Abstract

We propose a novel approach of making large effective area laser fiber with higher threshold for the stimulated Brillouin scattering (SBS) using Al/Ge co-doping in the fiber core. The increased SBS threshold is achieved by reducing the acoustic-optic overlap integral while keeping the optical refractive index profile with a step structure. The manipulation of the overlap integral is done by adjusting the relative doping level between Al2O3 and GeO2 in the core. The mechanism is validated by detailed examples of numerical modeling. An Yb-doped double clad fiber with the core co-doped with Al2O3 and GeO2 was fabricated by the OVD process. Measured acoustic velocity profile using a scanning acoustic microscope verified that the acoustic velocity in the fiber core changes with the design. An amplifier utilizing the fiber demonstrated that the proposed fiber yielded 6 dB higher SBS threshold than a fiber without using the co-doping scheme.

© 2007 Optical Society of America

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References

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  2. N. G. R. Broderick, H. L. Offerhaus, D. J. Richardson, R. A. Sammut, J. Caplen, and L. Dong, "Large mode area fibers for high power applications," Opt. Fiber Technol. 5, 185-196 (1999).
    [CrossRef]
  3. J. M. Fini, "Bend-resistant design of conventional and microstructure fibers with very large mode area," Optics Express 14, 69-81 (2006).
    [CrossRef] [PubMed]
  4. M.-J. Li, X. Chen, J. Wang, A. Liu, S. Gray, D. T. Walton, A. B. Ruffin, J. Demeritt, and L. Zenteno, "Fiber designs for higher power lasers," Proc. SPIE 6469, 64690H (2007).
    [CrossRef]
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    [CrossRef] [PubMed]
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    [CrossRef]
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    [CrossRef]
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    [CrossRef]
  9. P. D. Dragic, C. H. Liu, G. C. Papen, and A. Galvanauskas, "Optical Fiber with an acoustic guiding layer for Stimulated Brillouin Scattering Suppression," CLEO’2005, paper CThZ3, 2005.
  10. S. Gray, D. Walton, J. Wang, M.-J. Li, X. Chen, B. Ruffin, J. Demeritt, L. Zenteno, "High power, narrow linewidth fiber amplifiers, Optical Amplifiers and Applications 2006," Paper OSu B1, Whistler, BC, June 25-28, (2006).
  11. H. Yoda, P. Polynkin, and M. Mansuripur, "Beam quality factor of higher order modes in a Step-Index Fiber," J. Lightwave Technol. 24, 1350-1355 (2006).
    [CrossRef]
  12. S. Gray, D. T. Walton, J. Wang, A. Liu, M.-J. Li, X. Chen, A. Boh Ruffin, J. A. DeMeritt and L. A. Zenteno, "502 Watt, single transverse mode, narrow linewidth, bidirectionally pumped Yb-doped fiber amplifier," to be submitted to Opt. Express for publication.
  13. A. Liu, S. Gray, M.-J. Li, X. Chen, J. Wang, J. A. DeMeritt, A. M. Crowley, A. Boh Ruffin, L. A. Zenteno, and D. T. Walton, "SBS-suppressive fiber based single frequency amplifier and its potential for kW output," to be submitted to Opt. Lett.

2007

M.-J. Li, X. Chen, J. Wang, A. Liu, S. Gray, D. T. Walton, A. B. Ruffin, J. Demeritt, and L. Zenteno, "Fiber designs for higher power lasers," Proc. SPIE 6469, 64690H (2007).
[CrossRef]

2006

J. M. Fini, "Bend-resistant design of conventional and microstructure fibers with very large mode area," Optics Express 14, 69-81 (2006).
[CrossRef] [PubMed]

H. Yoda, P. Polynkin, and M. Mansuripur, "Beam quality factor of higher order modes in a Step-Index Fiber," J. Lightwave Technol. 24, 1350-1355 (2006).
[CrossRef]

2005

2004

1999

N. G. R. Broderick, H. L. Offerhaus, D. J. Richardson, R. A. Sammut, J. Caplen, and L. Dong, "Large mode area fibers for high power applications," Opt. Fiber Technol. 5, 185-196 (1999).
[CrossRef]

1988

C. K. Jen, J. E. B. Oliveira, N. Goto, and K. Abe, "Role of guided acoustic wave properties in single-mode optical fiber design," Electron. Lett. 24, 1419-1420 (1988).
[CrossRef]

Electron. Lett.

C. K. Jen, J. E. B. Oliveira, N. Goto, and K. Abe, "Role of guided acoustic wave properties in single-mode optical fiber design," Electron. Lett. 24, 1419-1420 (1988).
[CrossRef]

J. Lightwave Technol.

Opt. Express

Opt. Fiber Technol.

