OSA's Digital Library

Optics Express

Optics Express

  • Editor: Michael Duncan
  • Vol. 14, Iss. 7 — Apr. 3, 2006
  • pp: 2721–2726
« Show journal navigation

High power coherent beam combination from two fiber lasers

Bing He, Qihong Lou, Jun Zhou, Jingxing Dong, Yunrong Wei, Dong Xue, Yunfeng Qi, Zhoupin Su, Libo Li, and Fangpei Zhang  »View Author Affiliations


Optics Express, Vol. 14, Issue 7, pp. 2721-2726 (2006)
http://dx.doi.org/10.1364/OE.14.002721


View Full Text Article

Acrobat PDF (144 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

Phase locking of two fiber lasers is demonstrated experimentally by the use of a self-imaging resonator with a spatial filter. The high-contrast interference strips of the coherent beam profile are observed. The coherent output power of the fiber array exceeds 12W and the efficiency of coherent power combination is 88% with pump power of 60W. The whole system operates quite stably and, for the spatial filter, no thermal effects have been observed, which means that we can increase the coherent output power further by this method.

© 2006 Optical Society of America

1. Introduction

Recently, the output power of a single fiber laser has been improved rapidly and has exceeded kilowatt magnitude [1

1. G. Bonati, H. Voelckel, T. Gabler, U. Krause, A. Tünnermann, J. Limpert, A. Liem, T. Schreiber, S. Nolte, and H. Zellmer, “1.53 kW from a single Yb-doped photonic crystal fiber laser,” in Photonics West, San Jose, Late Breaking Developments, Session 5709–2a (2005).

,2

2. Y. Jeong, J. K. Sahu, D. N. 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/abstract.cfm?URI=oe-12-25-6088. [CrossRef] [PubMed]

]. However, the ultimate output from a single fiber laser is limited by the nonlinear effects such as stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS). Beam combination is an effective geometry which can improve output power with excellent beam quality. At present, many researchers have brought up various techniques of beam combination, including the Master-Oscillator-Power-Amplifier arrangement (MOPA) [3

3. M. K. Culpepper, “Coherent combination of fiber laser beams,” in Laser Resonators and Beam Contorl V, Alexis and V. Kudryashov, Editor, Proc. SPIE , 4629, 99–108 (2002). [CrossRef]

,4

4. M. Wicknham, J. Anderegg, S. Brosnan, D. Hammons, H. Komine, and M. Weber, “Coherently coupled high power fiber arrays,” in Advanced Solid State Photonics, Santa Fe, USA, February 1–4, 2004, paper MA4.

], the self-organization mechanism in a multicore fiber laser array [5

5. P. K. cheo, A. Liu, and G. G. King, “A High-Brightness laser beam from a Phase-Locked multicore Yb-Doped fiber laser Array,” IEEE Photonics Technol. Lett. 13, 439–441 (2001). [CrossRef]

,6

6. E. J. Bochove, P. K. cheo, and G. G. King, “Self-organization in a multicore fiber laser array,” Opt. Lett. 28, 1200–1202 (2003). [CrossRef] [PubMed]

], the all-fiber coherent beam combining technique [7–11

7. V. A. Kozlov, J. Henandez-Cordero, and T. F. Morse, “All-fiber coherent beam combining of fiber lasers,” Opt. Lett. 24, 1814–1816 (1999). [CrossRef]

], the self-Fourier (S-F) resonators [12

12. C. J. Corcoran and K. A. Pash, “Modal analysis of a self-Fourier laser cavity,” J. Opt. A: Pure Appl. Opt. 7, L1–L7 (2005). [CrossRef]

,13

13. C. J. Corcoran and F. Durville, “Experimental demonstration of a phase-locked laser arry using a self-Fourier cavity,” Appl. Phys. Lett. 86, 201118–1–201118–3 (2005). [CrossRef]

], etc.. The MOPA system, making use of active phase correction, involves complicated interferometric detection and phase modulation of each fiber laser of the array. The self-organization of a multicore fiber array and the all-fiber coherent beam combining can’t actually avoid the ultimate power limitation of a single fiber and the fabrication of a multicore fiber involves very complicated processings. Because the principle of the S-F resonator is the same as Talbot cavity, it involves complicated and rapidly evolving field amplitudes and wavefronts and can’t operate in single-mode. For various operation mediums such as Nd:YVO4 and Nd:YAG, beams coherent addition of laser arrays has been demonstrated by the use of self-image resonator [14

