OSA's Digital Library

Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 16 — Aug. 12, 2013
  • pp: 19173–19179
« Show journal navigation

Bend compensated large-mode-area fibers: achieving robust single-modedness with transformation optics

John M. Fini and Jeffrey W. Nicholson  »View Author Affiliations


Optics Express, Vol. 21, Issue 16, pp. 19173-19179 (2013)
http://dx.doi.org/10.1364/OE.21.019173


View Full Text Article

Acrobat PDF (1153 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

Fibers with symmetric bend compensated claddings are proposed, and demonstrate performance much better than conventional designs. These fibers can simultaneously achieve complete HOM suppression, negligible bend loss, and mode area >1000 square microns. The robust single-modedness of these fibers offers a path to overcoming mode instability limits on high-power amplifiers and lasers. The proposed designs achieve many of the advantages of our previous (asymmetric) bend compensation strategy in the regime of moderately large area, and are much easier to fabricate and utilize.

© 2013 OSA

1. Introduction

Fiber amplifiers and lasers continue to achieve ever higher powers, displace competing technologies, and make possible previously unattainable performance in material processing, directed energy, and other applications. While thermal management, pump combining, beam combining, and other techniques play crucial roles, the heart of a fiber laser is the gain fiber, and large mode area fiber design is essential in removing nonlinear limits: once intensity reaches a nonlinear limit, scaling up power requires spreading that intensity over a larger area. Many advanced design strategies have been proposed [1

1. M. O'Connor, V. Gapontsev, V. Fomin, M. Abramov, and A. Ferin, “Power Scaling of SM Fiber Lasers toward 10kW,” in Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, OSA Technical Digest (CD) (Optical Society of America, 2009), paper CThA3. [CrossRef]

4

4. H. W. Chen, T. Sosnowski, C. H. Liu, L. J. Chen, J. R. Birge, A. Galvanauskas, F. X. Kärtner, and G. Chang, “Chirally-coupled-core Yb-fiber laser delivering 80-fs pulses with diffraction-limited beam quality warranted by a high-dispersion mirror based compressor,” Opt. Express 18(24), 24699–24705 (2010). [CrossRef] [PubMed]

], and some have led to impressive demonstrations of large mode area, and yet the path towards scalable area remains unclear for the most demanding applications.

Many systems require a diffraction limited output with reasonable input coupling tolerances, and coiling of the gain fiber to a manageable package size. The fiber should have large mode area (LMA) and low bend loss, and it is increasingly clear that it should support very stable single-moded operation: Eliminating competing modes has always been desirable for improving efficiency, reducing the thermal management problem of dumping power in unwanted modes, etc. More recently, it was discovered that a thermally driven mode-coupling mechanism is a new nonlinearity that can limit power of pulsed and cw sources [5

5. A. V. Smith and J. J. Smith, “Mode instability in high power fiber amplifiers,” Opt. Express 19(11), 10180–10192 (2011). [CrossRef] [PubMed]

]. As power increases, this mechanism leads to an abrupt degradation of mode quality, so that higher-order modes (HOMs) can dominate the output. Mode instability can be limiting even for mode field diameters as small as 27microns [6

6. T. Eidam, C. Wirth, C. Jauregui, F. Stutzki, F. Jansen, H. J. Otto, O. Schmidt, T. Schreiber, J. Limpert, and A. Tünnermann, “Experimental observations of the threshold-like onset of mode instabilities in high power fiber amplifiers,” Opt. Express 19(14), 13218–13224 (2011). [CrossRef] [PubMed]

], and highlights the importance of more robust approaches to single-modedness.

