Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/12—Silica-free oxide glass compositions
  • C03C3/23—Silica-free oxide glass compositions containing halogen and at least one oxide, e.g. oxide of boron
  • C03C3/247—Silica-free oxide glass compositions containing halogen and at least one oxide, e.g. oxide of boron containing fluorine and phosphorus
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C4/00—Compositions for glass with special properties
  • C03C4/0071—Compositions for glass with special properties for laserable glass
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C4/00—Compositions for glass with special properties
  • C03C4/12—Compositions for glass with special properties for luminescent glass; for fluorescent glass
• • 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
  • H01S3/14—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
• • 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
  • H01S3/173—Solid materials amorphous, e.g. glass fluoride glass, e.g. fluorozirconate or ZBLAN [ ZrF4-BaF2-LaF3-AlF3-NaF]
• • 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
  • H01S2301/00—Functional characteristics
  • H01S2301/04—Gain spectral shaping, flattening
• • 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
  • H01S3/1608—Solid materials characterised by an active (lasing) ion rare earth erbium
• • 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
  • H01S3/17—Solid materials amorphous, e.g. glass
  • H01S3/175—Solid materials amorphous, e.g. glass phosphate glass

Definitions

• the present invention relates generally to the field of optical signal amplifiers and in particular, to fluorophosphate glass compositions for use in optical signal amplifiers operating at wavelengths around 1.55 ⁇ m.
• Optical signal amplifiers have quickly found use in optical telecommunication networks, particularly in those networks using optical fiber over long distances. Although modern silica-based optical fibers general exhibit relatively low loss in the 1.55 ⁇ m window, they are lossy to some extent and the loss accumulates over distance. To reduce this attenuation, opto-electronic devices have been used to boost signal power. These devices require that the optical signal be converted to an electronic signal. The electronic signal is then amplified using commonly known amplification techniques and is reconverted back to an optical signal for re-transmission.
• Optical signal amplifiers amplify optical signals without requiring an opto-electronic conversion of the signal.
• the weakened light signal is directed through a section of an amplifying medium that has been doped with ions from a rare earth element.
• Light from an external light source typically a semi-conductor laser, is pumped into the amplifying medium stimulating the rare earth atoms to a higher energy level.
• Light entering the amplifying medium at the signal wavelength further stimulates the excited rare earth ions to emit their excess photon energy as light at the signal wavelength in phase with the signal pulses, thereby amplifying the light signal.
• One type of optical amplifier uses a length of erbium-doped optical fiber.
• Erbium-doped fiber amplifiers are usually doped on the order of 100-500 ppm of erbium ion. Typical EDFA fiber lengths are on the order of 10-30 meters, depending on the final gain requirements necessary for a particular application. In some applications, it is impractical to use a 10-30 meter length of fiber. Planar-type optical amplifiers have been developed for use in more confined spaces. The useful length of a planar amplifying device is generally no more than 10 centimeters. To achieve the same amplification levels as a 10 to 30 meter length EDFA, a planar amplifier requires an amplifying medium with a higher concentration of erbium ions, on the order of up to 4 to 7 percent by weight.
• silica-based erbium-doped amplifiers exhibit a distinct spectral nonuniformity of gain.
• the lack of a flat gain spectrum over a wide bandwidth causes several problems. For instance, extremely short optical pulses have a relatively wide power spectrum and are not accurately amplified if the gain spectrum is not flat.
• WDM wavelength division multiplexing
• the fiber receives data-modulated optical signals from several optical transmitters, each using a different optical carrier frequency. If the gain spectrum from the optical amplifier is not flat over the operating wavelength, the carrier frequencies at gain peaks might saturate while the carrier frequencies at the skirts and valleys may not be sufficiently amplified.
• Past efforts to address gain flattening have primarily relied on passive or active filtering of the high gain features of the gain spectrum. However, this requires a close matching of the particular amplifier and filter and must account for temporal variations in the gain spectrum.
• the present invention is concerned with a family of glasses that find particular utility in production of optical signal amplifiers. These glasses are doped with high concentrations (up to 10 wt. %) of erbium oxide while exhibiting weak concentration quenching behavior. These glasses also provide higher fluorescence efficiency an more uniform gain characteristics than known silicate and fluorozirconate glass medium. These glasses provide high and flat gain characteristics that are particularly useful for optical amplification in the 1.55 ⁇ m optical wavelength window, and are particularly well suited for use in wavelength division multiplexing (WDM) systems.
