materials are configured downstream (or upstream) of the first laser and/or second laser. Such embodiments are herein further not discussed (but not excluded).
In embodiments, the first centroid laser wavelength (λcl,1) and the second centroid laser wavelength (λcl,2) are selected from the wavelength range of 495-780 nm (with especially 20 nm≤|λcl,2−λcl,1|≤100 nm). In more specific embodiments, the first centroid laser wavelength (λcl,1) and the second centroid laser wavelength (λcl,2) are selected from different wavelength ranges from the group of (i) 495-570 nm, (ii) 570-590 nm, (iii) 590-620 nm, and (iv) 620-780 nm. In this way, especially these wavelengths may be useful for allowing the generation of white light with a good or high CRI.
Hence, in specific embodiments the system may be configured to generate in an operational mode white system light. This does not exclude that in other operational modes the system light may be colored light. The system light may in the operational mode comprise one or more of first device light, first laser light, and second laser light. Especially, in embodiments the system light may in the operational mode comprise at least both the first laser light and second laser light. Therefore, in embodiments in a first operational mode of the light generating system the light generating system may be configured to provide system light comprising the first laser light and the second laser light, and especially in the first operational mode the system light is white light.
The term “white light” herein, is known to the person skilled in the art. It especially relates to light having a correlated color temperature (CCT) between about 1800 K and 20000 K, such as between 2000 and 20000 K, especially 2700-20000 K, for general lighting especially in the range of about 2700 K and 6500 K. In embodiments, for backlighting purposes the correlated color temperature (CCT) may especially be in the range of about 7000 K and 20000 K. Yet further, in embodiments the correlated color temperature (CCT) is especially within about 15 SDCM (standard deviation of color matching) from the BBL (black body locus), especially within about 10 SDCM from the BBL, even more especially within about 5 SDCM from the BBL.
In embodiments, the white system light may have a correlated color temperature selected from the range of 2000-6500 K, especially in the range of about 2700-6500 K, such as 2700-5000 K, like in specific embodiments 2700-4500 K, such as in embodiments at least 3000 K, like in embodiments up to about 4000 K. Further, the white system light may have a color rendering index of at least about 75, even more especially at least about 80. Further, the white system light may have a R9 value of equal to or larger than 0. Especially, in embodiments CRI≥80 and R9≥0. In specific embodiments, CRI may be at least 85, such as at least 90. Hence, in the operational mode of the light generating system the light generating system may be configured to generate white system light having a correlate color temperature selected from the range of 2700-4500 K and a color rendering index of at least 80. For instance, in embodiments, in the operational mode of the light generating system the light generating system may be configured to generate white system light having a correlate color temperature selected from the range of 2700-6500 K, such as at least 3000 K, like in embodiments in the range of 3000-4500 K, and a color rendering index of at least 80.
As indicated above, the first laser and the second laser may specially selected such that the laser light of the first laser and the second laser have different spectral power distributions. This may be achieved by selecting different luminescent materials and/or by choosing different lasing wavelengths for the same luminescent material. Especially, the different lasing wavelengths may be selected using different laser cavities. The different laser cavities may—amongst others—differ in one or more of (i) material that is brought to lasing and (ii) mirrors for the cavity.
In embodiments, the first laser may comprise a first arrangement comprising a first laser cavity and a first crystal comprising the first lanthanide based luminescent material, wherein the first crystal is configured within the first laser cavity. Alternatively, instead of a crystal, a glass body or a ceramic body may be applied. Especially, the first arrangement comprises a first reflector and a second reflector, wherein the first reflector is arranged upstream of the first crystal and wherein the second reflector is arranged downstream of the first crystal, wherein the first reflector is light transmissive for the first device light and reflective for the first laser light, wherein the second reflector is reflective for the first device light and partially reflective for the first laser light. With such reflectors, device light can enter the first laser cavity, but return in a direction of the first light generating device may be reduced. Further, with such reflectors, transmission of the first device light through the second reflector may be reduced, such that reflected first device light may have another chance to be converted by the first lanthanide based material. Especially, the second reflector is also partially transmissive for the first laser light. In this way, part of the first laser light may be used to support stimulated emission, and part of the first laser light may escape via the second reflector. Hence, in specific embodiment the first reflector may also be partially reflective for the first laser light.
In embodiments, the term “first laser cavity” may refer to the arrangement of the first reflector and the second reflector; the first lanthanide based luminescent material may be configured in between the first reflector and the second reflector.