14. S. Ménard, M. Vampouille, B. Colombeau, and C. Froehly, “ Highly efficient phase locking and extracavity coherent combination of two diode-pumped Nd:YAG laser beams,” Opt. Lett. 21, 1996–1998 (1996). [CrossRef] [PubMed]

,15

15. Y. Zhou, L. Liu, C. Etson, Y. Abranyos, A. Padilla, and Y. C. Chen, “Phase locking of a two-dimensional laser array by controlling the far-field pattern,” Appl. Phys. Lett. 84, 3025–3027 (2004). [CrossRef]

]. Fiber laser arrays with self-imaging resonator have been realized under low power condition [16

16. Q. Peng, Y. Zhou, Y. Chen, Z. Sun, Y. Bo, X. Yang, Z. Xu, Y. Wang, K. Li, and W. Zhao, “Phase locking of fibre lasers by self-imaging resonator,” Electron. Lett. 41, 171–173 (2005). [CrossRef]

,17

17. L. Liu, Y. Zhou, F. Kong, and Y. C. Chen, “Phase locking in a fiber laser array with varying path lengths,” Appl. Phys. Lett. 85, 4837–4839 (2004). [CrossRef]

]. In this method, phase correction of fiber lasers is passive, which is realized by means of self-adjusting process of the resonance frequencies of fiber lasers array to adapt to changes in the optical path lengths. Using this method, a number of fiber lasers with different lengths are coupled into a common self-imaging resonator with a spatial filter for phase locking. Generally speaking, the self-adjusting process does not easily occur, but performs best in laser systems with broad gain bandwidth, long and unequal lengths, and low-Q resonator. Fortunately, the fiber lasers array occupies these favored conditions. Therefore, this method allows a large number of longitude modes for mode-selecting and does not have to use single-mode fiber lasers. Furthermore, this method does not need polarization controlling of each fiber laser beam, because a polarization eigen state can always be fund in the two elements system regardless of relative orientation.

In this paper, we demonstrate experimentally phase locking of two fiber lasers via a self-imaging resonator with a spatial filter for mode selecting. The patterns of the beam profile at the output mirror exhibits the high-contrast interference strips. Even if the individual laser optic length changes, these strips are still in the state of relative stability. By using the time-independent steady-state rate equations, we have studied the distinction of the slope efficiency between two fiber lasers and obtain the optimum length for the Yb-doped double-cladding fiber. For pump power of 60W, the coherent output power of 12.3W is obtained and corresponding coherent power combination efficiency is as high as 88%. This is up to now the highest output power with the same method. The experiment shows that this method is a potential approach to high power beam combination.

2. Experiment setup

By using the self-imaging resonator with a spatial filter, the phase-locking of two fiber lasers with different fiber lengths has been demonstrated under low power level [16

16. Q. Peng, Y. Zhou, Y. Chen, Z. Sun, Y. Bo, X. Yang, Z. Xu, Y. Wang, K. Li, and W. Zhao, “Phase locking of fibre lasers by self-imaging resonator,” Electron. Lett. 41, 171–173 (2005). [CrossRef]

,17

17. L. Liu, Y. Zhou, F. Kong, and Y. C. Chen, “Phase locking in a fiber laser array with varying path lengths,” Appl. Phys. Lett. 85, 4837–4839 (2004). [CrossRef]

]. In Ref [16

16. Q. Peng, Y. Zhou, Y. Chen, Z. Sun, Y. Bo, X. Yang, Z. Xu, Y. Wang, K. Li, and W. Zhao, “Phase locking of fibre lasers by self-imaging resonator,” Electron. Lett. 41, 171–173 (2005). [CrossRef]

,17

17. L. Liu, Y. Zhou, F. Kong, and Y. C. Chen, “Phase locking in a fiber laser array with varying path lengths,” Appl. Phys. Lett. 85, 4837–4839 (2004). [CrossRef]

