EP2020062A2 - Matériau de verre de silice amplificateur haute puissance - Google Patents

Matériau de verre de silice amplificateur haute puissance

Info

Publication number
EP2020062A2
EP2020062A2 EP07722688A EP07722688A EP2020062A2 EP 2020062 A2 EP2020062 A2 EP 2020062A2 EP 07722688 A EP07722688 A EP 07722688A EP 07722688 A EP07722688 A EP 07722688A EP 2020062 A2 EP2020062 A2 EP 2020062A2
Authority
EP
European Patent Office
Prior art keywords
fibre
concentration
rare earth
high power
ytterbium
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Withdrawn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
EP07722688A
Other languages
German (de)
English (en)
Inventor
Kent Mattsson
Morten Østergaard PEDERSEN
Søren AGGER
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.)
Crystal Fibre AS
Original Assignee
Crystal Fibre AS
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 Crystal Fibre AS filed Critical Crystal Fibre AS
Publication of EP2020062A2 publication Critical patent/EP2020062A2/fr
Withdrawn legal-status Critical Current

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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
    • H01S3/06708—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
    • H01S3/14—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
    • H01S3/1618—Solid materials characterised by an active (lasing) ion rare earth ytterbium
    • 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
    • H01S3/1691—Solid materials characterised by additives / sensitisers / promoters as further dopants
    • 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
    • H01S3/17—Solid materials amorphous, e.g. glass
    • H01S3/176—Solid materials amorphous, e.g. glass silica or silicate glass

