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ABSTRACT: We report 33% efficient generation of the first Stokes in a high-concentration GeO 2 fiber Raman laser pumped by a 22 W thulium-doped fiber laser. An output power of 4.6 W at 2.105 m is demonstrated. Stimulated Raman scattering has permitted the de-velopment of a wide variety of continuous-wave (CW) fiber lasers and amplifiers at wavelengths for which there are no rare-earth-doped gain media available. This approached has also been applied to CW solid-state-based systems [1]. Recently Raman lasers have been demonstrated in photonic crystal [2] and chalco-genide glass fibers [3], allowing extension of opera-tional wavelengths of fiber lasers beyond the waveguiding loss and single-mode propagation re-gions of conventional silica-based fibers. For genera-tion of Raman fiber laser emission with wavelengths beyond 2 m the rapidly increasing losses of the bulk silica impose a limit on long-wavelength operation of conventional silica fibers. Alternative oxide-based glass forming hosts, such as high-concentration GeO 2 , were first suggested in 1975 [4] as a material to produce low-loss optical fi-bers. Shortly after, a comparison of the Raman scat-tering cross sections and Stokes intensities of vitre-ous bulk SiO 2 , GeO 2 , B 2 O 3 , and P 2 O 5 [5] indicated that the cross section in GeO 2 is nearly an order of magnitude greater than that of SiO 2 . It has also been shown that the intrinsic IR absorption of GeO 2 glass is shifted to longer wavelengths compared with silica glass because germanium atoms have a greater mass than silicon atoms, making GeO 2 a better candidate for Raman generation in the IR. Doping of silica fi-bers with low concentrations of GeO 2 has been rou-tinely used to enhance Raman gain. However manu-facturing of high-concentration, above 20– 40 mol. %, GeO 2 core fibers has until recently faced problems [6]. These problems arise from the mismatch of the thermal expansion coefficients of GeO 2 and SiO 2 com-bined with the narrow temperature range between nonsintering and the evaporation of the GeO 2 . Manufacturing of single-mode fibers with core con-centrations of 51– 97 mol. % GeO 2 was first reported in 2004 [6,7]. Apart from lower losses, above 2 m these fibers possess a significantly enhanced nonlin-earity as compared with silica fibers. The combina-tion of these two advantages makes the highly doped GeO 2 fibers an excellent candidate for extending Stokes generation in optical fibers in the IR. This po-tential has been demonstrated by using pump sources based on ytterbium-and erbium-doped fiber lasers [6–8]. As the Raman gain coefficient of such fi-bers is about an order of magnitude higher than that in silica fibers, the increasing losses with wavelength can be compensated for by using much shorter lengths of fiber for Raman generation. Here we re-port the efficient generation of a high-power Raman source at 2.1 m in a 75 mol. % GeO 2 fiber directly pumped with a single-mode thulium doped fiber la-ser. This approach allows a high optical-to-optical and overall efficiency to be achieved in the wave-length region above 2 m. The experimental setup is shown in Fig. 1. A 22 W, 1.938 m, 1 nm linewidth, single-mode CW thulium-doped fiber laser (IPG Photonics) was em-ployed as a pump. The free-space output of the thu-lium laser was bulk coupled into the GeO 2 fiber, avoiding spurious backreflection from the Raman la-ser cavity into the thulium laser. To reduce the ther-mal load in the coupling setup an optical chopper with a 25% duty factor was used. The pump light was coupled into a short length of STF (standard telecom fiber) with an efficiency of up to 80%. The STF was directly spliced to the 75 mol. % GeO 2 fiber by using a mode field matching technique on an arc-fusion splicer, which resulted in regular splice losses of less than 0.5 dB. Two fiber Bragg gratings (FBGs) at 2.105 m, corresponding to the first Raman shift of the pump wavelength, a high reflector HR, R 99% , and an output coupler OC, R 50% , were written in the same GeO 2 fiber and formed the Ra-man laser cavity. Because of the high photosensitiv-ity of the GeO 2 fiber the gratings were directly re-corded with 244 nm laser radiation without hydrogen loading of the fiber [9]. The gratings' spectral proper-Fig. 1. Schematic of the experimental setup.
06/2290; 56503550(140).
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ABSTRACT: An efficient CW bismuth fiber laser operating around 1.46 μm with an efficiency of >50% and an output power of >20 W has been developed on a bismuth-doped GeO(2)-SiO(2) fiber. The laser demonstrates weak dependence of the output power on temperature in comparison with bismuth lasers operating near 1.15 and 1.3 μm. The laser generation has been obtained in the range 1.39 to 1.54 μm. The first linearly polarized bismuth-doped fiber laser at 1.46 μm based on a PANDA-type fiber has been demonstrated.
Optics Letters 07/2012; 37(13):2589-91. · 3.40 Impact Factor
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ABSTRACT: We report holmium-doped fibre lasers with a Ho3+ concentration of 1.6 × 1019 cm-3 and lasing wavelengths of 2.02, 2.05, 2.07 and 2.1 μm at a pump wavelength of 1.15 μm. The slope efficiency of the lasers has been measured. The maximum efficiency, 0.455, has been obtained at a lasing wavelength of 2.05 μm. The laser efficiency is influenced by both the optical loss in the wing of a vibrational absorption band of silica and active-ion clustering.
Quantum Electronics 07/2011; 41(6):492. · 0.83 Impact Factor
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ABSTRACT: A bismuth-doped-pure-silica holey fiber is fabricated using a fiber preform made by the furnace chemical vapor deposition method. The spectroscopic properties of the fiber are studied, and laser action at λ=1450 nm with an efficiency of 12% is demonstrated.
Optics Letters 07/2011; 36(13):2599-601. · 3.40 Impact Factor
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ABSTRACT: In this study, bismuth-doped fiber lasers operating at the wavelength of 1179 nm with an optical efficiency of up to 28% are realized. The fiber gain upon 1-¿m pumping declines, while the unsaturable absorption increases with increasing the small-signal absorption. We conclude that up-conversion and excited-state absorption are responsible for limiting the efficiency of such lasers.
IEEE Journal of Quantum Electronics 03/2010; · 1.88 Impact Factor
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ABSTRACT: One of the promising ways to build such pulsed laser scheme consists in the application of a fiber saturable. This paper demonstrate the stable pulsed lasing with the pulse energy up to 0.1 mJ and the pulse duration in a range of approximately 1-2 mus. In this paper we suggest a new laser configuration with Ho-doped fiber as a saturable absorber.
Lasers and Electro-Optics 2009 and the European Quantum Electronics Conference. CLEO Europe - EQEC 2009. European Conference on; 07/2009
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ABSTRACT: We have made and studied a set of the fiber lasers based on Ho-doped fiber with high concentration of the active ions. For the first time the spectral efficiency in a range of 2.02–2.15 μ m was determined. The highest output power of 4.2 W was detected at 2.1 μ m with the efficiency slope of 34%. This value of the efficiency is highest for pure holmium-doped silica fibers. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
Laser Physics Letters 06/2009; 6(9):661 - 664. · 9.97 Impact Factor
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ABSTRACT: We report a Raman scattering study of photoinduced and thermal reactions between H2 and germanosilicate optical fibres with 22 mol % and 97 mol % GeO2 in the core (F1 and F2, respectively) after H2 loading at 150 MPa (1500 atm). The mechanisms of photoreactions are investigated in a wide range of incident laser wavelengths (244, 333, 354, 361 and 514 nm). Thermal reactions are studied at 500 °C. The results indicate that the main mechanism behind the formation of hydrogen-containing defects with Raman bands at 700, 750, 2190, 3600 and 3680 cm-1 involves ≡Ge—O—Ge≡ or ≡Ge—O—Si≡ bond breaking and formation of hydride and hydroxyl species: =GeH2 (700, 750 cm-1), ≡Ge—H (2190 cm-1), ≡GeO—H (3600 cm-1) and ≡SiO—H (3680 cm-1). The key features of the reactions in the F1 and F2 fibres are analysed. In particular, photoinduced reactions give ≡Si—OH groups only in the F1 fibres, whereas the formation of germanium nanoclusters at a relatively low temperature (~500 °C) or ≡GeO—H and ≡Ge—H defects under 514-nm irradiation has only been observed in the F2 fibres.
Quantum Electronics 03/2009; 38(12):1147. · 0.83 Impact Factor
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ABSTRACT: An emission band with a maximum at 1430 nm and a FWHM of 100 nm was observed in a Bi-doped fiber under core-pumping in the 1340- 1370 nm wavelength range. Net gain in 1430-1490 nm and laser action in 1443-1459 nm wavelength range in the Bi-doped aluminosilicate fiber have been demonstrated for the first time to our knowledge.
Optics Express 11/2008; 16(21):16971-6. · 3.59 Impact Factor
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ABSTRACT: For the first time we have suggested and realized passive Q-switched Yb-doped fiber laser with a saturable absorber based on Ho-doped fiber laser. The pulse duration was of 250 ns, the pulse energy – 70 μ J, the peak power – 300 W. The laser is perspective for technology processes. Possible ways of laser characteristics improving are discussed. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
Laser Physics Letters 10/2008; 6(2):135 - 138. · 9.97 Impact Factor
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ABSTRACT: The method of optical space-domain reflectometry for measuring local spatial characteristics of fibre Bragg gratings (FBGs) is described in detail. It is demonstrated experimentally that, by using IR and UV radiation sources, this method provides good sensitivity (~10-4) of measuring the modulation amplitude of the induced refractive index in the core of an optical fibre and a high spatial resolution (~100 μm and better). The factors affecting the accuracy of measurements as well as technical and methodological limitations of the method are considered. A comparative analysis of modern methods for studying the spatial properties of FBGs is performed and applications of these methods are considered.
Quantum Electronics 10/2007; 33(8):704. · 0.83 Impact Factor
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ABSTRACT: The effect of the inhomogeneous distribution of nitrogen impurity on the photosensitivity of germanosilicate fibres is studied. For this purpose, single-mode fibres with different alternations of the core layers sintered in nitrogen and oxygen atmospheres were specially prepared by the MCVD technique. Photoinduced variations in the quadratic nonlinear susceptibility and refractive index of these fibres were recorded. It is shown that the recording efficiency depends on the radial distribution of germanium oxygen-deficient centres, which can be controlled at the stage of sintering through a nonuniform doping by nitrogen over the cross-section.
Quantum Electronics 10/2007; 33(3):275. · 0.83 Impact Factor
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Andrei S Kurkov,
Evgenii M Dianov,
Vladimir M Paramonov,
A N Gur'yanov,
A Yu Laptev,
V F Khopin,
A A Umnikov,
N I Vechkanov, O I Medvedkov,
Sergei A Vasil'ev,
M M Bubnov,
O N Egorova,
S L Semenov,
E V Pershina
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ABSTRACT: A set of diode-pumped fibre lasers producing a cw output of 4–7.5 W in the range from 1.05 to 1.15-μm is realised on the basis of an ytterbium double-cladded fibre. The output of the ytterbium fibre laser was used to pump a Raman phosphor-silicate fibre converter, resulting in fibre lasers producing a cw output power of more than 3 W at 1.26 and 1.3-μm.
Quantum Electronics 10/2007; 30(9):791. · 0.83 Impact Factor
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ABSTRACT: A brief review is given of the state of the art in the research on the photosensitivity of fibres and photoinduced fibre gratings. The most important properties of fibre gratings are considered and the main methods of their production and their applications are discussed. The photosensitive compositions of silica glasses are presented and methods for increasing their photosensitivity are indicated.
Quantum Electronics 10/2007; 35(12):1085. · 0.83 Impact Factor
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ABSTRACT: A Mach—Zehnder fibre interferometer, based on two photoinduced long-period gratings, was used in an investigation of the dynamics of the refractive index Δnind induced in the core of a germanosilicate optical fibre by different types of UV irradiation. It was found that the value of Δnind could be approximated satisfactorily by a power-law function of the radiation dose at all the investigated wavelengths. A comparative analysis of the dynamics of the refractive index in the case of singlet and triplet photoexcitation of germanium oxygen-deficient centres showed that the dominant mechanism of the change in the refractive index by low-intensity continuous UV irradiation was transformation of these centres from an excited triplet state.
Quantum Electronics 10/2007; 27(9):785. · 0.83 Impact Factor
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ABSTRACT: Absorption spectra and spontaneous Raman spectra of optical fibres with a germanosilicate core loaded with molecular hydrogen at a pressure of 150–170 MPa are studied; the variation of these spectra during the outdiffusion of hydrogen from the fibres is also investigated. The purely rotational transitions of molecular hydrogen in Raman spectra of optical fibres are recorded for the first time. The changes in the spectral parameters of fibre Bragg gratings loaded with hydrogen are analysed. It is observed for the first time that under such high loading pressures, the decrease in the hydrogen concentration in the fibre core after completion of hydrogen loading occurs in two clearly manifested stages, the initial stage being characterised by a more rapid outlet of hydrogen as compared to the dynamics of hydrogen outdiffusing at pressures of 10–15 MPa. Barodiffusion of molecular hydrogen in optical fibres is considered as the main mechanism explaining this effect. An increase in the solubility of molecular hydrogen in germanosilicate fibres exposed to UV radiation is observed for the first time.
Quantum Electronics 10/2007; 35(3):278. · 0.83 Impact Factor
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ABSTRACT: We report 33% efficient generation of the first Stokes in a high-concentration GeO(2) fiber Raman laser pumped by a 22 W thulium-doped fiber laser. An output power of 4.6 W at 2.105 microm is demonstrated.
Optics Letters 08/2007; 32(13):1848-50. · 3.40 Impact Factor
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ABSTRACT: Q-switched fiber lasers have found a number of applications such as medical treatment, micromachining, diagnostics and others. Some of them require an emission at wavelengths which are not coincide with the optical transmissions of the rare-earth elements. Then, an investigation of Raman pulsed source seems to be interesting. Recently, a new type of optical fiber, namely, Bi-doped fiber was suggested. One of the applications of this fiber is the saturable absorber for Yb-doped fiber laser to get Q-switched regime. That allows one to build the all-fiber Raman source.
Lasers and Electro-Optics, 2007 and the International Quantum Electronics Conference. CLEOE-IQEC 2007. European Conference on; 07/2007
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ABSTRACT: CW lasing of a new type of lasers-Bi-doped fiber lasers- in a wavelength range of 1150-1215 nm at high output power level (15 W) and efficiency of 22% has been obtained for the first time.
Lasers and Electro-Optics, 2007. CLEO 2007. Conference on; 06/2007
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ABSTRACT: Yb-doped cladding-pumped fiber laser with linearlypolarized output emission was realized. To obtain linearpolarization operation we have applied Bragg grating written in the fiber with high birefringence as the input reflector. The polarization extinction ratio was of 17 dB. A maximum output power of 12 W was achieved with an efficiency slope of 69%. The laser linewidth was less than 0.1 nm even for maximum output power. (© 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
Laser Physics Letters 05/2007; 4(10):740 - 742. · 9.97 Impact Factor