N. G. R. Broderick, H. L. Offerhaus, D. J. Richardson, R. A. Sammut, J. Caplen, and L. Dong, "Large mode area fibers for high power applications," Opt. Fiber Technol. 5, 185-196 (1999).
[CrossRef]

Opt. Lett.

Optics Express

J. M. Fini, "Bend-resistant design of conventional and microstructure fibers with very large mode area," Optics Express 14, 69-81 (2006).
[CrossRef] [PubMed]

Proc. SPIE

M.-J. Li, X. Chen, J. Wang, A. Liu, S. Gray, D. T. Walton, A. B. Ruffin, J. Demeritt, and L. Zenteno, "Fiber designs for higher power lasers," Proc. SPIE 6469, 64690H (2007).
[CrossRef]

Other

G. P. Agrawal, Nonlinear Fiber Optics (Academic Press, San Diego, CA, 1989).

P. D. Dragic, C. H. Liu, G. C. Papen, and A. Galvanauskas, "Optical Fiber with an acoustic guiding layer for Stimulated Brillouin Scattering Suppression," CLEO’2005, paper CThZ3, 2005.

S. Gray, D. Walton, J. Wang, M.-J. Li, X. Chen, B. Ruffin, J. Demeritt, L. Zenteno, "High power, narrow linewidth fiber amplifiers, Optical Amplifiers and Applications 2006," Paper OSu B1, Whistler, BC, June 25-28, (2006).

S. Gray, D. T. Walton, J. Wang, A. Liu, M.-J. Li, X. Chen, A. Boh Ruffin, J. A. DeMeritt and L. A. Zenteno, "502 Watt, single transverse mode, narrow linewidth, bidirectionally pumped Yb-doped fiber amplifier," to be submitted to Opt. Express for publication.

A. Liu, S. Gray, M.-J. Li, X. Chen, J. Wang, J. A. DeMeritt, A. M. Crowley, A. Boh Ruffin, L. A. Zenteno, and D. T. Walton, "SBS-suppressive fiber based single frequency amplifier and its potential for kW output," to be submitted to Opt. Lett.

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Figures (7)

Fig. 1.
Fig. 1.

Dopant designs that can reduce the overlap between the optical and acoustic fields

Fig. 2.
Fig. 2.

(a). Optical delta profile of a step index file with core doped with GeO2 only. (b) The fundamental optical field LP01 and the two lowest order acoustic fields.

Fig. 3.
Fig. 3.

(a). Acoustic delta profile of a fiber with more Al2O3 doped in the inner region of the core. (b). Field distributions of the fundamental optical field LP01 and the two lowest order acoustic fields of the fiber with optical delta profile shown in Fig. 2(a) and acoustic delta profile shown in Fig. 3(a).

Fig. 4.
Fig. 4.

(a). Acoustic delta profile of a fiber with more Al2O3 doped in the outer region of the core. (b). Field distributions of the fundamental optical field LP01 and the two lowest order acoustic fields of the fiber with optical delta profile shown in Fig. 2(a) and acoustic delta profile shown in Fig. 4(a).

Fig. 5.
Fig. 5.

(a). The acoustic delta profile when the concentration of Al2O3 is linearly ramped down from the center of the core to the edge of the core. (b) the Schematic of a double clad fiber with Yb, Ge, and Al co-doped in the core.

Fig. 6.
Fig. 6.

Acoustic velocity profile of fiber preform with reduced acousto-optic overlap

Fig. 7.
Fig. 7.

SBS threshold measurements

Tables (2)

Tables Icon

Table 1. Trend of optical and acoustic refractive index change of different dopants in silica

Tables Icon

Table 2. Properties of fibers for SBS threshold measurement

Equations (8)

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P th KA eff α u G ( ν max , L ) I ¯ u ao
I ¯ u ao = ( E 0 E 0 * ρ u * rdrdθ ) 2 ( ( E 0 E 0 * ) 2 rdrdθ ) ( ρ u ρ u * rdrdθ )
d 2 ρ u dr 2 + 1 r u dr + ( Ω u 2 V L 2 ( r ) β u 2 ) ρ u = 0
n a ( r ) = V clad V L ( r )
k a = 2 π λ ( 2 n oeff ) = 2 π λ ,
d 2 f o dr 2 + 1 r df o dr + k o 2 ( n 0 2 ( r ) n o , eff 2 ) f o = 0
d 2 f a dr 2 + 1 r df a dr + k a 2 C ( n a 2 ( r ) n a , eff 2 ) f a = 0
Δ i = n i 2 ( r ) n ic 2 2 n i 2 ( r ) × 100 % i = o , a

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