EP3257119A1 - Guide optique utilisé comme fibre amplificatrice pour le fonctionnement haute puissance - Google Patents

Guide optique utilisé comme fibre amplificatrice pour le fonctionnement haute puissance

Info

Publication number
EP3257119A1
EP3257119A1 EP15709850.0A EP15709850A EP3257119A1 EP 3257119 A1 EP3257119 A1 EP 3257119A1 EP 15709850 A EP15709850 A EP 15709850A EP 3257119 A1 EP3257119 A1 EP 3257119A1
Authority
EP
European Patent Office
Prior art keywords
amplifier
laser
optical waveguide
fiber
rare earth
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.)
Withdrawn
Application number
EP15709850.0A
Other languages
German (de)
English (en)
Inventor
Hans Jürgen OTTO
César JAUREGUI MISAS
Jens Limpert
Andreas TÜNNERMANN
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.)
Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Friedrich Schiller Universtaet Jena FSU
Original Assignee
Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Friedrich Schiller Universtaet Jena FSU
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 Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV, Friedrich Schiller Universtaet Jena FSU filed Critical Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Publication of EP3257119A1 publication Critical patent/EP3257119A1/fr
Withdrawn legal-status Critical Current

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
    • H01S3/14—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
    • 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
    • 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
    • H01S3/06716—Fibre compositions or doping with active elements
    • 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
    • H01S3/06754—Fibre amplifiers
    • 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
    • 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
    • H01S3/08072—Thermal lensing or thermally induced birefringence; Compensation thereof
    • 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