The traditional approach to robustly single-moded operation is to make all higher-order modes (HOM) very lossy—that is, make the fiber intrinsically more single-moded. Another interesting approach is, counter-intuitively, to use a fiber with many modes, but carefully launch and amplify a specific higher-order mode that is resistant to mode-coupling by bend perturbations [3

3. S. Ramachandran, J. W. Nicholson, S. Ghalmi, M. F. Yan, P. Wisk, E. Monberg, and F. V. Dimarcello, “Light propagation with ultralarge modal areas in optical fibers,” Opt. Lett. 31(12), 1797–1799 (2006). [CrossRef] [PubMed]

]. It is not known whether such HOM amplifiers have any resistance to mode-coupling instabilities. On the other hand, fibers with HOM suppression were demonstrated to mitigate the mode-coupling instability [7

7. F. Stutzki, F. Jansen, T. Eidam, A. Steinmetz, C. Jauregui, J. Limpert, and A. Tünnermann, “High average power large-pitch fiber amplifier with robust single-mode operation,” Opt. Lett. 36(5), 689–691 (2011). [CrossRef] [PubMed]

]. That is, while the dynamics driving modulation instability are thermal, use of a fiber with sufficiently robust single-modedness increases the threshold for the instability by suppressing the modes, much as wavelength filtering can suppress Raman nonlinearities. Both approaches will need to be studied further, but here we focus on designs with intrinsic, robust single-modedness. We target very high levels of HOM suppression in order to significantly offset the large mode-instability gains estimated in the literature (e.g. 10’s or 100’s of dB/m [5

5. A. V. Smith and J. J. Smith, “Mode instability in high power fiber amplifiers,” Opt. Express 19(11), 10180–10192 (2011). [CrossRef] [PubMed]

],). The resulting designs should enable significant increases beyond current mode-instability limitations on power.

Here we propose a novel class of fiber designs that provide scalable area, robust suppression of HOMs, and excellent bend loss: symmetric bend compensated (BC) fibers essentially remove the tradeoff between these three requirements. These designs achieve improved single-modedness similar to asymmetric bend-compensated (ABC) fibers, which we have previously proposed [8

8. J. M. Fini, “Bend-resistant design of conventional and microstructure fibers with very large mode area,” Opt. Express 14(1), 69–81 (2006). [CrossRef] [PubMed]

,9

9. J. M. Fini, “Large mode area fibers with asymmetric bend compensation,” Opt. Express 19(22), 21866–21873 (2011). [CrossRef] [PubMed]

], but without the difficulty of fabricating and utilizing asymmetric fibers. The current proposed designs do not require any special management of bend-orientation when coiling the fiber, and can be fabricated with conventional (symmetrical) deposition methods, assuming high precision (δn~10−4) in the deposition.

2. Bend compensation and transformation optics

The designs proposed here beat the usual performance tradeoffs by recognizing the importance of bend perturbations. Bend loss has long been part of LMA design [10

10. J. P. Koplow, D. A. V. Kliner, and L. Goldberg, “Single-mode operation of a coiled multimode fiber amplifier,” Opt. Lett. 25(7), 442–444 (2000). [CrossRef] [PubMed]

], but it was only recently recognized that bends place crucial limitations on the other elements of the main performance tradeoff [8

8. J. M. Fini, “Bend-resistant design of conventional and microstructure fibers with very large mode area,” Opt. Express 14(1), 69–81 (2006). [CrossRef] [PubMed]

,9

9. J. M. Fini, “Large mode area fibers with asymmetric bend compensation,” Opt. Express 19(22), 21866–21873 (2011). [CrossRef] [PubMed]

,11

11. J. W. Nicholson, J. M. Fini, A. D. Yablon, P. S. Westbrook, K. Feder, and C. Headley, “Demonstration of bend-induced nonlinearities in large-mode-area fibers,” Opt. Lett. 32(17), 2562–2564 (2007). [CrossRef] [PubMed]

,12

12. R. L. Farrow, D. A. V. Kliner, G. R. Hadley, and A. V. Smith, “Peak-power limits on fiber amplifiers imposed by self-focusing,” Opt. Lett. 31(23), 3423–3425 (2006). [CrossRef] [PubMed]

]: the more tightly a fiber is coiled, the more it must resist not only bend loss, but also reduction of mode area and degradation of selectivity in HOM suppression. Bend perturbations are so essential that, without them, performance is limited only by fabrication precision.

While fully pre-compensating a profile may be simple conceptually, and can achieve extremely high performance in simulations [8

8. J. M. Fini, “Bend-resistant design of conventional and microstructure fibers with very large mode area,” Opt. Express 14(1), 69–81 (2006). [CrossRef] [PubMed]

], it requires difficult fabrication of an asymmetric index profile. This should be possible given recent impressive accomplishments of microstructure fibers [7

7. F. Stutzki, F. Jansen, T. Eidam, A. Steinmetz, C. Jauregui, J. Limpert, and A. Tünnermann, “High average power large-pitch fiber amplifier with robust single-mode operation,” Opt. Lett. 36(5), 689–691 (2011). [CrossRef] [PubMed]

,15

15. J. M. Fini, J. W. Nicholson, R. S. Windeler, E. M. Monberg, L. Meng, B. Mangan, A. Desantolo, and F. V. DiMarcello, “Low-loss hollow-core fibers with improved single-modedness,” Opt. Express 21(5), 6233–6242 (2013). [CrossRef] [PubMed]

,16

16. L. Dong, H. A. Mckay, A. Marcinkevicius, L. Fu, J. Li, B. K. Thomas, and M. E. Fermann, “Extending Effective Area of Fundamental Mode in Optical Fibers,” J. Lightwave Technol. 27(11), 1565–1570 (2009). [CrossRef]

]. However, the fabricated tilt only compensates the bend assuming it is oriented correctly, and so an ABC fiber would have to be carefully coiled with orientation control. Thus this performance comes at a high cost, and is suitable only where ultimate area scaling of robustly single-moded fiber is needed. The extension of this concept to symmetric BC designs removes these disadvantages in cases where more moderate areas are sufficient. The basic intuitive argument is simple: ABC designs simultaneous overcome bend distortion of the mode shape (by pre-compensating the core) and degradation of single-modedness (by pre-compensating the cladding). For moderately large mode area, bend distortion plays a much less important role, and pre-compensating the core is unnecessary. Bend-compensating the key portion of the cladding requires only a symmetrical index gradient, and is sufficient to drastically improve performance.

Figure 2
Fig. 2 In a conventional, un-compensated design (left), tighter bends lead to degradation of selectivity of the HOM loss. The tighter the bends and the larger the mode size, the more the fundamental and HOMs see a tunneling barrier of comparable width. A bend-compensated cladding (right) restores selectivity, since the compensated portion confines the fundamental but not HOMs. The width of the tunneling barrier seen by the fundamental can thus be engineered independently.
illustrates schematically how bend-compensation de-couples HOM suppression from fundamental-mode bend loss. Figure 2 (left) shows that for a conventional fiber, the potential to selectively suppress HOMs degrades as bends become tighter: At loose enough bends, the index in the entire cladding can fall below the fundamental mode index (an arrow indicating leakage loss is present only for HOM, and not for the fundamental) and so even simple SIF designs can have “complete” selectivity of HOM loss, if precisely the right core contrast is used. At tighter bends, this selectivity degrades. The fundamental and HOM modes must tunnel through comparable distances to find the high-index portion of the cladding, and so losses (indicated by arrows) are more comparable. In a fiber with BC cladding (right) selectivity is restored: the tunneling distance for the fundamental is engineered to be much larger than for the HOMs, so that large HOM loss and small fundamental loss can be achieved simultaneously.

Figure 3 (a-b)
Fig. 3 For conventional step-index profiles (a) of a given core size, one faces a tradeoff: core contrast can be chosen to lower fundamental-mode losses (b,solid) or increase HOM losses (dashed), but not both. Construction of bend-compensated designs (c) from conventional fiber with the same core profile beats this tradeoff: Calculated losses illustrate de-coupling of bend-loss and single-modedness, since fundamental mode-losses can be reduced orders of magnitude (at 30cm bend diameter) with little change in HOM losses.
further illustrates the essential design tradeoff for a conventional design. A step-index fiber (black) can easily be designed to meet a target mode area (e.g. 657μm2 at 1060nm) and level of HOM suppression (dashed, e.g., 100dB/m at Dbend = 30cm). The problem is that HOM suppression and fundamental bend loss are tied together; to achieve effective single-modedness at a large area, the core contrast must be extremely low, resulting in very high bend loss. If we increase the contrast (red) to lower the bend loss (solid), the HOM suppression degrades.

