Abstract

We demonstrated the successful combination and cleanup of four laser beams via stimulated Raman scattering (SRS) using a multi-port fiber combiner and a large multimode fiber. Multiple Stokes orders were observed in the output, but loss at longer wavelengths reduced the transmission of the higher Stokes orders and limited the SRS conversion efficiency. SRS beam cleanup was also investigated using a single laser beam. The output beam had a measured M 2 better than 2 for fiber lengths from 400–1400 meters.

© 2006 Optical Society of America

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References

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  1. H. J. Eichler, A. Haase and O. Mehl, in High Power Lasers-Science and Engineering, R. Kossowsky, M. Jelinek, and R. F. Walter, eds., (Kluwer Academic Publishers, Boston, 1996), p. 241.
  2. T. Y. Fan, "Laser Beam Combining for High-Power, High-Radiance Sources," IEEE J. Sel. Top. Quantum Electron. 11, 567-577 (2005).
    [CrossRef]
  3. K. S. Chiang, "Stimulated Raman scattering in a multimode optical fiber:evolution of modes in Stokes waves," Opt. Lett. 17, 352-354 (1992).
    [CrossRef] [PubMed]
  4. J. T. Murray, W. L. Austin, and R. C. Powell, "Intracavity Raman conversion and Raman beam cleanup," Opt. Mater. 11, 353-371 (1999).
    [CrossRef]
  5. T. H. Russell, S. M. Willis, M. B. Crookston, and W. B. Roh, "Stimulated Raman scattering in multimode fibers and its application to beam cleanup and combining," J. Nonlinear Opt. Phys. Mater. 11,303-316 (2002).
    [CrossRef]
  6. S. H. Baek, and W. B. Roh, "Single-mode Raman fiber laser based on a multimode fiber," Opt. Lett 29, 153-155 (2004).
    [CrossRef] [PubMed]
  7. C. A. Codemard, P. Dupriez, Y. Jeong, J. K. Sahu, M. Ibsen, and J. Nilsson, "High-power continuous-wave cladding-pumped Raman fiber laser," Opt. Lett. 31, 2290-2292 (2006).
    [CrossRef] [PubMed]
  8. G. P. Agrawal, Nonlinear Fiber Optics (Academic Press, New York, 2001).
  9. L. Lombard, A. Brignon, J. P. Huignard, E. Lallier and P. Georges, "Beam cleanup in a self-aligned gradient-index Brillouin cavity for high-power multimode fiber amplifiers," Opt. Lett. 31, 158-160 (2006).
    [CrossRef] [PubMed]

2006

2005

T. Y. Fan, "Laser Beam Combining for High-Power, High-Radiance Sources," IEEE J. Sel. Top. Quantum Electron. 11, 567-577 (2005).
[CrossRef]

2004

S. H. Baek, and W. B. Roh, "Single-mode Raman fiber laser based on a multimode fiber," Opt. Lett 29, 153-155 (2004).
[CrossRef] [PubMed]

2002

T. H. Russell, S. M. Willis, M. B. Crookston, and W. B. Roh, "Stimulated Raman scattering in multimode fibers and its application to beam cleanup and combining," J. Nonlinear Opt. Phys. Mater. 11,303-316 (2002).
[CrossRef]

1999

J. T. Murray, W. L. Austin, and R. C. Powell, "Intracavity Raman conversion and Raman beam cleanup," Opt. Mater. 11, 353-371 (1999).
[CrossRef]

1992

Austin, W. L.

J. T. Murray, W. L. Austin, and R. C. Powell, "Intracavity Raman conversion and Raman beam cleanup," Opt. Mater. 11, 353-371 (1999).
[CrossRef]

Baek, S. H.

S. H. Baek, and W. B. Roh, "Single-mode Raman fiber laser based on a multimode fiber," Opt. Lett 29, 153-155 (2004).
[CrossRef] [PubMed]

Brignon, A.

Chiang, K. S.

Codemard, C. A.

Crookston, M. B.

T. H. Russell, S. M. Willis, M. B. Crookston, and W. B. Roh, "Stimulated Raman scattering in multimode fibers and its application to beam cleanup and combining," J. Nonlinear Opt. Phys. Mater. 11,303-316 (2002).
[CrossRef]

Dupriez, P.

Fan, T. Y.

T. Y. Fan, "Laser Beam Combining for High-Power, High-Radiance Sources," IEEE J. Sel. Top. Quantum Electron. 11, 567-577 (2005).
[CrossRef]

Georges, P.

Huignard, J. P.

Ibsen, M.

Jeong, Y.

Lallier, E.

Lombard, L.

Murray, J. T.

J. T. Murray, W. L. Austin, and R. C. Powell, "Intracavity Raman conversion and Raman beam cleanup," Opt. Mater. 11, 353-371 (1999).
[CrossRef]

Nilsson, J.

Powell, R. C.

J. T. Murray, W. L. Austin, and R. C. Powell, "Intracavity Raman conversion and Raman beam cleanup," Opt. Mater. 11, 353-371 (1999).
[CrossRef]

Roh, W. B.

S. H. Baek, and W. B. Roh, "Single-mode Raman fiber laser based on a multimode fiber," Opt. Lett 29, 153-155 (2004).
[CrossRef] [PubMed]

T. H. Russell, S. M. Willis, M. B. Crookston, and W. B. Roh, "Stimulated Raman scattering in multimode fibers and its application to beam cleanup and combining," J. Nonlinear Opt. Phys. Mater. 11,303-316 (2002).
[CrossRef]

Russell, T. H.

T. H. Russell, S. M. Willis, M. B. Crookston, and W. B. Roh, "Stimulated Raman scattering in multimode fibers and its application to beam cleanup and combining," J. Nonlinear Opt. Phys. Mater. 11,303-316 (2002).
[CrossRef]

Sahu, J. K.

Willis, S. M.

T. H. Russell, S. M. Willis, M. B. Crookston, and W. B. Roh, "Stimulated Raman scattering in multimode fibers and its application to beam cleanup and combining," J. Nonlinear Opt. Phys. Mater. 11,303-316 (2002).
[CrossRef]

IEEE J. Sel. Top. Quantum Electron.

T. Y. Fan, "Laser Beam Combining for High-Power, High-Radiance Sources," IEEE J. Sel. Top. Quantum Electron. 11, 567-577 (2005).
[CrossRef]

J. Nonlinear Opt. Phys. Mater.

T. H. Russell, S. M. Willis, M. B. Crookston, and W. B. Roh, "Stimulated Raman scattering in multimode fibers and its application to beam cleanup and combining," J. Nonlinear Opt. Phys. Mater. 11,303-316 (2002).
[CrossRef]

Opt. Lett

S. H. Baek, and W. B. Roh, "Single-mode Raman fiber laser based on a multimode fiber," Opt. Lett 29, 153-155 (2004).
[CrossRef] [PubMed]

Opt. Lett.

Opt. Mater.

J. T. Murray, W. L. Austin, and R. C. Powell, "Intracavity Raman conversion and Raman beam cleanup," Opt. Mater. 11, 353-371 (1999).
[CrossRef]

Other

H. J. Eichler, A. Haase and O. Mehl, in High Power Lasers-Science and Engineering, R. Kossowsky, M. Jelinek, and R. F. Walter, eds., (Kluwer Academic Publishers, Boston, 1996), p. 241.

G. P. Agrawal, Nonlinear Fiber Optics (Academic Press, New York, 2001).

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Figures (8)

Fig. 1.
Fig. 1.

Experimental setup to demonstrate four channel beam combination and cleanup.

Fig. 2.
Fig. 2.

Experimental setup for observing beam cleanup in 100 um core size fiber.

Fig. 3.
Fig. 3.

Beam combination as demonstrated by pictures observed in the focal plane of a 175 mm lens of transmitted pump and generated Stokes beams from both 100 µm and 200 µm fibers. From top left: (a) 100 µm pump beam, M 2=26.10 (b) 100 µm Stokes beam, M 2=2.64 (c) 200 µm pump beam, M 2=42.10 (d) 200 µm Stokes beam, M 2=2.75

Fig. 4.
Fig. 4.

Stokes percent conversion as a function of coupled pump energy for 100 µm fiber (diamonds) and 200 µm fiber (squares).

Fig. 5.
Fig. 5.

Spectrum analyzer sweeps from 1050 nm to 1500 nm demonstrating fiber attenuation of higher Stokes orders. For all graphs, wavelength is displayed on the horizontal axis, while the vertical axis is a relative intensity measurement. (a) At 25 µJ per pulse, the Stokes threshold has been reached. The pump beam is shown at 1064 nm and the 1st order Stokes beam is present at 1116.5 nm. (b) At 35 µJ per pulse, the effects of four-wave mixing become apparent, with three well defined Stokes orders, and hints of a fourth and fifth order. (c) At 90 µJ per pulse, the higher attenuation of the fiber at longer wavelengths is shown, as the fifth and sixth Stokes orders are generated, but remain very low in intensity. (d) At 150 µJ per pulse, the relative intensities of the higher Stokes orders are almost unchanged from the sweep shown in (c).

Fig. 6.
Fig. 6.

Generated Stokes energy in 100 µm fiber (diamonds) and 200 µm fiber (squares) as a function of pump energy coupled into the fiber.

Fig. 7.
Fig. 7.

M2 value of the generated Stokes beam as a function of 100 µm core size fiber length. M2 values were calculated for a diode pump current on the Nd:YAG pump laser of 12.9 A (diamonds) and two times above the Stokes threshold (squares).

Fig. 8.
Fig. 8.

Far field pictures of generated Stokes beam output from 100 µm fiber as a function of length. Pictures were all taken at a pump energy two times above the Stokes threshold. From top left: (a) 1300 m, M 2=1.58 (b) 1000 m, M 2=1.84 (c) 700 m, M 2=1.60 (d) 200 m, M 2=1.85.

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