Definitions

  • the invention relates to an optical waveguide as a laser medium or amplifier medium for high-power operation, wherein the optical waveguide is an optical fiber whose light-guiding core is at least partially doped with rare earth ions.
  • the invention relates to the use of an optical waveguide as a laser or amplifier medium for high-power operation, wherein the optical waveguide is an optical fiber whose light-guiding core is at least partially doped with rare earth ions.
  • the invention relates to a laser / amplifier combination with a laser, an amplifier fiber and a pump light source, wherein the pump light source optically pumps the amplifier fiber and wherein the amplifier fiber amplifies the propagating therein radiation of the laser, wherein the laser beam leading core of the amplifier fiber at least partially doped with rare earth ions.
  • a light signal propagating through the optical fiber becomes unstable from a threshold of the power of the light signal, and energy is transmitted from a fundamental mode to higher order modes.
  • Optical fibers should therefore be designed so that non-linear effects and interactions with the fiber material are reduced. Most simply and effectively, non-linear effects are reduced by increasing the diameter of the core. This reduces the intensity of the light in the core and increases the absorption of pump light. Due to the improved absorption of the pump light, the optical fiber can be shortened and thus non-linear effects can be further reduced.
  • the high thermal load in high power operation can lead to mode instability.
  • the output signal of the optical waveguide or a fiber laser realized with it becomes unstable as soon as a power threshold is exceeded.
  • energy is transferred from a fundamental mode to higher order modes.
  • the originally stable Gaussian beam profile of the propagating in the optical waveguide radiation begins to change and the beam profile fluctuates in time due to a time-varying superposition of the fundamental mode with one or more modes of higher order. The timing of these fluctuations can deterministic or, depending on the power of the propagating radiation, also random or chaotic.
  • the cause of the mode instability is considered to be thermo-optic effects, namely temperature-induced local changes in the refractive index of the material of the optical waveguide which are caused by mode interference, i. by interference of the different modes propagating in the optical waveguide (see Jauregui et al., Opt. Express 19, 201 1, pages 3258 to 3271).
  • the invention has for its object to provide an optical waveguide as a laser or amplifier medium and a laser / amplifier combination realized therewith, in which the output signal of the amplifier fiber is better stabilized.
  • the invention solves the problem starting from an optical waveguide of the type mentioned in that the maximum small signal amplification of the optical waveguide due to the concentration of rare earth ions and / or their distribution in the light-conducting core up to 60 dB, preferably up to 50 dB, more preferably up to 40 dB, even more preferably up to 30 dB.
  • the invention is based on the recognition that there is a close link between the maximum small signal amplification of the optical waveguide and the power threshold, from which mode instability occurs.
  • Maximum maximum signal amplification of the optical waveguide in the sense of the invention means the maximum possible amplification of a laser radiation propagating in the optical waveguide, the intensity of which is so low that no gain saturation occurs. This maximum possible gain is achieved when the optical fiber is completely inverted, ie when all doping centers are at the upper laser level.
  • the performance threshold above which mode instability occurs can be significantly increased according to the invention by lengthening the optical waveguide, at the same time keeping the small signal gain constant (or even reducing it compared to optical waveguides conventionally used as amplifier fiber).
  • the reduction according to the invention of the maximum small signal amplification to less than 60 dB, preferably even to less than 30 dB, runs counter to the manner in which fiber laser systems are typically designed. Typically, a much higher small signal gain of the amplifier fiber is used.
  • the power amplification stage is usually operated completely saturated.
  • the corresponding amplification factors are therefore a few orders of magnitude below the small-signal amplification of the optical waveguide.
  • the finding of the invention is that this so-called unused amplification ensures the occurrence of mode instability with comparatively low power of the amplified radiation.
  • the reduction of the small signal gain according to the invention can be achieved by suitable choice of doping, i. the concentration of the rare earth ions are effected in the material of the optical waveguide. It is likewise possible to select the geometric distribution of the rare earth ions within the light-guiding core region of the optical waveguide so that the overlap of the propagating radiation modes with the doped core regions results in the desired small-signal amplification. Both variants can also be combined with each other.
  • further measures may be added to further increase the performance threshold beyond which mode instability occurs.
  • the wavelength of the to be amplified Radiation outside preferably below that wavelength at which the wavelength-dependent gain of the amplifier fiber is maximum.
  • the wavelength of the light of a pumping light source, with which the amplifier fiber is optically pumped be selected so that the wavelength of the pumping light outside, preferably above that wavelength at which the absorption of the amplifier fiber is maximum.
  • the problems associated with mode instability occur in high power operation, as explained above. at particularly high power of the amplified laser radiation. This applies in particular to the power range above an average power of 100 W.
  • the invention makes it possible to realize laser / amplifier combinations in which the average power of the amplified laser radiation is 10 kW or even more, without mode instability occurring.
  • the invention relates to the use of a rare earth ion doped optical waveguide as amplifier fiber for high power operation (ie more than 100 W average power, preferably more than 500 W), wherein due to the doping of the optical waveguide, the small signal gain less than 60 dB, possibly even less than 30 dB.
  • FIG. 1 is a schematic view of a laser / amplifier combination according to the invention
  • the laser / amplifier combination shown in Figure 1 comprises a laser 1, preferably in the form of a fiber laser, the laser radiation at generated low intensity and outputs via a coupling to an optical fiber 2.
  • the laser 1 may be a continuous wave laser or a pulsed laser.
  • the radiation generated by the laser 1 propagates - possibly after passing through one or more preamplifier stages (not shown) - in an amplifier fiber 3 and is amplified therein to the desired power.
  • the laser beam leading core of the amplifier fiber 3 is doped with rare earth ions.
  • the amplifier fiber 3 is optically pumped by means of a pump light source 4.
  • the light of the pump light source 4 is coupled via a coupler 5 in the amplifier fiber 3 in a conventional manner.
  • the pumping light then propagates together with the laser radiation to be amplified in the amplifier fiber 3.
  • the average power of the laser radiation at the output 6 of the amplifier fiber is more than 100 W, possibly even 10 kW or more.
  • the maximum small signal amplification of the amplifier fiber 3 is less than 60 dB, possibly even less than 30 dB, by suitable choice of the concentration of the rare earth ions and / or by suitable geometric distribution in the core guiding the laser radiation.
  • the graph of Figure 2 illustrates the dependence of the power threshold above which mode instability occurs, the small signal gain of the amplifier fiber, and the length of the amplifier fiber.
  • the diagram shows the power threshold P (in watts) at which the mode instability occurs, as a function of the fiber length (in meters).
  • the solid curve labeled 7 shows the behavior of a conventional amplifier fiber. With a length of the amplifier fiber of 15 m, mode instability occurs from a power of the amplified radiation of 3 kW. At lower small signal gain, the power threshold P is significantly increased.
  • Curve 8 shows the behavior of an amplifier fiber whose small signal gain is only 35 dB (here at a wavelength of 1030 nm). With a fiber length of 15 m mode instability occurs only from about 9 kW.
  • Curve 9 shows the behavior of a fiber whose small signal gain is as low as 22 dB (at 1010 nm). At 15 m length of the amplifier fiber, the power threshold P is already 13 kW. All this shows that, according to the invention, stable operation (without mode instability) is achieved by using an optical waveguide as amplifier fiber for the high power operation, wherein the maximum small signal gain of the optical fiber is reduced to less than 60 dB, preferably within the range of 30 dB or less can.

