Abstract

The impact of avoided crossings (also known as anti-crossings) in single and double-clad large mode area Photonic Crystal Fibers (PCFs) suitable for high-power laser systems is evaluated numerically. It is pointed out that an inappropriate choice of pump core diameter, bending radius and/or index depression may lead to avoided crossings that manifest themselves in unwanted deformations of the output beam.

© 2011 OSA

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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
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    [CrossRef]
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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]

2011

2010

2009

2008

2004

2003

C. M. Smith, N. Venkataraman, M. T. Gallagher, D. Müller, J. A. West, N. F. Borrelli, D. C. Allan, and K. W. Koch, “Low-loss hollow-core silica/air photonic bandgap fibre,” Nature 424(6949), 657–659 (2003).
[CrossRef] [PubMed]

P. Russell, “Photonic crystal fibers,” Science 299(5605), 358–362 (2003).
[CrossRef] [PubMed]

Alkeskjold, T. T.

Allan, D.

Allan, D. C.

C. M. Smith, N. Venkataraman, M. T. Gallagher, D. Müller, J. A. West, N. F. Borrelli, D. C. Allan, and K. W. Koch, “Low-loss hollow-core silica/air photonic bandgap fibre,” Nature 424(6949), 657–659 (2003).
[CrossRef] [PubMed]

Andersen, T. V.

Bassi, P.

Baumgartl, M.

Borelli, E.

Borrelli, N.

Borrelli, N. F.

C. M. Smith, N. Venkataraman, M. T. Gallagher, D. Müller, J. A. West, N. F. Borrelli, D. C. Allan, and K. W. Koch, “Low-loss hollow-core silica/air photonic bandgap fibre,” Nature 424(6949), 657–659 (2003).
[CrossRef] [PubMed]

Broeng, J.

Carstens, H.

Coscelli, E.

Cucinotta, A.

Dong, L.

Eidam, T.

Fermann, M. E.

Fu, L.

Gabler, T.

Gallagher, M. T.

C. M. Smith, N. Venkataraman, M. T. Gallagher, D. Müller, J. A. West, N. F. Borrelli, D. C. Allan, and K. W. Koch, “Low-loss hollow-core silica/air photonic bandgap fibre,” Nature 424(6949), 657–659 (2003).
[CrossRef] [PubMed]

Hädrich, S.

Hanf, S.

Jansen, F.

Jauregui, C.

Koch, K.

Koch, K. W.

C. M. Smith, N. Venkataraman, M. T. Gallagher, D. Müller, J. A. West, N. F. Borrelli, D. C. Allan, and K. W. Koch, “Low-loss hollow-core silica/air photonic bandgap fibre,” Nature 424(6949), 657–659 (2003).
[CrossRef] [PubMed]

Laegsgaard, J.

Leick, L.

Li, J.

Limpert, J.

Marcinkevicius, A.

McKay, H. A.

Müller, D.

C. M. Smith, N. Venkataraman, M. T. Gallagher, D. Müller, J. A. West, N. F. Borrelli, D. C. Allan, and K. W. Koch, “Low-loss hollow-core silica/air photonic bandgap fibre,” Nature 424(6949), 657–659 (2003).
[CrossRef] [PubMed]

Noordegraaf, D.

Ohta, M.

Otto, H.-J.

Passaro, D.

Poli, F.

Rothhardt, J.

Russell, P.

P. Russell, “Photonic crystal fibers,” Science 299(5605), 358–362 (2003).
[CrossRef] [PubMed]

Schreiber, T.

Scolari, L.

Seise, E.

Selleri, S.

Smith, C.

Smith, C. M.

C. M. Smith, N. Venkataraman, M. T. Gallagher, D. Müller, J. A. West, N. F. Borrelli, D. C. Allan, and K. W. Koch, “Low-loss hollow-core silica/air photonic bandgap fibre,” Nature 424(6949), 657–659 (2003).
[CrossRef] [PubMed]

Steinmetz, A.

Stutzki, F.

Suzuki, S.

Tanggaard Alkeskjold, T.

Tartarini, G.

Thomas, B. K.

Tünnermann, A.

Venkataraman, N.

C. M. Smith, N. Venkataraman, M. T. Gallagher, D. Müller, J. A. West, N. F. Borrelli, D. C. Allan, and K. W. Koch, “Low-loss hollow-core silica/air photonic bandgap fibre,” Nature 424(6949), 657–659 (2003).
[CrossRef] [PubMed]

West, J.

West, J. A.

C. M. Smith, N. Venkataraman, M. T. Gallagher, D. Müller, J. A. West, N. F. Borrelli, D. C. Allan, and K. W. Koch, “Low-loss hollow-core silica/air photonic bandgap fibre,” Nature 424(6949), 657–659 (2003).
[CrossRef] [PubMed]

Wirth, C.

Wu, S.-T.

Appl. Opt.