Symmetric BC designs can be constructed from the same nominal step-index fiber (SIF) design (black, with 100dB/m at Dbend = 30cm), as shown in Fig. 3 (c-d), by starting with the SIF and adding a BC trench of increasing width to the cladding [Fig. 3c]. Mode area is a local property of the core, and is essentially unchanged (changing from 657μm2 to 654μm2). The bend-compensation ensures that the HOMs can still penetrate through the cladding, and so single-modedness is also preserved. The trench does provide additional confinement of the fundamental, and so BC designs can achieve improved bend loss as the width of the BC region is increased, free of the usual tradeoff. This is confirmed by simulation results in Fig. 3d, showing loss vs. bend diameter for the fundamental (solid) and HOMs (dashed), where black curves are for the SIF and green, blue, and red have increasing BC region width, as in Fig. 3a. At the design diameter of 30cm, the HOM suppression shows little degradation due to the BC region, while the fundamental-mode bend loss drops orders of magnitude, indicating negligible loss on a length scale relevant for amplifiers.

3. Single-mode operation with scalable area

Since the usual performance tradeoff has been removed, an obvious question is what now limits the achievable performance. One answer is that there is a new tradeoff between fabrication precision and mode area. This is shown in the sensitivity analysis of Fig. 4 (c-d), which repeats the calculation of one of the target designs of Fig. 4(a), adding random index ripples of order 10−4 to model fabrication errors. These simulated irregularities were not azimuthally symmetric, but did have symmetry across the bend axis, to speed the calculation. The equivalent index profiles, which include the bend perturbation, are plotted in Fig. 4(c), with irregular profiles (blue) surrounded the ideal target (black). The cancelation of tilt in the compensated cladding is illustrated by the flat region on the outside of the bend (positive position). In Fig. 4(d), the bend radius of each fiber is adjusted to give the same fundamental bend loss (0.01dB/m), and simulated HOM loss and Aeff are summarized in the tradeoff plot (circles radiating from the target design). Robust single-modedness is still achieved even with this level of fabrication error; the performance is degraded, but still much better than the conventional designs. We note that the comparison to SIF here is entirely unfair, since the SIF performance indicated assumes ideal fabrication of very low-index-contrast profiles.

Single-modedness is not determined solely by loss selectivity, even in a fiber with no low-index outer layer. Furthermore, in a cladding-pumped configuration, the presence of a pump-guiding outer cladding means that true leakage losses are zero. Loss selectivity may still be a rough proxy for mode-coupling losses, and experience shows that a loss-based single-modedness analysis is still a useful guideline in explaining which double-clad fibers act single-moded. In either case, gain competition can play an important role, and depends in part on what fraction of each mode sees the gain region [10

10. J. P. Koplow, D. A. V. Kliner, and L. Goldberg, “Single-mode operation of a coiled multimode fiber amplifier,” Opt. Lett. 25(7), 442–444 (2000). [CrossRef] [PubMed]

,18

18. J. Bromage, J. M. Fini, C. Dorrer, and J. D. Zuegel, “Characterization and optimization of Yb-doped photonic-crystal fiber rod amplifiers using spatially resolved spectral interferometry,” Appl. Opt. 50(14), 2001–2007 (2011). [CrossRef] [PubMed]

]. Thus we show mode intensity profiles of the proposed design in Fig. 5
Fig. 5 Mode intensity profiles show that the fundamental mode (left) is much better confined to the core than LP11 modes (center and right), and will thus be preferentially amplified by gain in the core.
. The fundamental mode is well confined to the core (left), while the two LP11-like modes spill out into the cladding. These results suggest higher-order modes highly susceptible to mode-coupling losses, and illustrate that (in addition to any loss) gain will selectively suppress the HOMs, since they will overlap poorly with the gain dopant in the core.