Definitions

  • the invention relates to the field of high power light amplification in rare earth doped silica glass materials.
  • this invention relates to reduced photo darkening in rare earth doped high power amplifier silica glass materials.
  • High power optical fibre lasers are becoming of increasing interest as a consequence of their efficiency, low cost, and the availability of arrays of high power diode pump lasers.
  • Such arrays of diode pump lasers can have an output power of several hundred watts or greater, and serve as ideal pump sources for optical fibre lasers.
  • the function of the optical fibre is to convert the highly multi-mode output from a diode array to a high power single mode output of a power amplifier or laser.
  • the fibre converts the multimode high power low brightness diode array to a high brightness single mode source.
  • There are many situations in which the beam quality of a single mode fibre with less power is more desirable than a higher powered multi- mode array. These applications include materials processing (cutting, welding, and marking) and surgery.
  • Diode bar arrays are commercially available, and can be arranged to produce power levels of many hundreds of watts.
  • the power is delivered through multi-mode fibres, or arrays of fibres bundled together.
  • a fibre having a low numerical aperture will not efficiently accept the radiation of these devices in such a manner that single mode laser radiation will result, as would occur by having the pump radiation from the diode array serve as the energy source to create an inversion in a rare earth doped optical fibre laser. Since single mode operation is desired for high brightness, with a core typically 5 - 30 ⁇ m in diameter, it is not possible to focus the light from the fibre output of the diode array into the single mode core.
  • the brightness theorem specifies that the numerical aperture of the fibres coming from the diode sources, times the fibre area, must be a constant. Thus, the high intensity light from the fibre output of the diode array cannot be focused into the core of a single mode fibre.
  • the double clad fibre construction is applied.
  • a high numerical aperture outer cladding is constructed to accept the pump power whereas the ytterbium doped core with a low numerical aperture is placed in the inner core of the double clad fibre.
  • the multimode diode low brightness light is effectively brought in overlap with the ytterbium doped core material in which high power single mode light is generated through stimulated emission inside a laser cavity consisting of two fibre gratings constructed either directly in the ytterbium doped fibre or in a separately fibre spliced to the ytterbium doped fibre.
  • the optical flux i.e. the optical lasing power transmitted per unit area of the fibre core
  • the lasing output decreased by several percent during a 1000 hour time period. It has further been observed experimentally that a considerable increase in propagation loss is experienced in un-seeded amplifiers after only a few hours of operation.
  • the lasing or amplifier output power level at constant pump power is maintained substantially constant over an extended operating period.
  • a waveguide laser or amplifier material comprises a glass host material doped with one or more rare earth elements in concentrations adapted to the intended level of amplification, pump wavelength, amplifying wavelength, intended length of fibre, etc. Additionally the glass host material comprises network modifier elements. Preferably the ratio of atomic concentrations of the modifier elements to that of the rare earth elements is larger than 5, such as larger than 6, such as larger than 7.
  • the invention relates to glasses with a 'tetrahedron-like structure'.
  • the glass host material is preferably silica. This has the advantage of providing a material that is compatible with a huge variety of existing systems comprising optical fibres for communications, sensing and other applications.
  • the material may be based on other appropriate material systems having a 'tetrahedron-like structure', cf. e.g. Michel. J.F. Digonnet, "Rare-Earth-Doped Fiber Lasers and Amplifiers", 2 nd edition, 2001, Marcel Dekker, Inc., Chapter 2, p.l7-p.l 12, the book being referred to elsewhere in this application as [Digonnet].
  • the network modifier atoms for use in silica host glasses are preferably selected from the group of tri- or pentavalent atoms, such as e.g. aluminium, phosphor, boron, etc. for reducing the number of photo darkening pre-cursors ('chain-igniters').
  • the addition of fluorine has the effect of reducing the number of non-binding oxygen lone or paired electrons.
  • An object of the invention is attained in an embodiment by choosing the concentration of network modifiers in the silica glass material relative to the rare earth doping concentration.
  • the composition / ratio between rare earth atoms and other network modifiers determines the amount of ytterbium-ytterbium pairs inside the glass material and hereby the inherent generation of co-operative frequency up-converted light produced.
  • An object of the invention is in an embodiment for example as an alternative to the above or in combination therewith, achieved by a waveguide laser or amplifier material comprising a silica glass host material, one or more rare earth elements in concentrations C RE at.% (mol.), one or more network modifier elements selected from the group of tri- or pentavalent atoms of the periodic table of the elements in concentrations C NME at.% (mol.), and fluorine in concentrations c F at.% (mol.), wherein CNME ⁇ CRE and c F > CRE.
  • the network modifier atoms are added to the glass to counteract devitrification when the concentration of rare earth atoms is increased above approximately 0.01 at %.
  • An additional effect of the network modifiers are that when a sufficient amount of these is present, the concentration of rare earth pairs decreases with a reduction in the cooperative frequency up-conversion as result. The co-operative frequency up- conversion is unwanted as it reduces the amplification efficiency of the glass material.
  • An additional effect of the adding of network modifiers is, for example for an ytterbium-doped glass, that the concentration of Yb-Al-Yb atom strings is reduced with increasing Al concentration or alternatively increasing phosphor or boron concentration.
