Patent Description:
<CIT> discloses a wavelength converter which converts laser light of a first wavelength to second light having a different wavelength by means of a wavelength converting material. The surface of the wavelength converting material where the laser light enters the wavelength converting material is in good thermal contact with a transparent material. The transparent material on the other hand is in good thermal contact with a heat sink, which has a window to let the laser light pass before the laser light enters the wavelength converting material. A color point of the light emitted by the wavelength converter may change in a broad range.

<CIT> discloses a light source device including an excitation light source which generates excitation light, a fluorescent member containing a fluorescent substance which absorbs the excitation light to generate fluorescence, an emitting side optical member which is provided on an emitting end face of the fluorescent member, and a reflector which is provided on the side surface of the fluorescent member. The reflector has an optical property of reflecting the excitation light and the fluorescence. The emitting side optical member has an optical property of reflecting the excitation light and transmitting the fluorescence.

<CIT> discloses a light emitting device comprising: an excitation light source which radiates excitation light; a wavelength converting member which absorbs and converts the wavelength of at least part of the excitation light radiated from the excitation light source, and releases light with a predetermined wavelength band; a light guide for guiding the excitation light radiated from the excitation light source to the wavelength converting member, with one end at the excitation light source and the other end at the wavelength converting member, wherein the refractive index of the cross-sectional center.

region (core) is higher than that of the circumferential region (clad); and a thermally conductive transparent film which contacts with the wavelength converting member.

It is an object of the present invention to provide a light converting device with improved color stability.

According to a first aspect a light converting device is provided. The light converting device comprises a light converter and a translucent body. A first surface of the translucent body is coupled to a top surface of the light converter. A bottom surface of the light converter is coupled to a reflective bottom layer. The light converting device comprises a light coupling structure. The light coupling structure comprises a hole in the reflective bottom layer and at least a slot in the light converter for receiving a light guide. The light coupling structure comprises a light coupling surface for receiving laser light with a laser peak emission wavelength via the light guide. The light coupling surface is arranged such that at least <NUM>% of the laser light passing the light coupling surface is received by the translucent body and wherein the light coupling surface comprises the first surface of the translucent body or is within the translucent body. The translucent body comprises a second surface opposite to the first surface. The second surface of the translucent body is coupled to a reflective top layer for reflecting at least a part of the laser light back to the light converter. The light converter is adapted to convert reflected laser light to converted light. A peak emission wavelength of the converted light is in a longer wavelength range than the laser peak emission wavelength. The reflective bottom layer is adapted such that at least <NUM>% of the converted light is emitted via the translucent body and the reflective top layer.

The light coupling structure enables a decoupling of the conversion of the laser light and a transmission of a part of the laser light via the reflective top layer. The intensity of the converted light may be less sensitive to variations of the laser peak emission wavelength of the laser (see <FIG> and the corresponding description). Furthermore, a hotspot may be avoided by increasing a surface of the light converter receiving laser light by means of the reflective top layer.

The laser light is preferably in the blue wavelength range. The translucent body may comprise a glass plate, a body made ofAl<NUM>O<NUM>, Sapphire or any other translucent material or material composition which can withstand the conditions (light intensity, heat etc.) during conversion of the laser light. The reflective top layer may be a dichroic filter which is at least partly reflective in the wavelength range of laser light and essentially transparent in the wavelength range of the converted light. The slot in the light converter may be a cavity with a thin layer of light converting material between the light coupling surface and the translucent body. The layer is very thin such that less than <NUM>%, preferably less than <NUM>% and most preferably less than <NUM>% of the laser light is converted in this layer.

The translucent body may be arranged to cool the light converter. A heat sink may not be needed in this case. Alternatively, a heat sink may be used in addition. This may enable thicker layers of light converting material comprised by the light converter such that more laser light may be converted by means of the light converting material. The translucent body may comprise a translucent material with high thermal conductivity as, for example, Sapphire.

The light coupling structure may comprise a hole through the light converter. The light coupling surface may comprise in this case a surface of the translucent body. The slot in the light converter may end at a surface of the translucent body. The light coupling surface may preferably be a part of the interface between the light converter and the translucent body (a part of the first surface). Alternatively, the light coupling structure may comprise a cavity in the translucent body such that the light coupling surface is not at the same level as the interface between the light converter and the translucent body.

The light converter may be arranged to convert or absorb at least <NUM> %, preferably at least <NUM>%, most preferably at least <NUM> % of the laser light entering the light converter.