7. Conclusion

We propose a new class of fibers that have bend compensation in only part of the cladding. These designs are symmetrical: they can be fabricated using conventional deposition methods with improved tolerances, and can be utilized without onerous bend management or splicing requirements. They thus overcome the main obstacles of our previously proposed asymmetric bend compensated fibers, and are scalable to >1000μm2 mode area.

Simulations indicate that, even with reasonable fabrication imperfections and yield, these designs should achieve extremely selective HOM suppression, with the ratio of calculated HOM loss to fundamental loss >1000 on a dB scale (e.g. “complete” 50dB of HOM suppression and <0.05dB of fundamental loss). Such fibers would be ideal for scaling up power in applications where mode-instability is currently limiting, and for sources suitable for beam-combining [19

19. S. M. Redmond, D. J. Ripin, C. X. Yu, S. J. Augst, T. Y. Fan, P. A. Thielen, J. E. Rothenberg, and G. D. Goodno, “Diffractive coherent combining of a 2.5 kW fiber laser array into a 1.9 kW Gaussian beam,” Opt. Lett. 37(14), 2832–2834 (2012). [CrossRef] [PubMed]

].

References and links

1.

M. O'Connor, V. Gapontsev, V. Fomin, M. Abramov, and A. Ferin, “Power Scaling of SM Fiber Lasers toward 10kW,” in Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, OSA Technical Digest (CD) (Optical Society of America, 2009), paper CThA3. [CrossRef]

2.

L. Dong, X. Peng, and J. Li, “Leakage channel optical fibers with large effective area,” J. Opt. Soc. Am. B 24(8), 1689–1697 (2007). [CrossRef]

3.

S. Ramachandran, J. W. Nicholson, S. Ghalmi, M. F. Yan, P. Wisk, E. Monberg, and F. V. Dimarcello, “Light propagation with ultralarge modal areas in optical fibers,” Opt. Lett. 31(12), 1797–1799 (2006). [CrossRef] [PubMed]

4.

H. W. Chen, T. Sosnowski, C. H. Liu, L. J. Chen, J. R. Birge, A. Galvanauskas, F. X. Kärtner, and G. Chang, “Chirally-coupled-core Yb-fiber laser delivering 80-fs pulses with diffraction-limited beam quality warranted by a high-dispersion mirror based compressor,” Opt. Express 18(24), 24699–24705 (2010). [CrossRef] [PubMed]

5.

A. V. Smith and J. J. Smith, “Mode instability in high power fiber amplifiers,” Opt. Express 19(11), 10180–10192 (2011). [CrossRef] [PubMed]

6.

T. Eidam, C. Wirth, C. Jauregui, F. Stutzki, F. Jansen, H. J. Otto, O. Schmidt, T. Schreiber, J. Limpert, and A. Tünnermann, “Experimental observations of the threshold-like onset of mode instabilities in high power fiber amplifiers,” Opt. Express 19(14), 13218–13224 (2011). [CrossRef] [PubMed]

7.

F. Stutzki, F. Jansen, T. Eidam, A. Steinmetz, C. Jauregui, J. Limpert, and A. Tünnermann, “High average power large-pitch fiber amplifier with robust single-mode operation,” Opt. Lett. 36(5), 689–691 (2011). [CrossRef] [PubMed]

8.

J. M. Fini, “Bend-resistant design of conventional and microstructure fibers with very large mode area,” Opt. Express 14(1), 69–81 (2006). [CrossRef] [PubMed]

9.

J. M. Fini, “Large mode area fibers with asymmetric bend compensation,” Opt. Express 19(22), 21866–21873 (2011). [CrossRef] [PubMed]

10.

J. P. Koplow, D. A. V. Kliner, and L. Goldberg, “Single-mode operation of a coiled multimode fiber amplifier,” Opt. Lett. 25(7), 442–444 (2000). [CrossRef] [PubMed]

11.

J. W. Nicholson, J. M. Fini, A. D. Yablon, P. S. Westbrook, K. Feder, and C. Headley, “Demonstration of bend-induced nonlinearities in large-mode-area fibers,” Opt. Lett. 32(17), 2562–2564 (2007). [CrossRef] [PubMed]

12.