  • Yb-Al-Yb atom strings are the main suppliers of electrons to lone-electron pair colour centres established near non-binding oxygen sites due to the large absorption cross section of ytterbium when pumped resonantly.
  • the Yb-Al-Yb atom strings initiate the formation of paired- / empty non-binding oxygen sites (colour centre).
  • a similar function is observed for Yb-Al-Al atom strings with much less dominance for low population inversion of the ytterbium atoms, which are found when stimulated feed-back is given to the glass material (such as when operating the material in a laser setup).
  • the role of Al-Al-Al chains is negligible due to a much smaller absorption cross section when pumped resonant with the ytterbium absorption band.
  • an object is in an embodiment attained by loading the preform glass material with hydrogen and/or deuterium at elevated temperature in a sufficiently long period for the hydrogen and/or deuterium to diffuse through the core material.
  • the hydrogen/deuterium can be supplied in the form of H 2 O/D 2 O.
  • the loading can be performed in a post glass formation / fibre drawing process.
  • the function of the added hydrogen or deuterium is to occupy non-binding oxygen sites near tri- or penta-valence atoms in substitute tetra-valence atom sites. I.e. to occupy non-bridging oxygen near rare earth atoms or other network modifier atoms (such as e.g. aluminium, phosphor, boron) in substitute silicon sites.
  • the non-binding oxygen site will be occupied with a hydrogen or deuterium atom and no longer participate in the formation of colour centres when exposed to radiation resonant with the rare earth absorption bands.
  • a similar effect can be obtained by the addition of fluorine to the glass matrix, e.g. during preform fabrication.
  • the hydrogen/deuterium can be supplied by co-doping with phosphorous P 4 O 10 that under water and/or hydrogen load is converted into P 4 O 8- x (OH) 4+2x , (0 ⁇ x ⁇ 2) complexes in the silica glass during or after fibre manufacture. The hydrogen incorporated in these complexes is permanently incorporated into the glass material even under high optical load.
  • a combination of hydrogen and/or deuterium loading and/or fluorine addition and a selection of silica glass material with a low number of photo darkening pre-cursors is advantageously applied to achieve a relatively low photo darkening rate and a relatively low steady state photo darkening. Because of these features, the present invention can be used in practical equipments for applications such as materials processing (cutting, welding, and marking) and surgery.
  • an object of the invention is achieved by a high power amplifier comprising a diode bar array pump laser which operates at a wavelength ⁇ pump and with a pump power exceeding 5 W, a coupling device, a silica host glass fibre with a rare earth doped core co-doped with one or more network modifiers (such as aluminium, boron, and/or phosphor) in a concentration such that the total atomic network modifier concentration is at least 5 times, such as at least 6 times, such as at least 7 times the rare earth atomic concentration, an output delivery fibre, wherein the wavelength ⁇ pump is resonant with said rare earth doping absorption band.
  • a network modifiers such as aluminium, boron, and/or phosphor
  • fluorine in a concentration larger than or equal to the concentration of the rare earth element can be added.
  • At least part of the core or cladding is doped with phosphorous.
  • the co-doping with phosphorous leads by reaction with residual hydrogen or water during or after processing of the fibre to formation of P 4 O 8- X(OH) 4+2 X, (0 ⁇ x ⁇ 2) complexes in the silica glass. These complexes act as sources for hydrogen that effectively blocks non-binding oxygen sites (photo darkening precursors) during pump radiation to convert into absorption centres.
  • An advantage of this present aspect of the invention is that the concentration of rare earth atoms in chains with network modifiers, wherein more than one rare earth atom is present, is reduced when the network modifier concentration is increased. This will reduce the photo darkening steady state concentration of non-binding oxygen colour centres.
  • the term 'the wavelength ⁇ p u mp is resonant with the rare earth doping absorption band' is in the present context taken to mean that ⁇ p u mp is within the absorption band of the rare earth dopant element(s).
  • the term 'atomic concentration' (abbreviated at.% (mol.)) of a given network modifier or rare earth element, etc. in a given region of the waveguide laser and amplifier material is in the present context taken to mean the ratio of the number of atoms or the network modifier or rare earth element in question to the total number of atoms in a given volume of the material (e.g. one mole).
  • An increased amplification will be reached by increasing the ytterbium atomic concentration above 0.1 atomic percent, such as to more than 0.2 atomic percent, such as to more than 0.3 atomic percent, such as to more than 0.5 atomic percent, such as to more than 1.0 atomic percent.
  • an addition of network modifiers such as aluminium in a concentration of at least 7 times the ytterbium atomic concentration, such as at least 8 times the ytterbium concentration, such as at least 10 times the ytterbium concentration, such as at least 12 times the ytterbium concentration, such as at least 14 times the ytterbium concentration, is advantageous.
  • the silica host glass fibre to have a core diameter cU re > 4 ⁇ m with a numerical aperture less than 0.1, surrounded by a first cladding diameter > 30 ⁇ m with a numerical aperture larger than or equal to 0.4, surrounded by a second cladding comprising either polymeric material or an air/glass microstructure, and to provide that the coupling device is a fused fibre bundle tapered to fit in numerical aperture to the numerical aperture of the first cladding and that the fibre bundle fibres are attached to diode bar array lasers.
  • the high power amplifier can advantageously be configured such that between the coupling device and the silica host glass fibre a first fibre Bragg grating is formed, and wherein between the silica host glass fibre and the output delivery fibre a second fibre Bragg grating is formed.
  • These gratings can be either formed by fusion splicing a section of fibre wherein the fibre Bragg grating is formed to the respective fibre ends of the silica host glass fibre or be written directly into the rare earth doped core of the silica host glass fibre. The latter option requires the additional co-doping with germanium.
  • an object of the invention is achieved by a high power amplifier comprising a diode bar array pump laser which operates at a wavelength ⁇ pump and with a pump power exceeding 5 W, a coupling device, a silica host glass fibre with a rare earth doped core co-doped with one or more network modifiers (such as aluminium, boron, phosphor), and an output delivery fibre, where said rare earth doped core is loaded with hydrogen or deuterium.
  • the loading with hydrogen or deuterium can be performed either during or after formation of a rod preform from which the silica host glass fibre is drawn. Alternatively (or additionally), the loading with hydrogen or deuterium can be done during, and/or after drawing and possibly coating of said silica host glass fibre.
  • the loading with hydrogen or deuterium reduces the concentration of non-binding lone electrons and paired electrons in non-binding oxygen sites in the core material.
  • the non-binding lone electrons are partly produced during fibre preform production due to oxygen deficiency in the silica matrix and are partly due to the three- or penta- valent nature of the network modifiers.
  • the silica matrix non-binding oxygen sites can not be activated by the rare-earth resonant pumping radiation whereas the non-binding oxygen sites near network modifiers and rare earth atoms are activated by the resonant pumping radiation.
  • the silica host glass fibre to comprise a core having a core diameter cU re > 4 ⁇ m and a numerical aperture less than 0.1, and a first cladding surrounding the core and having a diameter > 30 ⁇ m and a numerical aperture larger than or equal to 0.4, surrounded by a second cladding comprising either polymeric material or an air/glass microstructure, and wherein the coupling device is a fused fibre bundle tapered to fit in numerical aperture to the numerical aperture of the first cladding and the fibre bundle fibres are attached to diode bar array lasers.
  • the high power amplifier can advantageously be configured such that between the coupling device and the silica host glass fibre a first fibre Bragg grating is formed, and wherein between the silica host glass fibre and the output delivery fibre a second fibre Bragg grating is formed.
  • These gratings can be either formed by fusion splicing a section of fibre wherein the fibre Bragg grating is formed to the respective fibre ends of the silica host glass fibre or be written directly into the rare earth doped core of the silica host glass fibre. The latter option requires an additional co-doping of the core with germanium.
  • an object of the invention is achieved by a high power amplifier by choosing a combination of silica host material with a low concentration of photo darkening pre-cursors (Yb-Al-Yb chains) and loading of the silica host material with hydrogen. This is in one aspect done by choosing the rare earth doping to be ytterbium in a concentration exceeding 0.1 atomic percent, such as more than 0.2 atomic percent, such as more than 0.3 atomic percent, such as more than 0.5 atomic percent, such as more than 1.0 atomic percent.
  • a network modifier such as aluminium in a network modifier atomic concentration of at least 7 times the ytterbium atomic concentration, such as at least 8 times the ytterbium concentration, such as at least 10 times the ytterbium concentration, such as at least 12 times the ytterbium concentration, such as at least 14 times the ytterbium concentration.
  • Fig. 1 shows a diagram of the high power amplifier according to the present invention
  • Fig. 2 shows a diagram of the high power amplifier according to the present invention in a laser configuration
  • Fig. 3 shows optical absorption spectra of high power amplifiers, where the upper curve represents an amplifier configuration with an ordinary network modifier to ytterbium concentration and the lower curve represents an amplifier with increased network modifier to ytterbium concentration, and wherein the core is co-doped with phosphorous according to the present invention
  • Fig. 4 shows optical absorption spectra of high power amplifiers, where the upper curve represents an amplifier configuration with ordinary network modifier to ytterbium concentration and the lower curve represents the same fibre loaded with deuterium according to the present invention
  • Fig. 5 shows optical absorption spectra of high power amplifiers, where the upper curve represents an amplifier configuration with increased network modifier to ytterbium concentration, wherein part of the core is co-doped with phosphorous, according to the present invention and the lower curve represents an amplifier with high phosphorous to ytterbium concentration according to the present invention
  • Fig. 1 shows a schematic diagram of a high power amplifier according to the present invention.
  • the input signal 1 is amplified through the high power amplifier 4 and delivered as output 6 from the output delivery fibre 5.
  • the pump radiation from diode bar arrays 2 is coupled into a double cladding fibre 4 through a section of fused and tapered fibre bundle 3, tapered to fit the bundle output numerical aperture to the numerical aperture of the inner cladding of the double cladding fibre 4.
  • the signal radiation 1 is here shown to be coupled into the centre core of the double cladding fibre by the same tapered fibre bundle 3.
  • the output signal is delivered by output fibre 5 to the output 6 in a substantially single mode core.
  • the coupling device or fused and tapered fibre bundle is spliced (preferably fusion spliced) - as indicated with 7 - to the double cladding fibre 4 as is the output delivery fibre 5.
  • Fig. 2 shows a schematic diagram of a high power amplifier according to the present invention in a laser configuration.
  • Fig. 2 is identical to Fig. 1, except that the input signal port (1, in Fig. 1) is replaced with a pump diode fibre receiving pump light from diode bar arrays 2.
  • the single mode input fibre 1 of Fig. 1 of the coupling device 3 here a fused and tapered fibre bundle
  • the laser action is achieved through adding gratings 8 in or next to (i.e. optically coupled to) the amplifier fibre 4.
  • the silica glass host fibre is preferably a double clad fibre and more preferably a micro-structured fibre, such as an air-clad fibre.
  • a micro-structured fibre such as an air-clad fibre.
  • an 'air-clad' fibre is taken to mean a micro-structured fibre wherein light to be propagated is confined to a part of the fibre within a circumferential distribution of longitudinally extending voids in the cladding of the fibre, cf. e.g. US-5,907,652 or WO-03/019257.
  • An example of such a fibre (without the material modifications of the present invention) is a DC-225-22-Yb fibre from Crystal Fibre A/S (Birkeroed, Denmark).
  • rare-earth doped silica fibre lasers are described in a variety of sources, e.g. in [Digonnet], chapter 3, pp. 113-170.
  • This example discloses how the photo darkening of a high power amplifier silica glass host material doped with a rare earth atom such as ytterbium is reduced by adding an excess amount of network modifiers to the glass matrix and wherein a part of the core is doped with phosphorous.
  • the photo darkening of fibre samples are performed in a un-seeded amplifier setup where the input signal 1 indicated in fig. 1 is zero and the absorption as a function of wavelength and time is characterised by measuring the absorption in the fibre 4 by coupling in white light radiation through the output port 6 and measuring the transmitted signal to the input port in a given interval of time.
  • fig. 3 the result of two such measurements are shown for a sample with a glass composition corresponding to a conventional ytterbium silica glass composition (upper curve) and an amplifier ytterbium silica glass according to the present invention (lower curve).
  • the conventional ytterbium silica glass composition is 0.3 at. % ytterbium and 1.2 at. % network modifiers (aluminium) whereas the ytterbium silica glass composition according to the present invention is 0.25 at. % ytterbium and 2.25 at. % network modifiers (aluminium and phosphor).
  • the two fibre cores are experiencing identical optical fluxes (160 kW/cm 2 , 915 nm radiation).
  • the conventional composition fibre of example 1 is subjected to deuterium loading prior to the photo darkening experiment.
  • the fibres are operated in un-seeded amplifier setup to achieve the highest possible photo darkening. This time the samples are run until no further increase in absorption is observed, which is after approximately 12 hours of operation at 160 kW/cm 2 optical flux at 915 nm pump.
  • a colour centre is a defect where at least one of the four bonds to neighbouring oxygen atoms has been replaced by non-binding oxygen (paired or empty) electrons.
  • the colour centres with more than one bond to neighbouring oxygen atoms replaced by non-binding oxygen electrons are to be located in the glass as lone atoms surrounded by silica material (three missing bonds) and in chains surrounded by silica material (two missing bonds).
  • the loading with hydrogen or deuterium will remove a considerable amount of the non-binding oxygen un-paired and paired electrons and hereby reduce the colour centre concentration in the as drawn glass material. Further the adding of hydrogen or deuterium to these non-binding oxygen sites will remove the possibility of forming colour centres here due to the presence of hydrogen, which blocks the transition of the electron to other non-binding sites.
  • the loading with hydrogen will therefore be observable in the optical spectrum of the fibre material through the absence of excess absorption for radiation with a wavelength longer than 600 nm. This is due to the reduced formation of colour centres based on two and three missing bond centres. It can be noted that it is advantageous for the H 2 and D 2 to connect to such sites as the two missing electrons of the hydrogen or deuterium electron is supplied by such sites. It can further be noted that the three missing bonds will be converted to a single missing bond site. These sites could possibly still give absorption to the radiation but the absorption centre has now shifted towards shorter wavelengths. This shift is believed to be from around 640 nm to around 400 nm. The hydrogen load appears to diffuse out of the samples after 60 - 100 hours of operation when operated at high optical load. Excess amount of hydrogen in the surrounding air counteracts this behaviour.
  • the loading with hydrogen and/or deuterium is preferably performed at elevated pressures and temperatures over a certain time period, e.g. 72 hours at 150 bar at 87 °C, cf. also U.S. Pat. No. 5,235,659.
  • Example 3
  • This example discloses how the photo darkening of a high power amplifier silica glass host material doped with a rare earth atom such as ytterbium is reduced by adding an excess amount of network modifier (phosphorous) to the glass matrix.
  • a rare earth atom such as ytterbium
  • the photo darkening of fibre samples are performed in a un-seeded amplifier setup where the input signal 1 indicated in fig. 1 is zero and the absorption as a function of wavelength and time is characterised by measuring the absorption in the fibre 4 by coupling in white light radiation through the output port 6 and measuring the transmitted signal to the input port in a given interval of time.
  • the ytterbium silica glass composition according to the present invention is for the first fibre 0.25 at % ytterbium and 2.25 at % network modifiers (aluminium and phosphor) (upper curve) and the ytterbium silica glass composition according to the present invention is for the second fibre 0.25 at % ytterbium and 4.26 at % network modifier (phosphor).
  • the phosphorous doped sample exhibit reduced pump absorption at 915 nm (not shown) compared with the phosphorous and aluminium co-doped sample. This suggest that a trade off between pump absorption and photo darkening is to be made and that a suitable composition is to be found in a trial an error process. Both fibres exhibit slope efficiencies exceeding 82 % under active operation of the fibre with external high reflector and end facet reflection, which indicates that the ytterbium in both fibres is efficiently incorporated into the glass as Er 3+ .

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

Abstract

La présente invention concerne un matériau de verre de silice amplificateur haute puissance, permettant une réduction considérable du noircissement photographique dû à un flux optique élevé. Pour la contrepartie du système amplificateur et laser de l'état de la technique reposant sur un matériau de verre de silice conventionnel, se pose le problème que leurs propriétés sont altérées au cours du temps en raison du noircissement photographique. Le matériau de verre de silice amplificateur et laser à fibres de l'invention se caractérise par moins de noircissement photographique grâce à la réduction de la concentration d'électrons d'oxygène non lié. A cet effet, on applique une charge d'hydrogène ou de deutérium au matériau de verre amplificateur, ou on réalise un co-dopage avec du phosphore P4O8-x(OH)4+2x, (0 x 2).
EP07722688A 2006-03-28 2007-03-19 Matériau de verre de silice amplificateur haute puissance Withdrawn EP2020062A2 (fr)

Applications Claiming Priority (3)

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US78637406P 2006-03-28 2006-03-28
DKPA200600446 2006-03-28
PCT/DK2007/050033 WO2007110081A2 (fr) 2006-03-28 2007-03-19 Matériau de verre de silice amplificateur haute puissance

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EP2020062A2 true EP2020062A2 (fr) 2009-02-04

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CN102576125B (zh) * 2009-07-29 2014-12-10 拉瓦勒大学 使用短波长超快脉冲写入耐大功率的布拉格光栅的方法
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GB201711849D0 (en) * 2017-07-24 2017-09-06 Nkt Photonics As Reducing light-induced loss in optical fibre

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