The laser peak emission wavelength usually varies for different lasers and further depends on operating temperature and driving current of the laser or lasers. Furthermore, absorption and conversion of the laser light in the light converting material of the light converter depends on the laser peak emission wavelength and may change with temperature. A major part of the back reflected laser light entering the light converter should therefore be converted or absorbed in order to reduce the influence of laser light which is not converted or absorbed within the light converter after entering the light converter. Stability of the color or white point of the light which can be generated by means of light converting device may therefore be increased.

The conversion device may be arranged such that an intensity of the converted light is essentially independent from the laser peak emission wavelength in a predetermined wavelength range of, for example, +/- <NUM>, preferably +/- <NUM> around the laser peak emission wavelength (e.g. <NUM>). It may be preferred that essentially all laser light entering the light converter is converted and/or absorbed by the light converting material. Full conversion may, for example, be enabled by the thickness of the light converting material and/or the concentration of the dopant (e.g. Cerium). The reflective bottom layer may, for example, be arranged to enable absorption of laser light at the peak emission wavelengths but arranged to reflect converted light. The reflective bottom layer may, for example, be a dichroic filter reflecting converted light but being transparent for laser light. The light converting device may, for example, further comprise an absorption layer or body coupled to the lower side of the reflective bottom layer opposite to the light converter. The light converting device may further comprise side coatings being arranged to reflect laser light and converted light.

The reflective top layer may be adapted to transmit at least <NUM>% and not more than <NUM>% of the laser light, preferably at least <NUM>% and not more than <NUM>% of the laser light, and more preferably at least <NUM>% and not more than <NUM>% of the laser light received via the light coupling surface.

Transmissivity of the reflective top layer may be used to determine a color point of mixed light which can be generated by means of the light converting device. The mixed light comprises the transmitted laser light and the converted light. A defined transmissivity in combination with nearly full conversion of laser light entering the light converter may enable a stable color point of the mixed light without active feedback as described above.

The light converting device may, for example, be used in an automotive headlight comprising one or more lasers emitting laser light at a laser peak emission wavelength of <NUM>. Around <NUM>% of the blue laser light may be transmitted and the remaining blue laser light is back reflected to the light converter and converted to yellow converted light. The light converter may in this case comprise or consist of a yellow phosphor garnet (e.g. Y(<NUM>-<NUM>)Gd<NUM>,Al<NUM>O<NUM>:Ce). This enables a ratio of <NUM>% blue laser light and <NUM>% yellow converted light in the mixed light emitted by the headlight by taking into account, for example, Stokes losses in the phosphor.

The translucent body may be arranged to scatter the laser light. The laser light may be scattered such that an emission cone of the laser light is broadened. The exit angle of laser light transferred by means of a light guide is determined by means of the numerical aperture of the light guide. The light guide may comprise more than one numerical aperture if the light guide comprises two or more claddings (e.g. optical fiber with two claddings). Distribution or exit angle of the laser light within the translucent body may be increased by means of scattering. Increasing the exit angle may enable to illuminate essentially the whole surface of the light converter with reflected laser light. Losses caused by the area covered by the light coupling surface may be reduced. Furthermore, the energy density within the light converter may be decreased by distributing the laser light across the whole light converter. Cooling of the light converter e.g. by means of a heat sink may be simpler and conversion efficiency of the light converting material comprised by the light converter may be increased.

The translucent body may, for example, comprise scattering structures like scattering particles. Scattering within the translucent body may be used to mix laser light and converted light in order to enable a nearly constant color point of the mixed light within a predefined solid angle which can be illuminated by means of the laser-based light source comprising the light converting device. Alternatively or in addition, the reflective top layer may be arranged to scatter light or an additional layer or body may be coupled to the outer layer of the reflective top layer away from the translucent body to scatter the mixed light.

The translucent body may comprise a lower translucent layer coupled to the top surface of the light converter and an upper translucent layer coupled to the reflective top layer. A surface of the lower translucent layer pointing away from the light coupling surface may be roughened in order to increase the exit angle of the laser light. Alternatively or in addition, the surface of the upper translucent layer away from the reflective top layer may be roughened in order to increase the exit angle of the laser light. There may be an air gap between the lower and the upper translucent layer. The upper translucent layer may in this case be carried by means of a carrier. Alternatively or in addition, a coupling material may be arranged between the upper and lower layer which can withstand the light and temperature within the light converting device during light conversion.

