WO2016169933A1 - Résonateur optique pour laser à fibre haute puissance - Google Patents

Résonateur optique pour laser à fibre haute puissance Download PDF

Info

Publication number
WO2016169933A1
WO2016169933A1 PCT/EP2016/058666 EP2016058666W WO2016169933A1 WO 2016169933 A1 WO2016169933 A1 WO 2016169933A1 EP 2016058666 W EP2016058666 W EP 2016058666W WO 2016169933 A1 WO2016169933 A1 WO 2016169933A1
Authority
WO
WIPO (PCT)
Prior art keywords
fiber
optical resonator
reflection element
multimode
laser
Prior art date
Application number
PCT/EP2016/058666
Other languages
German (de)
English (en)
Inventor
Ulrich Hefter
Original Assignee
Rofin Sinar Laser 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 Rofin Sinar Laser Gmbh filed Critical Rofin Sinar Laser Gmbh
Publication of WO2016169933A1 publication Critical patent/WO2016169933A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/0675—Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
    • 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
    • G02B6/028—Optical fibres with cladding with or without a coating with core or cladding having graded refractive index
    • G02B6/0288—Multimode fibre, e.g. graded index core for compensating modal dispersion
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
    • H01S3/06729—Peculiar transverse fibre profile
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/08018—Mode suppression
    • H01S3/0804—Transverse or lateral modes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094003—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
    • H01S3/09415—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/1601—Solid materials characterised by an active (lasing) ion
    • H01S3/1603—Solid materials characterised by an active (lasing) ion rare earth
    • H01S3/1611—Solid materials characterised by an active (lasing) ion rare earth neodymium

Definitions

  • the invention relates to an optical resonator for a high-power fiber laser with an optically active medium comprising a fiber having an at least partially doped fiber core, wherein the fiber between a highly reflective first reflection element and an at least partially transmitting second reflection element is arranged.
  • Optical resonators for generating laser radiation are well known from the prior art. For this purpose, it is particularly known to define an optical resonance space between two reflection elements, which is optically pumped to generate laser radiation.
  • the optically active medium of the optical resonator is formed by an active fiber which has an at least partially doped fiber core.
  • a reflection element arranged on the input side of the optical resonator is generally highly reflective in order to minimize the losses occurring, while a further output-side reflection element is at least partially transmissive in order to enable a coupling out of the laser radiation generated in the resonance space.
  • the second reflection element can therefore also be referred to as an output coupling element (English: Output coupler).
  • the generation of ideally one-mode laser radiation with at least approximately Gaussian beam profile is desirable.
  • the core diameter of the fiber serving as the optically active medium must be limited to a value only in the range of a few multiples the wavelength of the generated laser radiation is.
  • a division of fibers into monomode or multimode fibers can be made on the basis of the modality. With a modality of less than 2.4, a single-mode fiber is present, with larger values, the fiber is a multimode fiber.
  • the modality of a fiber is defined by the V-number:
  • ⁇ denotes the wavelength in vacuum
  • a the diameter of the fiber core
  • NA the numerical aperture, which is correspondingly defined by the refractive indices of the fiber core n cor e and the clad n c iaddin g .
  • the V-number or the modality is a function of the wavelength, corresponds to a modality of 2.4 at a wavelength of 1 ⁇ about a core diameter of 13 ⁇ .
  • the core diameter of single-mode fibers in the range of less than 20 ⁇ .
  • an optically active medium in an optical resonator for a high-power fiber laser, comprises a multimode fiber having an at least partially doped fiber core.
  • the multimode fiber is arranged between a highly reflective first reflection element and an at least partially transmitting second reflection element.
  • the first reflection element comprises a dielectric mirror.
  • the invention is based on the observation that the above-mentioned nonlinear effects increasingly occur in long fibers with comparatively small core diameters. As such, the nonlinear effects can be suppressed by using fibers with larger core diameters. As a result, the output power can be increased, since potential damage caused by the nonlinear effects only occur at correspondingly increased intensities. Moreover, with the increased core diameter (improved core / sheath ratio) compared to the sheath, there is an increased absorption which allows for the use of shorter fibers. These shorter fibers advantageously serve to further reduce the nonlinear effects.
  • optical resonators with multimode fibers produce comparatively broadband laser radiation, so that increased loss occurs at the fiber Bragg gratings suitable for multimode operation. Often, only a reflection of about 50% of such reflection elements is achieved. This is unsatisfactory especially for the training for highly reflective reflection elements.
  • the laser radiation generated by the optically pumped multimode active fiber according to the invention has an increased spectral bandwidth compared to single-mode laser radiation. This leads to increased losses at the reflection elements delimiting the optical resonance space.
  • the loss occurring on the input-side reflection element is disadvantageous since this reflection element is preferably highly reflective in order to minimize power losses.
  • the fiber Bragg gratings typically provided as reflective elements are highly reflective only for a narrowband spectral range.
  • the reflection behavior of fiber Bragg gratings is mode-dependent, so that increased losses occur in multimode fibers.
  • the invention thus proposes to support the multi-mode operation, the first reflection element, which is arranged on the input side of the optical resonance chamber, ie at the end from which pump radiation is coupled into the resonance chamber during operation to perform as a dielectric mirror.
  • Dielectric mirrors are highly reflective for a larger spectral range and, in contrast to fiber-optically implemented Bragg gratings, have no pronounced mode dependence of the reflection behavior. As a result, therefore, the losses occurring on the input side of the optical resonator can be minimized if multimode laser radiation is generated in the optical resonator.
  • Such an optical resonator is suitable for high-power fiber lasers with output powers of more than 2 kW, in particular more than 3 kW.
  • the resonant space formed between the first and second reflective elements is formed immediately by a mu-mode fiber.
  • no means, such as etalons or the like, are introduced, which would be suitable for limiting the oscillation behavior of the resonator essentially to a single-mode operation.
  • the invention proposes to support a true multi-mode operation in which a multiplicity of modes are amplified in the resonator. This direct approach makes it possible to further improve the efficiency of the optical resonator or of the high-power fiber laser comprising this optical resonator. As a result, greater output power can be used.
  • the optical resonator according to the invention is preferably a primary resonator.
  • An amplification of the laser beam generated in the optical resonator is not absolutely necessary.
  • the V-number defined at the outset which characterizes the modality of the mu ltimode fiber of the optical resonator, is preferably 5 or more. Particularly preferably, the V-number of the multimode fiber assumes a value between 5 and 10. It has been found that in this area enough modes flock, so that Stability problems are avoided.
  • the multimode fiber is preferably designed so that not only a few transversal modes can oscillate but a plurality of transverse modes.
  • the number of oscillating transverse modes is preferably at least 10.
  • the at least partially transmitting second reflection element provided for decoupling of laser radiation amplified in the optical resonator is preferably designed as a fiber Bragg grating.
  • a decoupling of laser radiation on the output side is comparatively uncritical, so that reflection elements can be used here whose reflectivity averaged over the bandwidth is, for example, only 10%.
  • the fiber Bragg grating is preferably written inexpensively in the corresponding region of the multimode fiber.
  • the dielectric mirror is disposed on a quartz support member. Quartz has relatively low absorption for the wavelengths typically employed, and is thus particularly suitable for high power applications where the heating generated by the laser power must be minimized.
  • the carrier element is block-shaped or tubular. In any case, with the integrated directly on the support element dielectric mirror is given a monolithic structure, which allows a particularly easy and easy to adjust mounting. Such training can be implemented particularly well as a fiber optic overall concept.
  • the dielectric mirror concavely in the direction of a coupling-in side of the multimode fiber.
  • the radius of curvature of the dielectric mirror is selected so that the laser radiation emerging from the fiber core of the multimode fiber is reflected back onto it.
  • the dielectric mirror has a substantially constant radius of curvature.
  • the multimode fiber of the optical resonator is preferably at least partially doped with a rare earth metal, in particular erbium, Er (1.5 ⁇ ), ytterbium, Yb (1 ⁇ ), holmium, Ho 21 ⁇ ), thulium and / or neodymium.
  • a core diameter of the fiber core of the multimode fiber is according to preferred embodiments, at least 50 ⁇ , in particular 50 ⁇ to 100 ⁇ . Accordingly, a shell surrounding the fiber core, can be coupled via the pump radiation in the fiber core, a thickness of several hundred ⁇ , in particular 400 ⁇ on.
  • the invention further relates to a fiber laser with an optical resonator described above.
  • the fiber laser includes a pump module for optically pumping the multimode active fiber of the optical resonator.
  • FIG. 1 shows an optical resonator according to a possible embodiment of the invention in a schematic representation
  • FIG. 2 shows a first reflection element limiting the optical resonator on the input side according to a first embodiment, in a schematic sectional illustration
  • FIG. 1 shows a fiber laser 100 having an optical resonator 1 comprising a multi-mode active fiber 2.
  • a fiber core of the multimode fiber 2 is partially doped with neodymium and has a core diameter of 50 ⁇ on.
  • the resonant space of the optical resonator 1 is limited by two reflection elements 3, 4.
  • a first reflection element 3 is provided which comprises a dielectric mirror 5 which is monolithic Construction is integrated on a support element 6 made of quartz. Possible embodiments of the first reflection element 3 are shown in detail in the sectional views of Figures 2 and 3.
  • the optical resonator 1 is coupled on the input side to a pump module 7.
  • the pump module 7 comprises, in a manner known per se, means for generating a population inversion in the active multimode fiber 2. For this purpose, it is provided to couple pump radiation into the active multimode fiber 2, which is generated, for example, by laser diodes.
  • a transport fiber 8 connects to the serving as an output coupler second reflection element 4, by means of which the generated multimode radiation can be directed in particular for material processing on a workpiece.
  • FIG. 2 shows a first exemplary embodiment of the first reflection element 3 in monolithic construction.
  • the dielectric mirror 5 is arranged on the end of the support element 6, which is designed in the example shown as a solid quartz block and concave curved towards a Einkoppelseite 9 of the multimode fiber 2.
  • the radius of curvature of the dielectric mirror 5 in this case corresponds to an optical length which results from the longitudinal length L of the carrier element 6 taking into account the refraction.
  • the multimode fiber 2 is connected in a form-fitting manner by splicing to the carrier element 6.
  • the core diameter d of the fiber core 10 is 50 ⁇
  • the cladding diameter D of the fiber core 10 surrounding shell 11 is 400 ⁇ .
  • Such a dimensioning of the multimode fiber 2 favors the formation of multimode laser radiation in common gene fiber dopings.
  • the ultimode fiber 2 furthermore has a protective coating 12 which forms the jacket 11.
  • FIG. 3 shows a second embodiment of the first reflection element 3.
  • the dielectric mirror 5 is fixed on the end to the support element 6, which has a tubular shape.
  • the carrier element 6 of the second embodiment is made of quartz.
  • the curvature ius of the dielectric mirror 5 preferably corresponds to the distance of the dielectric mirror 5 from the coupling side 9 of the ultimode fiber 2, which corresponds to the longitudinal length L.
  • the distance of the dielectric mirror 5 from the coupling side 9 can be particularly easily adjusted by an axial displacement of the tu bus-shaped reflection element 3bezügl the multimode fiber 2.
  • the dimensioning of the core diameter d of the fiber core 10 and the cladding diameter D of the shell 11 essentially corresponds to the dimensioning of the embodiment shown in FIG.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Lasers (AREA)