In embodiments, the second laser may comprise a second arrangement comprising a second laser cavity and a second crystal comprising the second lanthanide based luminescent material, wherein the second crystal is configured within the second laser cavity. Alternatively, instead of a crystal, a glass body or a ceramic body may be applied. Especially, the second arrangement may comprise a third reflector and a fourth reflector, wherein the third reflector is arranged upstream of the second crystal and wherein the fourth reflector is arranged downstream of the second crystal, wherein the third reflector is light transmissive for the first device light and reflective for the second laser light, wherein the fourth reflector is reflective for the first device light and partially reflective for the second laser light. With such reflectors, device light can enter the second cavity, but return in a direction of the first light generating device may be reduced. Further, with such reflectors, transmission of the first device light through the fourth reflector may be reduced, such that reflected first device light may have another chance to be converted by the first lanthanide based material. Especially, the fourth reflector is also partially transmissive for the second laser light. In this way, part of the second laser light may be used to support stimulated emission, and part of the second laser light may escape via the fourth reflector. Hence, in specific embodiment the third reflector may also be partially reflective for the first laser light.
In embodiments, the term “second laser cavity” may refer to the arrangement of the third reflector and the fourth reflector; the second lanthanide based luminescent material may be configured in between the third reflector and the fourth reflector.
The spectral power distribution of the light that may escape from the first cavity via the second reflector and may escape from the second cavity via the fourth reflector, may however differ. First laser light may escape from the first cavity and second laser light may escape from the second cavity.
Therefore, in specific embodiments (A) the first laser comprises a first arrangement comprising a first laser cavity and a first crystal comprising the first lanthanide based luminescent material, wherein the first crystal is configured within the first laser cavity; (B) the second laser comprises a second arrangement comprising a second laser cavity and a second crystal comprising the second lanthanide based luminescent material, wherein the second crystal is configured within the second laser cavity; (C) the first arrangement comprises a first reflector and a second reflector, wherein the first reflector is arranged upstream of the first crystal and wherein the second reflector is arranged downstream of the first crystal, wherein the first reflector is light transmissive for the first device light and reflective for the first laser light, wherein the second reflector is reflective for the first device light and partially reflective for the first laser light; (D) the second arrangement comprises a third reflector and a fourth reflector, wherein the third reflector is arranged upstream of the second crystal and wherein the fourth reflector is arranged downstream of the second crystal, wherein the third reflector is light transmissive for the first device light and reflective for the second laser light, wherein the fourth reflector is reflective for the first device light and partially reflective for the second laser light; and (E) the first arrangement and the second arrangement are different. Hence, the first laser cavity, in combination with the first light generating device, may especially be configured to generate first laser light; the second laser cavity, in combination with the first light generating device, may especially be configured to generate second laser light. Hence, especially the second reflector may have a wavelength dependent reflection different from the fourth reflector.
Instead of the term “laser cavity”, also the terms “optical cavity”, “resonating cavity” or “optical resonator” may be applied.
Herein, when an element is indicated to be transmissive this may in embodiments imply that at one or more wavelengths the part of the radiation that is transmitted may be larger than the part of the radiation that is reflected or absorbed. Herein, when an element is indicated to be reflective this may in embodiments imply that at one or more wavelengths the part of the radiation that is reflected may be larger than the part of the radiation that is transmitted or absorbed.
The term “transmissive” with regards to the light source light may herein may especially refer to at least 50% of incident light source light passing through the material, such as at least 60%, especially at least 70%, such as at least 80%, especially at least 90%, such as at least 95%, under perpendicular irradiation. Similarly, the term “reflective” with regards to the light source light may herein refer to at least 50% of incident light source light being reflected, such as at least 60%, especially at least 70%, such as at least 80%, especially at least 90%, such as at least 95%, under perpendicular irradiation. Here, the percentages may refer to percentages based on Watts.
In the case of the laser cavity, however, the reflectivity of a reflective element may be relatively high, such as at least about 80%, more especially at least about 85% (especially for non-lasing wavelengths). The transmissiveness for the laser light of one of the reflectors (here the second and fourth, respectively) may in embodiments be high (but small for non-lasing wavelengths).
For generating white light, it may be useful when the first light generating device is configured to generate first device light in the blue. Would this blue light partially be converted by the first luminescent material and/or the second luminescent material, especially both, into complementary wavelengths (for obtaining white light), white light may be provided.
