Dopant interactions in high-power laser fibers

Kirchhof, J.; Unger, Sonja; Schwuchow, Anka; Jetschke, Sylvia; Knappe, B.

doi:10.1117/12.590021

Cited by 34 publications

(12 citation statements)

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“…In this case, the absorption coefficient in the fiber is related with the absorption coefficient in the core simply by the cross section area ratio of core and cladding.The core absorption coefficient is dependent of the co-doping For the aluminium codoped fibers here investigated, absorption cross sections of 0.8@10 -24 m 2 (915 nm) and 2.5@10 -24 m 2 (976 nm) have been used. 22 For a D-shaped fiber cross section, a practically exponential decay of the intensity is observed, which closely agrees with the calculated absorption coefficient (Fig.10a ). The intensity decay in a circular fiber, however, is not exponentially and much smaller as calculated (Fig.10b).…”

Section: Pump Absorption In Microstructured Fiberssupporting

confidence: 88%

“…1 mol% RE 2 O 3 doping leads to a refractive index increase ) n relative to pure SiO 2 of 67@10 -4 . 22 Moreover, an excess of Al 2 O 3 doping is required for optimal optical properties of the lasing element, that additionally increases ) n. We can conclude that a NA of 0.05 cannot be simply realized with RE 2 O 3 concentrations > 1000 mol-ppm. In the case of the ytterbium doped high power cw laser, this restriction can be accepted, because the low doping can be compensated by relatively long laser fiber lenghts.…”

Section: Preparation Aspects For "Large Mode Area" (Lma) Fibersmentioning

confidence: 96%

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Materials and technologies for microstructured high power laser fibers

et al. 2005

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In the last years rare earth doped double-clad fibers have been developed to high-power laser sources. Important progress was possible by increasing numerical aperture of the pump cladding and decreasing numerical aperture of the laser core. The high NA of the pump cladding enables the acceptance of large pump intensities whereas the low NA of the laser core makes possible to increase the core diameter and to decrease the laser power density retaining high beam quality. Here, actual challanges are discussed and possibilities are demonstrated to use microstructures for improved fiber designs which are realized by stacking and drawing of capillaries and rods. The rare earth doped parts are prepared by modified chemical vapor deposition and solution doping, but other routes of powder technology are also studied. Concerning the currently most important laser and amplifier types -Yb doped at 1.1 : m wavelength and Er/Yb doped at 1.55 : m wavelength -, the question of a high pump aperture is similar, but the limitations concerning a low core aperture are fairly different, because an efficient Er/Yb laser demands high phosphorus co-doping which naturally increases the core NA. The applied microstructures comprise "holey" fiber cross sections in form of "air clads" for the pump light and multiple hole ring structures for laser core and inner cladding. Moreover, microstructured cores made from solid parts yield new possibilities and parameters to compensate the high refractive index of the active material and to optimize the large mode area design. key words: fiber laser, rare-earth doping, microstructured fiber

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Section: Pump Absorption In Microstructured Fiberssupporting

confidence: 88%

Section: Preparation Aspects For "Large Mode Area" (Lma) Fibersmentioning

confidence: 96%

Materials and technologies for microstructured high power laser fibers

et al. 2005

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“…In order to achieve suitable gain in laser resonator with shorter length of active fiber, highly Yb-doped fiber operated in the single mode or low mode regime is necessary. For making highly Ybdoped fibers co-dopants like phosphorous (P) and/or aluminum (Al) are required at higher concentration to increase RE solubility, preventing clusters and phase separation [6], [7]. But these co-dopants, in addition, increases the core refractive index (RI), formation of central dips in RI and "star-like" defect at the coreclad boundary [6], [8] which can deteriorate the beam quality as well as the power stability of the fiber laser.…”

Section: Introductionmentioning

confidence: 99%

An Optimized Vapor Phase Doping Process to Fabricate Large Core Yb-Doped Fibers

Saha

Pal

et al. 2015

J. Lightwave Technol.

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The paper demonstrates a standardized process of vapor phase doping to fabricate large core Yb-doped preforms with longer useful length in reproducible manner. The optimization of the process led to successful achievement of Yb-doped core thickness of 4.5 mm (in 14.8 mm of preform diameter) by depositing up to 30 number of core layers with controlled amount of generated precursor vapors. The influence of the process parameters was studied rigorously to enhance the useful preform length up to 380 mm. A combination of Yb and Al in different proportions was doped into the core with uniform dopant concentration along the length by adjusting few process parameters efficiently. The Al 2 O 3 concentration up to the level of 17.8 mol% has been achieved successfully which resulted in NA of 0.31. This is the highest ever doping of Al in passive fibers by any modified chemical vapor deposition process. The Yb 2 O 3 content in the active fibers is as high as 0.47 mol%.

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“…Ytterbium (Yb) is regarded as the most suitable RE dopant for high power laser systems [3] as it exhibits high lasing efficiency, simple energy level as well as broad absorption and emission bands. Aluminium (Al) and/or Phosphorous (P) are normally co-doped along with REs as they act as network modifier, reduce phase separation and increase the solubility of RE ions into the silica glass matrix [4].…”

Section: Introductionmentioning

confidence: 99%

Vapor Phase Doping of Rare-Earth in Optical Fibers for High Power Laser

Saha

Pal

Sen

2014

IEEE Photon. Technol. Lett.

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This letter describes an optimized vapor phase doping technique using modified chemical vapor deposition system to fabricate rare-earth doped optical fibers for a high power laser. The process comprises deposition of aluminium oxide and ytterbium oxide in vapor phase simultaneously in combination with silica during formation of the core layer. The process parameters have been judiciously controlled to deliver aluminium chloride and rare-earth-chelate compounds to the reaction zone without decomposition and/or condensation of the precursor materials prior to the reaction zone. The standardization of the process parameters resulted in a good repeatability with a very low (< 1%) variation of dopant concentrations throughout the length of the preform. The fabricated fibers exhibit good optical properties with lasing efficiency of 76% at 1.06 µm.

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Dopant interactions in high-power laser fibers

Cited by 34 publications

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Materials and technologies for microstructured high power laser fibers

Materials and technologies for microstructured high power laser fibers

An Optimized Vapor Phase Doping Process to Fabricate Large Core Yb-Doped Fibers

Vapor Phase Doping of Rare-Earth in Optical Fibers for High Power Laser

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