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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 15 — Jul. 28, 2014
  • pp: 18036–18043
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Novel bending-resistant design of two-layer low-index trench fiber with parabolic-profile core

Jiang Sun, Zexin Kang, Jing Wang, Chao Liu, and Shuisheng Jian  »View Author Affiliations


Optics Express, Vol. 22, Issue 15, pp. 18036-18043 (2014)
http://dx.doi.org/10.1364/OE.22.018036


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Abstract

A novel design, two-layer low-index trench fiber with parabolic-profile core, is proposed and investigated numerically in this paper. Based on scalar FD-BPM algorithm, the excellent performance over other types of structures and great potential in mode area enlargement are demonstrated. The effective mode area of our design (D = 100μm) is approximately 890 μm2. Both the high order mode (HOM) suppression and bending resistance of our design are better than that of Multi-Trench Fiber (MTF). The mode loss ratio and effective mode area are independent on the bending radius. Due to the circular symmetry of our proposed configuration design, the bending property is not varied with the changing of bending directions.

© 2014 Optical Society of America

1. Introduction

For the past decades, high power fiber lasers and amplifiers have shown the potential to be as highly attractive coherent light sources due to their compact design, high-power capability, output stability, robustness, cost effectiveness, and power scalability [1

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

2. S. C. Kumar, G. K. Samanta, K. Devi, S. Sanguinetti, and M. Ebrahim-Zadeh, “Single-frequency, high-power, continuous-wave fiber-laser-pumped Ti:sapphire laser,” Appl. Opt. 51(1), 15–20 (2012). [CrossRef] [PubMed]

]. 10kW beam power in continuous wave regime has been reported in a diffraction limited beam in 2010 [3

3. V. Gapontsev, V. Fomin, A. Ferin, and M. Abramov, “Diffraction limited ultra-high-power fiber lasers,” in Advanced Solid-State Photonics (Optical Society of America, 2010), p. AWA1.

]. However, optical non-linear effects are some of the key limiting factors in power scaling [4

4. 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]

]. An effective method for mitigating these non-linear effects is the effective mode-area scaling of the fundamental mode, while maintaining the single-mode output.

In recent years, several fiber structure have been proposed to achieve single-mode operation and large mode area (LMA), such as low-NA step-index fibers [5

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]

], chirally-coupled-core (CCC) fibers [6

6. C.-H. Liu, G. Chang, N. Litchinitser, D. Guertin, N. Jacobsen, K. Tankala, and A. Galvanauskas, “Chirally coupled core fibers at 1550-nm and 1064-nm for effectively single-mode core size scaling,” in Conference on Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference and Photonic Applications Systems Technologies (Optical Society of America, Baltimore, Maryland, 2007), p. CTuBB3. [CrossRef]

], tailored cladding fibers for HOMs suppression [7

7. M. Devautour, P. Roy, and S. Février, “3-D modeling of modal competition in fiber laser: application to HOM suppression in multi-layered fiber,” in Conference on Lasers and Electro-Optics/International Quantum Electronics Conference (Optical Society of America, Baltimore, Maryland, 2009), p. JWA54. [CrossRef]

], Photonic Band-gap Fibers [4

4. 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]

], Photonic Crystal Fibers (PCF) [8

8. M. Napierała, T. Nasilowski, E. Bereś-Pawlik, P. Mergo, F. Berghmans, and H. Thienpont, “Large-mode-area photonic crystal fiber with double lattice constant structure and low bending loss,” Opt. Express 19(23), 22628–22636 (2011). [CrossRef] [PubMed]

], parabolic-profile fiber [9

9. 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]

], gain-guided and index anti-guided (GG + IAG) optical fibers [10

10. A. E. Siegman, “Gain-guided, index-antiguided fiber lasers,” J. Opt. Soc. Am. B 24(8), 1677–1682 (2007). [CrossRef]

], Leakage Channel Fibers (LCF) [11

11. L. A. Dong, J. Li, H. A. McKay, L. B. Fu, and B. K. Thomas, “Large effective mode area optical fibers for high power lasers,” Proc. SPIE 7195, 71950N (2009). [CrossRef]

] and Multi-Trench Fiber(MTF) [12

12. D. Jain, C. Baskiotis, and J. K. Sahu, “Mode area scaling with multi-trench rod-type fibers,” Opt. Express 21(2), 1448–1455 (2013). [CrossRef] [PubMed]

, 13

13. D. Jain, C. Baskiotis, and J. K. Sahu, “Bending performance of large mode area multi-trench fibers,” Opt. Express 21(22), 26663–26670 (2013). [CrossRef] [PubMed]

]. However, the application limits of these fibers are the complex and expensive fabrication and detrimental bending effects [13

13. D. Jain, C. Baskiotis, and J. K. Sahu, “Bending performance of large mode area multi-trench fibers,” Opt. Express 21(22), 26663–26670 (2013). [CrossRef] [PubMed]

].

In this paper, a novel all-solid structure, two-layer low-index trench fiber with parabolic-profile core, has been presented. The great potentials of our design in single-mode operation, mode area enlargement and resistance to bending are demonstrated. In the following, the simulation method, Multi-Trench Fiber (MTF), parabolic-profile fiber and our design are introduced orderly.

2. Scalar finite-difference beam propagation method (scalar FD-BPM)

A scalar finite-difference beam propagation method (FD-BPM) is used in our simulation, since our structures in this work are low-contrast and some studies have also demonstrated the efficient potential of scalar BPM for the modeling of such structures [14

14. A. Abeeluck, N. Litchinitser, C. Headley, and B. Eggleton, “Analysis of spectral characteristics of photonic bandgap waveguides,” Opt. Express 10(23), 1320–1333 (2002). [CrossRef] [PubMed]

]. FD-BPM algorithm is a most widely used propagation technique for modeling integrated and fiber optic photonic devices. First, the main advantage of BPM algorithm is undoubtedly its ability to handle both the guided and the radiating parts of the field with the same simple formalism [15

15. J. Van Roey, J. van derDonk, and P. E. Lagasse, “Beam-propagation method: analysis and assessment,” J. Opt. Soc. Am. 71(7), 803–810 (1981). [CrossRef]

]. Besides, FD-BPM algorithm is more efficient and stable compared to FFT-BPM [16

16. Y. Chung and N. Dagli, “An assessment of finite difference beam propagation method,” IEEE J. Quantum Electron. 26(8), 1335–1339 (1990). [CrossRef]

].

The boundary conditions used in this work is the simple implementation of the transparent boundary condition which effectively lets the radiation pass through the boundary and leave the computational domain. In [17

17. 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]

], the simulated HOM suppression of a LCF with high index coating seems to provide a good agreement with the experimental HOM suppression of a double clad LCF with low index coating. In [18

18. G. C. Gu, F. T. Kong, T. W. Hawkins, P. Foy, K. X. 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]

], a suitable boundary condition in low-index coated fibers leads to the measured mode losses being very close to the simulations based on infinite cladding. So the transparent boundary condition is accredited.

Bending is modeled here using the equivalent index model [19

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

]. In order to save computation, the equivalent index profile is simplified,
neff=n1+2xRn(1+xR)
(1)
where neff is the equivalent index profile of the bent fiber, n is the index profile of the unbent fiber, x is the transverse position, and R is the bending radius. This simplification is accurate because of xmax<<R in all our simulation, where xmax is the transverse domain boundary.

Actually, the practical limit of bending radius is about 0.25m. So here the simulated bending radius is fixed at 0.25m if not specially mentioned. And in all our simulations, cladding refractive index nc is 1.444 and wavelength λ is 1.05μm. Given the simulation errors, the too-low mode loss (<5x10−5 dB/m) approximates at 5x10−5 dB/m.

3. Multi-trench fiber (MTF)

Figure 1(a)
Fig. 1 (a) The cross section of the MTF structure. (b) The refractive index profiles of the unbent (blue) and bent (red) MTF and the notations in this paper, where D is the core diameter, t is the thickness of the low-index rings (trenches), d is the thickness of the high-index rings, and Δn is the refractive index difference between the core and the trenches.
shows the cross section of the MTF structure and Fig. 1(b) shows the refractive index profiles of the unbent and bent MTF as well as the notations used in this paper, where D is the core diameter, t is the thickness of all the low-index rings (trenches), d is the thickness of the all high-index rings, nc is the cladding index and Δn is the refractive index difference between the core and the trenches.