], the stable interference strips and the modulation of longitudinal modes, which caused by the length difference, are observed. The researchers have found that the self-imaging resonator with a spatial filter appears a self-adjusting process and explained the self-adjusting process in reason by means of selection of common resonances in a compound resonator. The experimental setup, shown in Fig. 1, is the same with that in Ref. [16

16. Q. Peng, Y. Zhou, Y. Chen, Z. Sun, Y. Bo, X. Yang, Z. Xu, Y. Wang, K. Li, and W. Zhao, “Phase locking of fibre lasers by self-imaging resonator,” Electron. Lett. 41, 171–173 (2005). [CrossRef]

,17

17. L. Liu, Y. Zhou, F. Kong, and Y. C. Chen, “Phase locking in a fiber laser array with varying path lengths,” Appl. Phys. Lett. 85, 4837–4839 (2004). [CrossRef]

]. The self-imaging resonator consists of two flat dichroic input mirrors (M1 and M2) with high reflectivity of >99.8% for 1080nm~1150nm and high transmission of ~95% for 975nm, a convergent lens (L3) with focal length f=500mm as Fourier transform lens in this system, and a flat semitransparent output mirror (M3) with 50% transmission at 975nm. It is demonstrated experimentally that M1 and M2 can tolerate high pump power of ~280W [18

18. D. Xue, Q. Lou, J. Zhou, L. Kong, J. Li, and S. Li, “A 110-W fiber laser with homemade double-clad fiber,” Chinese Optics Letters 3, 345–347 (2005).

]. Two 975nm diode lasers are used as pump source in the experiment of phase locking. Two Yb-doped double-clad D-shape fibers with a core diameter of 16μm and a inner clad diameter of 400/450μm for the shorter/longer axis are used as active media. Both the two fibers belong to the same pre-form. The fiber lengths are 18.5m and 13.2m, respectively. The nominal numerical aperture is 0.16 for the core and 0.37 for the inner cladding. The small-signal absorption coefficient is 1.05 dB/m at 975nm and the slope efficiency is ~50% as free-running lasers with the fiber length of 20m. Both CW output and pulse output exceed 100W using this fiber [18

18. D. Xue, Q. Lou, J. Zhou, L. Kong, J. Li, and S. Li, “A 110-W fiber laser with homemade double-clad fiber,” Chinese Optics Letters 3, 345–347 (2005).

,19

19. Q. Lou, J. Zhou, J. Zhu, and Z. Wang, “133 watts high power pulsed fiber laser,” in Cleo-Pacific-Rim, Japan, 11–15 Jul. (2005).

]. M1 and M2 are attached to the input end of fibers, and the other ends of fibers are perpendicularly cleaved with 4% Fresnel reflectivity. Two plano-convex lenses (L1 and L2) with 6.28mm diameter are set on the output end of fibers as the collimators. The beams from fiber ends are expanded to a diameter of 2.56mm. The collimated beams are placed symmetrically about the resonator optical axis on the front focal planes of Fourier transform lens L3, and their center-to-center spacing is 6.3mm. The semitransparent output mirror M3 is set on the back focal panes of L3.

Fig. 1. Schematic diagram of experimental setup.

3. Results and discussion

Fig. 2. Beam pattern of laser array in (a) free running, (b) in-phase modes.
Fig. 3. Output power versus pump power relation of the laser array and the individual laser.

Fig. 4. Output power with different pump powers as a function of fiber length.

When the total pump power rises to 60W, the coherent output power of the phase locking fiber laser array, 12.3W, is obtained, and the coherent power combination is 88%. When the whole system operates under the high power condition, the physical properties of the spatial filter do not change such as glowing, breaking, melting and so on, which means that the filter may tolerate the high power. Therefore, reducing properly the reflectivity of the output mirror (M3), increasing the number of fibers, enhancing the pump power, selecting the optimum length fibers, or optimizing the construct of the resonator, we can improve the coherent output power greatly, which will be done in the future work.