Hence, in specific embodiments the first light generating device is configured to generate first device light having a first device centroid wavelength (λcd,1) selected from the range of 430-495 nm, more especially 440-495 nm. Yet, in embodiments, a first device centroid wavelength (λcd,1) selected from the range of 440-485 nm. More especially, the first device centroid wavelength (λcd,1) may selected from the range of 440-480 nm, even more especially 440-460 nm.
Hence, in specific embodiments the second light generating device is configured to generate second device light having a second device centroid wavelength (λcd,2) selected from the range of 420-485 nm, more especially 430-485 nm. Yet, in embodiments, a first device centroid wavelength (λcd,1) selected from the range of 430-475 nm. More especially, the first device centroid wavelength (λcd,2) may selected from the range of 430-470 nm, even more especially 430-450 nm.
Further, in specific embodiments the first light generating device may comprise a diode laser.
Part of the first device light may not be converted. This unconverted device light may comprised by the system light. Hence, when using a blue device light emitting first light generating device, a blue component of the system light in an operational mode may be provided by the first light generating device. Other components comprised by the system light in an operational mode may be one or more of the first laser light, and the second laser light. Therefore, in embodiments in the first operational mode of the light generating system the light generating system may be configured to provide system light comprising the first device light, the first laser light, and the second laser light.
As indicated above, especially the luminescent materials may be based on lanthanide materials having relatively sharp spectral f-f transitions. By appropriately selected the lanthanide as well as its host material, and the spectral power distribution of the first light generating device, it is possible to generate a laser comprising the luminescent material with the host material comprising the specific lanthanide, which can be pumped to lasing with the first light generating device.
It appears that especially suitable may be luminescent materials which comprise (trivalent) terbium (4f8 configuration) as dopant and/or (trivalent) praseodymium (4f9 configuration). With such lanthanide ions, it may be possible to generate light in the desired wavelength range(s). The term “terbium based luminescent material” or the term “praseodymium based luminescent material” especially refers to luminescent materials wherein terbium or praseodymium, respectively, are dopants (like e.g. trivalent cerium or divalent europium in above-mentioned luminescent materials).
As an excitation of a lanthanide ion may lead to different emissions, it may be possible to select the mirrors such that one emission transition may be get into lasing, whereas other emission transitions are much less or not stimulated. Hence, in this way it may be possible to use the same luminescent material for different types of laser light. Further, the host materials may have some impact on the emission transitions in terms of wavelength and in terms of oscillator strength. Hence, the same type of lanthanide ion may be used in different optical cavities to get different types of laser light.
In embodiments, the first lanthanide based luminescent material may comprise a trivalent terbium based luminescent material, and the second lanthanide based luminescent material may comprise a trivalent terbium based luminescent material. Hence, both luminescent materials may comprise trivalent terbium. The host materials may in embodiments be the same or may in other embodiments be different.
Instead of or in addition to a trivalent terbium based luminescent material, a praseodymium based material may be applied. Hence, in embodiments the first lanthanide based luminescent material may comprise a praseodymium based luminescent material, and/or the second lanthanide based luminescent material may comprise a praseodymium based luminescent material.
Therefore, in specific embodiments the first lanthanide based luminescent material may comprise a trivalent terbium based luminescent material or a trivalent praseodymium based luminescent material, and the second lanthanide based luminescent material may comprise a trivalent praseodymium based luminescent material or a trivalent terbium based luminescent material, and wherein the first lanthanide based luminescent material and the second lanthanide based luminescent material are different luminescent materials. The luminescent material may be different in that the comprise a different trivalent lanthanide as dopant and/or in that the host materials differ.
As there may in embodiments different transitions possible and as different trivalent lanthanides may be applied. It is also possible to generate system light with more than two laser light contributions. In specific embodiments, the system may comprise a third laser, wherein (a) the third laser comprises a third lanthanide based luminescent material configured to convert at least part of the first device light into third luminescent material light, wherein the third laser is configured downstream of the first light generating device and is configured to provide third laser light comprising at least part of the third luminescent material light, wherein the third laser light has a third centroid laser wavelength (λcl,3) in the visible, wherein |λcl,3−λcl,1|≥25 nm and |λcl,3−λcl,2|≥25 nm; and (b) the first centroid laser wavelength (λcl,1), the second centroid laser wavelength (λcl,2), and the third centroid laser wavelength (λcl,1) are selected from different wavelength ranges from the group of (i) 495-570 nm, (ii) 570-590 nm, (iii) 590-620 nm, and (iv) 620-780 nm.
