Population inversion factor dependence of photodarkening of Yb-doped fibers and its suppression by highly aluminum doping

Kilabayashi, T.; Ikeda, Masahiro; Nakai, Michihiro; Sakai, Tetsuya; Himeno, K.; Ohashi, Keisuke

doi:10.1109/ofc.2006.215694

Cited by 36 publications

(52 citation statements)

References 7 publications

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“…This result, the appearance in the YF exposed to in-band 977-nm pumping of spectrally wide excess loss in the visible, is practically a replica of the previous results (see [6][7][8][9]), and namely these pumpinduced spectral changes are called the photo-darkening effect. A novelty stemming from our data (see inset) is the detecting of a simultaneous decrease of absorption in a very narrow spectral range, corresponding to the resonant Yb 3+ -band maximum (probably, the authors of the preceding studies could not capture this important feature due to the work with much longer YF samples, where it is latent under the noise level, see [6][7][8]). Also notice in Fig.1 the spectral changes occurring at 470-480 nm, i.e., in the spectral range, "signing" the presence in an YF of Yb 3+ -Yb 3+ ion pairs [14,15,[20][21][22][23].…”

Section: Wwwlphysorgsupporting

confidence: 85%

“…1, 2), our attribution of these processes as Yb 3+ → Yb 2+ (which can involve Yb 3+ -Yb 3+ ion pairs, see our notes above and [8,10,15]) might be meant doubtful and explained by another way, say, by the mentioned (but to-date unidentified) "structural defects or color centers" [7,9,10,13,15]. However, remind other interesting literature data concerning the question under scope.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 65%

“…The pump induced excess loss within the Yb 3+ spectral band is responsible for the degradation of output power of an YFL [4,[6][7][8]. Notice that the photodarkening effect is observed when an YF is pumped with the light falling into the resonant (0.9-1.0-µm) Yb 3+ band even at no-lasing conditions, i.e., when an YF is not closed by a cavity [6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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Reversible photo-darkening and resonant photo-bleaching of Ytterbium-doped silica fiber at in-core 977-nm and 543-nm irradiation

et al. 2007

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Abstract:We report experimental results showing novel features in photo-darkening and photo-bleaching of a heavily-doped Ytterbium silica fiber exposed to in-core 977-nm and 543-nm irradiation. It is shown that pumping of the fiber at the resonant 977-nm wavelength leads to an increase of absorption in the spectrally wide range (400-1000 nm, photo-darkening) and a simultaneous decrease of the resonant (Yb 3+ ) absorption coefficient near ∼ 1 µm (resonant photo-bleaching). Such a character of the Ytterbium fiber spectra transformations allows us to propose that they are a signature of the 977-nm light-induced Yb 3+ → Yb 2+ conversion process, with the spectrally wide absorption, or photo-darkening, to arise owing to the Yb 2+ centers formation and the resonant photo-bleaching to stem from the corresponding decrease of Yb 3+ ions concentration. It is as well demonstrated that an exposure of the Ytterbium fiber, where the aforementioned transformations have occurred, to the 543-nm light results in a partial return of the initial fiber propertiesbleaching of the spectrally wide excess loss in the visible and increasing of the resonant 977-nm (Yb 3+ ) absorption peak. Therefore, we reveal a reverse process, Yb 2+ → Yb 3+ , possibly taking place in the last case.

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Section: Wwwlphysorgsupporting

confidence: 85%

Section: Discussion and Concluding Remarksmentioning

confidence: 65%

Section: Introductionmentioning

confidence: 99%

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Reversible photo-darkening and resonant photo-bleaching of Ytterbium-doped silica fiber at in-core 977-nm and 543-nm irradiation

et al. 2007

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“…Formation of colour centres in the silica glass host is often believed to be the reason behind PD [1]. Yb-doped aluminosilicate fiber suffers PD as a permanent excess optical loss (unless optically or thermally photobleached) having a low-energy absorption tail extending into the 0.9-1.0 um absorption band and 1.1 um emission band of YDFLs [2,3]. Our previous studies emphasised on oxygen deficient centres (ODC) as a precursor of PD in Yb-doped aluminosilicate fiber [4] under a 488 om CW pump and also revealed the post-irradiation temporal evolution of the induced loss [5].…”

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confidence: 99%

Influence of temperature on the post-irradiation temporal loss evolution in Yb-doped aluminosilicate fibers, photodarkened by 488 nm CW irradiation

Basu

Yoo

Boyland

et al. 2009

CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference

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Photodarkening (PD) in optical fibers is a serious concern for the development and maintenance of the reliable operation of high -power ytterbium fiber lasers (YDFL) , over a long period of time . Formation of colour centres in the silica glass host is often believed to be the reason behind PD [1]. Yb-doped aluminosilicate fiber suffers PD as a permanent excess optical loss (unless optically or thermally photobleached) having a low-energy absorption tail extending into the 0.9-1.0 um absorption band and 1.1 um emission band of YDFLs [2,3]. Our previous studies emphasised on oxygen deficient centres (ODC) as a precursor of PD in Yb-doped aluminosilicate fiber [4] under a 488 om CW pump and also revealed the post-irradiation temporal evolution of the induced loss [5]. To the best of our knowledge, our present report is the first of its kind to show the temperature dependance of the post-irradiation induced excess loss in VIS-NIR in Yb-doped aluminosilicate fiber, even after stopping the 488 nm CW pump . A 488 nm CW laser was used to photodarken a 2 m long sample ofYb-doped aluminosilicate fiber (Yb cone, 17000 ppm-wt, N.A. 0.15, core dia 8.3/lm, OD 125 urn). Drop (-21%) in the throughput power at 488 om was monitored, using a suitable silicon detector and a power meter . In one case, the fiber was photodarkened at room temperature for 90 minutes. Then this photodarkened fiber was immediately set up to monitor the white light transmission (at room temperature), using an Optical Spectrum Analyzer (OSA) , for more than 24 hours . The post-irradiation temporal increase in loss, over 24 hours, was almost saturated to 2.5 dB/m at 633 om. In another case, a fresh fiber was similarly photodarkened under 488 om irradiation and then , while monitoring the white light transmission, it was heated at 120°C for the first 30 minutes just after PD. Then it was kept at room temperature for more than 24 hours. The post-irradiation loss evolution over this 30 minutes of heating was around 2.6 dB/m and this loss, after 24 hours , was almost saturated to 3.1 dB/m , both at 633 nm. These results are shown in Fig. 1 (a) & (b). Also, the influence of external heating on PD, during irradiation, and the postirradiation temporal loss evaluation of such fibers will be presented. This is a clear indication that the post-irradiation temporal evolution of loss, in a photodarkened Yb-doped aluminosilicate fiber, depends on the temperature and this loss dynamics can be accelerated and possibly enhanced by external heating. This kind of spontaneous relaxation processes, involving electron and hole centres , was studied in germanosilicate glass [6]. Further studies in that direction , especially on aluminosilicate host, can be useful for the optimal design and operation of high power fiber lasers, in order to avoid or minimize photodarkening..so • j ust aft er PD: (b) -j us t en er room temp -55 PD:room temp ;< :;;t -60 If> If> o -es • 30 mlns aft er 0 • aft e r po : 30 c PD: room .£. -65 mln s at 120 0 S -7 0 temp deg C E ttl~-70 -e • 24 hou rs .to...

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“…High concentrations of aluminum and the simultaneous input of Yb chemicals with chloride chemicals into the silica tube during preform fabrication are reported to suppress photodarkening. [13,14]. …”

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confidence: 99%

Progress in active fibers

Sahu

Yoo

Kim

et al. 2007

OFC/NFOEC 2007 - 2007 Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference

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Progress in active fibers for high power fiber sources is discussed. The waveguiding geometry naturally lends itself to high-power diffraction-limited operation. Further refinements allow for the control of nonlinearities and wavelength. Fabrication advances mitigate photodarkening.OCIS codes: (060.2280) Fiber design and fabrication, (060.2320) Fiber optics amplifiers and oscillators Low-loss rare-earth doped silica fibers, first realized using MCVD and solution-doping in mid 1980s, made erbium-doped fiber amplifiers (EDFAs) [1] possible. These revolutionized optical communications. After successful implementation of EDFAs in communications, high-power cladding pumped fiber lasers and amplifiers have become a major field of operation of rare-earth doped fibers. Ytterbium-doped fiber lasers have been powerscaled beyond the kW level at ~1.1 mm. Also other fiber devices, including those at other wavelengths and with different temporal and spectral properties have seen rapid progress. This presentation will review the progress in high power fiber lasers and amplifiers, highlighting the advances in the active fibers seen to date and those that will be required in the future.The output power of fiber lasers and amplifiers has rapidly grown over the past years and has now reached a point where they are looking to become the laser of choice in a wide range of applications beyond optical communications such as materials processing, micro-machining, medicine, and LIDAR to name a few. The attractions of cladding-pumped fiber lasers and amplifiers derive from the high beam quality, high power, high gain, and broad gain bandwidth. Thermal properties are crucial for high-power operation with high beam quality Fiber lasers benefit from a geometry that makes the thermal management less critical than in bulk lasers. Thus, the generated heat is distributed over a long length, which reduces the risk of thermal damage of the fiber. Waveguiding of the signal as well as the pump is essential for making long-length devices. Moreover, the output beam quality in a fiber laser is greatly determined by the waveguiding properties of the core in the fiber and can be tailored to generate a single-mode output beam. The relatively low thermal load per unit length mitigates thermal distortions of the waveguiding even at high powers. Recent demonstrations of Yb-doped fiber lasers with excellent beam quality at power levels of > 1 kW in the 1100 nm regime [2], and Yb sensitized Er-and Tm-doped fiber lasers with output powers of 188 W [3] and 75 W [4] in the 1550 and 2000 nm wavelength range respectively, show the potential of the fiber-based sources. An important point here is the considerable amounts of heat generated by these devices. Advances in both the pump waveguide (NA, size) of double-clad fibers, which enable the multimode diode pump sources with continuously increasing output power to be used, and the core (large mode area and low numerical aperture even at high dopant concentrations), lie behind the current rapid progress.In a master os...

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Population inversion factor dependence of photodarkening of Yb-doped fibers and its suppression by highly aluminum doping

Abstract: We have confirmed that the photodarkening of Yb-doped fiber (YbDF) has the second-power dependence on a population inversion factor. The photodarkening of a newly developed highly aluminum-doped YbDF has been significantly suppressed.

Cited by 36 publications

References 7 publications

Reversible photo-darkening and resonant photo-bleaching of Ytterbium-doped silica fiber at in-core 977-nm and 543-nm irradiation

Reversible photo-darkening and resonant photo-bleaching of Ytterbium-doped silica fiber at in-core 977-nm and 543-nm irradiation

Influence of temperature on the post-irradiation temporal loss evolution in Yb-doped aluminosilicate fibers, photodarkened by 488 nm CW irradiation

Progress in active fibers

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