The translucent body may further comprise a deflection layer arranged between the lower translucent layer and the upper translucent layer. The deflection layer may be arranged to increase the exit angle of the laser light as described above.

In a non-claimed embodiment thee light converting device may comprise an anti-reflection layer arranged between the light converter and the translucent body. The anti-reflection layer may be adapted to suppress reflection of the laser light. The anti-reflection layer may decrease the likelihood that laser light is reflected in the direction of the reflective top layer by means of the interface between the light converter and the translucent body. The anti-reflection layer may increase stability of the color point, and especially the white point of light, which can be generated by means of the light converting device.

The reflective top layer may alternatively be adapted to reflect at least <NUM>% of the laser light, more preferably at least <NUM>% of the laser light and most preferably at least <NUM>% of the laser light.

The color point of light which can be emitted by means of the light converting device is in this case mainly or even completely determined by the converted light. Such a light converting device may be used in projection applications to produce primary colors green, amber and red. The light converting device may be especially arranged to convert blue light, especially blue laser light, in the light converter, which fully converts blue light into green, amber or red light. The light converter may in this case comprise a light converting material which can be sintered to dense ceramics to form, for example, a Lumiramic body. Typical light converting materials for green, yellow, amber and red light use Ce<<NUM>+>or ions in a variety of (oxo-) nitride, oxide, or silicate materials.

Examples are:
(Ca<NUM>-x-y-zSrxBayMgz)<NUM>-nAl<NUM>-a+bBaSi<NUM>-bN<NUM>-bOb:M, with <NUM> < x,y,z < l, <NUM> < a < l, <NUM> < b < <NUM>, <NUM> < n < <NUM> and M being a metal, selected out of the group, comprising Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu or mixtures thereof as well as a mixture of these materials with additives which may be added during ceramic processing.

Europium(II)-activated oxonitridoalumino silicate of general formula
EA<NUM>-zSi<NUM>-aAlaN<NUM>-bOb:Euz wherein <NUM> < a < <NUM>, <NUM> < b < <NUM> and <NUM> < z < <NUM>; where EA is at least one earth alkaline metal chosen from the group of calcium, barium and strontium.

Europium(II)-activated oxonitridosilicate of general formula
(Sr<NUM>-a-b-c-d-e-fCabBacMgdZneCef)Six-gGeg NyOz:Eua, wherein <NUM> < a < <NUM>, <NUM> < b < <NUM>, <NUM> < c < <NUM>. <NUM>, <NUM> < d < <NUM>, <NUM> < e < <NUM>, <NUM> < f < <NUM>,<NUM>, <NUM> < g < <NUM>, <NUM> < x < <NUM>, <NUM> < y < <NUM> and <NUM> < z < <NUM>.

Cerium(III) - activiated garnet materials.

Other light converting materials or phosphor materials which may be comprised by the light converter are:.

The light converting device may comprise an anti-reflection layer arranged between the light converter and the translucent body as described above. The anti-reflection layer may improve color saturation if, for example, the reflective top layer is not fully reflective with respect to the wavelength range of the laser light.

The light converting device may comprise a light absorbing layer coupled to the reflective top layer opposite to the translucent body. The light absorbing layer is adapted to absorb transmitted laser light after passing the reflective top layer. The light absorbing layer is further adapted to transmit at least <NUM>% of the converted light after passing the reflective top layer.

The light absorbing layer may comprise one or more sub layers which are arranged as an absorptive color filter to absorb, for example, the blue laser light in order to prevent desaturation of the emission color which can be emitted by means of the light converting device.

According to a further aspect a laser-based light source is provided. The laser based light source comprises a light converting device as described above, a light guide and a laser. The light guide is coupled to the light coupling structure. A light exit surface of the light guide is arranged such that the laser light emitted by the laser via the light guide is received by the light coupling surface.

The laser-based light source may comprise two, three, four or more lasers (e.g. in the form of an array) emitting, for example blue laser light. The light guide may be, for example, an optical fiber comprising one, two or more claddings. The light guide may penetrate an optional heatsink before penetrating the light converter. It may also penetrate a part of the translucent body.

According to a further aspect a vehicle headlight is provided. The vehicle headlight comprises at least one laser-based light source as described above. The vehicle headlight may comprise two, three, four or more laser-based light sources as described above.