J. Lightwave Technol.

Nature

C. M. Smith, N. Venkataraman, M. T. Gallagher, D. Müller, J. A. West, N. F. Borrelli, D. C. Allan, and K. W. Koch, “Low-loss hollow-core silica/air photonic bandgap fibre,” Nature 424(6949), 657–659 (2003).
[CrossRef] [PubMed]

Opt. Express

J. West, C. Smith, N. Borrelli, D. Allan, and K. Koch, “Surface modes in air-core photonic band-gap fibers,” Opt. Express 12(8), 1485–1496 (2004), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-12-8-1485 .
[CrossRef] [PubMed]

F. Poli, E. Coscelli, T. T. Alkeskjold, D. Passaro, A. Cucinotta, L. Leick, J. Broeng, and S. Selleri, “Cut-off analysis of 19-cell Yb-doped double-cladding rod-type photonic crystal fibers,” Opt. Express 19(10), 9896–9907 (2011), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-10-9896 .
[CrossRef] [PubMed]

F. Jansen, F. Stutzki, H.-J. Otto, M. Baumgartl, C. Jauregui, J. Limpert, and A. Tünnermann, “The influence of index-depressions in core-pumped Yb-doped large pitch fibers,” Opt. Express 18(26), 26834–26842 (2010), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-26-26834 .
[CrossRef] [PubMed]

L. Dong, H. A. McKay, L. Fu, M. Ohta, A. Marcinkevicius, S. Suzuki, and M. E. Fermann, “Ytterbium-doped all glass leakage channel fibers with highly fluorine-doped silica pump cladding,” Opt. Express 17(11), 8962–8969 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-11-8962 .
[CrossRef] [PubMed]

T. Eidam, J. Rothhardt, F. Stutzki, F. Jansen, S. Hädrich, H. Carstens, C. Jauregui, J. Limpert, and A. Tünnermann, “Fiber chirped-pulse amplification system emitting 3.8 GW peak power,” Opt. Express 19(1), 255–260 (2011), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-1-255 .
[CrossRef] [PubMed]

Opt. Lett.

Science

P. Russell, “Photonic crystal fibers,” Science 299(5605), 358–362 (2003).
[CrossRef] [PubMed]

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Figures (12)

Fig. 1
Fig. 1

Exemplary large pitch fiber and calculated transverse mode profiles: without (upper half) and with (lower half) air-clad. The modes are sorted by ascending loss and, respectively, descending overlap with the doped region.

Fig. 2
Fig. 2

Schematic structure of a rare-earth doped (green) double-clad LPF.

Fig. 3
Fig. 3

Qualitative scheme of refractive indices and effective indices of core (red horizontal lines) and cladding modes (orange horizontal lines) in a step index fiber and a large pitch fiber, both with double-clad.

Fig. 4
Fig. 4

Detailed plot of one broad and two narrow avoided crossings. The modes involved are shown in black, red, green and blue, respectively. Crossing modes are grayed. The position of the fixed reference mode to which all other modes are compared is highlighted.

Fig. 5
Fig. 5

Transverse mode profiles of the modes involved in the broad avoided-crossing of Fig. 4 around 188.5µm. The narrow avoided crossings were left out for clarity. Across the avoided crossing the former FM evolves into a HOM, and a HOM takes over the role as the FM.

Fig. 6
Fig. 6

Effective index of all modes in the displayed effective index interval versus the air-clad diameter (upper half) and the corresponding overlap of each mode with a well confined FM of the waveguide structure (lower half). The core-guided fundamental mode of each waveguide (i.e. of the fibers with the different air-clad diameters) is represented as a black dot in both graphs. The green vertical lines indicate the position of the seven resolved avoided crossings.

Fig. 7
Fig. 7

One broad avoided-crossing for a constant pitch Λ = 30µm but with three different d/Λ-values.

Fig. 8
Fig. 8

Avoided crossings in a LPF with air-clad (inset): effective index (upper graph) and overlap (lower graph) with the FM of the straight fiber against the bend radius. For each bend radius the mode with the highest overlap with the FM of the straight fiber is shown in black, all other modes are grayed out. Vertical green lines indicate the position of avoided crossings.

Fig. 9
Fig. 9

Modal pictures of the two modes involved in the first avoided-crossing (at a bending radius of ~2.2 m) and the corresponding bending radius. Note that the mode in the upper row is the FM at large bend radii, while the mode in the lower row takes over the role of the FM at smaller bend radii.

Fig. 10
Fig. 10

Avoided crossings in a LPF without air-clad. Both the effective index (upper graph) and the overlap (lower graph) with the FM of the straight fiber are plotted against the bend radius. For each bend radius the mode with the highest overlap with the FM of the straight fiber is shown in black, all other modes are grayed out. Vertical green lines indicate the position of avoided crossings.

Fig. 11
Fig. 11

Effective index (upper graph) and overlap (lower graph) of the mode 1 (black), the HOMs that lead to the first two avoided crossings (mode 2 in red and mode 3 in blue) and all other modes in this effective index region (gray). The position of the two broadest avoided crossings between a HOM and the FM are indicated with green vertical lines.

Fig. 12
Fig. 12

Modal pictures of the modes involved in three avoided-crossing. It can be seen that these modes exchange their role as the most Gaussian-like mode of the waveguide with changing index depression.

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