R. L. Farrow, D. A. V. Kliner, G. R. Hadley, and A. V. Smith, “Peak-power limits on fiber amplifiers imposed by self-focusing,” Opt. Lett. 31(23), 3423–3425 (2006). [CrossRef] [PubMed]

13.

L. H. Gabrielli, D. Liu, S. G. Johnson, and M. Lipson, “On-chip transformation optics for multimode waveguide bends,” Nat. Commun. 3, 1217 (2012). [CrossRef] [PubMed]

14.

D. Marcuse, “Influence of curvature on the losses of doubly clad fibers,” Appl. Opt. 21(23), 4208–4213 (1982). [CrossRef] [PubMed]

15.

J. M. Fini, J. W. Nicholson, R. S. Windeler, E. M. Monberg, L. Meng, B. Mangan, A. Desantolo, and F. V. DiMarcello, “Low-loss hollow-core fibers with improved single-modedness,” Opt. Express 21(5), 6233–6242 (2013). [CrossRef] [PubMed]

16.

L. Dong, H. A. Mckay, A. Marcinkevicius, L. Fu, J. Li, B. K. Thomas, and M. E. Fermann, “Extending Effective Area of Fundamental Mode in Optical Fibers,” J. Lightwave Technol. 27(11), 1565–1570 (2009). [CrossRef]

17.

J. M. Fini, “Design of large-mode-area amplifier fibers resistant to bend-induced distortion,” J. Opt. Soc. Am. B 24(8), 1669–1676 (2007). [CrossRef]

18.

J. Bromage, J. M. Fini, C. Dorrer, and J. D. Zuegel, “Characterization and optimization of Yb-doped photonic-crystal fiber rod amplifiers using spatially resolved spectral interferometry,” Appl. Opt. 50(14), 2001–2007 (2011). [CrossRef] [PubMed]

19.

S. M. Redmond, D. J. Ripin, C. X. Yu, S. J. Augst, T. Y. Fan, P. A. Thielen, J. E. Rothenberg, and G. D. Goodno, “Diffractive coherent combining of a 2.5 kW fiber laser array into a 1.9 kW Gaussian beam,” Opt. Lett. 37(14), 2832–2834 (2012). [CrossRef] [PubMed]

OCIS Codes
(060.2280) Fiber optics and optical communications : Fiber design and fabrication
(140.3510) Lasers and laser optics : Lasers, fiber

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: June 12, 2013
Revised Manuscript: July 26, 2013
Manuscript Accepted: July 27, 2013
Published: August 5, 2013

Citation
John M. Fini and Jeffrey W. Nicholson, "Bend compensated large-mode-area fibers: achieving robust single-modedness with transformation optics," Opt. Express 21, 19173-19179 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-16-19173