The white point of a vehicle headlight, and especially of an automotive headlight used for forward lighting, is preferably characterized by a correlated color temperature (CCT) of <NUM>, or a v' color point of about <NUM>. White light areas are defined in standards. <NUM> is a standard for chromaticity specified by the American National Standards Institute. Most automotive headlights use the <NUM> range as described above. Alternatively, it may also be possible to use a color temperature of <NUM> such that the share of the blue light increases.

It shall be understood that an inventive laser-based light source may have similar and/or identical embodiments, in particular, as defined in the dependent claims and their combinations as well as in the description provided above as long as they fall under the scope claimed.

It shall be understood that a preferred embodiment of the invention can also be any combination of the dependent claims with the respective independent claim as long as they fall under the scope claimed.

Further advantageous embodiments are defined below.

The invention will now be described, by way of example, based on embodiments with reference to the accompanying drawings.

In the Figures, like numbers refer to like objects throughout. Objects in the Figures are not necessarily drawn to scale.

Various embodiments of the invention will now be described by means of the Figures.

<FIG> shows a principal sketch of a first laser-based light source <NUM> comprising a light converting device <NUM>, a light guide <NUM> and a laser <NUM> not claimed by the resent invention. The light converting device <NUM> comprises a reflective bottom layer <NUM> attached to a light converter <NUM> which is in this case a rectangular block (alternatively a cylindrical body or any other suitable shape may be used) of a yellow phosphor garnet (YAG:Ce). The light converter <NUM> is attached to a translucent body <NUM> which consists of sapphire with a high thermal conductivity in order to provide cooling for the light converter <NUM>. On top of the translucent body <NUM> is a reflective top layer <NUM> provided. The light guide <NUM> is coupled to a light coupling structure <NUM>. The light coupling structure <NUM> comprises a hole in the reflective bottom layer <NUM> and a slot in the form of a cavity in the light converter <NUM>. A light exit surface of the light guide <NUM> is arranged such that laser light <NUM> emitted by the laser <NUM> via the light guide <NUM> is received by a light coupling surface <NUM>. The laser light <NUM> with the wavelength of <NUM> has to pass a thin layer of the light converter <NUM>. The thickness of the layer between the light coupling surface <NUM> and the translucent body <NUM> is arranged such that less than <NUM>% of the laser light <NUM> is converted to converted light <NUM> in order to limit the influence of changes in the laser peak emission wavelength or temperature of the light converter <NUM>. The remaining <NUM>% of the la- ser light <NUM> is emitted in the direction of the reflective top layer via the translucent body <NUM>. <NUM>% of the laser light <NUM> reaching the reflective top layer <NUM> passes the reflective top layer (transmitted laser light <NUM>). The rest of the laser light <NUM> is reflected at the reflective top layer <NUM> back in the direction of the light converter <NUM> (reflected laser light <NUM>). The light converter <NUM> converts essentially all of the reflected laser light <NUM> to converted light <NUM>. Converted light <NUM> generated within the yellow phosphor garnet is reflected at the reflective bottom layer <NUM> in the direction of the reflective top layer <NUM>. The reflective top layer <NUM> is arranged such that all converted light <NUM> reaching the reflective top layer <NUM> can pass the layer. The reflective top layer <NUM> is in this case a dichroic filter comprising a number of sub layers which are arranged that only part of the laser light <NUM> but essentially all converted light is transmitted. The laser-based light source <NUM> therefore emits white light comprising a mixture of transmitted laser light <NUM> and converted light <NUM>.

The sheet of the light converting material has preferably a thickness between <NUM>µ<IMG>η and <NUM>µ<IMG>η. The light guide <NUM> usually has circular cross-section with a diameter between <NUM>µ<IMG>η and <NUM>µ<IMG>η. The thickness of the translucent body <NUM> is chosen to realize transmitted laser light <NUM> filling the acceptance cone of optical devices (e.g. one or more lenses, reflectors and the like) which may be coupled with the laser-based light source in a lamp arrangement.

Numerical aperture (NA) of the light guide: <NUM>.