Like described above, such third laser may comprise a third laser cavity. Hence, in embodiments, the third laser may comprise a third arrangement comprising a third laser cavity and a third crystal comprising the third lanthanide based luminescent material, wherein the third crystal is configured within the third laser cavity. Alternatively, instead of a crystal, a glass body or a ceramic body may be applied. Further, especially the third arrangement may comprise a fifth reflector and a sixth reflector, wherein the fifth reflector may be arranged upstream of the third crystal and wherein the sixth reflector may be arranged downstream of the third crystal, wherein the fifth reflector may be light transmissive for the first device light and reflective for the third laser light, wherein the sixth reflector may be reflective for the first device light and partially reflective for the third laser light. Especially, the sixth reflector is also partially transmissive for the first laser light. In this way, part of the first laser light may be used to support stimulated emission, and part of the first laser light may escape via the sixth reflector. Hence, in specific embodiment the fifth reflector may also be partially reflective for the first laser light. Especially, the first arrangement, the second arrangement, and the third arrangement are different.
In embodiments, the term “third laser cavity” may refer to the arrangement of the fifth reflector and the sixth reflector; a third lanthanide based luminescent material may be configured in between the fifth reflector and the sixth reflector.
The spectral power distributions of the light that may escape from the third cavity via the sixth reflector and light that may escape from the second cavity via the fourth reflector, and light that may escape from the first cavity via the second reflector, may however differ (different spectral power distributions). First laser light may escape from the first cavity and second laser light may escape from the second cavity and third laser light may escape from the third cavity.
Hence, the first laser cavity, in combination with the first light generating device, may especially be configured to generate first laser light; the second laser cavity, in combination with the first light generating device, may especially be configured to generate second laser light; and the third laser cavity, in combination with the first light generating device, may especially be configured to generate third laser light.
Therefore, in embodiments the third laser may comprise a third arrangement comprising a third laser cavity and a third crystal comprising the third lanthanide based luminescent material, wherein the third crystal is configured within the third laser cavity; wherein the third arrangement comprises a fifth reflector and a sixth reflector, wherein the fifth reflector is arranged upstream of the third crystal and wherein the sixth reflector is arranged downstream of the third crystal, wherein the fifth reflector is light transmissive for the first device light and reflective for the third laser light, wherein the sixth reflector is reflective for the first device light and partially reflective for the third laser light; the first arrangement, the second arrangement, and the third arrangement are different.
Hence, especially the sixth reflector may have a wavelength dependent reflection different from the fourth reflector and also different from the second reflector. In embodiments, the second reflector, the fourth reflector, and the sixth reflector may have different wavelength dependent reflections.
For generating three different types of laser light, that may be useful for generating the (white) system light, it appears useful to use at least one trivalent terbium based luminescent material and at least one praseodymium based luminescent material. Hence, in embodiments two of the first lanthanide based luminescent material, the second lanthanide based luminescent material, and the third lanthanide based luminescent material comprise trivalent terbium based luminescent materials, and wherein one of the first lanthanide based luminescent material, the second lanthanide based luminescent material, and the third lanthanide based luminescent material comprises a trivalent praseodymium based luminescent material.
In embodiments, the first lanthanide based luminescent material, the second lanthanide based luminescent material, and the optional third lanthanide based luminescent material may be selected from (a) (ALnF4:Tb3+), wherein A is selected from the group of Li, Na, and K, and wherein Ln is selected from the group of Y, La, Gd, and Lu, and (b) M10.7Ln0.3M20.3Al11.7O19:Pr3+, wherein M1 is selected from the group of Ca, Sr, and Ba, wherein Ln is selected from the group of Y, La, Gd, and Lu, and wherein M2 is selected from the group of Mg and Ca. Especially, in specific embodiments the first lanthanide based luminescent material, the second lanthanide based luminescent material, and the optional third lanthanide based luminescent material may be selected from (a) (LiLuF4:Tb3+) and (b) Sr0.7La0.3Mg0.3Al11.7O19:Pr3+.
The first laser and the second laser may be configured parallel. For instance, part of the light of the first light generating device may be directed to the first laser and part of the light of the first light generating device may be directed to the second laser. Note that the term “first light generating device” may also refer to a plurality of first light generating devices. Alternatively, the first laser may be configured downstream of the first light generating device but upstream of the second laser. Or, in other words, the second laser may be configured downstream of the first laser, which is configured downstream of the first light generating device. Alternatively, the second laser may be configured downstream of the first light generating device but upstream of the first laser. Or, in other words, the first laser may be configured downstream of the second laser, which is configured downstream of the first light generating device.
