EP4291825A1 - Fibre à noyau creux permettant la transmission de la lumière laser - Google Patents

Fibre à noyau creux permettant la transmission de la lumière laser

Info

Publication number
EP4291825A1
EP4291825A1 EP22713527.4A EP22713527A EP4291825A1 EP 4291825 A1 EP4291825 A1 EP 4291825A1 EP 22713527 A EP22713527 A EP 22713527A EP 4291825 A1 EP4291825 A1 EP 4291825A1
Authority
EP
European Patent Office
Prior art keywords
fiber
hollow
cladding
core
refractive index
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22713527.4A
Other languages
German (de)
English (en)
Inventor
Markus Jung
Klaus Ludewigt
Björn Wedel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rheinmetall Waffe Munition GmbH
Original Assignee
Rheinmetall Waffe Munition GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rheinmetall Waffe Munition GmbH filed Critical Rheinmetall Waffe Munition GmbH
Publication of EP4291825A1 publication Critical patent/EP4291825A1/fr
Pending legal-status Critical Current

Links

Classifications

    • 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
    • G02B6/02323—Core having lower refractive index than cladding, e.g. photonic band gap guiding
    • G02B6/02328—Hollow or gas filled core
    • 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
    • G02B6/023—Microstructured optical fibre having different index layers arranged around the core for guiding light by reflection, i.e. 1D crystal, e.g. omniguide
    • 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
    • G02B6/032—Optical fibres with cladding with or without a coating with non solid core or cladding

Definitions

  • the present invention relates to a microstructured hollow core fiber set up for the transmission of laser light according to the preamble of claim 1.
  • a microstructured hollow core fiber has a microstructured hollow core extending along the hollow core fiber.
  • the hollow core has microstructures with at least a first refractive index n and is surrounded by an inner fiber cladding with a refractive index n_internal.
  • fiber claddings made of transparent material which are conductive for the laser light are meant in which the laser light can be guided by total internal reflections.
  • the glass used as the core of the fiber in well-known optical fibers solid core fibers
  • a gas or vacuum which gives the fiber a holey center.
  • the cladding has at least one fiber cladding concentrically surrounding the hollow core and a protective cladding (jacket or buffer) concentrically surrounding the fiber cladding.
  • a protective cladding jacket or buffer
  • the jacket material and/or also the fiber claddings and thus the hollow core fiber as a whole can be damaged by the power loss radiated transversely to the longitudinal extension of the hollow core fiber.
  • the object of the present invention is to specify a hollow-core fiber of the type mentioned at the outset, with which higher average laser light powers than before, such as occur, for example, with continuous wave laser light, can be transmitted.
  • the continuous wave powers that are involved here are in the kilowatt range.
  • the pulse peak powers reach into the gigawatt range.
  • the solution according to the invention differs from the prior art mentioned at the outset in particular in that the hollow-core fiber has at least one further Has fiber cladding, which is arranged cladding the innermost fiber cladding and has a further refractive index n_w, and that the refractive index n_inner of the innermost fiber cladding is greater than the further refractive index n_w.
  • the invention thus provides at least one additional fiber cladding that encases the inner fiber cladding, with this additional fiber cladding having a lower refractive index than the inner fiber cladding.
  • the radially inner first fiber cladding is therefore optically denser than the radially outer second fiber cladding. This promotes total internal reflection of light propagating in the radially inner first fiber cladding and incident on the interface between the radially inner first and radially outer second fiber cladding, which promotes low-loss wave guidance in the radially inner first fiber cladding and thus an undesired transition from im radially inner first fiber cladding propagating loss light reduced in the radially outer second fiber cladding.
  • the invention thus allows laser radiation of high average power to be transmitted through microstructured hollow-core fibers by means of the targeted guidance within the fiber cladding of the lost light that occurs when the beam is guided through hollow-core fibers.
  • the invention in particular prevents this radiation loss from escaping laterally from the microstructured fiber line in an uncontrolled manner and thereby damaging either the jacket or buffer or the environment.
  • the lost light can then be dissipated in a controlled manner and, if necessary, absorbed by the waveguide achieved with the invention when exiting the microstructured hollow-core fiber guide.
  • the present invention thus provides a hollow-core fiber that prevents the power loss from escaping, which could otherwise cause the hollow-core fiber or the surrounding protective sheath to be destroyed.
  • the invention thus enables laser light of high average power (cw laser light) to be transmitted through a hollow-core fiber.
  • the invention enables a targeted derivation and guidance of the lost light and thus a transmission of higher average laser powers than in the prior art, which consists of microstructured hollow-core fibers with only one fiber cladding and one protective cladding.
  • First the Invention enables the use of microstructured hollow-core fibers for the transmission of high cw laser powers.
  • a preferred embodiment of the invention is characterized in that the hollow-core fiber has at least two additional fiber claddings, each of which has a refractive index, with at least one of the refractive indices of the at least two additional fiber claddings being smaller than the refractive index of the innermost fiber cladding.
  • the refractive index of one of two further fiber claddings, which encases the other of the two further fiber claddings is smaller than the refractive index of the encased further fiber cladding.
  • Preferred configurations are characterized in that at least two further fiber claddings are present, so that an innermost (first) fiber cladding is concentrically encased by a second fiber cladding (which can also be a protective cladding), and this by a third fiber cladding (which can also be a protective cladding can) is concentrically encased, and that the fiber claddings each have a fiber cladding-individual refractive index, the refractive index of a radially outer fiber cladding always being greater than the refractive index of a fiber cladding that extends further radially inwards.
  • a further preferred embodiment of the invention is characterized in that the material thicknesses Fiber claddings and the outer protective cladding are dimensioned in such a way that lost light coupled from the microstructured hollow core into the inner fiber cladding or the further fiber cladding experiences total internal reflections there.
  • Material thicknesses preferred for this purpose are between four times and six times, in particular five times, the laser light wavelength.
  • the microstructured hollow-core fiber has an input end, which is set up for coupling laser light into the microstructured hollow core, and has an output end, which is set up for coupling laser light out of the microstructured hollow core.
  • the hollow-core fiber is set up to conduct laser light (loss light) coupled from the microstructured hollow core into the inner fiber cladding or the further fiber cladding by waveguide to the output end of the microstructured hollow-core fiber and to let the laser light emerge from the fiber claddings there.
  • laser light loss light
  • a further preferred embodiment is characterized in that the hollow core fiber has at least one mode stripper which is arranged between the input end and the output end and which is set up to couple laser light from the microstructured hollow core into the fiber cladding and/or the protective cladding (Loss) to decouple transversely to the longitudinal extent of these fiber claddings from these fiber claddings.
  • the mode stripper which is arranged between the input end and the output end and which is set up to couple laser light from the microstructured hollow core into the fiber cladding and/or the protective cladding (Loss) to decouple transversely to the longitudinal extent of these fiber claddings from these fiber claddings.
  • the hollow-core fiber has several mode strippers, which are distributed over the length of the microstructured hollow-core fiber.
  • This refinement allows power loss to be dissipated in a controlled manner.
  • the power loss can thus be decoupled laterally from the hollow core fiber in a controlled manner without causing damage.
  • a transport of undesirably high power loss along the longitudinal extension can be avoided because the part that is coupled out laterally no longer has to be guided to the exit end of the hollow-core fiber.
  • a further embodiment is the additional or alternative use of a so-called “airclad” between the first and second fiber cladding or other optional claddings.
  • these air jackets Compared to configurations without such air jackets, these air jackets have the advantage of a higher numerical aperture.
  • FIG. 1 shows a cross section through a known hollow-core fiber
  • FIG. 2 shows a longitudinal section of the hollow-core fiber from FIG. 1;
  • FIG. 3 shows a cross section of a hollow-core fiber according to the invention.
  • Figure 4 shows a longitudinal section of the hollow-core fiber from Figure 3.
  • Figure 1 shows a cross section of a known microstructured hollow core fiber 10.
  • the cutting plane is perpendicular to the longitudinal extension of the hollow-core fiber.
  • the cutting plane is one XY plane of a Cartesian coordinate system.
  • the longitudinal extent is aligned locally, ie in the section plane, parallel to the z-direction of the coordinate system.
  • FIG. 2 shows a microstructured hollow core fiber 10, as shown in FIG. 1, in a longitudinal section.
  • the longitudinal section is defined in that it follows the longitudinal extension of the hollow-core fiber 10 in such a way that the center of a hollow core 12 of the hollow-core fiber 10 always lies in the plane of the drawing.
  • the microstructured hollow-core fiber 10 has a microstructured hollow core 12 extending along the hollow-core fiber 10 .
  • the hollow core 12 has microstructures 14 with at least a first refractive index n and is surrounded by an inner fiber cladding 16 with a refractive index n_inside, so that the inner fiber cladding delimits the hollow core radially.
  • the inner fiber cladding is encased by an outer protective cladding 18, which has a protective cladding refractive index n_outside.
  • Figures 1 and 2 thus illustrate the overall structure of a hollow-core fiber 10, which is assumed to be known.
  • the first refractive index n is typically equal to the refractive index n inside the inner fiber cladding 16, while the Refractive index n_outside of the protective jacket 18 is typically greater than the refractive index n_inside.
  • lost light 22 When propagating single-mode laser light 20 with a high average power value, losses occur which are also referred to below as lost light 22 .
  • this lost light 22 escapes laterally in an uncontrolled manner from the hollow-core fiber 10 via the inner fiber cladding 16 and the outer protective cladding 18 and can in particular damage the outer protective cladding 18 and possibly also objects in the vicinity of the hollow-core fiber 10 and/or people in it hurt the environment.
  • FIG. 3 shows a cross section of an exemplary embodiment of a hollow core fiber 100 according to the invention for the transmission of laser light.
  • the sectional plane is, for example, an x-y plane of a Cartesian coordinate system.
  • FIG. 4 shows a microstructured hollow-core fiber 100, as shown in FIG. 3, in one
  • the longitudinal section is defined in that it follows the longitudinal extent of the hollow-core fiber 100 in such a way that the center of the hollow core of the hollow-core fiber always lies in the plane of the drawing.
  • the microstructured hollow-core fiber 100 has a microstructured hollow core 12 extending along the hollow-core fiber 100 .
  • the hollow core 12 has microstructures 14 with at least a first refractive index n and is of an innermost
  • the innermost fiber cladding 16 is encased by an outer protective cladding 18 which has a protective cladding refractive index n_outside.
  • the microstructured hollow core fiber 100 has an input end 24 which is set up for coupling laser light into the microstructured hollow core 12 and it has an output end 26 which is set up for coupling laser light 20 out of the microstructured hollow core 12 .
  • the input end 24 and the output end 26 each have an end surface 24.1, 26.1, which is aligned transversely to the longitudinal direction of the hollow-core fiber 100.
  • the hollow-core fiber 100 has at least one further cladding 28 which is arranged between the innermost fiber cladding 16 and the outer protective cladding 18 encasing the innermost fiber cladding 16 .
  • the shrouds referred to in this application are preferably concentric shrouds.
  • the microstructures 14 have a first refractive index n.
  • the innermost fiber cladding 16 has a refractive index n_inside and the outer protective cladding 18 has a protective cladding index of refraction n_outside.
  • the at least one further fiber cladding 28 provided in a preferred embodiment, which is arranged between the innermost fiber cladding 16 and the outer protective cladding 18 so as to encase the innermost fiber cladding 16, has a further refractive index n_w.
  • the further refractive index n_W is smaller than the refractive index n_internal, and the further refractive index n_w is larger than the refractive index n_external of the protective casing 18.
  • the inner fiber cladding 16 lying radially further inward relative to the further fiber cladding 28 and thus closer to the microstructures 14 and the hollow core 12 is optical denser than the further fiber cladding 28.
  • the greater optical density of the innermost fiber cladding 16 favors the occurrence of total internal reflections of lost light 22 propagating in the innermost fiber cladding 16 and incident on the interface to the further fiber cladding 28.
  • the further refractive index n_w is greater than the refractive index n_outside of the protective jacket 18.
  • the material thicknesses of the fiber claddings 16, 28 and the outer protective cladding 18 are dimensioned such that lost light 22 coupled from the microstructured hollow core 12 into the fiber claddings 16, 28 experiences total internal reflections there.
  • the hollow core fiber 100 is configured to be made of the microstructured hollow core 12 to guide laser light coupled into the fiber claddings 16, 28 by waveguide to the output end 26 of the microstructured hollow-core fiber 100 and to let the lost light 22 emerge from the fiber claddings 16, 28 there.
  • the lost light 22 propagating along the hollow-core fiber 100 in the fiber claddings 16, 28 can, alternatively or in addition to controlled decoupling at the output end 26 of the hollow-core fiber 100, also be decoupled from the fiber claddings 16, 18 in a controlled manner by mode strippers attached to the side of the hollow-core fiber 100.
  • mode strippers can be implemented, for example, as local projections or cuts in the fiber claddings 16, 28 carrying power loss 22.
  • Such projections or incisions have boundary surfaces which are oriented in such a way that lost light 22 incident there does not experience total internal reflection, but is instead radially deflected in a controlled manner and thus laterally decoupled from the hollow-core fiber 100 in a controlled manner.
  • One or more mode strippers can be arranged between the input end 24 and the output end 26 and in this way decouple lost light 22 coupled from the microstructured hollow core 12 into the fiber claddings 16, 28 and/or the protective cladding 18 transversely to the longitudinal extent of these claddings.
  • Another possible variant is the additional or alternative use of a so-called "Airclad" between the innermost fiber cladding 16 and the further fiber cladding 28 or further optional fiber claddings.
  • the exemplary embodiment of a waveguide illustrated in FIGS. 3 and 4 has two further fiber claddings 28 and 18 in addition to the radially innermost fiber cladding 16 .
  • the further fiber cladding 18 lying radially furthest to the outside is preferably a protective cladding and concentrically surrounds the other further fiber cladding 28 .
  • the additional fiber cladding 28 surrounds the innermost fiber cladding 16 concentrically.
  • At least one of the refractive indices of the at least two other fiber claddings 18, 28 is lower than the refractive index of the innermost fiber cladding 16.
  • the refractive index of one of the two further fiber claddings, which encases the other of the two further fiber claddings, is lower than the refractive index of the encased further fiber cladding, here the further fiber cladding 28.
  • the encasing further fiber cladding is here the fiber cladding 18.
  • this can be the protective cladding at the same time.
  • This protective cladding can be made of silicone and thus also guide the exiting laser light through total internal reflections in the first fiber cladding.
  • Such an embodiment is, for example, from the embodiment of Figures 3 and 4 by omitting the radially outermost fiber cladding 18 emerges.
  • the outermost fiber cladding does not necessarily also have to have a small refractive index, since the laser light is already guided through the middle fiber cladding in the innermost fiber cladding. It would also be sufficient if only one of the two other fiber claddings has a lower refractive index than the radially innermost fiber cladding in order to guide the laser light through total internal reflections within the arrangement.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Optical Couplings Of Light Guides (AREA)
  • Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
  • Multicomponent Fibers (AREA)

Abstract

L'invention concerne une fibre à noyau creux (100) microstructurée comprenant un noyau creux microstructuré (12) s'étendant le long de la fibre à noyau creux (100). Ledit noyau creux : présente des microstructures (14) ayant au moins un premier indice de réfraction n ; est entouré par une gaine de fibre interne (816) ayant un indice de réfraction n_inner ; et a une gaine de protection externe (18) qui a un indice de réfraction de gaine de protection n_outer et qui encapsule la gaine de fibre interne (16). La fibre à noyau creux est caractérisée en ce que : la fibre à noyau creux présente au moins une autre gaine (28) qui est disposée entre la gaine de fibre intérieure (16) et la gaine de protection extérieure (18) de manière à encapsuler la gaine de fibre interne (16) et qui a un indice de réfraction supplémentaire n_w ; et l'indice de réfraction supplémentaire n_w est supérieur à l'autre indice de réfraction.
EP22713527.4A 2021-02-10 2022-02-07 Fibre à noyau creux permettant la transmission de la lumière laser Pending EP4291825A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102021103135.4A DE102021103135A1 (de) 2021-02-10 2021-02-10 Hohlkernfaser zur Übertragung von Laserlicht
PCT/EP2022/052904 WO2022171576A1 (fr) 2021-02-10 2022-02-07 Fibre à noyau creux permettant la transmission de la lumière laser

Publications (1)

Publication Number Publication Date
EP4291825A1 true EP4291825A1 (fr) 2023-12-20

Family

ID=80978894

Family Applications (1)

Application Number Title Priority Date Filing Date
EP22713527.4A Pending EP4291825A1 (fr) 2021-02-10 2022-02-07 Fibre à noyau creux permettant la transmission de la lumière laser

Country Status (7)

Country Link
US (1) US20230384510A1 (fr)
EP (1) EP4291825A1 (fr)
JP (1) JP2024505747A (fr)
AU (1) AU2022220718A1 (fr)
DE (1) DE102021103135A1 (fr)
IL (1) IL304632A (fr)
WO (1) WO2022171576A1 (fr)

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010114847A1 (fr) * 2009-03-31 2010-10-07 Imra America, Inc. Fibres à bande interdite photonique à bande passante large et perte faible
CA3008053A1 (fr) * 2015-12-23 2017-06-29 Nkt Photonics A/S Fibre optique a cƒur creux et systeme laser
US11835755B2 (en) * 2018-10-03 2023-12-05 Microsoft Technology Licensing, Llc Optical fibre assemblies and methods of use

Also Published As

Publication number Publication date
IL304632A (en) 2023-09-01
WO2022171576A1 (fr) 2022-08-18
AU2022220718A1 (en) 2023-08-03
DE102021103135A1 (de) 2022-08-11
JP2024505747A (ja) 2024-02-07
US20230384510A1 (en) 2023-11-30

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