Landscapes

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

Abstract

L'invention concerne un guide optique (3) utilisé comme milieu laser ou milieu amplificateur pour le fonctionnement haute puissance, le guide optique (3) étant une fibre optique dont le cœur conduisant la lumière est doté au moins par endroits d'ions de terres rares. L'objet de l'invention est de fournir un guide optique utilisé comme milieu laser ou amplificateur ainsi qu'une combinaison laser/amplificateur réalisée avec ce dernier, le signal de sortie du milieu laser ou amplificateur étant mieux stabilisé. L'invention résout cet objectif par le fait que l'amplification maximale pour les signaux faibles du guide optique (1) atteint, du fait de la concentration des ions des terres rares et/ou de leur répartition dans le cœur conduisant la lumière, jusqu'à 60 d B, de préférence jusqu'à 50 d B, plus préférablement jusqu'à 40 d B, d'une manière particulièrement préférée jusqu'à 30 d B. L'invention concerne en outre l'utilisation d'un guide optique de ce type comme fibre amplificatrice (3) dans une combinaison laser/amplificateur.
EP15709850.0A 2015-02-09 2015-02-12 Guide optique utilisé comme fibre amplificatrice pour le fonctionnement haute puissance Withdrawn EP3257119A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102015101830 2015-02-09
PCT/EP2015/052987 WO2016128058A1 (fr) 2015-02-09 2015-02-12 Guide optique utilisé comme fibre amplificatrice pour le fonctionnement haute puissance

Publications (1)

Publication Number Publication Date
EP3257119A1 true EP3257119A1 (fr) 2017-12-20

Family

ID=52682664

Family Applications (1)

Application Number Title Priority Date Filing Date
EP15709850.0A Withdrawn EP3257119A1 (fr) 2015-02-09 2015-02-12 Guide optique utilisé comme fibre amplificatrice pour le fonctionnement haute puissance

Country Status (3)

Country Link
US (1) US10340655B2 (fr)
EP (1) EP3257119A1 (fr)
WO (1) WO2016128058A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102017121368A1 (de) * 2017-07-17 2019-01-17 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Vermeidung von Modeninstabilität in einer optischen Verstärkerfaser

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2371100C (fr) * 1999-04-30 2012-10-02 University Of Southampton Dispositif a fibre optique
GB2385460B (en) 2002-02-18 2004-04-14 Univ Southampton "Pulsed light sources"
US7557986B2 (en) 2004-05-13 2009-07-07 Soreq Nuclear Research Center High power fiber amplifier
US7106501B2 (en) * 2004-10-14 2006-09-12 Coherent, Inc. Fiber amplifier with suppression of amplified spontaneous emission
US7876803B1 (en) * 2007-03-21 2011-01-25 Lockheed Martin Corporation High-power, pulsed ring fiber oscillator and method

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
None *
See also references of WO2016128058A1 *

Also Published As

Publication number Publication date
US20180034234A1 (en) 2018-02-01
WO2016128058A1 (fr) 2016-08-18
US10340655B2 (en) 2019-07-02

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