Hence, in a serial configuration part of the first device light which is transmitted by the first laser may downstream thereof at least partially be converted by the second laser. Hence, in a parallel configuration part of the first device light which may be transmitted by the first laser may downstream thereof not at least partially be converted by the second laser.
The first laser, the second laser, and the third laser may be configured parallel. For instance, part of the light of the first light generating device may be directed to the first laser and part of the light of the first light generating device may be directed to the second laser and part of the light of the first light generating device may be directed to the third laser.
Alternatively, the one of the three lasers may be configured downstream of the first light generating device but upstream of at least one of the two other lasers. Or, in other words, one or two of the three lasers may be configured downstream of the other of the three lasers, which is configured downstream of the first light generating device. It is even possible that the third laser is configured downstream of the second laser, which is configured downstream of the first laser, which is configured downstream of the first light generating device. Other orders, however, may also be possible.
Therefore, in specific embodiments at least one of the first laser, the second laser, and the optional third laser, may be configured downstream of at least another one of the first laser, the second laser, and the optional third laser. Especially, however, the at least one and the at least other one are configured to be pumped by the first device light. Therefore, in embodiments first device light may propagate through the first laser to the second laser, or first device light may propagate through the first laser to the third laser, or first device light may propagate through the first laser and subsequently through the second laser to the third laser.
As indicated above, a parallel configuration may also be possible. Hence, in embodiments at least one of the first laser, the second laser, and the optional third laser, may be configured parallel to at least another one of the first laser, the second laser, and the optional third laser. As also indicated above, especially the at least one and the at least other one may be configured to be pumped by the first device light.
Hence, in a serial configuration part of the first device light which is transmitted by the first laser may downstream thereof at least partially be converted by the second laser; further, part of the first device light which is transmitted by the second laser may downstream thereof at least partially be converted by the third laser. Hence, in a parallel configuration part of the first device light which may be transmitted by the first laser may downstream thereof not at least partially be converted by the second laser. Likewise, part of the first device light which may be transmitted by the second laser may downstream thereof not at least partially be converted by the third laser. However, with three lasers, also hybrid configurations may be possible (see also
It is desirable to provide a second light generating device. Such second light generating device may be used to provide an additional emission in the system light. In embodiments, this may be a broad band emission (e.g. at least 40 nm FWHM). Especially, however, this second light generating device may be also a laser or a superluminescent diode.
Hence, in embodiments the system may further comprise a second light generating device, wherein: (a) the second light generating device may be configured to generate second device light having a second device centroid wavelength (λcd,2) in the visible, wherein |λcd,2−λcd,1|≥5 nm; and (b) in the first operational mode of the light generating system the light generating system may be configured to provide system light comprising the first laser light, the second laser light, and the second device light. In specific embodiments, the second light generating device may comprise one or more of a solid state material laser and a super luminescent diode. In specific embodiments, |λcd,2−λcd,1|≥10 nm, such as λcd,2−λcd,1|≥15 nm. Yet, in embodiments 5 nm≤|λcd,2−λcd,1≤50 nm, more especially 5 nm≤|λcd,2−λcd,1≤40 nm, such as 10 nm≤|λcd,2−λcd,1≤35 nm.
For instance, the pump wavelength may be in the blue, but an additional blue component at another wavelength may be beneficial, such as for creating white light. the additional second device light may improve color gamut and/or improve CRI and/or increase CCT tunability range.
The term “first light generating device” may refer in an embodiment to a single first light generating device or in an embodiment to a plurality identical first light generating devices, or in a specific embodiment to a plurality of different first light generating devices. The term “second light generating device” may refer in an embodiment to a single second light generating device or in an embodiment to a plurality identical second light generating devices, or in a specific embodiment to a plurality of different second light generating devices.
In specific embodiments, a compact package may e.g. be provided. For instance, in embodiments the system may comprise an integrated light source package, wherein the integrated light source package comprises a common support member configured to support the first light generating device, the first laser, and the second laser, wherein common support member comprises a thermally conductive support. The thermally conductive support may comprise one or more of a heatsink, a heat spreader, and a vapor chamber.
As indicated above, the system may comprise a control system or may be functionally coupled to a control system. The control system may especially control the first light generating device, the first laser, and the second laser, and the optional third laser, and the optional second light generating device.
The term “controlling” and similar terms especially refer at least to determining the behavior or supervising the running of an element. Hence, herein “controlling” and similar terms may e.g. refer to imposing behavior to the element (determining the behavior or supervising the running of an element), etc., such as e.g. measuring, displaying, actuating, opening, shifting, changing temperature, etc. Beyond that, the term “controlling” and similar terms may additionally include monitoring. Hence, the term “controlling” and similar terms may include imposing behavior on an element and also imposing behavior on an element and monitoring the element. The controlling of the element can be done with a control system, which may also be indicated as “controller”. The control system and the element may thus at least temporarily, or permanently, functionally be coupled. The element may comprise the control system. In embodiments, the control system and element may not be physically coupled. Control can be done via wired and/or wireless control. The term “control system” may also refer to a plurality of different control systems, which especially are functionally coupled, and of which e.g. one control system may be a master control system and one or more others may be slave control systems. A control system may comprise or may be functionally coupled to a user interface.
The control system may also be configured to receive and execute instructions form a remote control. In embodiments, the control system may be controlled via an App on a device, such as a portable device, like a Smartphone or I-phone, a tablet, etc. The device is thus not necessarily coupled to the lighting system, but may be (temporarily) functionally coupled to the lighting system.
Hence, in embodiments the control system may (also) be configured to be controlled by an App on a remote device. In such embodiments the control system of the lighting system may be a slave control system or control in a slave mode. For instance, the lighting system may be identifiable with a code, especially a unique code for the respective lighting system. The control system of the lighting system may be configured to be controlled by an external control system which has access to the lighting system on the basis of knowledge (input by a user interface of with an optical sensor (e.g. QR code reader) of the (unique) code. The lighting system may also comprise means for communicating with other systems or devices, such as on the basis of Bluetooth, Wifi, ZigBee, BLE or WiMax, or another wireless technology.
The system, or apparatus, or device may execute an action in a “mode” or “operation mode” or “operational mode” or “mode of operation” or “control mode”. Likewise, in a method an action or stage, or step may be executed in a “mode” or operation mode” or “operational mode” or “mode of operation” or “control mode”. The term “mode” may also be indicated as “controlling mode”. This does not exclude that the system, or apparatus, or device may also be adapted for providing another controlling mode, or a plurality of other controlling modes. Likewise, this may not exclude that before executing the mode and/or after executing the mode one or more other modes may be executed.
However, in embodiments a control system may be available, that is adapted to provide at least the controlling mode. Would other modes be available, the choice of such modes may especially be executed via a user interface, though other options, like executing a mode in dependence of a sensor signal or a (time) scheme, may also be possible. The operation mode may in embodiments also refer to a system, or apparatus, or device, that can only operate in a single operation mode (i.e. “on”, without further tunability).
Hence, in embodiments, the control system may control in dependence of one or more of an input signal of a user interface, a sensor signal (of a sensor), and a timer. The term “timer” may refer to a clock and/or a predetermined time scheme.
In yet a further aspect, the invention also provides a lamp or a luminaire comprising the light generating system as defined herein. The luminaire may further comprise a housing, optical elements, louvres, etc. etc. The lamp or luminaire may further comprise a housing enclosing the light generating system. The lamp or luminaire may comprise a light window in the housing or a housing opening, through which the system light may escape from the housing. In yet a further aspect, the invention also provides a projection device comprising the light generating system as defined herein. Especially, a projection device or “projector” or “image projector” may be an optical device that projects an image (or moving images) onto a surface, such as e.g. a projection screen. The projection device may include one or more light generating systems such as described herein. Hence, in an aspect the invention also provides a light generating device selected from the group of a lamp, a luminaire, a projector device, a disinfection device, a photochemical reactor, and an optical wireless communication device, comprising the light generating system as defined herein. The light generating device may comprise a housing or a carrier, configured to house or support, one or more elements of the light generating system. For instance, in embodiments the light generating device may comprise a housing or a carrier, configured to house or support one or more of the first light generating device, the first laser, and the second laser, and the optional third laser, and the optional second light generating device.
In specific embodiments, colors or color points of a first type of light and a second type of light may be different when the respective color points of the first type of light and the second type of light differ with at least 0.01 for u′ and/or with at least 0.01 for v′, even more especially at least 0.02 for u′ and/or with at least 0.02 for v′. In yet more specific embodiments, the respective color points of first type of light and the second type of light may differ with at least 0.03 for u′ and/or with at least 0.03 for v′. Here, u′ and v′ are color coordinate of the light in the CIE 1976 UCS (uniform chromaticity scale) diagram.