• WDM wavelength division multiplexing
• One aspect of the present invention is directed to a family of glasses, particularly fluorophosphate glasses, that are particularly well suited for high rare earth ion concentration levels.
• the fluorophosphate glasses of the present invention comprise high concentrations of erbium ions (i.e. close to 10% by weight) and provide a more spectrally uniform gain, similar to ZBLAN ⁇ ->, and significantly improved over typical silicate and phosphate glass compositions.
• the present invention is directed to a family of glass for optical amplification comprising a substantially silica free fluorophosphate glass medium, doped for 100 parts by weight constituted of:
• fluorinated glasses that is, the fluorinated glasses for optical fibers containing the fluorides ZrF 4 , BaF 2 , LaF 3 , AIF 3 , and NaF
• the fluorophosphate glass according to the present invention has a composition, comprising in parts by weight:
• the fluorophosphate glass according to the present invention may also be co-doped with up to 15 parts by weight of Yb 2 0 3 as a sensitizer to increase pump efficiency at around 980 nm.
• the fluorophosphate glass according to the invention preferably has an index of refraction between about 1.48 and 1.58.
• the present invention is directed to an erbium-doped optical amplifier for a wavelength band of approximately 1.55 ⁇ m, having a medium for optical amplification comprising a substantially silica free fluorophosphate glass composition that further comprises in addition to 100 parts by weight of other components, about 0.01 to 10 parts by weight of Er 2 O 3 .
• the optical amplifier according to the present invention may be either a planar-type optical amplifier or a single mode fiber type optical amplifier.
• the optical amplifier according to the present invention includes fluorophosphate glass comprising, for 100 parts by weight constituted by:
• the fluorophosphate glass used for the optical amplifier according to the present invention may also be doped with up to 15 parts by weight of Yb 2 0 3 as a sensitizer to increase pump efficiency at around 980 nm, and preferably has an index of refraction between about 1.48 and 1.58.
• Optical amplifiers according to the present invention are particularly useful in wavelength division multiplexing (WDM) systems.
• FIGS. 1 and 2 are graphs illustrating typical behavior of concentration quenching on fluorescence lifetime and efficiency of binary silicate glass.
• FIGS. 3 and 4 are graphs illustrating fluorescence lifetime and efficiency of fluorophosphate glasses according to the present invention.
• FIG. 5 is a graph illustrating gain shape versus wavelength for a typical silicate based glass.
• FIG. 6 is a graph illustrating gain shape versus wavelength for a typical silicate based glass.
• FIGS. 7-9 are graphs illustrating gain shape versus wavelength for fluorophosphate glasses according toJhe present invention.
• the present invention relates to a family of glasses having utility particularly in lighting, optical and electronic applications.
• the glasses have unique features that render them particularly useful in the production of optical signal amplifiers.
• the glasses according to the present invention contain a relatively high concentration of P 2 O 3 .
• the present invention is directed to a family of glasses for optical amplification comprising a substantially silica free fluorophosphate glass medium, doped for 100 parts by weight of other components, with up to 10 parts by weight of erbium oxide. Table 1 sets forth the essential composition ranges for the fluorophosphate glass according to the present invention.
• the family of erbium-doped glasses according to the invention may further comprise about .01 to 15 parts by weight of Yb 2 0 3 to be used as a sensitizer to increase pump efficiency at around 980 nm.
• Table 2 defines narrower, preferred ranges of oxide constituents of the present glasses. Optimum properties for optical signal amplifiers, and their production, obtain within these narrower ranges.
• the glasses according to the present invention is their ability to be doped with relatively high concentrations of erbium oxide (Er 2 0 3 ).
• erbium oxide Er 2 0 3
• high concentrations of Er 2 0 3 doping provide excellent fluorescent effects that are important for optical signal amplification by laser pumping due to the reduction of ion clustering and upconversion quenching.
• This property provides an excellent amplification medium for use in optical amplifiers for the 1550 nm wavelength.
• the present invention is directed to an erbium-doped optical amplifier comprising a medium for optical amplification comprising a fluorophosphate glass composition.