Depending on the refractive index of the translucent body (nr) or the medium between the exit surface of the light guide <NUM> and the dichroic filter, blue light will be distributed over a certain area on the light converter <NUM>.

nr =<NUM> :
The ratio of the illuminated area of the light converter <NUM> without the area of the light guide <NUM> and the total area including the light guide <NUM> will be <NUM>% (for <NUM>µ<IMG>η distance between light coupling surface <NUM> and reflective top layer <NUM>). This ratio takes into account that essentially no converted light is generated in the layer between the light coupling surface <NUM> and the translucent body <NUM> (especially in case the light coupling surface <NUM> is a surface of the translucent body <NUM>; see <FIG> below). The bigger the ratio the less light may be lost via the light guide <NUM>. The diameter of the illuminated area would in this case be <NUM>µ<IMG>η.

For nr =<NUM>:
The illuminated area of the light converter <NUM> without the area of the light guide <NUM> and the total area including the light guide <NUM> will be <NUM>% (with perfect optical coupling to the light guide). The diameter of the illuminated area would in this case be <NUM>µ<IMG>η.

<FIG> shows an absorption coefficient <NUM> of a yellow phosphor garnet. The ordinate <NUM> shows the absorption coefficient and the abscissa <NUM> the wavelength. The spectrum of the absorption coefficient across the wavelength shows a typical absorption spectrum of the yellow phosphor garnet (Y(<NUM>-<NUM>)Gd<NUM>,Al<NUM>O<NUM>:Ce) as used in today's automotive front lighting applications (automotive headlight). From <NUM> to <NUM>, which is a typical wavelength range for blue laser (diode) emission, the absorption coefficient increases by more than a factor of <NUM>, which may lead to a large color point shift of the laser-based light source by about <NUM> in CIE <NUM> v' color point. The blue laser light <NUM> needed for the white light is separated from the main part of the laser light <NUM> which has to be converted prior to the conversion within the light converter <NUM>. The light converting device <NUM> of the laser-based light source <NUM> is arranged such that the emission of the converted light <NUM> is essentially independent of the peak emission or wavelength range of the laser light <NUM> emitted by e.g. the laser <NUM> shown in <FIG> and <FIG> below.

<FIG> shows a principal sketch of a second laser-based light source <NUM>. The basic arrangement is the same as described with respect to <FIG>. The light coupling surface <NUM> is in this embodiment arranged at the interface between the light converter <NUM> and the translucent body <NUM>. The laser light <NUM> directly enters the translucent body <NUM> without passing any material of the light converter <NUM>. The light converting device <NUM> further comprises a heat sink <NUM>. A surface of the heat sink <NUM> is arranged as reflective bottom layer <NUM> which is glued by means of silicone to the light converter <NUM>. The sides of the light converter <NUM> essentially perpendicular to the light emission direction and in this case also the translucent body <NUM> are covered by a side coating 134a which prevents that light can exit through the sides. The combination of the heat sink <NUM> and the translucent body <NUM> which comprises glass or alternatively sapphire can be used to cool the light converter <NUM> more efficient such that a light converter <NUM> with a thickness of more than <NUM>µ<IMG>η can be used in order to enable essentially complete light conversion of reflective laser light <NUM>. The additional cooling pre- vents that the temperature of the Lumiramic light converter <NUM> increases well above <NUM> and avoids severe thermal quenching. Thermal quenching can easily destroy the light converter <NUM>.

<FIG> shows a principal sketch of a third laser-based light source <NUM>. The basic arrangement is the same as described with respect to <FIG> with heat sink <NUM>. The light coupling surface <NUM> is in this embodiment arranged slightly within the translucent body <NUM> such that the light coupling structure <NUM> comprises a cavity in the translucent body <NUM>. The translucent body <NUM> comprises a lower translucent layer 136a made of glass and an upper translucent layer 136c made of glass wherein the lower translucent layer 136a is attached to the light converter <NUM> and the upper translucent layer 136c is attached to the reflective top layer <NUM>. The upper translucent layer 136c is further attached to a carrier <NUM> such that a translucent spacing 136b is built between the lower translucent layer 136a and the upper translucent layer 136c. Furthermore, a deflection layer <NUM> is arranged between the lower translucent layer 136a and the upper translucent layer 136c. The deflection layer <NUM> is in this case a surface of the lower translucent layer 136a which is structured such that the exit cone of the laser light is broadened by deflecting the laser light <NUM>. The carrier <NUM> is reflective as well as the side coating 134a of the light converter <NUM> in order to avoid light losses via the sides of the light converting device <NUM>. The reflective bottom layer <NUM> is in this case a dichroic filter arranged between the heat sink <NUM> and the light converter <NUM> which is reflective for converted light <NUM> but essentially transparent for reflected laser light <NUM>. Reflected laser light <NUM> which is not converted in the light converter <NUM> passes the reflective bottom layer <NUM> and is absorbed by the heat sink <NUM>.