Spectral power distributions of different sources of light having centroid wavelengths differing least 10 nm, such as at least 20 nm, or even at least 30 nm may be considered different spectral power distributions, e.g. different colors.
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:
The schematic drawings are not necessarily to scale.
The first laser 2100 may comprise a first lanthanide based luminescent material 2110 configured to convert at least part of the first device light 111 having the first device centroid wavelength (λcd,1) into first luminescent material light 2111. The first laser 2100 may be configured downstream of the first light generating device 110 and may be configured to provide first laser light 2101 comprising at least part of the first luminescent material light 2111. The first laser light 2101 has a first centroid laser wavelength (λcl,1) in the visible. The second laser 2200 may comprise a second lanthanide based luminescent material 2210 configured to convert at least part of the first device light 111 having the first device centroid wavelength (λcd,1) into second luminescent material light 2211. The second laser 2200 may be configured downstream of the first light generating device 110 and may be configured to provide second laser light 2201 comprising at least part of the second luminescent material light 2211. The second laser light 2201 has a second centroid laser wavelength (λcl,2) in the visible. Especially, λcl,2−λcl,1|≥25 nm. The first centroid laser wavelength (λcl,1) and the second centroid laser wavelength (λcl,2) may be selected from different wavelength ranges from the group of (i) 495-570 nm, (ii) 570-590 nm, (iii) 590-620 nm, and (iv) 620-780 nm. In a first operational mode of the light generating system 1000 the light generating system 1000 may be configured to provide system light 1001 comprising the first laser light 2101 and the second laser light 2201. In the first operational mode the system light 1001 may be white light.
In specific embodiments the first laser 2100 may comprise a first arrangement 2150 comprising a first laser cavity and a first crystal comprising the first lanthanide based luminescent material 2110. The first crystal may be configured within the first laser cavity. In embodiments, the second laser 2200 may comprise a second arrangement 2250 comprising a second laser cavity and a second crystal comprising the second lanthanide based luminescent material 2210. The second crystal may be configured within the second laser cavity. Especially, the first arrangement 2150 may comprise a first reflector 2151 and a second reflector 2152. The first reflector 2151 may be arranged upstream of the first crystal. The second reflector 2152 may be arranged downstream of the first crystal. The first reflector 2151 may be light transmissive for the first device light 111 and reflective for the first laser light 2101. The second reflector 2152 may be reflective for the first device light 111 and partially reflective for the first laser light 2101. Alternatively, the second reflector 2152 may be partially reflective or transmissive for the first device light 111.
In embodiments, the second arrangement 2250 may comprise a third reflector 2251 and a fourth reflector 2252. The third reflector 2251 may be arranged upstream of the second crystal. The fourth reflector 2252 may be arranged downstream of the second crystal. The third reflector 2251 may be light transmissive for the first device light 111 and reflective for the second laser light 2201. The fourth reflector 2252 may be reflective for the first device light 111 and partially reflective for the second laser light 2201. Alternatively, Alternatively, the fourth reflector 2252 may be partially reflective or transmissive for the first device light 111.
Especially, the first arrangement 2150 and the second arrangement 2250 may be different.
The second reflector 2152 has a wavelength dependent reflection different from the fourth reflector 2252.
The first light generating device 110 may be configured to generate first device light 111 having a first device centroid wavelength (λcd,1) selected from the range of 440-495 nm. The first light generating device 110 may comprise a diode laser.
In the first operational mode of the light generating system 1000 the light generating system 1000 may be configured to provide system light 1001 comprising the first device light 111, the first laser light 2101, and the second laser light 2201.
The first lanthanide based luminescent material 2110 may comprise a trivalent terbium based luminescent material. The second lanthanide based luminescent material 2210 may comprise a trivalent terbium based luminescent material.
In embodiments, the first lanthanide based luminescent material 2110 may comprise a trivalent terbium based luminescent material or a trivalent praseodymium based luminescent material. The second lanthanide based luminescent material 2210 may comprise a trivalent praseodymium based luminescent material or a trivalent terbium based luminescent material. Especially, the first lanthanide based luminescent material 2110 and the second lanthanide based luminescent material 2210 are different luminescent materials.