• the fluorophosphate glass composition is doped for 100 parts by weight constituted by:
• the erbium-doped optical amplifier medium comprises, with regard to components other than erbium oxide, 100 parts by weight constituted as shown in Table 4 below. TABLE 4
• the erbium-doped optical amplifier according the invention may further comprising about 01 to 15 parts by weight of Yb 2 O 3 , to be used as a sensitizer to increase pump efficiency at around 980 nm
• the optical amplifier according to the present invention may take any number of forms, as long as the medium is capable of being doped with erbium ions
• the optical amplifier can be a single mode fiber type optical amplifier Alternatively, the optical amplifier could also be a planar-type optical amplifier
• FIG 1 At low concentration levels of
• concentration Cq b corresponds to the onset of concentration quenching
• concentration C q corresponds to the concentration level where the fluorescence lifetime is divided by 2
• fluorescence lifetime is approximately 13ms
• FIG 2 is a graph illustrating the effects of concentration quenching on fluorescence efficiency of typical silica based glasses Fluorescence efficiency is defined as the 1.55 ⁇ m fluorescence per Er ion versus Er concentration. For the ion concentrations levels of interest, i.e., between 3 to 5 E20 Er ions/cc (approximately 4-7 parts by weight), the fluorescence efficiency of the silica-based glasses is between .5 to 2 E-19nW/ion.
• FIG. 3 is a graph illustrating the effects of concentration quenching on the fluorescence lifetime of three types of fluorophosphate-based glasses according to the present invention.
• FIG. 1 is a graph illustrating the effects of concentration quenching on the fluorescence lifetime of three types of fluorophosphate-based glasses according to the present invention.
• FIGS. 3 and 4 are a graph illustrating the effects of concentration quenching on fluorescence efficiency of three types of fluorophosphate-based glasses according to the present invention.
• both C qb and C q are one order of magnitude higher than the corresponding values for the silica-based glasses. This indicates that the concentration quenching behavior at high concentration levels of Er ions is relatively weak in the fluorophosphate glasses according to the invention, and that these glasses are very good candidates for short length, high gain optical signal amplifiers.
• a comparison of composition with associated measured and calculated properties of three types of fluorophosphate glasses according to the present invention, a typical borosilicate-based glass and ZBLAN are provided in Table 5. The compositions in Table 5 are expressed as batch quantity.
• the actual ingredients of the batch can consist of any type of raw material, oxides, fluorides or phosphates, which when melted together, are converted into desired oxides and fluorides in the proper proportions.
• raw materials (not exhaustive ) are: Ca(PO 3 ) 2 , Ba 2 P 2 0 7 , AI 4 (P 2 0 7 ) 3 , AI(PO 3 ) 3 , NaPO 3 , K 2 TiF 6 , X 2 0 y , XF y where X is the metal ion of valence y-
• Example 2 Borosilicate ZBLAN2 type glass parts by wei ght molar %
• the batch ingredients are mixed together to provide homogeneity, placed inside a platinum crucible, and Joule-heated at about 1000°C.
• the temperature is raised to between 1050 to 1350°C to obtain glass homogeneity and fining.
• the melt then is cooled and simultaneously formed into the desired shape, and finally transferred into an annealing furnace operating at about 400°C.
• An alternative melting process consists of forming the glass from batch ingredients and remeiting this glass together with the desired proportion of Er or/and Yb raw materials. This procedure can in some cases increase homogeneity of the glass.
• the Quantum Efficiency ⁇ obs / ⁇ ⁇ a ⁇ is in the range of 70 to 100% for the fluorophosphate glasses according to the present invention at the desired Er concentration levels, whereas the Quantum Efficiency for the silica-based glasses at the same concentration level is in the range of 20 to 35%.
• the glass medium according to the present invention preferably has a fluorine content of at least 18 parts by weight.
• Ni is the ground state ( 1 152 ) ion population (averaged over the length;
• Equation 2 was used to calculate the gain shape versus wavelength of different glass compositions, the results of which are shown in FIGS. 5-9.
• FIG. 5 illustrates the gain shape of a typical borosilicate type glass used in optical signal amplifiers. It is clear that the gain spectrum around the 1550 nm bandwidth which is used in WDM, is nonuniform in character. Amplification between about 1535 nm and 1565 nm, a typical range used in WDM, is uneven. The variation between the maximum and minimum gain can reach 250%.
