Abstract

In this paper, we report an advance in increasing core size of effective single-mode chirally-coupled-core (CCC) Ge-doped and Yb-doped double-clad fibers into 55µm to 60µm range, and experimentally demonstrate their robust single-mode performance. Theoretical and numerical description of CCC fibers structures with multiple side cores and polygon-shaped central core is consistent with experimental results. Detailed experimental characterization of 55µm-core CCC fibers based on spatially and spectrally resolved broadband measurements (S2 technique) shows that modal performance of these large core fibers well exceeds that of standard 20μm core step-index large mode area fibers.

© 2014 Optical Society of America

Full Article  |  PDF Article
OSA Recommended Articles
Extending single mode performance of all-solid large-mode-area single trench fiber

D. Jain, Y. Jung, M. Nunez-Velazquez, and J. K. Sahu
Opt. Express 22(25) 31078-31091 (2014)

Energy scaling of mode-locked fiber lasers with chirally-coupled core fiber

Simon Lefrancois, Thomas S. Sosnowski, Chi-Hung Liu, Almantas Galvanauskas, and Frank W. Wise
Opt. Express 19(4) 3464-3470 (2011)

Angular-momentum coupled optical waves in chirally-coupled-core fibers

Xiuquan Ma, Chi-Hung Liu, Guoqing Chang, and Almantas Galvanauskas
Opt. Express 19(27) 26515-26528 (2011)