4. Conclusions

We have demonstrated experimentally the phase locking of two fiber lasers by means of a self-imaging resonator and a special spatial filter. The pattern of the coherent beam profile exhibits the steady interference strips. The phase locking is due to a self-adjusting process of the fiber laser array with the long lengths, broad gain bandwidth, and low-Q value. When pump power rise to 60W, the coherent output power of 12.3W is obtained and the coherent power combination is 88%. There is no doubt that the coherent output power can be increased greatly by the same method if we optimize the parameters of the resonator and the fiber laser array.

Acknowledgments

The authors gratefully acknowledge Jinyan Li, Shiyu Li and other colleagues in Fiberhome Telecommunication Tech Co. Ltd for their great endeavor in designing and fabricating the fiber. This work was supported by the 863 Key Program Foundation of China (NO. 2005AA828030) and by the Knowledge Innovation Program of the Chinese Academy of Science.

References and links

1.

G. Bonati, H. Voelckel, T. Gabler, U. Krause, A. Tünnermann, J. Limpert, A. Liem, T. Schreiber, S. Nolte, and H. Zellmer, “1.53 kW from a single Yb-doped photonic crystal fiber laser,” in Photonics West, San Jose, Late Breaking Developments, Session 5709–2a (2005).

2.

Y. Jeong, J. K. Sahu, D. N. 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/abstract.cfm?URI=oe-12-25-6088. [CrossRef] [PubMed]

3.

M. K. Culpepper, “Coherent combination of fiber laser beams,” in Laser Resonators and Beam Contorl V, Alexis and V. Kudryashov, Editor, Proc. SPIE , 4629, 99–108 (2002). [CrossRef]

4.

M. Wicknham, J. Anderegg, S. Brosnan, D. Hammons, H. Komine, and M. Weber, “Coherently coupled high power fiber arrays,” in Advanced Solid State Photonics, Santa Fe, USA, February 1–4, 2004, paper MA4.

5.

P. K. cheo, A. Liu, and G. G. King, “A High-Brightness laser beam from a Phase-Locked multicore Yb-Doped fiber laser Array,” IEEE Photonics Technol. Lett. 13, 439–441 (2001). [CrossRef]

6.

E. J. Bochove, P. K. cheo, and G. G. King, “Self-organization in a multicore fiber laser array,” Opt. Lett. 28, 1200–1202 (2003). [CrossRef] [PubMed]

7.

V. A. Kozlov, J. Henandez-Cordero, and T. F. Morse, “All-fiber coherent beam combining of fiber lasers,” Opt. Lett. 24, 1814–1816 (1999). [CrossRef]

8.

T. B. simpson, A. Gavrielides, and P. Peterson, “Extraction characteristics of a dual fiber compound cavity,” Opt. Express 101060–1073 (2002), http://www.opticsinfobase.org/abstract.cfm?URI=oe-10-20-1060. [PubMed]

9.

D. Sabourdy, V. Kermene, A. Desfarges-Berthelemot, L. Lefort, A. Barthelemy, C. Mahodaux, and D. Pureur, “Power scaling of fibre lasers with all-fibre interferometric cavity,” Electron. Lett. 38, 692–693 (2002). [CrossRef]

10.

D. Sabourdy, V. Kermene, A. Desfarges-Berthelemot, L. Lefort, A. Barthelemy, P. Even, and D. Pureur, “Efficient coherent combining of widely tunable fiber lasers,” Opt. Express , 11, 87–97 (2003), http://www.opticsinfobase.org/abstract.cfm?URI=oe-11-2-87. [CrossRef] [PubMed]

11.

A. Shirakawa, T. Saitou, T. Sekiguchi, and K. Ueda, “Coherent addition of fiber lasers by use of a fiber coupler,” Opt. Express 10, 1167–1172 (2002), http://www.opticsinfobase.org/abstract.cfm?URI=oe-10-21-1167. [PubMed]

12.

C. J. Corcoran and K. A. Pash, “Modal analysis of a self-Fourier laser cavity,” J. Opt. A: Pure Appl. Opt. 7, L1–L7 (2005). [CrossRef]

13.

C. J. Corcoran and F. Durville, “Experimental demonstration of a phase-locked laser arry using a self-Fourier cavity,” Appl. Phys. Lett. 86, 201118–1–201118–3 (2005). [CrossRef]

14.

