Abstract

Pump propagation and absorption in active tapered double-clad fiber has been analyzed based on a ray optics approach. Optimization of the longitudinal shape, absorption and angular distribution of the pump beam allowed for power scaling of a ytterbium fiber laser up to 600 W with high beam quality (M2≤1.08) and a slope efficiency of 63%. It is shown that the influence of vignetting in a tapered fiber can be avoided, resulting in high overall efficiency, in good agreement with the presented model.

© 2009 Optical Society of America

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References

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  1. www.ipgphotonics.com
  2. S. Gray, A. Liu, D. T. Walton, J. Wang, M. Li, X. Chen, A. B. Ruffin, J. A. DeMeritt, and L. A. Zenteno, "502 Watt, single transverse mode, narrow linewidth, bidirectionally pumped Yb-doped fiber amplifier," Opt. Express 15, 17044-17050 (2007), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-25-17044.
    [CrossRef] [PubMed]
  3. Y. Jeong, J. Sahu, D. Payne, and J. Nilsson, "Ytterbium-doped large-core fiber laser with 1.36 kW continuous-wave output power," Opt. Express 12, 6088-6092 (2004), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-12-25-6088.
    [CrossRef] [PubMed]
  4. G. Bonati, H. Voelckel, T. Gabler, U. Krause, A. Tunnermann, J. Limpert, A. Liem, T. Schreiber, S. Nolte and H. Zellmer, "1.53 kW from a single mode Yb-doped crystal fiber laser," Photonics West, Late Breaking Developments, Session 5709-2a (The International Society for Optical Engineering, 2005).
  5. V. Filippov, Y. Chamorovskii, J. Kerttula, K. Golant, M. Pessa, and O. G. Okhotnikov, "Double clad tapered fiber for high power applications," Opt. Express 16, 1929-1944 (2008), http://www.opticsinfobase.org/abstract.cfm?URI=oe-16-3-1929.
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  6. V. Filippov, Y. Chamorovskii, J. Kerttula, A. Kholodkov, and O. G. Okhotnikov, "Single-mode 212 W tapered fiber laser pumped by a low-brightness source," Opt. Lett. 33, 1416-1418 (2008), http://www.opticsinfobase.org/ol/abstract.cfm?URI=ol-33-13-1416.
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  7. V. Filippov, Y. Chamorovskii, J. Kerttula, A. Kholodkov, and O. G. Okhotnikov, "High power tapered ytterbium fiber laser pumped by a low-brightness source," 3rd EPS-QEOD Europhoton Conference on Solid-State, Fiber and Waveguided Light Sources, 31 August - 05 September 2008, Paris (France), Europhysics Conference Abstract vol.32G, ISBN: 2-914771-55-X, paper TUoC.3, p. 33.
  8. N. S. Kapany and J. J. Burke, Optical waveguides (Academic Press, New York, 1972).
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    [CrossRef] [PubMed]

2008

2007

2005

2004

Bennett, C. R.

Broeng, J.

Chamorovskii, Y.

Chen, X.

Deguil-Robin, N.

DeMeritt, J. A.

Filippov, V.

Golant, K.

Gray, S.

Jakobsen, C.

Jeong, Y.

Kerttula, J.

Kholodkov, A.

Li, M.

Liem, A.

Limpert, J.

Liu, A.

Manek-Hönninger, I.

Michaille, L.

Nilsson, J.

Nolte, S.

Okhotnikov, O. G.

Payne, D.

Pessa, M.

Petersson, A.

Röser, F.

Ruffin, A. B.

Sahu, J.

Salin, F.

Schreiber, T.

Shepherd, T. J.

Simonsen, H. R.

Taylor, D. M.

Tünnermann, A.

Walton, D. T.

Wang, J.

Zellmer, H.

Zenteno, L. A.

Opt. Express

Opt. Lett.

Other

V. Filippov, Y. Chamorovskii, J. Kerttula, A. Kholodkov, and O. G. Okhotnikov, "High power tapered ytterbium fiber laser pumped by a low-brightness source," 3rd EPS-QEOD Europhoton Conference on Solid-State, Fiber and Waveguided Light Sources, 31 August - 05 September 2008, Paris (France), Europhysics Conference Abstract vol.32G, ISBN: 2-914771-55-X, paper TUoC.3, p. 33.

N. S. Kapany and J. J. Burke, Optical waveguides (Academic Press, New York, 1972).

V. B. Veinberg and D. K. Sattarov, Waveguide Optics (Mashinostroenie, Leningrad, 1977), Chap.5 (in Russian).

http://www.laserline.de/

G. Bonati, H. Voelckel, T. Gabler, U. Krause, A. Tunnermann, J. Limpert, A. Liem, T. Schreiber, S. Nolte and H. Zellmer, "1.53 kW from a single mode Yb-doped crystal fiber laser," Photonics West, Late Breaking Developments, Session 5709-2a (The International Society for Optical Engineering, 2005).

www.ipgphotonics.com

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Figures (10)

Fig. 1.
Fig. 1.

Ray trajectory in: (a) tapered fiber and (b) cylindrical fiber.

Fig. 2.
Fig. 2.

T-DCF characteristics: (a) clad diameter versus length and (b) image of taper end face.

Fig. 3.
Fig. 3.

Normalized vignetting length (left) and absorption (right) in T-DCF as a function of the launching angle.

Fig. 4.
Fig. 4.

Measured angular power distribution of pump sources with NA=0.15 (a) and NA=0.18 (b) and pump absorption (red curves).

Fig. 5.
Fig. 5.

Pump absorption in T-DCF versus numerical aperture of launched pump beam for actual shape of T-DCF and paraxial ray absorption of 0.2 dB/m (black), 1.2 dB/m (red) and 2 dB/m (blue).

Fig. 6.
Fig. 6.

The experimental setup

Fig. 7.
Fig. 7.

Output characteristics of laser: (a) Output power versus launched pump power. The solid circles correspond to a pump beam with NA=0.15 and the open circles to pump with NA=0.18. (b) Spectrum of output radiation, pump beam with NA=0.15.

Fig. 8.
Fig. 8.

Output beam profile with M2=1.08.

Fig. 9.
Fig. 9.

Shape of the taper: diameter (solid line) and local angle (dashed line) as function of the length; red color – actual T-DCF used in the experiment, blue color – a hypothetical linear T-DCF.

Fig. 10.
Fig. 10.

Pump absorption versus numerical aperture of launched pump beam for linear T-DCF (corresponding to Fig. 9, blue curves) for different paraxial ray absorption, 0.2 dB/m (black curve), 1.2 dB/m (red) and 2 dB/m (blue). The green curve corresponds to the experimental T-DCF.

Equations (14)

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θ = D 1 D 2 2 L
D ( z ) = D 1 2 θ · z ,
α ( z ) = α in n clad + 2 θ · η ( z ) ,
d η = d z D ( z ) t g α ( z ) .
d η t g ( α in n clad + 2 θ . η ) = d z D 1 2 θ · z .
η ( z ) = a sin ( D 1 · sin ( α in n clad ) D 1 2 θ · z ) α in n clad 2 θ .
α ( z ) = a sin ( D 1 · sin ( α in n clad ) D 1 2 θ · z ) .
α = a sin ( D 1 D 2 sin ( α in n clad ) ) = a sin ( T sin ( α in n clad ) ) ,
sin ( α in n clad ) = 1 T · NA n clad ,
α in NA T
α = α in n clad · d 1 d 2 · d 2 d 3 · . · d n 2 d n 1 · d n 1 d n = T · α in n clad ,
( z L ) vgnt = T T 1 ( 1 n core sin ( α in n clad ) NA ) .
P abs = ( P ( α ) P ( α ) exp ( γ L ( α ) ) ) d α P ( α ) d α ,
P vgnt = 1 P abs P unabs

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