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. M. O'Connor, V. Gapontsev, V. Fomin, M. Abramov, and A. Ferin, “Power Scaling of SM Fiber Lasers toward 10kW,” in Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, OSA Technical Digest (CD) (Optical Society of America, 2009), paper CThA3. [CrossRef]
  2. L. Dong, X. Peng, and J. Li, “Leakage channel optical fibers with large effective area,” J. Opt. Soc. Am. B24(8), 1689–1697 (2007). [CrossRef]
  3. S. Ramachandran, J. W. Nicholson, S. Ghalmi, M. F. Yan, P. Wisk, E. Monberg, and F. V. Dimarcello, “Light propagation with ultralarge modal areas in optical fibers,” Opt. Lett.31(12), 1797–1799 (2006). [CrossRef] [PubMed]
  4. H. W. Chen, T. Sosnowski, C. H. Liu, L. J. Chen, J. R. Birge, A. Galvanauskas, F. X. Kärtner, and G. Chang, “Chirally-coupled-core Yb-fiber laser delivering 80-fs pulses with diffraction-limited beam quality warranted by a high-dispersion mirror based compressor,” Opt. Express18(24), 24699–24705 (2010). [CrossRef] [PubMed]
  5. A. V. Smith and J. J. Smith, “Mode instability in high power fiber amplifiers,” Opt. Express19(11), 10180–10192 (2011). [CrossRef] [PubMed]
  6. T. Eidam, C. Wirth, C. Jauregui, F. Stutzki, F. Jansen, H. J. Otto, O. Schmidt, T. Schreiber, J. Limpert, and A. Tünnermann, “Experimental observations of the threshold-like onset of mode instabilities in high power fiber amplifiers,” Opt. Express19(14), 13218–13224 (2011). [CrossRef] [PubMed]
  7. F. Stutzki, F. Jansen, T. Eidam, A. Steinmetz, C. Jauregui, J. Limpert, and A. Tünnermann, “High average power large-pitch fiber amplifier with robust single-mode operation,” Opt. Lett.36(5), 689–691 (2011). [CrossRef] [PubMed]
  8. J. M. Fini, “Bend-resistant design of conventional and microstructure fibers with very large mode area,” Opt. Express14(1), 69–81 (2006). [CrossRef] [PubMed]
  9. J. M. Fini, “Large mode area fibers with asymmetric bend compensation,” Opt. Express19(22), 21866–21873 (2011). [CrossRef] [PubMed]
  10. J. P. Koplow, D. A. V. Kliner, and L. Goldberg, “Single-mode operation of a coiled multimode fiber amplifier,” Opt. Lett.25(7), 442–444 (2000). [CrossRef] [PubMed]
  11. J. W. Nicholson, J. M. Fini, A. D. Yablon, P. S. Westbrook, K. Feder, and C. Headley, “Demonstration of bend-induced nonlinearities in large-mode-area fibers,” Opt. Lett.32(17), 2562–2564 (2007). [CrossRef] [PubMed]
  12. R. L. Farrow, D. A. V. Kliner, G. R. Hadley, and A. V. Smith, “Peak-power limits on fiber amplifiers imposed by self-focusing,” Opt. Lett.31(23), 3423–3425 (2006). [CrossRef] [PubMed]
  13. L. H. Gabrielli, D. Liu, S. G. Johnson, and M. Lipson, “On-chip transformation optics for multimode waveguide bends,” Nat. Commun.3, 1217 (2012). [CrossRef] [PubMed]
  14. D. Marcuse, “Influence of curvature on the losses of doubly clad fibers,” Appl. Opt.21(23), 4208–4213 (1982). [CrossRef] [PubMed]
  15. J. M. Fini, J. W. Nicholson, R. S. Windeler, E. M. Monberg, L. Meng, B. Mangan, A. Desantolo, and F. V. DiMarcello, “Low-loss hollow-core fibers with improved single-modedness,” Opt. Express21(5), 6233–6242 (2013). [CrossRef] [PubMed]
  16. L. Dong, H. A. Mckay, A. Marcinkevicius, L. Fu, J. Li, B. K. Thomas, and M. E. Fermann, “Extending Effective Area of Fundamental Mode in Optical Fibers,” J. Lightwave Technol.27(11), 1565–1570 (2009). [CrossRef]
  17. J. M. Fini, “Design of large-mode-area amplifier fibers resistant to bend-induced distortion,” J. Opt. Soc. Am. B24(8), 1669–1676 (2007). [CrossRef]
  18. J. Bromage, J. M. Fini, C. Dorrer, and J. D. Zuegel, “Characterization and optimization of Yb-doped photonic-crystal fiber rod amplifiers using spatially resolved spectral interferometry,” Appl. Opt.50(14), 2001–2007 (2011). [CrossRef] [PubMed]
  19. S. M. Redmond, D. J. Ripin, C. X. Yu, S. J. Augst, T. Y. Fan, P. A. Thielen, J. E. Rothenberg, and G. D. Goodno, “Diffractive coherent combining of a 2.5 kW fiber laser array into a 1.9 kW Gaussian beam,” Opt. Lett.37(14), 2832–2834 (2012). [CrossRef] [PubMed]

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 Fig. 5
 

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited