WO2020038770A1 - Agencement de guide d'ondes optiques, système de couplage de lumière et procédé de fabrication d'un agencement de guide d'ondes optiques - Google Patents

Agencement de guide d'ondes optiques, système de couplage de lumière et procédé de fabrication d'un agencement de guide d'ondes optiques Download PDF

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Publication number
WO2020038770A1
WO2020038770A1 PCT/EP2019/071697 EP2019071697W WO2020038770A1 WO 2020038770 A1 WO2020038770 A1 WO 2020038770A1 EP 2019071697 W EP2019071697 W EP 2019071697W WO 2020038770 A1 WO2020038770 A1 WO 2020038770A1
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Prior art keywords
light
optical waveguide
light guide
scattering
scattering portions
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PCT/EP2019/071697
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English (en)
Inventor
Jan Christian KOCH
Wolfgang SCHIPPER
Philip Erik GÜHLKE
Christian Waltermann
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Fisens Gmbh
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Publication of WO2020038770A1 publication Critical patent/WO2020038770A1/fr

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02295—Microstructured optical fibre
    • G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
    • G02B6/02319—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by core or core-cladding interface features
    • G02B6/02338—Structured core, e.g. core contains more than one material, non-constant refractive index distribution in core, asymmetric or non-circular elements in core unit, multiple cores, insertions between core and clad
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/262—Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/02—Optical fibres with cladding with or without a coating
    • G02B6/02295—Microstructured optical fibre
    • G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
    • G02B6/02342—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by cladding features, i.e. light confining region

Definitions

  • OPTICAL WAVEGUIDE ARRANGEMENT LIGHT COUPLING SYSTEM AND METHOD FOR MANUFACTURING AN OPTICAL WAVEGUIDE ARRANGEMENT
  • the present invention relates to an optical waveguide
  • an optical waveguide arrangement and in particular to an optical waveguide arrangement comprising an outer cladding member having a second refractive index and an inner light guide having a first refractive index along a light propagation axis being interrupted by a plurality of scattering portions.
  • a waveguide For several applications in fiber optics and specifically in sensor technologies using fiber optics based devices, it is desired to couple as much light as possible in a waveguide. For example, if a waveguide is used to transport light to a sample to excite fluorescence or to generate reflectance, it is usually desired to provide a sufficient amount of light to the sample, in order to obtain fluorescence or reflectance, respectively, having a good signal-to-noise ratio, i.e. a response signal with reasonably high intensity. Coupling in a large amount of light into the fiber in this example is even more important if the excited fluorescent light of the sample is to be collected by fiber optics so that the fraction of fluorescence or reflectance can be transported back to a detector .
  • SLEDs super-luminescent light- emitting diodes
  • the inner light guide such as the core of the optical fiber, usually has a small diameter and thus is mode specific, another reason is the ability to better focus and bundle light of a laser.
  • FIG. 1 An example of a broad light source in front of a fiber optic waveguide is schematically illustrated in figure 1.
  • the light source 150 is a LED illuminating the waveguide 100 having an inner light guide 110 and an outer cladding member 120.
  • Light rays are indicated by dashed lines 140, wherein in this illustration only one light ray travels along the light propagation axis indicated by arrow 130 in the inner light guide 110.
  • Light can only be coupled into a waveguide if it is
  • this critical angle is indicated as a, wherein this critical angle for coupling light into the waveguide can be calculated from the numerical aperture, NA, according to the following relationship
  • the numerical aperture defines the acceptance cone of light entering the waveguide at different angles.
  • Figure 2 is an example of light propagation in an optical fiber having a fiber core as an inner light guide and
  • cladding as an outer cladding member.
  • light can be confined to a fiber core if the angle with respect to the surface of the cladding is smaller than the critical angle.
  • the critical angle depends on the refractive index difference between the fiber core having a refractive index n ⁇ and the surrounding cladding having a refractive index n c .
  • figure 2 is merely a qualitative example according to geometrical optics and if single mode optical fibers or graded-index fibers are used Gaussian Beam Optics may lead to more accurate predictions. Furthermore, the light-emitting surface of an LED is
  • an inner light guide e.g. fiber core of an optical fiber.
  • the diameter of the core of a single mode optical fiber is usually several micrometers, e.g. approximately 9
  • cladding 120 surrounding the inner light guide 110, which is a fiber core in the example of an optical fiber shown in figure 1.
  • the cladding is typically also optically
  • n c refractive index difference between the cladding (e.g. n c is approximately 1.46) and the surrounding air (e.g. n is approximately 1)
  • Snell's law defines that light which is outside an inner light guide having an index of refraction larger than the index of refraction of a cladding member surrounding the inner light guide and enters the inner light guide is refracted in such a way that the light leaves the inner light guide again on the opposite side without being totally internally reflected.
  • tapered fibers fibers with an enlarged core at the end becoming gradually smaller like a cone, are used to at least receive some light which would otherwise be lost in the cladding.
  • the idea is to funnel light into the core.
  • this approach does not change the angle distribution, since the angle of the incoming light with respect to the propagation direction gets larger with each reflection on the interfaces core/cladding so that the coupling improvement using tapers is limited, as shown in figure 4.
  • an optical waveguide arrangement comprises an inner light guide having a first refractive index and an outer cladding member having a second refractive index which are configured so as to guide light along a light propagation axis in the inner light guide.
  • This arrangement further comprises a plurality of scattering portions having a third refractive index and being arranged along the light propagation axis in the inner light guide.
  • Each scattering portion has a long axis substantially parallel to the light propagation axis as well as a short axis substantially perpendicular to the light propagation axis and the long axis so that light traveling through the inner light guide is scattered by the scattering portions in different directions.
  • the light is scattered on the scattering portions anisotropically in different directions so that light with different intensities can be measured in different directions.
  • the orientation of the scattering portions especially that the long axis is basically parallel and aligned with the light propagation axis, leads to a main scattering direction along this axis, and hence a higher probability that light is guided in the inner light guide.
  • the optical waveguide arrangement further comprises additional scattering portions having the third refractive index or a fourth refractive index and being arranged in parallel to the plurality of scattering portions in the inner light guide. Since the additional scattering portions are also arranged in the inner light guide in parallel to the scattering portions, i.e. the long axes of both portions are in parallel, the effect of scattering more light along the light propagation axis than in a perpendicular direction can be enhanced since more scatterers can be placed in a length section of the inner light guide.
  • scattering portions are arranged to surround the plurality of scattering portions in the inner light guide. Accordingly, even more scattering portions can be placed in a length section enhancing the scattering and thus coupling
  • the optical waveguide arrangement further comprises a plurality of outer scattering portions having the third refractive index or a fifth
  • the outer scattering portions have a long axis and a short axis substantially perpendicular to the long axis, wherein the long axis of the outer scattering portions is tilted at an angle in the range between 1 degree and 40 degrees, preferably between 2 (or 3) and 20 degrees, with respect to the long axis of the
  • the coupling efficiency for coupling light into the inner light guide is further
  • the outer scattering portions are arranged one after the other and/or parallel to each other. Accordingly, the number of outer scattering portions in a length section of the optical waveguide
  • At least one of the groups of the scattering portions, the additional scattering portions and the outer scattering portions is arranged in the end section of the optical waveguide arrangement.
  • light from a light source arranged at the end face of the end section can be coupled easier in the inner light guide.
  • the inner light guide comprises a light reflecting surface at one of its end faces perpendicular to the light propagation direction so as to reflect light traveling towards the light reflecting surface back into the inner light guide. Accordingly, light traveling along the light propagation axis in two opposite directions can be directed in only one direction.
  • the scattering portions are adapted to have shapes approximating an ellipsoid so that light traveling through the inner light guide is scattered by the scattering portions more in a main scattering direction being substantially parallel and aligned to the long axis than in a scattering direction being substantially parallel and aligned to the short axis. Accordingly, preferred
  • directions of light propagation can be chosen by designing the shape of the scattering portions.
  • the long axis is in the order of or larger than twice the wavelength of the light guided in the inner light guide and the short axis is in the order of or smaller than the wavelength of the light.
  • preferred directions of light propagation can be chosen by designing the shape of the scattering portions.
  • the distances between the scattering portions along the light propagation axis are in the order of or smaller than the long axis. Accordingly, interference effects can be used to improve light propagation in the inner light guide.
  • the inner light guide and the outer cladding member form a single mode optical waveguide. Accordingly, coupling light into the inner light guide of a single mode optical fiber and thus the amount of light propagated therein can be improved.
  • a light coupling system comprises the above mentioned optical waveguide arrangement and a light source for inputting light into the optical waveguide arrangement.
  • the distance between the light source and a scattering portion of the plurality of scattering portions is preferably less than 1 cm. Accordingly, a system for efficiently coupling light from at least one light source into an inner light guide can be provided.
  • the light source is arranged at one of the end faces of the optical waveguide arrangement for coupling light in the inner light guide and/or outer cladding member.
  • the at least one light source is arranged at a section of the outer surface of the outer cladding member so that the light of the light source is coupled into the inner light guide through the outer cladding member. Accordingly, a system for efficiently coupling light from a light source into an inner light guide can be
  • a method for manufacturing an optical waveguide arrangement comprises providing an optical waveguide comprising an inner light guide having a first refractive index and an outer cladding member having a second refractive index which are configured so as to guide light along a light propagation axis in the inner light guide.
  • the method further comprises focusing a pulsed laser beam into the inner light guide so as to generate a plurality of scattering portions having a third refractive index and being arranged along the light propagation axis in the inner light guide and so that each scattering portion has a long axis substantially parallel to the light propagation axis as well as a short axis substantially perpendicular to the light propagation axis and the long axis.
  • an optical waveguide arrangement can be manufactured including
  • Fig. 1 illustrates an example of an optical waveguide and its elements being illuminated by a light source.
  • Fig. 2 illustrates an example of an optical waveguide to better explain light propagation therein.
  • Fig. 3 illustrates the refractive behavior of a light ray in an optical fiber, as an example of a waveguide.
  • Fig. 4 illustrates a tapered fiber and light propagation therein .
  • Fig. 5 illustrates the effect on light scattered by a scattering portion included in an inner light guide of an optical waveguide arrangement.
  • Fig. 6A illustrates an optical waveguide arrangement comprising scattering portions according to an embodiment as well as a light source.
  • Fig. 6B shows a scattering portion in more detail.
  • Fig. 6C illustrates a cross section of the optical waveguide arrangement .
  • Fig. 6D illustrates an optical waveguide arrangement, such as in Fig. 6A, comprising additional scattering portions.
  • Fig. 7A illustrates an optical waveguide arrangement comprising scattering portions and outer scattering portions according to an embodiment.
  • Fig. 7B illustrates an optical waveguide arrangement comprising scattering portions and outer scattering portions according to another embodiment.
  • Fig. 8 illustrates an optical waveguide arrangement with a light reflecting surface according to another embodiment.
  • Figs. 9A and 9B explain the function of the optical waveguide arrangement of figure 8.
  • Fig. 10 illustrates a light coupling system according to another embodiment.
  • Fig. 11 illustrates steps of a method for manufacturing an optical wave guide arrangement according to another
  • the arrangement comprising an inner light guide having a first refractive index and an outer cladding member having a second refractive index.
  • the cladding member and the inner light guide which form together a waveguide, are configured so as to guide light along a light propagation axis in the inner light guide.
  • the inner light guide is interrupted along its light propagation axis by a plurality of scattering portions having a shape approximating an ellipsoid and having a third refractive index, wherein the long axis of the ellipsoid is substantially parallel to the light propagation axis, i.e., if at all present, an angle between the long axis and the light propagation axis should preferably be less than 3° and maximally 6 ° .
  • the light is scattered on the scattering portions anisotropically in different directions so that light with different intensities can be measured in different directions.
  • the orientation of the scattering portions especially that the long axis is basically parallel and aligned with the light propagation axis, leads to a main scattering direction along this axis, and hence a higher probability that light is guided in the inner light guide.
  • the configuration of the scattering portions is such that it allows for better and easier coupling of light in the inner light guide.
  • the differences in the dimensions of the long and short axes of the scattering portion lead to large differences in the intensity of the scattered/diffracted light so that more light is emitted in a main scattering direction lying in a direction defined by the long axis and the light propagation axis than in a scattering direction lying in a minor scattering plane perpendicular thereto and defined by the short axis.
  • Figure 5 illustrates a rough schematic of an example of an optical waveguide arrangement 500 including an inner light guide 110 and an outer cladding member 120 as well as a scattering portion 540 having a long axis and a short axis approximating an ellipse in a two dimensional cross section shown in the figure and an ellipsoid in three dimensions.
  • the light scattered and diffracted from portion 540 is largely emitted within a symmetrical cone shape where the symmetry axis of the cone is the long axis, which corresponds to the direction of the fiber core in the fiber example.
  • the light propagation axis corresponds to the optical waveguide arrangement's optical axis which may be its symmetry axis, e.g. if the optical waveguide arrangement has a cylindrical shape.
  • figure 5 shows how light approaching the scattering portion from different angles is scattered in a preferred direction, the main scattering direction, which is approximately collinear with the long axis of the scattering portion, i.e. parallel and aligned so as to be located along a common axis.
  • the fraction of the light of a light source which is coupled into the inner light guide can be increased.
  • such a scattering portion also scatters light which is already guided out of the inner light guide, e.g.
  • one or more scattering portions provide a net gain for light coupling .
  • the end section may start from the light guide's end face facing a light source (compare figure 6A) up to 0.1 to 2 millimeters (or even longer) away in the light propagation direction, which will be explained with respect to figure 6A below, wherein the distance between the light source and a
  • FIG. 6A illustrates a rough schematic of an example of an optical waveguide arrangement 600 including an inner light guide 110 and an outer cladding member 120 as well as a plurality of scattering portions 640.
  • the inner light guide 110 and the outer cladding member 120 may be some form of optical waveguide, e.g. optical fiber, such as a glass fiber, polymer fiber, or a bulk-glass substrate with waveguide, polymer with waveguide structure, etc., and the invention is not limited to a particular waveguide.
  • the outer cladding member 120 may surround, like in an optical fiber, or sandwich the inner light guide 110. In the sandwich case, the outer cladding member 120 may have a first part arranged above the inner light guide and a second part arranged below the inner light guide.
  • the fiber core 110 usually guides the largest parts of the light intensity so that the center of the core of the optical fiber may thus be considered to basically determine the direction of the light propagation axis .
  • the inner light guide 110 corresponds to a fiber core and the outer cladding member 120 corresponds to a fiber cladding.
  • the waveguide arrangement may be a single mode optical fiber comprising scattering portions in the fiber core.
  • the inner light guide 110 has a first refractive index and an outer cladding member 120 has a second refractive index.
  • the first refractive index is larger than the second refractive index.
  • the refractive index of the inner light guide 110 may be chosen as 1.480 and the refractive index of the outer cladding member 120 (second refractive index) may be chosen as 1.450.
  • the refractive index of the core is 1.4682 and of the cladding is 1.4486.
  • an abrupt change from first to second refractive index does not need to be present, i.e. instead of a stepwise change from one refractive index to the other, there can be a gradient index changing slowly from one index to the other.
  • the inner light guide 110 and the outer cladding member 120 are configured so as to guide light along the light propagation axis in the inner light guide, wherein this axis has been indicated by
  • the central or symmetry axis of a waveguide such as the center of a fiber core of an optical fiber (optical axis of fiber) , may thus be considered to basically determine the light propagation axis.
  • a plurality of scattering portions 640 are arranged one after another, i.e. sequentially, along the light propagation axis in the inner light guide 110.
  • the scattering portions 640 have a third refractive index different, usually larger, to the first and second refractive indices.
  • the third refractive index may be chosen as 1.470.
  • the scattering portions 640 are arranged so as to interrupt the first refractive index of the inner light guide .
  • Each scattering portion has a long axis substantially
  • the scattering is anisotropic exhibiting properties with different values when measured in different directions. In other words, more scattering is observed in a solid angle including a main scattering
  • Fig. 6B shows a cross-section in a plane defined by the light propagation axis (long axis) and short axis of a scattering portion in more detail.
  • the long axis and the short axis are shown in the elliptical cross section of figure 6B .
  • the elliptical cross-section may look the same way in the plane perpendicular to the paper-plane and including the long axis. That is, in the plane perpendicular to the long axis, the cross-section of the ellipsoid may be a circle, see e.g. figure 6C. This is particularly true for the example of an optical fiber which usually has cylindrical geometry. However, other ellipsoid structures are feasible and in three dimensions the scattering portions may form any kind of ellipsoid structures with the long axis being
  • the scattering portions are adapted to have shapes approximating an ellipsoid so that light traveling through the inner light guide is scattered by the scattering portions more in a main scattering direction being substantially parallel and aligned to the long axis than in a scattering direction being substantially parallel and aligned to the short axis.
  • the dimensions of the scattering portions are such to cause light scattering as mentioned above.
  • the long axis of the ellipsoid may be in the order of (i.e. 2 x wavelength +/-0.3 x wavelength) or larger than twice the wavelength of the light guided in the inner light guide and the short axis of the ellipsoid may be in the order of (i.e.
  • the long axis may be three times the wavelength or larger and the short axis may be 1.5 times the wavelength or smaller.
  • the scattering portions 640 in the embodiment of figure 6A are arranged one after the other, wherein in one example, these portions may be arranged so that the distances between the scattering portions 640 along the light propagation axis are in the order of or smaller than twice the length of the long axis and preferably in the order of the long axis (i.e.
  • the scattering portions 640 may be arranged periodically leaving approximately equal distances between the individual scattering portions.
  • scattering portions 640 are placed in the core so that light propagating in the core experiences a refractive index change basically along the optical fiber's optical axis, and
  • the waveguide in figure 6A is considered a single mode optical fiber having a fiber core of approximately 10 ym in diameter, in which infrared (IR) light having a wavelength of approximately 1 ym is used, the short axis may also be approximately 1 ym and the long axis 2 micrometers.
  • IR infrared
  • a circular cross section 640 of 1 ym in diameter of the scattering portion may be recognized in the center.
  • the light source 150 e.g. a LED
  • the optical waveguide arrangement 600 may further comprise additional scattering portions 670 as shown in figure 6C (not shown in figure 6A) .
  • These additional scattering portions 670 have a short axis and a long axis as scattering portions 640 and may have the same refractive index (third refractive index) as the scattering portions 640 or may have a different (fourth) refractive index.
  • the additional scattering portions 670 are arranged next to, i.e. in parallel when considering their long axes, to the plurality of scattering portions 640 in the inner light guide 110. That is, the long axis of each additional scattering portion 640 is parallel to the light propagation axis (normal to the paper plane in figure 6C) so that the long axes of the scattering portions 640 are substantially parallel to the long axes of the additional scattering portions 670.
  • the scattering portions 640 and the additional scattering portions 670 are spaced apart by a distance of a length of at least one wavelength of light.
  • scattering portions and additional scattering portions are provided in the same plane.
  • the additional scattering portions may be arranged to surround the scattering portions 640 which are arranged one after another along the light propagation axis in the inner light guide.
  • the additional scattering portions 670 surround the scattering portions 640 so that in the exemplary cross-section in figure 6C additional scattering portions would be placed at least to the left, right, top and bottom of the illustrated scattering portion 640.
  • the same pattern may repeat further along the light propagation axis, i.e. for the next scattering portions 640 in the sequence.
  • Figure 6D illustrates an example of the optical waveguide arrangement 600 of figure 6A comprising additional scattering portions 670.
  • Several scattering portions 640 are illustrated to be placed close or on the center axis (optical axis) of the inner light guide 110 and additional scattering portions 670 are placed closer to the surface of the inner light guide 110 and parallel to the scattering portions 640.
  • the scattering portions can be arranged one after the other and/or parallel to each other having a material with another refractive index to scatter light due to refractive index differences between the refractive index of the portions and of the inner light guide in the optical waveguide, the scattered light may interfere constructively or destructively at certain angles with respect to the light propagation axis of the optical waveguide.
  • light can be directed depending on the configuration of the scattering portions .
  • Figure 7A illustrates an optical waveguide arrangement 700A comprising scattering portions 740 and outer scattering portions 745. Additional scattering portions as discussed with respect to figure 6C are not shown, but may also be present, e.g. in patterns, as discussed above, in the inner light guide 110.
  • the optical waveguide arrangement 700A comprises, in addition to the portions discussed with respect to figures 6A-6B, a plurality of outer scattering portions 745 having the third refractive index or a fifth refractive index and being arranged in the outer cladding member, as illustrated in figure 7A.
  • the outer scattering portions 745 may have a long axis and a short axis
  • the long axis of the outer scattering portions 745 may be tilted at an angle in the range between 2 degrees and 40 degrees, and preferably 4 to 15 degrees, with respect to the long axis of the scattering portions 740.
  • the outer scattering portion 745 in the outer cladding member 120 may be directed to the inner light guide .
  • the outer scattering portions 745 are
  • the outer scattering portions 745 are parallel to each other so that their long axes are parallel to each other, as shown in figures 7A and 7B.
  • the scattering portions, the additional scattering portions and/or the outer scattering portions may thus be arranged in an end section (or end segment) 770 of the optical waveguide arrangement 700A, e.g. at the proximal end of an optical fiber, which may start at the end face 760 and extend along the light propagation axis for 0.1 mm or longer.
  • Figure 7B illustrates an optical waveguide arrangement 700B comprising scattering portions 740 and outer scattering portions 748 according to another embodiment.
  • This embodiment differs from the embodiment of figure 7A in that the surface of the end face 760 is processed to provide the same advantage as a tapered fiber.
  • the outer scattering portions 748 are arranged in parallel to each other as the outer scattering portions 745 but even closer to the end face 760 and with a shorter distance between each other.
  • Figure 8 illustrates an optical waveguide arrangement 800 which is based on the optical waveguide arrangement 700A
  • a light reflecting surface 880 which is a reflector such as a mirror. Since light is scattered on the elliptical scattering portions not only in the light propagation direction defined by the light source in the figures, i.e. to the right side, but also to the opposite side, i.e. to the left side in the figures, a light reflecting surface 880 is provided to reflect the light back to the right side.
  • This light reflecting surface 880 may be simply coated, e.g. by vapor deposition, on the end face of the inner light guide 110.
  • figure 9A light is coupled into the inner light guide via the end face of the inner light guide and the cladding. Then, the light is scattered on the scattering portions in the two preferred directions along the long axis, so that 50% of the light is scattered to the right and 50% to the left. Accordingly, 50% may be lost, i.e. coupled out of the waveguide again and therefore lost.
  • the inner light guide comprises a light
  • light is only coupled into the inner light guide via the cladding and the