• FIG. 6 illustrates the gain shape of a ZBLAN glass for use in an optical signal amplifier.
• ZBLAN offers a flattened gain shape over a range of wavelengths about 30 nm wide.
• FIG. 7 illustrates the gain shape for a first fluorophosphate type glass according to the present invention.
• This glass identified as Example 1 has an Er concentration over 7 parts by weight for 100 parts by weight of other components, yet still exhibits a substantially flat gain shape over a 28nm spectrum in the 1530 - 1560 nm band.
• FIG. 8 illustrates the gain shape for a second type of fluorophosphate glass according to the present invention.
• This glass identified as Example 2
• This glass has an Er concentration over 4 parts by weight for 100 parts by weight of other components and exhibits a flattened gain shape over about a 26nm spectrum.
• FIG. 9 illustrates the gain shape a phosphate-based glass.
• This glass, identified as Example 3 has an Er concentration slightly less than 3 parts by weight, for 100 parts by weight of other components, and exhibits two relatively flat areas of gain; the first being about 10nm wide arid the second about 9nm in width.
• Another aspect of the present invention is the ability to efficiently pump the amplifying medium at 980 nm while maintaining relatively low noise levels.
• Optical amplification requires excitation of erbium ions in the glass medium to a higher energy level, and then relaxation of the ions This process causes emission of photons as the erbium ions relax to ground level.
• the photons emitted during this process are at a wavelength so as to amplify optical signals at the same wavelength.
• the gain medium To have population inversion (population at level 2 higher or equal than 50%) and, therefore, gain, the gain medium must be pumped with an external source. Generally, with optical signal amplification, the gain medium is pumped with a 980 or 1480 nm diode laser. When a 980 nm diode laser is used, electrons move to the third level ( 4 l- ⁇ 1 / 12 ) and then relax to the second level and then to the ground level by emitting a 1.55 ⁇ m photon.
• Er-doped fluorophosphate glass according to the present invention as an amplification medium with a 980 nm pump, has advantages over other Er-doped fluorides.
• ZBLAN-like (100% fluoride no oxygen) compositions due to high fluorescence lifetime (9 ms) at the 4 ln / ⁇ 2 pumping level, lose pumping efficiency.
• ZBLAN-like compositions are, therefore, usually pumped at 1480 nm.
• drawbacks to pumping at wavelengths this high For example, the ion population cannot be fully inverted at this level and noise in the amplifier increases.
• the fluorophosphates glass medium according to the present invention can be efficiently pumped at 980 nm since the 4 l 1 ⁇ /12 lifetime time is in the range of 10 to 70 ⁇ s.
• FIGS. 5-9 illustrate that fluorophosphate glasses according to the present invention show gain flattening characteristics using a 980 nm pump similar to ZBLAN, and significantly improved in comparison with silicates and phosphates.
• the glass compositions according to the present invention provide high and flattened gain characteristics in short length optical amplifiers, and then can be used for the manufacturing of planar amplifiers and/or short length single mode fibers having ZBLAN-like gain that are useful in WDM and other similar applications.

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• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Optics & Photonics (AREA)
• Plasma & Fusion (AREA)
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• Geochemistry & Mineralogy (AREA)
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• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Life Sciences & Earth Sciences (AREA)
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• Lasers (AREA)

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• 1997
  • 1997-09-05 FR FR9711054A patent/FR2768143B1/fr not_active Expired - Fee Related
• 1998
  • 1998-08-12 WO PCT/US1998/016791 patent/WO1999013541A1/en not_active Application Discontinuation
  • 1998-08-12 KR KR1020007002291A patent/KR20010023640A/ko not_active Application Discontinuation
  • 1998-08-12 CN CN98808791A patent/CN1269915A/zh active Pending
  • 1998-08-12 BR BR9811411-5A patent/BR9811411A/pt not_active IP Right Cessation
  • 1998-08-12 AU AU91040/98A patent/AU734647B2/en not_active Ceased
  • 1998-08-12 CA CA002297331A patent/CA2297331A1/en not_active Abandoned
  • 1998-08-12 JP JP2000511219A patent/JP2001516958A/ja active Pending
  • 1998-08-12 EP EP98943193A patent/EP1010220A4/de not_active Withdrawn

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