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Proceedings Paper

Laser beam quality improvement of REPUSIL-based rod amplifier with local short adiabatic taper (Conference Presentation)
Author(s): Yuan Zhu; Martin Lorenz; Tina Eschrich; Martin Leich; Claudia Aichele; Jens Kobelke; Hartmut Bartelt; Matthias Jäger
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Paper Abstract

Fiber amplifiers with a robust monolithic seed coupling and very high peak power in a near diffraction-limited beam are increasingly demanded by many industrial applications in laser materials processing. A tapered all-solid rod-type fiber amplifier scheme is proposed. The principle of this approach is the use of a local adiabatic taper to provide a monolithic signal path and selectively excite the fundamental mode in highly multimode fiber. A large mode area fiber is used to scale up the peak power and suppress the nonlinear effects. The powder-sintering technology (REPUSIL) was employed to achieve rod-type fibers with excellent refractive index homogeneity. In this work, we present a double-clad Yb3+-doped rod-type REPUSIL fiber with a core/clad diameter of 45µm/190µm and a core/clad numerical aperture of 0.09/0.19.This developed fiber has a relatively low Al3+-concentration to reduce diffusion during tapering and an optimized outer cladding material to reduce the taper process temperature. Finally it is demonstrated that the diffusion phenomenon is successfully eliminated and the near-diffraction limited beam quality during the amplification process is maintained. First experiments with improved Yb3+-doped rod-type amplifiers delivered 2ns pulses with peak powers of 210kW for the non-tapered rod and 140kW for the tapered rod (limited by facet damage). For the tapered fiber, the beam quality was between 1.3 and 1.7, significantly improved compared to the beam quality of the non-tapered fiber (M2 = 3.3 ~ 4.5). Future work will concentrate on adopting endcaps to protect the fiber facets from damage while scaling up the peak power.

Paper Details

Date Published: 14 March 2018
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Proc. SPIE 10512, Fiber Lasers XV: Technology and Systems, 105121H (14 March 2018); doi: 10.1117/12.2286895
Show Author Affiliations
Yuan Zhu, Leibniz-Institut für Photonische Technologien e.V. (Germany)
Martin Lorenz, Leibniz-Institut für Photonische Technologien e.V. (Germany)
Tina Eschrich, Leibniz-Institut für Photonische Technologien e.V. (Germany)
Martin Leich, Leibniz-Institut für Photonische Technologien e.V. (Germany)
Claudia Aichele, Leibniz-Institut für Photonische Technologien e.V. (Germany)
Jens Kobelke, Leibniz-Institut für Photonische Technologien e.V. (Germany)
Hartmut Bartelt, Leibniz-Institut für Photonische Technologien e.V. (Germany)
Matthias Jäger, Leibniz-Institut für Photonische Technologien e.V. (Germany)


Published in SPIE Proceedings Vol. 10512:
Fiber Lasers XV: Technology and Systems
Ingmar Hartl; Adrian L. Carter, Editor(s)

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