More Recommended Articles

References

  • View by:
  • Article Order
  • |
  • Year
  • |
  • Author
  • |
  • Publication
  1. D. J. Richardson, J. Nilsson, and W. A. Clarkson, “High power fiber lasers: current status and future perspectives [Invited],” J. Opt. Soc. Am. B 27(11), B63–B92 (2010).
    [Crossref]
  2. A. Tünnermann, T. Schreiber, and J. Limpert, “Fiber lasers and amplifiers: an ultrafast performance evolution,” Appl. Opt. 49(25), F71–F78 (2010).
    [Crossref] [PubMed]
  3. J. A. Buck, Fundamentals of Optical Fibers, 2nd ed. (John Wiley, 2004).
  4. M. E. Fermann, “Single-mode excitation of multimode fibers with ultrashort pulses,” Opt. Lett. 23(1), 52–54 (1998).
    [Crossref] [PubMed]
  5. 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]
  6. H. Injeyan and G. D. Goodno, High Power Laser Handbook, Chapter 18 (McGraw-Hill Professional, 2011).
  7. J. Limpert, A. Liem, M. Reich, T. Schreiber, S. Nolte, H. Zellmer, A. Tünnermann, J. Broeng, A. Petersson, and C. Jakobsen, “Low-nonlinearity single-transverse-mode ytterbium-doped photonic crystal fiber amplifier,” Opt. Express 12(7), 1313–1319 (2004).
    [Crossref] [PubMed]
  8. C. D. Brooks and F. Di Teodoro, “Multimegawatt peakpower, single-transverse-mode operation of a 100 µm core diameter, Yb-doped rod-like photonic crystal fiber amplifier,” Appl. Phys. Lett. 89(11), 111119 (2006).
    [Crossref]
  9. H. P. Uranus, “Theoretical study on the multimodeness of a commercial endlessly single-mode PCF,” Opt. Commun. 283(23), 4649–4654 (2010).
    [Crossref]
  10. K. R. Hansen, T. T. Alkeskjold, J. Broeng, and J. Lægsgaard, “Thermo-optical effects in high-power Ytterbium-doped fiber amplifiers,” Opt. Express 19(24), 23965–23980 (2011).
    [Crossref] [PubMed]
  11. X. Ma, C.-H. Liu, G. Chang, and A. Galvanauskas, “Angular-momentum coupled optical waves in chirally-coupled-core fibers,” Opt. Express 19(27), 26515–26528 (2011).
    [Crossref] [PubMed]
  12. 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]
  13. 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]
  14. V. Sudesh, T. Mccomb, Y. Chen, M. Bass, M. Richardson, J. Ballato, and A. E. Siegman, “Diode-pumped 200 μm diameter core, gain-guided, index-antiguided single mode fiber laser,” Appl. Phys. B 90(3-4), 369–372 (2008).
    [Crossref]
  15. 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]
  16. J. R. Marciante, R. G. Roides, V. V. Shkunov, and D. A. Rockwell, “Near-diffraction-limited operation of step-index large-mode-area fiber lasers via gain filtering,” Opt. Lett. 35(11), 1828–1830 (2010).
    [Crossref] [PubMed]
  17. M. Kashiwagi, K. Saitoh, K. Takenaga, S. Tanigawa, S. Matsuo, and M. Fujimaki, “Effectively single-mode all-solid photonic bandgap fiber with large effective area and low bending loss for compact high-power all-fiber lasers,” Opt. Express 20(14), 15061–15070 (2012).
    [Crossref] [PubMed]
  18. TIA Standards, FOTP-80 IEC-60793–1-44 Optical Fibres - Part 1–44: Measurement Methods and Test Procedures - Cut-Off Wavelength.
  19. S. Wielandy, “Implications of higher-order mode content in large mode area fibers with good beam quality,” Opt. Express 15(23), 15402–15409 (2007).
    [Crossref] [PubMed]
  20. J. W. Nicholson, A. D. Yablon, S. Ramachandran, and S. Ghalmi, “Spatially and spectrally resolved imaging of modal content in large-mode-area fibers,” Opt. Express 16(10), 7233–7243 (2008).
    [Crossref] [PubMed]
  21. M. Laurila, T. T. Alkeskjold, J. Lægsgaard, and J. Broeng, “Spatial and spectral imaging of LMA photonic crystal fiber amplifiers,” Proc. SPIE 7914, 79142D (2011).
    [Crossref]
  22. F. Kong, K. Saitoh, D. Mcclane, T. Hawkins, P. Foy, G. Gu, and L. Dong, “Mode area scaling with all-solid photonic bandgap fibers,” Opt. Express 20(24), 26363–26372 (2012).
    [Crossref] [PubMed]
  23. G. Gu, F. Kong, T. W. Hawkins, P. Foy, K. Wei, B. Samson, and L. Dong, “Impact of fiber outer boundaries on leaky mode losses in leakage channel fibers,” Opt. Express 21(20), 24039–24048 (2013).
    [Crossref] [PubMed]
  24. X. Ma, “Understanding and controlling angular momentum coupled optical waves in chirally-coupled-core (CCC) fibers,” PhD Thesis, University of Michigan at Ann Arbor.
  25. C. Zhu, I.-N. Hu, X. Ma, and A. Galvanauskas, “Single mode 9.1mJ and 10ns pulses from 55um core Yb-doped CCC fiber MOPA,” in CLEO: Science and Innovations, San Jose, California, United States, June 9–14, 2013, Paper CTu1K.
  26. X. Ma, I.-N. Hu, and A. Galvanauskas, “Propagation-length independent SRS threshold in chirally-coupled-core fibers,” Opt. Express 19(23), 22575–22581 (2011).
    [Crossref] [PubMed]
  27. X. Ma, I.-N. Hu, and A. Galvanauskas, “Propagation length independent nonlinearity threshold in Stokes-wave suppressed SRS in chirally-coupled-core fibers,” in Nonlinear Optics (NLO) (2011), Paper NTuE7.
  28. I.-N. Hu, X. Ma, C. Zhu, W.-Z. Chang, C.-H. Liu, T. Sosnowski, A. Galvanauskas, “Experimental demonstration of SRS suppression in chirally-coupled-core fibers,” in ASSP (2012), Paper AT1A.
  29. M. L. Stock, C.-H. Liu, A. Kuznetsov, G. Tudury, A. Galvanauskas, and T. Sosnowski, “Polarized, 100 kW peak power, high brightness nanosecond lasers based on 3C optical fiber,” Proc. SPIE 7914, 79140U (2011).
    [Crossref]
  30. C. Zhu, I.-N. Hu, X. Ma, L. Siiam, and A. Galvanauskas, “Single-frequency and single-transverse mode Yb-doped CCC fiber MOPA with robust polarization SBS-free 511W output,” in ASSP (2011), Paper AMC5.

2013 (1)

2012 (2)

2011 (6)

2010 (4)

2008 (2)

V. Sudesh, T. Mccomb, Y. Chen, M. Bass, M. Richardson, J. Ballato, and A. E. Siegman, “Diode-pumped 200 μm diameter core, gain-guided, index-antiguided single mode fiber laser,” Appl. Phys. B 90(3-4), 369–372 (2008).
[Crossref]

J. W. Nicholson, A. D. Yablon, S. Ramachandran, and S. Ghalmi, “Spatially and spectrally resolved imaging of modal content in large-mode-area fibers,” Opt. Express 16(10), 7233–7243 (2008).
[Crossref] [PubMed]

2007 (2)

2006 (2)

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]

C. D. Brooks and F. Di Teodoro, “Multimegawatt peakpower, single-transverse-mode operation of a 100 µm core diameter, Yb-doped rod-like photonic crystal fiber amplifier,” Appl. Phys. Lett. 89(11), 111119 (2006).
[Crossref]

2004 (1)

2000 (1)

1998 (1)

Alkeskjold, T. T.

K. R. Hansen, T. T. Alkeskjold, J. Broeng, and J. Lægsgaard, “Thermo-optical effects in high-power Ytterbium-doped fiber amplifiers,” Opt. Express 19(24), 23965–23980 (2011).
[Crossref] [PubMed]

M. Laurila, T. T. Alkeskjold, J. Lægsgaard, and J. Broeng, “Spatial and spectral imaging of LMA photonic crystal fiber amplifiers,” Proc. SPIE 7914, 79142D (2011).
[Crossref]

Ballato, J.

V. Sudesh, T. Mccomb, Y. Chen, M. Bass, M. Richardson, J. Ballato, and A. E. Siegman, “Diode-pumped 200 μm diameter core, gain-guided, index-antiguided single mode fiber laser,” Appl. Phys. B 90(3-4), 369–372 (2008).
[Crossref]

Bass, M.

V. Sudesh, T. Mccomb, Y. Chen, M. Bass, M. Richardson, J. Ballato, and A. E. Siegman, “Diode-pumped 200 μm diameter core, gain-guided, index-antiguided single mode fiber laser,” Appl. Phys. B 90(3-4), 369–372 (2008).
[Crossref]

Broeng, J.

Brooks, C. D.

C. D. Brooks and F. Di Teodoro, “Multimegawatt peakpower, single-transverse-mode operation of a 100 µm core diameter, Yb-doped rod-like photonic crystal fiber amplifier,” Appl. Phys. Lett. 89(11), 111119 (2006).
[Crossref]

Chang, G.

Chen, Y.

V. Sudesh, T. Mccomb, Y. Chen, M. Bass, M. Richardson, J. Ballato, and A. E. Siegman, “Diode-pumped 200 μm diameter core, gain-guided, index-antiguided single mode fiber laser,” Appl. Phys. B 90(3-4), 369–372 (2008).
[Crossref]

Clarkson, W. A.

Di Teodoro, F.

C. D. Brooks and F. Di Teodoro, “Multimegawatt peakpower, single-transverse-mode operation of a 100 µm core diameter, Yb-doped rod-like photonic crystal fiber amplifier,” Appl. Phys. Lett. 89(11), 111119 (2006).
[Crossref]

Dimarcello, F. V.

Dong, L.

Eidam, T.

Fermann, M. E.

Foy, P.

Fujimaki, M.

Galvanauskas, A.

Ghalmi, S.

Goldberg, L.

Gu, G.

Hansen, K. R.

Hawkins, T.

Hawkins, T. W.

Hu, I.-N.

Jakobsen, C.

Jansen, F.

Jauregui, C.

Kashiwagi, M.

Kliner, D. A. V.

Kong, F.

Koplow, J. P.

Kuznetsov, A.

M. L. Stock, C.-H. Liu, A. Kuznetsov, G. Tudury, A. Galvanauskas, and T. Sosnowski, “Polarized, 100 kW peak power, high brightness nanosecond lasers based on 3C optical fiber,” Proc. SPIE 7914, 79140U (2011).
[Crossref]

Lægsgaard, J.

M. Laurila, T. T. Alkeskjold, J. Lægsgaard, and J. Broeng, “Spatial and spectral imaging of LMA photonic crystal fiber amplifiers,” Proc. SPIE 7914, 79142D (2011).
[Crossref]

K. R. Hansen, T. T. Alkeskjold, J. Broeng, and J. Lægsgaard, “Thermo-optical effects in high-power Ytterbium-doped fiber amplifiers,” Opt. Express 19(24), 23965–23980 (2011).
[Crossref] [PubMed]

Laurila, M.

M. Laurila, T. T. Alkeskjold, J. Lægsgaard, and J. Broeng, “Spatial and spectral imaging of LMA photonic crystal fiber amplifiers,” Proc. SPIE 7914, 79142D (2011).
[Crossref]

Li, J.

Liem, A.

Limpert, J.

Liu, C.-H.

X. Ma, C.-H. Liu, G. Chang, and A. Galvanauskas, “Angular-momentum coupled optical waves in chirally-coupled-core fibers,” Opt. Express 19(27), 26515–26528 (2011).
[Crossref] [PubMed]

M. L. Stock, C.-H. Liu, A. Kuznetsov, G. Tudury, A. Galvanauskas, and T. Sosnowski, “Polarized, 100 kW peak power, high brightness nanosecond lasers based on 3C optical fiber,” Proc. SPIE 7914, 79140U (2011).
[Crossref]

Ma, X.

Marciante, J. R.

Matsuo, S.

Mcclane, D.

Mccomb, T.

V. Sudesh, T. Mccomb, Y. Chen, M. Bass, M. Richardson, J. Ballato, and A. E. Siegman, “Diode-pumped 200 μm diameter core, gain-guided, index-antiguided single mode fiber laser,” Appl. Phys. B 90(3-4), 369–372 (2008).
[Crossref]

Monberg, E.

Nicholson, J. W.

Nilsson, J.

Nolte, S.

Peng, X.

Petersson, A.

Ramachandran, S.

Reich, M.

Richardson, D. J.

Richardson, M.

V. Sudesh, T. Mccomb, Y. Chen, M. Bass, M. Richardson, J. Ballato, and A. E. Siegman, “Diode-pumped 200 μm diameter core, gain-guided, index-antiguided single mode fiber laser,” Appl. Phys. B 90(3-4), 369–372 (2008).
[Crossref]

Rockwell, D. A.

Roides, R. G.

Saitoh, K.

Samson, B.

Schreiber, T.

Shkunov, V. V.

Siegman, A. E.

V. Sudesh, T. Mccomb, Y. Chen, M. Bass, M. Richardson, J. Ballato, and A. E. Siegman, “Diode-pumped 200 μm diameter core, gain-guided, index-antiguided single mode fiber laser,” Appl. Phys. B 90(3-4), 369–372 (2008).
[Crossref]

Sosnowski, T.

M. L. Stock, C.-H. Liu, A. Kuznetsov, G. Tudury, A. Galvanauskas, and T. Sosnowski, “Polarized, 100 kW peak power, high brightness nanosecond lasers based on 3C optical fiber,” Proc. SPIE 7914, 79140U (2011).
[Crossref]

Steinmetz, A.

Stock, M. L.

M. L. Stock, C.-H. Liu, A. Kuznetsov, G. Tudury, A. Galvanauskas, and T. Sosnowski, “Polarized, 100 kW peak power, high brightness nanosecond lasers based on 3C optical fiber,” Proc. SPIE 7914, 79140U (2011).
[Crossref]

Stutzki, F.

Sudesh, V.

V. Sudesh, T. Mccomb, Y. Chen, M. Bass, M. Richardson, J. Ballato, and A. E. Siegman, “Diode-pumped 200 μm diameter core, gain-guided, index-antiguided single mode fiber laser,” Appl. Phys. B 90(3-4), 369–372 (2008).
[Crossref]

Takenaga, K.

Tanigawa, S.

Tudury, G.

M. L. Stock, C.-H. Liu, A. Kuznetsov, G. Tudury, A. Galvanauskas, and T. Sosnowski, “Polarized, 100 kW peak power, high brightness nanosecond lasers based on 3C optical fiber,” Proc. SPIE 7914, 79140U (2011).
[Crossref]

Tünnermann, A.

Uranus, H. P.

H. P. Uranus, “Theoretical study on the multimodeness of a commercial endlessly single-mode PCF,” Opt. Commun. 283(23), 4649–4654 (2010).
[Crossref]

Wei, K.

Wielandy, S.

Wisk, P.

Yablon, A. D.

Yan, M. F.

Zellmer, H.

Appl. Opt. (1)

Appl. Phys. B (1)

V. Sudesh, T. Mccomb, Y. Chen, M. Bass, M. Richardson, J. Ballato, and A. E. Siegman, “Diode-pumped 200 μm diameter core, gain-guided, index-antiguided single mode fiber laser,” Appl. Phys. B 90(3-4), 369–372 (2008).
[Crossref]

Appl. Phys. Lett. (1)

C. D. Brooks and F. Di Teodoro, “Multimegawatt peakpower, single-transverse-mode operation of a 100 µm core diameter, Yb-doped rod-like photonic crystal fiber amplifier,” Appl. Phys. Lett. 89(11), 111119 (2006).
[Crossref]

J. Opt. Soc. Am. B (2)

Opt. Commun. (1)

H. P. Uranus, “Theoretical study on the multimodeness of a commercial endlessly single-mode PCF,” Opt. Commun. 283(23), 4649–4654 (2010).
[Crossref]

Opt. Express (9)

K. R. Hansen, T. T. Alkeskjold, J. Broeng, and J. Lægsgaard, “Thermo-optical effects in high-power Ytterbium-doped fiber amplifiers,” Opt. Express 19(24), 23965–23980 (2011).
[Crossref] [PubMed]

X. Ma, C.-H. Liu, G. Chang, and A. Galvanauskas, “Angular-momentum coupled optical waves in chirally-coupled-core fibers,” Opt. Express 19(27), 26515–26528 (2011).
[Crossref] [PubMed]

J. Limpert, A. Liem, M. Reich, T. Schreiber, S. Nolte, H. Zellmer, A. Tünnermann, J. Broeng, A. Petersson, and C. Jakobsen, “Low-nonlinearity single-transverse-mode ytterbium-doped photonic crystal fiber amplifier,” Opt. Express 12(7), 1313–1319 (2004).
[Crossref] [PubMed]

M. Kashiwagi, K. Saitoh, K. Takenaga, S. Tanigawa, S. Matsuo, and M. Fujimaki, “Effectively single-mode all-solid photonic bandgap fiber with large effective area and low bending loss for compact high-power all-fiber lasers,” Opt. Express 20(14), 15061–15070 (2012).
[Crossref] [PubMed]

F. Kong, K. Saitoh, D. Mcclane, T. Hawkins, P. Foy, G. Gu, and L. Dong, “Mode area scaling with all-solid photonic bandgap fibers,” Opt. Express 20(24), 26363–26372 (2012).
[Crossref] [PubMed]

G. Gu, F. Kong, T. W. Hawkins, P. Foy, K. Wei, B. Samson, and L. Dong, “Impact of fiber outer boundaries on leaky mode losses in leakage channel fibers,” Opt. Express 21(20), 24039–24048 (2013).
[Crossref] [PubMed]

S. Wielandy, “Implications of higher-order mode content in large mode area fibers with good beam quality,” Opt. Express 15(23), 15402–15409 (2007).
[Crossref] [PubMed]

J. W. Nicholson, A. D. Yablon, S. Ramachandran, and S. Ghalmi, “Spatially and spectrally resolved imaging of modal content in large-mode-area fibers,” Opt. Express 16(10), 7233–7243 (2008).
[Crossref] [PubMed]

X. Ma, I.-N. Hu, and A. Galvanauskas, “Propagation-length independent SRS threshold in chirally-coupled-core fibers,” Opt. Express 19(23), 22575–22581 (2011).
[Crossref] [PubMed]

Opt. Lett. (5)

Proc. SPIE (2)

M. Laurila, T. T. Alkeskjold, J. Lægsgaard, and J. Broeng, “Spatial and spectral imaging of LMA photonic crystal fiber amplifiers,” Proc. SPIE 7914, 79142D (2011).
[Crossref]

M. L. Stock, C.-H. Liu, A. Kuznetsov, G. Tudury, A. Galvanauskas, and T. Sosnowski, “Polarized, 100 kW peak power, high brightness nanosecond lasers based on 3C optical fiber,” Proc. SPIE 7914, 79140U (2011).
[Crossref]

Other (8)

C. Zhu, I.-N. Hu, X. Ma, L. Siiam, and A. Galvanauskas, “Single-frequency and single-transverse mode Yb-doped CCC fiber MOPA with robust polarization SBS-free 511W output,” in ASSP (2011), Paper AMC5.

X. Ma, I.-N. Hu, and A. Galvanauskas, “Propagation length independent nonlinearity threshold in Stokes-wave suppressed SRS in chirally-coupled-core fibers,” in Nonlinear Optics (NLO) (2011), Paper NTuE7.

I.-N. Hu, X. Ma, C. Zhu, W.-Z. Chang, C.-H. Liu, T. Sosnowski, A. Galvanauskas, “Experimental demonstration of SRS suppression in chirally-coupled-core fibers,” in ASSP (2012), Paper AT1A.

X. Ma, “Understanding and controlling angular momentum coupled optical waves in chirally-coupled-core (CCC) fibers,” PhD Thesis, University of Michigan at Ann Arbor.

C. Zhu, I.-N. Hu, X. Ma, and A. Galvanauskas, “Single mode 9.1mJ and 10ns pulses from 55um core Yb-doped CCC fiber MOPA,” in CLEO: Science and Innovations, San Jose, California, United States, June 9–14, 2013, Paper CTu1K.

H. Injeyan and G. D. Goodno, High Power Laser Handbook, Chapter 18 (McGraw-Hill Professional, 2011).

J. A. Buck, Fundamentals of Optical Fibers, 2nd ed. (John Wiley, 2004).

TIA Standards, FOTP-80 IEC-60793–1-44 Optical Fibres - Part 1–44: Measurement Methods and Test Procedures - Cut-Off Wavelength.

Supplementary Material (1)

» Media 1: AVI (171 KB)     

Cited By

OSA participates in Crossref's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (9)

Fig. 1
Fig. 1 Polygonal-CCC Fiber Structure: In this structure on-axis central core has a polygonal shape (octagon in this example), with side cores (8 side cores in this case) positioned at the corners of this polygon.

Download Full Size | PPT Slide | PDF

Fig. 2
Fig. 2 Image of fabricated P-CCC fibers: (a) Cross-section of 60µm-core P-CCC fiber (left-hand image) and comparison to a standard 125μm clad single-mode fiber (right-hand image). (b) Cross-section of 55μm core Yb-doped triple-clad fiber. The structure has all-glass (fluorine-doped silica) second cladding with 0.22NA, and fluoro-acrylate-polymer third cladding with 0.45NA.

Download Full Size | PPT Slide | PDF

Fig. 3
Fig. 3 Numerical simulation of P-CCC fibers: Simulated parameters are: central core diameter (inscribed into octagon) 55µm, central core NA = 0.068, side core diameter 10µm, side core NA = 0.088, side-center core separation 6.8µm, and helix period 5.3mm. (a) Simulated modal loss vs. wavelength for central core LP01 and LP11 mode are shown with blue solid line and red solid line respectively, which indicates low loss performance (~0.2dB/m) for fundamental mode and high loss performance (>20dB/m) for higher order modes from ~1020nm to ~1120nm. The simulation for only octagonal central core and no side cores is shown with thick dash lines, and the simulation for round central core with side cores is shown with thin dash lines. The phase matching points between central core modes are also marked. (b) Numerical simulation for lowest order modes from LP01 through LP41 in such a P-CCC fiber structure are shown with colored solid lines. It indicates E-SM performance of this P-CCC structure.

Download Full Size | PPT Slide | PDF

Fig. 4
Fig. 4 Quasi-phase matching between central-core guided modes and central-core leaky modes: The dispersion curves are shown as calculated modal propagation constant as function of optical wavelength. Due to quasi-phase matching mechanism of helically-symmetric CCC structures, each propagation constant is accompanied by its corresponding quasi-phase matching additions (product of modal number l and 2π/Λ), which is labeled in the figure. Each crossing point is below the cutoff of each higher order modes (950nm, 1050nm, and 1170nm for LP91, LP81, and LP71 respectively), so these higher order modes are leaky modes with high propagation loss. These crossing points explained the origin of wavelength-dependent loss of central core guided modes, which also agree with the numerical simulation in Fig. 3(a).

Download Full Size | PPT Slide | PDF

Fig. 5
Fig. 5 Setup for modal beating measurement used to characterize the modal output of the test fiber: Broadband ASE source is launched through SMF into the test fiber at “Input Excitation” position, where the modal excitation can be adjusted by translation stages T1 and T2. Another SMF is used to receive the beam coming out of the test fiber at “SMF Reception” position, so that T3 and T4 can adjust the SMF transverse position for sampling different parts of the beam. By adding an automatic 2-dimensional scan on T4, this setup can perform S2 measurement. Flip mirror M1 and mirror M2 are used to record the near field image of the output beam with the CCD camera. L1, L2, L3, L4, L5 are collimating and focusing aspherical lenses. OSA is an optical spectrum analyzer which receives the broadband signal captured by the sampling-SMF.

Download Full Size | PPT Slide | PDF

Fig. 6
Fig. 6 Varying sampling position at fiber output: Performance comparison between industry-standard 20µm LMA fiber and 55µm CCC fiber, both less than 50cm diameter loosely coiled condition. A 6µm mode field diameter sampling-SMF is used to receive light at different parts of a beam with around 40µm mode field diameter. 20µm LMA fiber is under single mode excitation condition and 55µm CCC fiber under maximum transmission condition. Blue curve corresponds to the signal received by the SMF at the peak center of the beam profile. The CCD images shown at upper-right position of each sub-plot are acquired at blue curve conditions. Red curve corresponds to the signal received by the SMF at intensity −3dB down position comparing to the peak center of the beam profile, and the black curve corresponds to the intensity −10dB down position. (a) Transmission spectrum of 20µm LMA fiber at different parts of the beam profile. It shows the further away from the peak center of the beam profile, the more pronounced spectral beating observed, which is consistent with the fact that the fundamental mode has more distribution in the center whereas the HOM have more distribution in the wings of the modal profile. (b) Despite slightly octagonal shape of the 55µm CCC fiber output modal profile (due to the shape of the central core), there are no modal beating across the entire beam profile, which indicates that it is a pure single mode beam.

Download Full Size | PPT Slide | PDF

Fig. 7
Fig. 7 Varying excitation position at fiber input: Experimental demonstration of robust effectively-single-mode output from 1.5 m long 55µm core CCC fiber at different lateral offset excitation positions. Figure (a) shows broad band spectra and the near-field beam images measured for four different misalignment positions (relative transverse positions of the fiber input) of the 1.5 meter 20µm LMA fiber. Figure (b) shows the same test performed with 1.5 meter 55µm CCC fiber. All transmission spectra are obtained with the sampling-SMF positioned at the peak center of the beam. (a) At 0µm position, 20µm LMA fiber is under the single mode excitation condition. At 5, 10, and 15 microns offset positions, both the beating spectra and the near-field images show the increase in HOM contents. (b) At 0µm position, 55µm CCC fiber is under the maximum transmission condition. At 20, 30, and 40 microns offset positions, no beating is observed in the transmission spectra, and the near-field images remain the same shape with only the intensity decreasing with the increasing offset, indicating that CCC fiber behaves as a single mode fiber. (See Media 1.)

Download Full Size | PPT Slide | PDF

Fig. 8
Fig. 8 S2 measurement for 3meter 20µm-core 0.065NA LMA fiber and 1.5meter 55µm-core 0.068NA CCC fiber with corresponding near field image taken with CCD camera: (a) Fourier transform of the beating spectrum obtained with the S2 measurement of 20µm-core LMA fiber under the condition of single mode excitation and the near field image taken at fiber output. A prominent peak indicating LP11 appearance in the fiber output, even though the near field image is so round and Gaussian-like, which his consistent with Fig. 6(a). (b) Fourier transform of the beating spectrum obtained with the S2 measurement of 55µm CCC fiber under the condition of maximum transmission, and the near field image taken at fiber output. It is clear that all HOM are well suppressed in this case, which is consistent with Fig. 6(b). (c) 20µm LMA fiber with −3dB transmission comparing to the optimum single mode excitation condition, and the near field image taken at fiber output. Obviously, the LP11 mode is actually excited more than fundamental mode in this case, which can be verified by using the least square fitting method on the near field image. This is consistent with Fig. 7(a). (d) Fourier transform of the beating spectrum obtained with the S2 measurement of 55µm CCC fiber under the condition of −3dB transmission comparing to the maximum transmission condition, and the near field image taken at fiber output. All HOM excited at this offset condition are well suppressed, and near field image looks the same except carrying less power output. This is consistent with Fig. 7(b).

Download Full Size | PPT Slide | PDF

Fig. 9
Fig. 9 Lasing performance of 55µm P-CCC fiber samples: The blue dash line represents the data of laser power versus absorbed power. The red solid line represents the linear fit of the blue dash line, which indicates the slope efficiency with this fiber sample is 57.1%. The M2 is measured to be 1.12.

Download Full Size | PPT Slide | PDF

Equations (2)

Equations on this page are rendered with MathJax. Learn more.

Δβ= β l 1 m 1 − β l 2 m 2 ⋅ 1+ K 2 R 2 −Δm⋅K=0,
Δβ= β l 1 m 1 − β l 2 m 2 −Δl⋅K=0,

Metrics