S. Ménard, M. Vampouille, B. Colombeau, and C. Froehly, “ Highly efficient phase locking and extracavity coherent combination of two diode-pumped Nd:YAG laser beams,” Opt. Lett. 21, 1996–1998 (1996). [CrossRef] [PubMed]

15.

Y. Zhou, L. Liu, C. Etson, Y. Abranyos, A. Padilla, and Y. C. Chen, “Phase locking of a two-dimensional laser array by controlling the far-field pattern,” Appl. Phys. Lett. 84, 3025–3027 (2004). [CrossRef]

16.

Q. Peng, Y. Zhou, Y. Chen, Z. Sun, Y. Bo, X. Yang, Z. Xu, Y. Wang, K. Li, and W. Zhao, “Phase locking of fibre lasers by self-imaging resonator,” Electron. Lett. 41, 171–173 (2005). [CrossRef]

17.

L. Liu, Y. Zhou, F. Kong, and Y. C. Chen, “Phase locking in a fiber laser array with varying path lengths,” Appl. Phys. Lett. 85, 4837–4839 (2004). [CrossRef]

18.

D. Xue, Q. Lou, J. Zhou, L. Kong, J. Li, and S. Li, “A 110-W fiber laser with homemade double-clad fiber,” Chinese Optics Letters 3, 345–347 (2005).

19.

Q. Lou, J. Zhou, J. Zhu, and Z. Wang, “133 watts high power pulsed fiber laser,” in Cleo-Pacific-Rim, Japan, 11–15 Jul. (2005).

20.

I. Kelson and A. A. Hardy, “Strongly pumped fiber lasers,” IEEE J. Quantum Electron. 34, 1570–1577 (1998). [CrossRef]

21.

Z. Wu, G. Chen, X. Wang, Y. Wang, S. Zhao, Y. Ren, W. Zhao, and X. Hou, “Numerical analysis of Yb3+ doped double clad fiber laser,” Acta. Photonic. Sinica. (in Chinese) 31, 332–336 (2002).

OCIS Codes
(070.6110) Fourier optics and signal processing : Spatial filtering
(140.3290) Lasers and laser optics : Laser arrays
(140.3410) Lasers and laser optics : Laser resonators
(140.3510) Lasers and laser optics : Lasers, fiber

ToC Category:
Lasers and Laser Optics

History
Original Manuscript: January 3, 2006
Revised Manuscript: March 21, 2006
Manuscript Accepted: March 25, 2006
Published: April 3, 2006

Citation
Bing He, Qihong Lou, Jun Zhou, Jingxing Dong, Yunrong Wei, Dong Xue, Yunfeng Qi, Zhoupin Su, Libo Li, and Fangpei Zhang, "High power coherent beam combination from two fiber lasers," Opt. Express 14, 2721-2726 (2006)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-14-7-2721