Abstract

L'invention concerne un résonateur optique (1) pour un laser à fibre haute puissance comprenant un milieu optiquement actif, lequel milieu comporte selon l'invention une fibre multimodale (2) présentant un cœur de fibre (10) au moins en partie dopé, la fibre multimodale (2) étant disposée entre un premier élément de réflexion (3) hautement réfléchissant et un deuxième élément de réflexion au moins en partie transmetteur (4). Le premier élément de réflexion (3) comprend un miroir diélectrique (5). L'invention concerne en outre un laser à fibre (100) comprenant un résonateur optique (1) présentant une conception de ce type. Le premier élément de réflexion (3) peut être réalisé sous la forme d'un miroir dichroïque courbé, ce qui simplifie d'une part l'injection du rayonnement de pompage émanant d'un module de pompe (7) et réduit d'autre part les pertes du résonateur. Le deuxième élément de réflexion (4) peut être réalisé sous la forme d'un réseau de Bragg sur fibre en partie réfléchissant.
PCT/EP2016/058666 2015-04-20 2016-04-19 Résonateur optique pour laser à fibre haute puissance WO2016169933A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102015105989.4 2015-04-20
DE102015105989 2015-04-20

Publications (1)

Publication Number Publication Date
WO2016169933A1 true WO2016169933A1 (fr) 2016-10-27

Family

ID=55802365

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2016/058666 WO2016169933A1 (fr) 2015-04-20 2016-04-19 Résonateur optique pour laser à fibre haute puissance

Country Status (1)

Country Link
WO (1) WO2016169933A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE69320657T2 (de) * 1993-10-13 1999-05-06 Italtel Spa EIN DIODENGEPUMPTER,KONTINUIERLICH ARBEITENDER OPTISCHER EINZELMODEN-FASERLASER, der bei 976 nm emittiert
US20060280217A1 (en) * 2003-06-12 2006-12-14 Spi Lasers Uk Ltd. Optical apparatus, comprising a brightness converter, for providing optical radiation
US20090080469A1 (en) * 2005-07-08 2009-03-26 Crystal Fibre A/S Optical coupler devices, methods of their production and use
EP2592704A2 (fr) * 2011-11-08 2013-05-15 Lisa Laser Products Ohg Fuhrberg & Teichmann Dispositif laser comprenant un guide d'onde optique multimodes présentant un matériau optique actif

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE69320657T2 (de) * 1993-10-13 1999-05-06 Italtel Spa EIN DIODENGEPUMPTER,KONTINUIERLICH ARBEITENDER OPTISCHER EINZELMODEN-FASERLASER, der bei 976 nm emittiert
US20060280217A1 (en) * 2003-06-12 2006-12-14 Spi Lasers Uk Ltd. Optical apparatus, comprising a brightness converter, for providing optical radiation
US20090080469A1 (en) * 2005-07-08 2009-03-26 Crystal Fibre A/S Optical coupler devices, methods of their production and use
EP2592704A2 (fr) * 2011-11-08 2013-05-15 Lisa Laser Products Ohg Fuhrberg & Teichmann Dispositif laser comprenant un guide d'onde optique multimodes présentant un matériau optique actif

Similar Documents

Publication Publication Date Title
DE19828154C5 (de) Auf Multimodefasern basierende Einzelmodenverstärker
DE19956739B4 (de) Modenverkoppelte Multimoden-Faserlaserimpulsquelle und Verfahren
DE19635919B4 (de) Vorrichtung zur Erzeugung von Femtosekunden- und Pikosekunden-Impulsen von mit Breitbereich-Laserdiodenfeldern mantelgepumpten modenverkoppelten Faserlasern
DE60304029T2 (de) Mit seltenen erden dotierter einmodiger phosphatglas-faserlaser
DE69824493T2 (de) Verjüngte Faserbündel zum Ein- und Auskoppeln von Licht aus mantelgepumpten Faservorrichtungen
DE60024002T2 (de) Anordnung mit faseroptischer Ramanvorrichtung
DE102006063046B3 (de) Optische Multimoden-Faser und optische Systeme mit einer solchen Faser
DE60214461T2 (de) Mantelgepumpter 3-Niveau Faserlaser/Verstärker
DE60104588T2 (de) Optische Faser für optischen Verstärker, optischer Faserverstärker und optischer Faserlaser
DE102005042073B4 (de) Faserlaser
EP3206830B1 (fr) Système optique muni d'un dispositif de couplage et d'un système de laser à fibre, ainsi que procédé d'usinage d'une pièce au moyen d'un tel système optique
DE60100903T2 (de) Optischer Faserverstärker und Kommunikationssystem unter Verwendung desselben
DE112019007185T5 (de) Faserlaserpumpreflektor
EP2478400B1 (fr) Filtres de modes transversaux pour guide d'onde
DE60220399T2 (de) Kaskadierter Ramanlaser
DE102022132736A1 (de) Faserlaser mit doppelpass-pumparchitektur
WO2016169933A1 (fr) Résonateur optique pour laser à fibre haute puissance
WO2021250127A1 (fr) Amplificateur à fibre ou laser à fibre
EP2592704B1 (fr) Dispositif laser comprenant un guide d'onde optique multimodes présentant un matériau optique actif
DE202015101942U1 (de) Optischer Resonator für einen Hochleistungs-Faserlaser
WO2012119608A2 (fr) Procédé et dispositif d'amplification d'ondes de signal optiques guidées dans un guide optique à plusieurs coeurs
DE102019114974A1 (de) Lichtwellenleiter
EP4292176A1 (fr) Ensemble fibre laser et procédé de génération de rayonnement laser haute puissance
DE10203392B4 (de) Anordnung zur Einkopplung von Strahlung in eine Lichtleitfaser
Lin et al. Experimental optimization of a high power fiber laser with raman filter

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 16717625

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 16717625

Country of ref document: EP

Kind code of ref document: A1