The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform
Valérie Doya - One of the best experts on this subject based on the ideXlab platform.
-
Enhancement of pump absorption efficiency by bending and twisting of double clad Rare earth doped Fibers (Conference Presentation)
Proceedings of SPIE, 2017Co-Authors: Pavel Koška, Pavel Peterka, Valérie Doya, Jan Aubrecht, Ivan Kasik, Ondřej PodrazkýAbstract:High-power operation of fiber lasers was enabled by the invention of cladding-pumping in a double-clad fiber structure. Because of existence of so called skew rays in the inner clad of the fiber, pump absorption saturates along the fiber and pumping becomes inefficient. First studies of pump absorption efficiency enhancement were focused on Fibers with broken circular symmetry of inner cladding eliminating skew rays [1,2]. Later, techniques of unconventional fiber coiling were proposed [3]. However, theoretical studies were limited to the assumption of a straight fiber. Even recently, the rigorous model accounting for fiber bending and twisting was described [4-6]. It was found that bending of the fiber influences modal spectra of the pump radiation and twisting provides quite efficient mode-scrambling. These effects in a synergic manner significantly enhances pump absorption rate in double clad Fibers and improves laser system efficiency. In our contribution we review results of numerical modelling of pump absorption in various types of double-clad Fibers, e.g., with cross section shape of hexagon, stadium, and circle; two-fiber bundle (so-called GTWave fiber structure) a panda Fibers are also analyzed. We investigate pump field modal spectra evolution in hexagonally shaped fiber in straight, bended, and simultaneously bended and twisted fiber which brings new quality to understanding of the mode-scrambling and pump absorption enhancement. Finally, we evaluate the impact of enhanced pump absorption on signal gain in the fiber. These results can have practical impact in construction of fiber lasers: with pump absorption efficiency optimized by our new model (the other models did not take into account fiber twist), the double-clad fiber of shorter length can be used in the fiber lasers and amplifiers. In such a way the harmful influence of background losses and nonlinear effects can be minimized. [1] Doya, V., Legrand, O., Mortessagne, F., “Optimized absorption in a chaotic double-clad fiber amplifier,” Opt. Lett., vol. 26, no. 12, pp. 872-874, (2001). [2] Kouznetsov, D., Moloney, J. V., “Efficiency of pump absorption in double-clad fiber amplifiers. II. Broken circular symmetry,” J. Opt. Soc. Am. B, vol. 19, no. 6, pp. 1259-1263, June 2002. [3] Li, Y., Jackson, S. D., Fleming, S., “High absorption and low splice loss properties of hexagonal double-clad fiber,” IEEE Photonics Technol. Lett., vol 16, no. 11, pp. 2502-2504, Nov. 2004. [4] Koska, P. and Peterka, P., "Numerical analysis of pump propagation and absorption in specially tailored double-clad Rare-earth doped fiber," Optical and Quantum Electronics, vol. 47, no. 9, pp. 3181-3191 (2015). [5] Koska, P., Peterka, P., and Doya, V., “Numerical modeling of pump absorption in coiled and twisted double-clad Fibers,” IEEE J. Sel. Top. Quantum Electron., vol. 22, no. 2 (2016). [6] Koska, P., Peterka, P., Aubrecht, J., Podrazký, O., Todorov, F., Becker, M., Baravets, Y., Honzatko, P., and Kasik, I., "Enhanced pump absorption efficiency in coiled and twisted double-clad thulium-doped Fibers," Opt. Express, vol. 24, no. 1, pp. 102-107 (2016).
-
Numerical Modeling of Pump Absorption in Coiled and Twisted Double-Clad Fibers
IEEE Journal of Selected Topics in Quantum Electronics, 2016Co-Authors: Pavel Koška, Pavel Peterka, Valérie DoyaAbstract:We report the analysis of multimode pump absorption in double-clad Rare-Earth-Doped Fibers under realistic bending conditions. The finite-element beam-propagation method is used for the analysis. The fiber bending is approximated by the transformation of the refractive index profile of the fiber. Double-clad Fibers of hexagonal, circular and stadium-like cross-sections are studied as examples. In addition, the double-clad waveguide structure of a two-fiber bundle is investigated. Simulations show that the bending effects cannot be neglected in double-clad fiber multimode pump propagation analysis and optimization. The reported rigorous numerical model opens new way to design double-clad Fibers and to optimize the pump absorption efficiency. We show that high pump-absorption efficiency better than the ideal (ergodic) limit, can be achieved by simultaneous coiling and twisting of the double-clad fiber.
-
Numerical modeling of pump absorption in coiled and twisted double-clad Fibers
IEEE Journal of Selected Topics in Quantum Electronics, 2015Co-Authors: Pavel Koška, Pavel Peterka, Valérie DoyaAbstract:We report the analysis of multimode pump absorption in double-clad Rare-Earth-Doped Fibers under realistic bending conditions. The finite-element beam-propagation method is used for the analysis. The fiber bending is approximated by the transformation of the refractive index profile of the fiber. Double-clad Fibers of hexagonal, circular and stadium-like cross-sections are studied as examples. In addition, the double-clad waveguide structure of a two-fiber bundle is investigated. Simulations show that the bending effects cannot be neglected in double-clad fiber multimode pump propagation analysis and optimization. The reported rigorous numerical model opens new way to design double-clad Fibers and to optimize the pump absorption efficiency. We show that high pump-absorption efficiency better than the ideal (ergodic) limit, can be achieved by simultaneous coiling and twisting of the double-clad fiber. Index Terms—double-clad optical Fibers, optical pumping, fiber lasers, fiber amplifiers, finite element method, beam propagation method
Michalis N. Zervas - One of the best experts on this subject based on the ideXlab platform.
-
Yb3+-doped silica WGM milled microrod laser
2015 Conference on Lasers and Electro-Optics (CLEO), 2015Co-Authors: Shahab Bakhtiari Gorajoobi, Ganapathy Senthil Murugan, Michalis N. ZervasAbstract:A fast and versatile fabrication method for high Q milled microrod resonators, directly on Rare-earth doped Fibers, is demonstrated using a pulsed CO2 laser. Evanescently pumped WGM microlaser with ~9μW output power has been achieved.
-
Yb 3+ -doped silica WGM milled microrod laser
CLEO: 2015, 2015Co-Authors: Shahab Bakhtiari Gorajoobi, Ganapathy Senthil Murugan, Michalis N. ZervasAbstract:A fast and versatile fabrication method for high Q milled microrod resonators, directly on Rare-earth doped Fibers, is demonstrated using a pulsed CO 2 laser. Evanescently pumped WGM microlaser with ∼9μW output power has been achieved.
Lei Xu - One of the best experts on this subject based on the ideXlab platform.
-
Optical Properties and Laser Output of Heavily Yb-Doped Fiber Prepared by Sol-Gel Method and DC-RTA Technique
Journal of Lightwave Technology, 2008Co-Authors: Yigang Li, Jianping Huang, Yingfeng Li, Hao Li, Yaoji He, Shaoyi Gu, Guanghui Chen, Lei XuAbstract:Heavily Yb-doped (14300 ppm) preforms and Fibers were prepared by the sol-gel method and dip coating-rapid thermal annealing technique. Optical properties of these preforms and Fibers were measured and discussed. A fiber laser at a 1053-nm wavelength was realized and its slope efficiency was measured to be 88.4%. The excellent performance of the fiber laser and repeatability show that the novel approach described in this paper is capable of providing low-cost high-level Rare Earth-Doped Fibers for amplifiers and fiber lasers.
Pavel Koška - One of the best experts on this subject based on the ideXlab platform.
-
Enhancement of pump absorption efficiency by bending and twisting of double clad Rare earth doped Fibers (Conference Presentation)
Proceedings of SPIE, 2017Co-Authors: Pavel Koška, Pavel Peterka, Valérie Doya, Jan Aubrecht, Ivan Kasik, Ondřej PodrazkýAbstract:High-power operation of fiber lasers was enabled by the invention of cladding-pumping in a double-clad fiber structure. Because of existence of so called skew rays in the inner clad of the fiber, pump absorption saturates along the fiber and pumping becomes inefficient. First studies of pump absorption efficiency enhancement were focused on Fibers with broken circular symmetry of inner cladding eliminating skew rays [1,2]. Later, techniques of unconventional fiber coiling were proposed [3]. However, theoretical studies were limited to the assumption of a straight fiber. Even recently, the rigorous model accounting for fiber bending and twisting was described [4-6]. It was found that bending of the fiber influences modal spectra of the pump radiation and twisting provides quite efficient mode-scrambling. These effects in a synergic manner significantly enhances pump absorption rate in double clad Fibers and improves laser system efficiency. In our contribution we review results of numerical modelling of pump absorption in various types of double-clad Fibers, e.g., with cross section shape of hexagon, stadium, and circle; two-fiber bundle (so-called GTWave fiber structure) a panda Fibers are also analyzed. We investigate pump field modal spectra evolution in hexagonally shaped fiber in straight, bended, and simultaneously bended and twisted fiber which brings new quality to understanding of the mode-scrambling and pump absorption enhancement. Finally, we evaluate the impact of enhanced pump absorption on signal gain in the fiber. These results can have practical impact in construction of fiber lasers: with pump absorption efficiency optimized by our new model (the other models did not take into account fiber twist), the double-clad fiber of shorter length can be used in the fiber lasers and amplifiers. In such a way the harmful influence of background losses and nonlinear effects can be minimized. [1] Doya, V., Legrand, O., Mortessagne, F., “Optimized absorption in a chaotic double-clad fiber amplifier,” Opt. Lett., vol. 26, no. 12, pp. 872-874, (2001). [2] Kouznetsov, D., Moloney, J. V., “Efficiency of pump absorption in double-clad fiber amplifiers. II. Broken circular symmetry,” J. Opt. Soc. Am. B, vol. 19, no. 6, pp. 1259-1263, June 2002. [3] Li, Y., Jackson, S. D., Fleming, S., “High absorption and low splice loss properties of hexagonal double-clad fiber,” IEEE Photonics Technol. Lett., vol 16, no. 11, pp. 2502-2504, Nov. 2004. [4] Koska, P. and Peterka, P., "Numerical analysis of pump propagation and absorption in specially tailored double-clad Rare-earth doped fiber," Optical and Quantum Electronics, vol. 47, no. 9, pp. 3181-3191 (2015). [5] Koska, P., Peterka, P., and Doya, V., “Numerical modeling of pump absorption in coiled and twisted double-clad Fibers,” IEEE J. Sel. Top. Quantum Electron., vol. 22, no. 2 (2016). [6] Koska, P., Peterka, P., Aubrecht, J., Podrazký, O., Todorov, F., Becker, M., Baravets, Y., Honzatko, P., and Kasik, I., "Enhanced pump absorption efficiency in coiled and twisted double-clad thulium-doped Fibers," Opt. Express, vol. 24, no. 1, pp. 102-107 (2016).