  • the light scattered in the direction to the left is reflected by reflector 880 so that not only light
  • the light reflecting surface 880 hinders the light from the light source 150 to directly couple into the inner light guide 110, the net effect of the reflecting surface is still positive, since more light enters the inner light guide from the cladding than directly from the light source.
  • the light coupling system comprises one of the above optical waveguide arrangements and a light source for inputting light into the optical waveguide arrangement.
  • the light coupling system of figure 10 is based on the previously discussed optical waveguide arrangements 600, 700A, 700B, 800 illustrated in figures 6 to 8 and comprises a light
  • reflective surface over the complete end face may be simpler in production than the other alternative to provide only such a reflective surface to the inner light guide.
  • the light source around the optical waveguide arrangement (i.e. around a section of the cylindrical surface of a cylindrical waveguide, such as a fiber, or above and below planar surfaces of a section of a slab waveguide) , as indicated by reference numerals 1050.
  • the light rays 1040 coming from the light source 1050 enter the inner light guide 110 and are scattered/diffracted on the scattering portions within the inner light guide 110. Some of the light is scattered directly to the right indicated by solid arrow 1045 and other light is scattered to the left and then reflected back as indicated by the dashed arrow 1048.
  • the outer cladding member 120 may be illuminated via a suitable coating from all sides, e.g. along the end section and/or the end face.
  • a fluorescent or luminescent material may be coated onto the outer surface of the outer cladding member, which is then illuminated by LEDs or other light sources.
  • the light source 1050 may be a combination of pump sources and fluorescent/luminescent material (s) .
  • the light source of the light coupling system is arranged at one of the end faces of the optical waveguide arrangement for coupling light in the inner light guide, wherein the light source may have its main light emission axis (optical axis) substantially parallel to the light propagation direction.
  • the light source is arranged at the outer cladding member.
  • the light source is arranged at a section of the outer surface of the outer cladding member so that the light of the light source is coupled into the inner light guide through the outer cladding member, as show in figure 10.
  • the light source may be one or more of an LED, SLED, high power white light lamp, or laser or maybe a combination of one or more of the above with a fluorescent or luminescent layer .
  • Figure 11 illustrates steps of a method for manufacturing an optical waveguide arrangement, such as the ones mentioned above .
  • first step 1110 providing an optical waveguide comprising an inner light guide having a first refractive index and an outer cladding member having a second refractive index.
  • the light guide and the cladding member are configured so as to guide light along a light propagation axis in the inner light guide.
  • Step 1120 comprises focusing a pulsed laser beam into the inner light guide so as to generate a plurality of scattering portions having a third refractive index.
  • the scattering portions are being generated by the focused pulsed laser beam so as to be arranged along the light propagation axis in the inner light guide and so that each scattering portion has a long axis substantially parallel to the light propagation axis as well as a short axis substantially perpendicular to the light propagation axis and the long axis.
  • the pulsed laser beam is provided by a high power femtosecond laser or UV laser that provides highly focused light through a suitable lens arrangement so as to operate above the damage threshold of glass, for example.
  • a femtosecond laser may be used to write a plurality of scattering portions point-by-point with a pulse energy of approximately 0.1 pJ or more and pulse a duration of
  • a section/segment of the optical waveguide arrangement can be specifically engineered to incorporate the optical function realized by the plurality of scattering portions, additional scattering portions and/or outer
  • the high power laser pulses may be focused just below an end face of the waveguide and the focus may be moved in the light propagation direction to generate one scattering portion after the other.
  • this portion may not be homogenous and several microscopic
  • the (third) refractive index of a scattering portion may be regarded as an average refractive index resulting from several different microscopic defects resulting from the pulsed laser pulses destroying the homogenous structure of the inner light guide of the waveguide.
  • microcavities can be produced in the fiber core, which have the desired ellipsoid-like structures.
  • an ellipsoid structure as a scattering portion but merely a structure which has more microscopic defects in the direction of the light propagation axis, the long axis of the scattering portion, than in the direction perpendicular thereto.
  • interferences in certain angles with respect to the light propagation direction By manipulating the sizes of and distances between the portions, the optical characteristics of the interferences can be engineered.
  • the elongated, preferably ellipsoidal, scattering structures lead to more predominant scattering in the direction of the long axis of the ellipsoid and the light propagation axis.
  • the above-mentioned effects can be used for coupling in or coupling out (optical reciprocity) light in a
  • optical waveguides suitable to form the inner light guide and outer cladding member are known, e.g. optical fibers, such as glass fibers, polymer fibers, or a bulk-glass substrate with waveguides, polymers with waveguide structures, etc., and the invention is not limited to a particular waveguide.
  • an optical waveguide may be a dielectric slap waveguide having three dielectric layers with different refractive indices, wherein the refractive indices are chosen so as to guide light in the second
  • the inner light guide (middle) dielectric layer, herein called the inner light guide.
  • a common example which was referred to in the above purely as an illustrative example is an optical fiber in which the inner light guide 110 is regarded as the core surrounded by the cladding 120.
  • the shown outer cladding member 120 parts above and below the light guide 110 are the same belonging to the same cladding.
  • Preferred embodiments of a fiber as an exemplary optical waveguide were discussed above. These waveguides may then be engineered, i.e. provided with suitable scattering portions, to produce the optical waveguide arrangement discussed herein.
  • an optical waveguide arrangement for better and easier coupling of light into the inner light guide may be provided.

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  • Optical Couplings Of Light Guides (AREA)

Abstract

L'invention concerne un agencement de guide d'ondes optiques et, en particulier, un agencement de guide d'ondes optiques permettant un couplage de lumière amélioré, ledit agencement comprenant un élément de gaine extérieur ayant un deuxième indice de réfraction et un guide de lumière interne ayant un premier indice de réfraction le long d'un axe de propagation de lumière. Une pluralité de parties de diffusion possèdent un troisième indice de réfraction et sont agencées le long de l'axe de propagation de lumière dans le guide de lumière interne, chaque partie de diffusion ayant un axe long sensiblement parallèle à l'axe de propagation de la lumière ainsi qu'un axe court sensiblement perpendiculaire à l'axe de propagation de la lumière et à l'axe long.
PCT/EP2019/071697 2018-08-20 2019-08-13 Agencement de guide d'ondes optiques, système de couplage de lumière et procédé de fabrication d'un agencement de guide d'ondes optiques WO2020038770A1 (fr)

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DE102018214025 2018-08-20
DE102018214025.1 2018-08-20

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WO2020038770A1 true WO2020038770A1 (fr) 2020-02-27

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PCT/EP2019/071697 WO2020038770A1 (fr) 2018-08-20 2019-08-13 Agencement de guide d'ondes optiques, système de couplage de lumière et procédé de fabrication d'un agencement de guide d'ondes optiques

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060215976A1 (en) * 2005-03-22 2006-09-28 Matsushita Electric Industrial Co., Ltd. Multicore optical fiber with integral diffractive elements machined by ultrafast laser direct writing
DE102010018538A1 (de) * 2010-04-28 2011-11-03 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Verfahren zur Modenbeeinflussung von optischer Strahlung in einem Medium

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060215976A1 (en) * 2005-03-22 2006-09-28 Matsushita Electric Industrial Co., Ltd. Multicore optical fiber with integral diffractive elements machined by ultrafast laser direct writing
DE102010018538A1 (de) * 2010-04-28 2011-11-03 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Verfahren zur Modenbeeinflussung von optischer Strahlung in einem Medium

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