In embodiments, the light generating system 1000 may further comprise a third laser 2300. The third laser 2300 may comprise a third lanthanide based luminescent material 2310 configured to convert at least part of the first device light 111 into third luminescent material light 2311. The third laser 2300 may be configured downstream of the first light generating device 110 and may be configured to provide third laser light 2301 comprising at least part of the third luminescent material light 2311. The third laser light 2301 has a third centroid laser wavelength (λcl,3) in the visible. Especially, |λcl,3−λcl,1|≥25 nm and |λcl,3−λcl,2|≥25 nm. The first centroid laser wavelength (λcl,1), the second centroid laser wavelength (λcl,2), and the third centroid laser wavelength (λcl,1) may be selected from different wavelength ranges from the group of (i) 495-570 nm, (ii) 570-590 nm, (iii) 590-620 nm, and (iv) 620-780 nm. The third laser 2300 may comprise a third arrangement 2350 comprising a third laser cavity and a third crystal comprising the third lanthanide based luminescent material 2310. The third crystal may be configured within the third laser cavity. The third arrangement 2350 may comprise a fifth reflector 2351 and a sixth reflector 2352. The fifth reflector 2351 may be arranged upstream of the third crystal. The sixth reflector 2352 may be arranged downstream of the third crystal. The fifth reflector 2351 may be light transmissive for the first device light 111 and reflective for the third laser light 2301. The sixth reflector 2352 may be reflective for the first device light 111 and partially reflective for the third laser light 2301. Alternatively, the fourth reflector 2352 may be partially reflective or transmissive for the first device light 111.
Especially, the first arrangement 2150, the second arrangement 2250, and the third arrangement 2350 are different.
The second reflector 2152, the fourth reflector 2252, and the sixth reflector 2352 may have different wavelength dependent reflections.
In specific embodiments, two of the first lanthanide based luminescent material 2110, the second lanthanide based luminescent material 2210, and the third lanthanide based luminescent material 3210 may comprise trivalent terbium based luminescent materials. One of the first lanthanide based luminescent material 2110, the second lanthanide based luminescent material 2210, and the third lanthanide based luminescent material 3210 may comprise a trivalent praseodymium based luminescent material. In embodiments, the first lanthanide based luminescent material 2110, the second lanthanide based luminescent material 2210, and the optional third lanthanide based luminescent material 2310 according to claim 10 are selected from (a) (Liluf4:Tb3+) and (b) Sr0.7La0.3Mg0.3Al11.7O19:Pr3+.
Reference 300 refers to a control system.
Referring to
In order to be able to produce a high brightness white laser based light source it appears interesting to provide a laser emitting in the blue, green, yellow, and red part of the spectrum. Amongst others for this purpose, amongst others herein a special combination of line absorber crystals for producing all laser white light using a blue laser is proposed.
Optical pumping of a Tb3+-doped lithium-lutetium-fluoride (LiLuF4) crystal with a diode laser emitting at a wavelength of about 488 nm can be used. At this wavelength light is absorbed and in combination with a mirror enables stimulated emission of yellow laser light at 587 nm and green lasing at 543 nm.
It can be seen that the laser light source has a relatively low CRI. This can be improved by the addition of a second blue laser emitting at 470 nm and substantially full conversion of 488 nm emission by using a reflector at the end as shown in
Here it can be seen that the CRI is relatively high, but not above 90. For increasing CRI further in addition to all stimulated emissions we included a second blue laser emitting at 450 nm as shown in
In a configuration below,
Above crystals were aligned in series however it is possible to put them in parallel and combining them all together. The relative intensity of colors can be tuned by adjusting the size of the crystals and/or adjusting the laser intensity at suitable points.
The yellow light can be combined with blue laser light to make for example high brightness white light which can be used for using in various applications such as stage lighting.
Referring to
The term “plurality” refers to two or more.
The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%.
The term “comprise” also includes embodiments wherein the term “comprises” means “consists of”.
The term “and/or” especially relates to one or more of the items mentioned before and after “and/or”. For instance, a phrase “item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term “comprising” may in an embodiment refer to “consisting of” but may in another embodiment also refer to “containing at least the defined species and optionally one or more other species”.
Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.
The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation.
It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.
In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.
Use of the verb “to comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.
The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.
The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. In yet a further aspect, the invention (thus) provides a software product, which, when running on a computer is capable of bringing about (one or more embodiments of) the method as described herein.
The invention also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system.
The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.
The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.
Number | Date | Country | Kind |
---|---|---|---|
21202189.3 | Oct 2021 | EP | regional |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/EP2022/078048 | 10/10/2022 | WO |