-
Numerical Modeling of Pump Absorption in Coiled and Twisted Double-Clad Fibers
IEEE Journal of Selected Topics in Quantum Electronics, 2016Co-Authors: Pavel Koška, Pavel Peterka, Valérie DoyaAbstract:We report the analysis of multimode pump absorption in double-clad Rare-Earth-Doped Fibers under realistic bending conditions. The finite-element beam-propagation method is used for the analysis. The fiber bending is approximated by the transformation of the refractive index profile of the fiber. Double-clad Fibers of hexagonal, circular and stadium-like cross-sections are studied as examples. In addition, the double-clad waveguide structure of a two-fiber bundle is investigated. Simulations show that the bending effects cannot be neglected in double-clad fiber multimode pump propagation analysis and optimization. The reported rigorous numerical model opens new way to design double-clad Fibers and to optimize the pump absorption efficiency. We show that high pump-absorption efficiency better than the ideal (ergodic) limit, can be achieved by simultaneous coiling and twisting of the double-clad fiber.
-
Numerical modeling of pump absorption in coiled and twisted double-clad Fibers
IEEE Journal of Selected Topics in Quantum Electronics, 2015Co-Authors: Pavel Koška, Pavel Peterka, Valérie DoyaAbstract:We report the analysis of multimode pump absorption in double-clad Rare-Earth-Doped Fibers under realistic bending conditions. The finite-element beam-propagation method is used for the analysis. The fiber bending is approximated by the transformation of the refractive index profile of the fiber. Double-clad Fibers of hexagonal, circular and stadium-like cross-sections are studied as examples. In addition, the double-clad waveguide structure of a two-fiber bundle is investigated. Simulations show that the bending effects cannot be neglected in double-clad fiber multimode pump propagation analysis and optimization. The reported rigorous numerical model opens new way to design double-clad Fibers and to optimize the pump absorption efficiency. We show that high pump-absorption efficiency better than the ideal (ergodic) limit, can be achieved by simultaneous coiling and twisting of the double-clad fiber. Index Terms—double-clad optical Fibers, optical pumping, fiber lasers, fiber amplifiers, finite element method, beam propagation method
R. Oron - One of the best experts on this subject based on the ideXlab platform.
-
Amplified spontaneous emission and Rayleigh backscattering in strongly pumped fiber amplifiers
Journal of Lightwave Technology, 1998Co-Authors: A.a. Hardy, R. OronAbstract:Amplified spontaneous emission (ASE) and Rayleigh backscattering (RBS) in strongly pumped fiber amplifiers are studied, employing a rate equation model. Approximate expressions for the ASE and RES, as well as for the amplifier noise figure are derived, based on approximate analytical expressions for the amplified signal, which are valid for both three-level and four-level systems. Numerical examples for Rare-Earth-Doped Fibers, show good agreement between these approximate expressions and the exact numerical solutions for strong pumping and for injected signals which are not too weak.
-
Signal amplification in strongly pumped fiber amplifiers
IEEE Journal of Quantum Electronics, 1997Co-Authors: A. Hardy, R. OronAbstract:Signal amplification is analyzed in strongly pumped fiber amplifiers both for three-level and four-level transitions, including scattering loss and excited state absorption. Simple analytic expressions are derived for the signal amplification and pump attenuation, along the fiber length, when either the signal and the pump are injected at the same fiber end (forward pumping) or when they are injected at the two opposite ends (backward pumping). Numerical examples for Rare-earth doped Fibers show excellent agreement between the analytical solution and the exact numerical solutions of the rate-equations for practical operating conditions.