In the papers [12

12. D. Jain, C. Baskiotis, and J. K. Sahu, “Mode area scaling with multi-trench rod-type fibers,” Opt. Express 21(2), 1448–1455 (2013). [CrossRef] [PubMed]

, 13

13. D. Jain, C. Baskiotis, and J. K. Sahu, “Bending performance of large mode area multi-trench fibers,” Opt. Express 21(22), 26663–26670 (2013). [CrossRef] [PubMed]

], the width of the low-index trenches and the index difference between the core and trenches can be used to adjust the leakage loss of the fundamental mode (LP01) and HOMs, but these are slightly effective on the loss ratio between low-loss HOM and LP01. In this paper, the result of the HOM loss (dB/m) divided by the FM loss (dB/m) is defined as the ratio of mode losses, so the ratio unit is just 1. In this paper, the total loss of LP01 is tried to adjust below 1 dB/m but it is not fixed. The effects of the width of the low-index trenches and the index difference between the core and trenches are not the point researched here.

Figure 2
Fig. 2 (a) The leakage loss of the LP01 and HOMs and loss ratio between the low-loss HOM and LP01 in the range of the thickness d (4-38μm) in the unbent MTF. (b) The total loss of LP01 and HOMs and loss ratio between the low-loss HOM and LP01, including the leakage and bending loss, in the bent MTF. (c) and (d) The effective index of the corresponding core modes and first leaky cladding mode in the unbent MTF and in the bent MTF, respectively.
shows the performance of an unbent and bent MTF with structural parameters D = 50μm, t = 7μm, Δn = 0.0012 and bending radius R = 0.25m. Figure 2(a) plots the leakage loss of the LP01 and HOMs and loss ratio between the low-loss HOM and LP01 at a range of the thickness d (4-38μm) in this unbent MTF. Similarly, Fig. 2(b) plots the total loss of LP01 and HOMs, including the leakage and bending loss, and loss ratio between the low-loss HOM and LP01 in this bent MTF. Figures 2(c) and 2(d) plot the effective index of the corresponding core modes in this unbent and bent MTF, respectively. And the index of the first leaky cladding mode is also plotted in Figs. 2(c) and 2(d), since the effect of first leaky cladding mode is important and representative.

And our unbent MTF results are concordant with those reported in [12

12. D. Jain, C. Baskiotis, and J. K. Sahu, “Mode area scaling with multi-trench rod-type fibers,” Opt. Express 21(2), 1448–1455 (2013). [CrossRef] [PubMed]

]. Compared with Fig. 2(a), the total loss curves in Fig. 2(b) like to be compressed in the range of d, 4-10μm and confused in the range of d, 10-38μm. And the vertical and horizontal polarizations of LP11 are separated, named LP11v and LP11h [as shown in Fig. 2(b)] in this paper, respectively. Just near d = 9μm and d = 20μm, the loss ratio between the low-loss HOM and LP01 in the bent MTF is more than 30.

The first leakage loss peak of LP01 is at d = 30μm, LP11 at d = 17μm and LP21 at d = 12μm [as shown in Fig. 2(a)], that are near the cross points of the index curves of LP01, LP11, LP21 and the first leaky cladding mode [as shown in Fig. 2(c)], respectively. The similar phenomenon is also revealed in Fig. 2(d). These are corresponding to the principle of mode suppression through index-matched mixing with leaky cladding modes reported in [20

20. J. Fini, “Design of solid and microstructure fibers for suppression of higher-order modes,” Opt. Express 13(9), 3477–3490 (2005). [CrossRef] [PubMed]

]. And this principle can help us to understand the MTF performance well.

The bend-induced increase of the index of leaky cladding modes causes the compressions (4μm<d<10μm) and confusions (10μm<d<38μm) of all cross points of the index curves of core modes and leaky cladding modes. So the poor HOM suppression of the bent MTF occurs accordingly. Besides, since the bend-induced birefringence of this MTF causes the separation of LP11v and LP11h, the HOM suppression of the bent MTF becomes worse. Therefore, this MTF is sensitive to bending.

4. Parabolic-profile fiber

The parabolic-profile fiber has the bending resistance [9

9. 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]

] and slower degradation of the injected beam quality [21

21. R. Zuitlin, Y. Shamir, Y. Sintov, and M. Shtaif, “Modeling the evolution of spatial beam parameters in parabolic index fibers,” Opt. Lett. 37(17), 3636–3638 (2012). [CrossRef] [PubMed]

]. Figure 3(a)
Fig. 3 (a) The index profiles of unbent (blue) and bent (red) parabolic-profile fiber and parameters, where core diameter is D, and index difference of the top of the parabolic profile and cladding is Δn. (b), (c) and (d) are total loss of LP01 and the low-loss HOM in the unbent and bent parabolic-profile fiber with core diameter D = 50μm, 75μm and 100μm, respectively, and the yellow areas are where total loss of the low-loss HOM are about 10dB/m.
shows index profiles of unbent (blue) and bent (red) parabolic-profile fiber and parameters, where core diameter is D, and index difference of the top of the parabolic profile and cladding is Δn. Figures 3(b)3(d) plot the total loss of LP01 and the low-loss HOM in the unbent and bent parabolic-profile fiber with core diameter D = 50μm, 75μm and 100μm, respectively. Given the simulation errors, the too-low mode loss (<5x10−5 dB/m) approximates at 5x10−5 dB/m. Obviously, bending the parabolic-profile fiber causes the increase of the total loss of LP01 and HOMs and the increase of the loss ratio between low-loss HOM and LP01. These results indicate that the bent parabolic-profile fiber is excellent for HOM suppression. However, in the bent parabolic-profile fibers, even considering the points of the 10dB/m total loss of the low-loss HOM [as marked in yellow in Figs. 3(b)3(d)], the index difference Δn is 0.0006 at core diameter D = 50μm, 0.00055 at D = 75μm and 0.0005 at D = 100μm, respectively. Since a fiber core NA lower than 0.05 (Δn = 0.0087 at cladding index nc = 1.444) is generally difficult to achieve in conventional manufacturing processes [22

22. M.-J. Li, X. Chen, A. Liu, S. Gray, J. Wang, D. T. Walton, and L. A. Zenteno, “Limit of effective area for single-mode operation in step-index large mode area laser fibers,” J. Lightwave Technol. 27(15), 3010–3016 (2009). [CrossRef]

], the parabolic-profile fibers with such low index differences are hardly fabricated.

5. Two-layer low-index trench fiber with parabolic-prolife core

Based on the aforementioned analyses, a novel design, two-layer low-index trench fiber with parabolic-profile core is presented in this paper. Figures 4(a)
Fig. 4 (a) the cross section of two trench fiber with parabolic-profile core. (b) The index profiles of this unbent (blue) and bent (red) design and the parameters in this paper, where D stands for core diameter, Δn for index difference of trenches and cladding, d for the thickness of the high-index rings, t1 for the thickness of the inner low-index trench and t2 for the thickness of the outside low-index trench.
and 4(b) display its index profile and the key parameters, respectively. D stands for core diameter, Δn for index difference of trenches and cladding, d for the thickness of the high-index rings, t1 for the thickness of the inner low-index trench and t2 for the thickness of the outside low-index trench. The inner trench and parabolic core are conjoint, which design is easily fabricated.

In Fig. 5
Fig. 5 (a) The leakage loss of LP01 and HOMs and loss ratio between the low-loss HOM and LP01 in our unbent design. (b) The total loss of LP01 and HOMs and loss ratio between the low-loss HOM and LP01 in our bent design. (c) and (d) The effective index of core modes and the first leaky cladding mode in our unbent design and in our bent design, respectively.
, we present the performance of unbent and bent two trench fiber with parabolic-profile core with structural parameters D = 50μm, t1 = 3μm, t2 = 6μm, Δn = 0.0012 and bending radius R = 0.25m.

Figure 5(a) plots the leakage loss of LP01 and HOMs and loss ratio between the low-loss HOM and LP01, and Fig. 5(c) displays the effective index of core modes and the first leaky cladding mode in the unbent two trench fiber with parabolic-profile core. It is found in Fig. 5(a) that the loss ratio between the low-loss HOM and LP01 is more than 30 at 2μm<d<9μm in this unbent design. So the HOM suppression of this unbent design is excellent. Figure 5(b) plots the total loss of LP01 and HOMs and loss ratio between the low-loss HOM and LP01, and Fig. 5(d) displays the effective index of core modes and first leaky cladding mode in this bent design. From Fig. 5(b), the loss ratio between the low-loss HOM and LP01 is more than 30 at 2μm<d<7μm. Clearly, in this bent design, the compression (d<9μm) and confusion (d>9μm) of total loss curves is weaker than that in the bent MTF above. The HOM suppression is better than that in the bent MTF above.

As shown in Figs. 5(c) and 5(d), the cross points of index curves of core modes and the first leaky cladding mode are also near the loss peaks of the corresponding core modes. Because of the parabolic index core, the effective-index difference of LP01 and LP11 is about twice that in the bent MTF above and two polarizations of LP11, LP11v and LP11h, are not separated. The performance of our design is evidently improved. The effective mode area of LP01 is 446μm2 in our unbent design and 448μm2 in our bent design, respectively.

6. Mode area scaling

For scaling the effective mode area, the simulated core diameter of our design is scaled to 100μm. Figure 6(a)
Fig. 6 (a) The leakage loss of LP01 and low-loss HOM and loss ratio between the low-loss HOM and LP01 in the unbent two trench fiber with parabolic-profile core with D = 100μm, t1 = 1μm, t2 = 3μm, Δn = 0.0012. (b) The total loss of LP01 and low-loss HOM and loss ratio between the low-loss HOM and LP01 in this bent design with bending radius R = 0.25m.
shows the leakage loss of LP01, low-loss HOM and loss ratio between the low-loss HOM and LP01 in the unbent design with D = 100μm, t1 = 1μm, t2 = 3μm and Δn = 0.0012. And Fig. 6(b) shows the corresponding case of bent design with bending radius R = 0.25m. As shown in Fig. 6(a), the performance of our unbent design is very well. From Fig. 6(b), the loss ratio between the low-loss HOM and LP01 in this bent design is more than 30 in the range of d, 3-7μm, 16-20μm and 29-33μm, respectively. The range of d with the high loss ratio in our bent design (D = 100μm) is wider than that in the bent MTF (D = 50μm), obviously.

Figure 7
Fig. 7 The influence of the bending radius and the thickness (d) of the high-index ring on the total loss of the low-loss HOM and LP01 in our bent design (D = 100μm, t1 = 1μm, t2 = 3μm and Δn = 0.0012), and the influence of the bending radius on the total loss of the low-loss HOM and LP01 in the parabolic-profile fiber (D = 100μm and Δn = 0.0012).
plots the influence of the bending radius and the thickness (d) of the high-index ring on the total loss of the low-loss HOM and LP01 in our bent design (D = 100μm, t1 = 1μm, t2 = 3μm and Δn = 0.0012). From Fig. 7, the HOM suppression and bending resistance at 4μm<d<6μm keep well when the HOM total loss is below 10dB/m (marked by red arrow dotted lines) in our bent design. In consideration of the 3.3dB/m average gain in the final-stage power fiber amplifier [23

23. Y. Jeong, J. Nilsson, J. K. Sahu, D. N. Payne, R. Horley, L. M. B. Hickey, and P. W. Turner, “Power scaling of single-frequency ytterbium-doped fiber master-oscillator power-amplifier sources up to 500 W,” IEEE J. Sel. Top. Quantum Electron. 13(3), 546–551 (2007). [CrossRef]

] and the average gain below 1dB/m in high power fiber lasers [24

24. Y. Jeong, J. Sahu, D. Payne, and J. Nilsson, “Ytterbium-doped large-core fiber laser with 1.36 kW continuous-wave output power,” Opt. Express 12(25), 6088–6092 (2004). [CrossRef] [PubMed]

, 25

25. Y. Jeong, A. J. Boyland, J. K. Sahu, S. Chung, J. Nilsson, and D. N. Payne, “Multi-kilowatt single-mode ytterbium-doped large-core fiber laser,” J. Opt. Soc. Korea. 13(4), 416–422 (2009). [CrossRef]

], this HOM suppression in our design is sufficient.

As a comparison, Fig. 7 also plots the influence of the bending radius on the total loss of the low-loss HOM and LP01 in the parabolic-profile fiber (D = 100μm and Δn = 0.0012). As seen in Fig. 7, the simulated HOM-total-loss curves in our design have smaller slopes than the curve in this parabolic-profile fiber. So the bending sensitivity of our design is weaker than that of the parabolic-profile fiber with the same index difference.

Figure 8(a)
Fig. 8 (a) The influence of the bending radius on the effective mode area of LP01 in the bent MTF (D = 50μm) and our bent design (D = 100μm). (b) The LP01 surface profiles of the unbent (top left) and bent (top right) MTF (D = 50μm), our unbent (bottom left) and bent (bottom right) design (D = 100μm), where bending radius is 0.25m. The 50μm-diameter central regions are marked by red circles.
plots the influence of bending radius on the effective mode area of LP01 in our design (D = 100μm) and MTF (D = 50μm). With the decrease of the bending radius, the effective mode area of LP01 in our bent design (D = 100μm) which is about 890μm2, keeps constant, while the one in the bent MTF (D = 50μm) reduces. Figure 8(b) displays the LP01 surface profiles of our design (D = 100μm) and MTF (D = 50μm). Obviously, the bend-induced LP01 distortion of our design is lower than that of MTF. And the bend-induced distortion of fiber modes can severely impact the amplifier performance [26

26. 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]

].

7. Discussions and conclusions

In this paper, a novel design, two-layer low-index trench fiber with the parabolic-profile core, is proposed and investigated numerically. Based on scalar FD-BPM algorithm, the excellent performance over other types of structures and great potential in mode area enlargement are demonstrated. The range of the thickness d with high loss ratio in our bent design (D = 100μm) is larger than the bent MTF (D = 50μm). The mode loss ratio and effective mode area of our design (d = 6μm, D = 100μm) are 890 μm2 and independent on the bending radius. Due to the circular symmetry of our proposed configuration design, the bending property is not varied with the changing of bending directions. Like the parabolic-profile fiber, our design also has the slower degradation of the injected beam quality [21

21. R. Zuitlin, Y. Shamir, Y. Sintov, and M. Shtaif, “Modeling the evolution of spatial beam parameters in parabolic index fibers,” Opt. Lett. 37(17), 3636–3638 (2012). [CrossRef] [PubMed]

] and little bend-induced distortion of fiber modes. Compared with the parabolic profile fiber, the performance of our design isn’t limited by the index difference of the parabolic profile. Given the fabrication, our design can be fabricated by conventional processes, such as MCVD with careful control, and the rare-earth ions can also be easily doped simultaneously, while other designs, like PCF and LCF, are difficultly fabricated, due to the requirement of stack and draw technique. In conclusion, the HOM suppression and bending resistance of our design are excellent.

Acknowledgments

I thank Junhua Ji (at Nanyang Technological University), Seongwoo Yoo (at Nanyang Technological University) and Johan Nilsson (at University of Southampton) for all the useful discussions. This work was supported by the Major State Basic Research Development Program of China granted No. 2010CB328206.

References and links

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.

S. C. Kumar, G. K. Samanta, K. Devi, S. Sanguinetti, and M. Ebrahim-Zadeh, “Single-frequency, high-power, continuous-wave fiber-laser-pumped Ti:sapphire laser,” Appl. Opt. 51(1), 15–20 (2012). [CrossRef] [PubMed]

3.

V. Gapontsev, V. Fomin, A. Ferin, and M. Abramov, “Diffraction limited ultra-high-power fiber lasers,” in Advanced Solid-State Photonics (Optical Society of America, 2010), p. AWA1.

4.

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]

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.

C.-H. Liu, G. Chang, N. Litchinitser, D. Guertin, N. Jacobsen, K. Tankala, and A. Galvanauskas, “Chirally coupled core fibers at 1550-nm and 1064-nm for effectively single-mode core size scaling,” in Conference on Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference and Photonic Applications Systems Technologies (Optical Society of America, Baltimore, Maryland, 2007), p. CTuBB3. [CrossRef]

7.

M. Devautour, P. Roy, and S. Février, “3-D modeling of modal competition in fiber laser: application to HOM suppression in multi-layered fiber,” in Conference on Lasers and Electro-Optics/International Quantum Electronics Conference (Optical Society of America, Baltimore, Maryland, 2009), p. JWA54. [CrossRef]

8.

M. Napierała, T. Nasilowski, E. Bereś-Pawlik, P. Mergo, F. Berghmans, and H. Thienpont, “Large-mode-area photonic crystal fiber with double lattice constant structure and low bending loss,” Opt. Express 19(23), 22628–22636 (2011). [CrossRef] [PubMed]

9.

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]

10.

A. E. Siegman, “Gain-guided, index-antiguided fiber lasers,” J. Opt. Soc. Am. B 24(8), 1677–1682 (2007). [CrossRef]

11.

L. A. Dong, J. Li, H. A. McKay, L. B. Fu, and B. K. Thomas, “Large effective mode area optical fibers for high power lasers,” Proc. SPIE 7195, 71950N (2009). [CrossRef]

12.

D. Jain, C. Baskiotis, and J. K. Sahu, “Mode area scaling with multi-trench rod-type fibers,” Opt. Express 21(2), 1448–1455 (2013). [CrossRef] [PubMed]

13.

D. Jain, C. Baskiotis, and J. K. Sahu, “Bending performance of large mode area multi-trench fibers,” Opt. Express 21(22), 26663–26670 (2013). [CrossRef] [PubMed]

14.

A. Abeeluck, N. Litchinitser, C. Headley, and B. Eggleton, “Analysis of spectral characteristics of photonic bandgap waveguides,” Opt. Express 10(23), 1320–1333 (2002). [CrossRef] [PubMed]

15.

J. Van Roey, J. van derDonk, and P. E. Lagasse, “Beam-propagation method: analysis and assessment,” J. Opt. Soc. Am. 71(7), 803–810 (1981). [CrossRef]

16.

Y. Chung and N. Dagli, “An assessment of finite difference beam propagation method,” IEEE J. Quantum Electron. 26(8), 1335–1339 (1990). [CrossRef]

17.

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]

18.

G. C. Gu, F. T. Kong, T. W. Hawkins, P. Foy, K. X. 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]

19.

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

20.

J. Fini, “Design of solid and microstructure fibers for suppression of higher-order modes,” Opt. Express 13(9), 3477–3490 (2005). [CrossRef] [PubMed]

21.

R. Zuitlin, Y. Shamir, Y. Sintov, and M. Shtaif, “Modeling the evolution of spatial beam parameters in parabolic index fibers,” Opt. Lett. 37(17), 3636–3638 (2012). [CrossRef] [PubMed]

22.

M.-J. Li, X. Chen, A. Liu, S. Gray, J. Wang, D. T. Walton, and L. A. Zenteno, “Limit of effective area for single-mode operation in step-index large mode area laser fibers,” J. Lightwave Technol. 27(15), 3010–3016 (2009). [CrossRef]

23.

Y. Jeong, J. Nilsson, J. K. Sahu, D. N. Payne, R. Horley, L. M. B. Hickey, and P. W. Turner, “Power scaling of single-frequency ytterbium-doped fiber master-oscillator power-amplifier sources up to 500 W,” IEEE J. Sel. Top. Quantum Electron. 13(3), 546–551 (2007). [CrossRef]

24.

Y. Jeong, J. Sahu, D. Payne, and J. Nilsson, “Ytterbium-doped large-core fiber laser with 1.36 kW continuous-wave output power,” Opt. Express 12(25), 6088–6092 (2004). [CrossRef] [PubMed]

25.

Y. Jeong, A. J. Boyland, J. K. Sahu, S. Chung, J. Nilsson, and D. N. Payne, “Multi-kilowatt single-mode ytterbium-doped large-core fiber laser,” J. Opt. Soc. Korea. 13(4), 416–422 (2009). [CrossRef]

26.

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]

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

History
Original Manuscript: May 26, 2014
Revised Manuscript: June 27, 2014
Manuscript Accepted: July 7, 2014
Published: July 17, 2014

Citation
Jiang Sun, Zexin Kang, Jing Wang, Chao Liu, and Shuisheng Jian, "Novel bending-resistant design of two-layer low-index trench fiber with parabolic-profile core," Opt. Express 22, 18036-18043 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-15-18036


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References

  1. D. J. Richardson, J. Nilsson, and W. A. Clarkson, “High power fiber lasers: current status and future perspectives [Invited],” J. Opt. Soc. Am. B27(11), B63–B92 (2010). [CrossRef]
  2. S. C. Kumar, G. K. Samanta, K. Devi, S. Sanguinetti, and M. Ebrahim-Zadeh, “Single-frequency, high-power, continuous-wave fiber-laser-pumped Ti:sapphire laser,” Appl. Opt.51(1), 15–20 (2012). [CrossRef] [PubMed]
  3. V. Gapontsev, V. Fomin, A. Ferin, and M. Abramov, “Diffraction limited ultra-high-power fiber lasers,” in Advanced Solid-State Photonics (Optical Society of America, 2010), p. AWA1.
  4. 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. Express20(24), 26363–26372 (2012). [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. C.-H. Liu, G. Chang, N. Litchinitser, D. Guertin, N. Jacobsen, K. Tankala, and A. Galvanauskas, “Chirally coupled core fibers at 1550-nm and 1064-nm for effectively single-mode core size scaling,” in Conference on Lasers and Electro-Optics/Quantum Electronics and Laser Science Conference and Photonic Applications Systems Technologies (Optical Society of America, Baltimore, Maryland, 2007), p. CTuBB3. [CrossRef]
  7. M. Devautour, P. Roy, and S. Février, “3-D modeling of modal competition in fiber laser: application to HOM suppression in multi-layered fiber,” in Conference on Lasers and Electro-Optics/International Quantum Electronics Conference (Optical Society of America, Baltimore, Maryland, 2009), p. JWA54. [CrossRef]
  8. M. Napierała, T. Nasilowski, E. Bereś-Pawlik, P. Mergo, F. Berghmans, and H. Thienpont, “Large-mode-area photonic crystal fiber with double lattice constant structure and low bending loss,” Opt. Express19(23), 22628–22636 (2011). [CrossRef] [PubMed]
  9. J. M. Fini, “Bend-resistant design of conventional and microstructure fibers with very large mode area,” Opt. Express14(1), 69–81 (2006). [CrossRef] [PubMed]
  10. A. E. Siegman, “Gain-guided, index-antiguided fiber lasers,” J. Opt. Soc. Am. B24(8), 1677–1682 (2007). [CrossRef]
  11. L. A. Dong, J. Li, H. A. McKay, L. B. Fu, and B. K. Thomas, “Large effective mode area optical fibers for high power lasers,” Proc. SPIE7195, 71950N (2009). [CrossRef]
  12. D. Jain, C. Baskiotis, and J. K. Sahu, “Mode area scaling with multi-trench rod-type fibers,” Opt. Express21(2), 1448–1455 (2013). [CrossRef] [PubMed]
  13. D. Jain, C. Baskiotis, and J. K. Sahu, “Bending performance of large mode area multi-trench fibers,” Opt. Express21(22), 26663–26670 (2013). [CrossRef] [PubMed]
  14. A. Abeeluck, N. Litchinitser, C. Headley, and B. Eggleton, “Analysis of spectral characteristics of photonic bandgap waveguides,” Opt. Express10(23), 1320–1333 (2002). [CrossRef] [PubMed]
  15. J. Van Roey, J. van derDonk, and P. E. Lagasse, “Beam-propagation method: analysis and assessment,” J. Opt. Soc. Am.71(7), 803–810 (1981). [CrossRef]
  16. Y. Chung and N. Dagli, “An assessment of finite difference beam propagation method,” IEEE J. Quantum Electron.26(8), 1335–1339 (1990). [CrossRef]
  17. 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]
  18. G. C. Gu, F. T. Kong, T. W. Hawkins, P. Foy, K. X. Wei, B. Samson, and L. Dong, “Impact of fiber outer boundaries on leaky mode losses in leakage channel fibers,” Opt. Express21(20), 24039–24048 (2013). [CrossRef] [PubMed]
  19. D. Marcuse, “Influence of curvature on the losses of doubly clad fibers,” Appl. Opt.21(23), 4208–4213 (1982). [CrossRef] [PubMed]
  20. J. Fini, “Design of solid and microstructure fibers for suppression of higher-order modes,” Opt. Express13(9), 3477–3490 (2005). [CrossRef] [PubMed]
  21. R. Zuitlin, Y. Shamir, Y. Sintov, and M. Shtaif, “Modeling the evolution of spatial beam parameters in parabolic index fibers,” Opt. Lett.37(17), 3636–3638 (2012). [CrossRef] [PubMed]
  22. M.-J. Li, X. Chen, A. Liu, S. Gray, J. Wang, D. T. Walton, and L. A. Zenteno, “Limit of effective area for single-mode operation in step-index large mode area laser fibers,” J. Lightwave Technol.27(15), 3010–3016 (2009). [CrossRef]
  23. Y. Jeong, J. Nilsson, J. K. Sahu, D. N. Payne, R. Horley, L. M. B. Hickey, and P. W. Turner, “Power scaling of single-frequency ytterbium-doped fiber master-oscillator power-amplifier sources up to 500 W,” IEEE J. Sel. Top. Quantum Electron.13(3), 546–551 (2007). [CrossRef]
  24. Y. Jeong, J. Sahu, D. Payne, and J. Nilsson, “Ytterbium-doped large-core fiber laser with 1.36 kW continuous-wave output power,” Opt. Express12(25), 6088–6092 (2004). [CrossRef] [PubMed]
  25. Y. Jeong, A. J. Boyland, J. K. Sahu, S. Chung, J. Nilsson, and D. N. Payne, “Multi-kilowatt single-mode ytterbium-doped large-core fiber laser,” J. Opt. Soc. Korea.13(4), 416–422 (2009). [CrossRef]
  26. 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]

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