<FIG> shows a principal sketch of a fourth laser-based light source <NUM> which can be used as light source for projection applications not claimed by the present invention. The basic arrangement is very similar to the arrangement described with respect to <FIG> with heat sink <NUM>. The reflective top layer <NUM> reflects at least <NUM>% of the laser light <NUM> such that essentially only converted light <NUM> passes the reflective top layer <NUM>. The color point of the light source is therefore determined by means of the wavelength range of the converted light <NUM>. The light converting device <NUM> further comprises an anti-reflection layer <NUM> which is arranged between the light converter <NUM> and the translucent body <NUM>. The anti-reflection layer <NUM> suppresses reflection of reflective laser light <NUM> at the interface between the translucent body <NUM> and the light converter <NUM>.

The examples provided above with typical numbers apply also to the laser-based light source <NUM> according to <FIG> or <FIG> below. <FIG> shows a principal sketch of a fifth laser-based light source <NUM>. The basic arrangement is the same as the arrangement described with respect to <FIG> but the light converting device <NUM> does not comprise an anti-reflection layer <NUM> between the light converter <NUM> and the translucent body <NUM>. A light absorbing layer <NUM> is attached to the upper side of the reflective top layer <NUM> such that transmitted laser light <NUM> is absorbed within the light absorbing layer <NUM> after passing the reflective top layer <NUM> in order to enable a good color saturation of the converted light <NUM> emitted by the laser-based light source <NUM>.

The light absorbing layer <NUM> or color filter layer is chosen according to the intended color emission of the laser-based light source <NUM>. The color filter layers are preferably inorganic pigment materials as:.

These materials are preferably used with particle diameters < <NUM>, to avoid light losses due to backscattering of light.

Additionally, temperature stable organic pigment can be applied which can be chosen from the group of metal Phthalocyanines or Perylenes.

The position of the light coupling structure <NUM> and especially the light coupling surface <NUM> may be adapted to the overall arrangement of the lamp (e.g. vehicle headlight, projection lamp. It is therefore not necessary that the light converter <NUM> is arranged in the center of the light converter <NUM> as shown in <FIG> and <FIG>. Furthermore, the light guide <NUM> and the light converter <NUM> may enclose an angle different than <NUM>° shown in <FIG> and <FIG>. While the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive.

From reading the present disclosure, other modifications will be apparent to persons skilled in the art. Such modifications may involve other features which are already known in the art and which may be used instead of or in addition to features already described herein as long as they fall under the scope claimed.

Claim 1:
A light converting device (<NUM>) comprising a light converter (<NUM>) and a translucent body (<NUM>), wherein a first surface of the translucent body (<NUM>) is coupled to a top surface of the light converter (<NUM>), wherein a bottom surface of the light converter (<NUM>) is coupled to a reflective bottom layer (<NUM>), wherein the light converting device (<NUM>) comprises a light coupling structure (<NUM>), wherein the light coupling structure (<NUM>) comprises a hole in the reflective bottom layer (<NUM>) and a slot in the light converter (<NUM>) configured to receive a light guide (<NUM>), wherein the light coupling structure (<NUM>) comprises a light coupling surface (<NUM>) for receiving laser light (<NUM>) with a laser peak emission wavelength via the light guide (<NUM>), wherein the light coupling surface (<NUM>) is arranged such that at least <NUM>% of the laser light (<NUM>) passing the light coupling surface (<NUM>) is received by the translucent body (<NUM>) and wherein the light coupling surface (<NUM>) comprises the first surface of the translucent body (<NUM>) or is within the translucent body (<NUM>), wherein the translucent body (<NUM>) comprises a second surface opposite to the first surface, wherein the second surface of the translucent body (<NUM>) is coupled to a reflective top layer (<NUM>) for reflecting at least a part of the laser light (<NUM>) back to the light converter (<NUM>), wherein the light converter (<NUM>) is adapted to convert reflected laser light (<NUM>) to converted light (<NUM>), wherein a peak emission wavelength of the converted light (<NUM>) is in a longer wavelength range than the laser peak emission wavelength, and wherein the reflective bottom layer (<NUM>) is adapted such that at least <NUM>% of the converted light (<NUM>) is emitted via the translucent body (<NUM>) and the reflective top layer (<NUM>).