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. G. Bonati, H. Voelckel, T. Gabler, U. Krause, A. Tünnermann, J. Limpert, A. Liem, T. Schreiber, S. Nolte, and H. Zellmer, "1.53 kW from a single Yb-doped photonic crystal fiber laser," in Photonics West, San Jose, Late Breaking Developments, Session 5709-2a (2005).
  2. Y. Jeong, J. K. Sahu, D. N. Payne, 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/abstract.cfm?URI=oe-12-25-6088. [CrossRef] [PubMed]
  3. M. K. Culpepper, "Coherent combination of fiber laser beams," in Laser Resonators and Beam Contorl V, Alexis V. Kudryashov, Editor, Proc. SPIE, 4629, 99-108 (2002). [CrossRef]
  4. M. Wicknham, J. Anderegg, S. Brosnan, D. Hammons, H. Komine and M. Weber, "Coherently coupled high power fiber arrays," in Advanced Solid State Photonics, Santa Fe, USA, February 1-4, 2004, paper MA4.
  5. P. K. cheo, A. Liu, and G. G. King, "A High-Brightness laser beam from a Phase-Locked multicore Yb-Doped fiber laser Array," IEEE Photonics Technol. Lett. 13, 439-441 (2001). [CrossRef]
  6. E. J. Bochove, P. K. cheo, and G. G. King, "Self-organization in a multicore fiber laser array," Opt. Lett. 28, 1200-1202 (2003). [CrossRef] [PubMed]
  7. V. A. Kozlov, J. Henandez-Cordero, and T. F. Morse, "All-fiber coherent beam combining of fiber lasers," Opt. Lett. 24, 1814-1816 (1999). [CrossRef]
  8. T. B. simpson, A. Gavrielides, and P. Peterson, "Extraction characteristics of a dual fiber compound cavity," Opt. Express 101060-1073 (2002), http://www.opticsinfobase.org/abstract.cfm?URI=oe-10-20-1060. [PubMed]
  9. D. Sabourdy, V. Kermene, A. Desfarges-Berthelemot, L. Lefort, A. Barthelemy, C. Mahodaux, and D. Pureur, "Power scaling of fibre lasers with all-fibre interferometric cavity," Electron. Lett. 38, 692-693 (2002). [CrossRef]
  10. D. Sabourdy, V. Kermene, A. Desfarges-Berthelemot, L. Lefort, A. Barthelemy, P. Even, and D. Pureur, "Efficient coherent combining of widely tunable fiber lasers," Opt. Express,  11, 87-97 (2003), http://www.opticsinfobase.org/abstract.cfm?URI=oe-11-2-87. [CrossRef] [PubMed]
  11. A. Shirakawa, T. Saitou, T. Sekiguchi, and K. Ueda, "Coherent addition of fiber lasers by use of a fiber coupler," Opt. Express 10, 1167-1172 (2002), http://www.opticsinfobase.org/abstract.cfm?URI=oe-10-21-1167. [PubMed]
  12. C. J. Corcoran, and K. A. Pash, "Modal analysis of a self-Fourier laser cavity," J. Opt. A: Pure Appl. Opt. 7, L1-L7 (2005). [CrossRef]
  13. C. J. Corcoran, and F. Durville, "Experimental demonstration of a phase-locked laser arry using a self-Fourier cavity," Appl. Phys. Lett. 86, 20111812011183 (2005). [CrossRef]
  14. S. Ménard, M. Vampouille, B. Colombeau, and C. Froehly, " Highly efficient phase locking and extracavity coherent combination of two diode-pumped Nd:YAG laser beams," Opt. Lett. 21, 1996-1998 (1996). [CrossRef] [PubMed]
  15. Y. Zhou, L. Liu, C. Etson, Y. Abranyos, A. Padilla, and Y. C. Chen, "Phase locking of a two-dimensional laser array by controlling the far-field pattern," Appl. Phys. Lett. 84, 3025-3027 (2004). [CrossRef]
  16. Q. Peng, Y. Zhou, Y. Chen, Z. Sun, Y. Bo, X. Yang, Z. Xu, Y. Wang, K. Li, and W. Zhao, "Phase locking of fibre lasers by self-imaging resonator," Electron. Lett. 41, 171-173 (2005). [CrossRef]
  17. L. Liu, Y. Zhou, F. Kong, and Y. C. Chen, "Phase locking in a fiber laser array with varying path lengths," Appl. Phys. Lett. 85, 4837-4839 (2004). [CrossRef]
  18. D. Xue, Q. Lou, J. Zhou, L. Kong, J. Li, and S. Li, "A 110-W fiber laser with homemade double-clad fiber," Chinese Optics Letters 3, 345-347 (2005).
  19. Q. Lou, J. Zhou, J. Zhu, and Z. Wang, "133 watts high power pulsed fiber laser," in Cleo-Pacific-Rim, Japan, 11-15 Jul. (2005).
  20. I. Kelson and A. A. Hardy, "Strongly pumped fiber lasers," IEEE J. Quantum Electron. 34, 1570-1577 (1998). [CrossRef]
  21. Z. Wu, G. Chen, X. Wang, Y. Wang, S. Zhao, Y. Ren, W. Zhao, and X. Hou, "Numerical analysis of Yb3+ doped double clad fiber laser," Acta. Photonic. Sinica.(in Chinese) 31, 332-336 (2002).

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

Figures

Fig. 1. Fig. 2. Fig. 3.
 
Fig. 4.
 

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited