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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 22 — Oct. 22, 2012
  • pp: 24575–24584
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Scaling the effective area of higher-order-mode erbium-doped fiber amplifiers

J. W. Nicholson, J. M. Fini, A. M. DeSantolo, X. Liu, K. Feder, P. S. Westbrook, V. R. Supradeepa, E. Monberg, F. DiMarcello, R. Ortiz, C. Headley, and D. J. DiGiovanni  »View Author Affiliations


Optics Express, Vol. 20, Issue 22, pp. 24575-24584 (2012)
http://dx.doi.org/10.1364/OE.20.024575


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Abstract

We demonstrate scaling of the effective area of higher-order mode, Er-doped fiber amplifiers. Two Er-doped higher-order mode fibers, one with 3800 μm2 Aeff in the LP0,11 mode, and one with 6000 μm2 effective area in the LP0,14 mode, are demonstrated. Output beam profiles show clean higher order modes, and S2 imaging measurements show low extraneous higher order mode content. CW and pulsed amplifier experiments are reported. Nanosecond pulses are amplified to 0.5 mJ pulse energy with 0.5 MW peak power.

© 2012 OSA

1. Introduction

The drive to higher output powers and pulse energies in high-power fiber lasers brings with it a corresponding need to mitigate nonlinearities such as self-phase modulation, Brillouin scattering, and Raman scattering. Consequently there have been a number of strategies proposed to increase the fiber effective area (Aeff), in order to achieve large-mode area (LMA) high power fiber lasers. One approach, the rod-type fiber, is to scale up the core size, in order to strictly enforce single mode operation and make the fiber rigid to avoid macrobend losses associated with a weakly guiding core [1

1. J. Limpert, N. Deguil-Robin, I. Manek-Hönninger, F. Salin, F. Röser, A. Liem, T. Schreiber, S. Nolte, H. Zellmer, A. Tünnermann, J. Broeng, A. Petersson, and C. Jakobsen, “High-power rod-type photonic crystal fiber laser,” Opt. Express 13(4), 1055–1058 (2005). [CrossRef] [PubMed]

]. However the restriction that the fiber must be held straight eliminates many of the advantages of the conventional fiber geometry. Another approach, taken by chirally coupled fibers [2

2. 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]

], leakage channel fibers [3

3. W. S. Wong, X. Peng, J. M. McLaughlin, and L. Dong, “Breaking the limit of maximum effective area for robust single-mode propagation in optical fibers,” Opt. Lett. 30(21), 2855–2857 (2005). [CrossRef] [PubMed]

], and helically coiled cores [4

4. Z. Jiang and J. R. Marciante, “Mode-area scaling of helical-core, dual-clad fiber lasers and amplifiers using an improved bend-loss model,” J. Opt. Soc. Am. B 23(10), 2051–2058 (2006). [CrossRef]

], is to use a core contrast that is not single moded, operate the fiber in the fundamental mode, and introduce additional structures into the fiber to add differential loss to unwanted higher order modes. However, all these approaches use the fundamental mode, which suffers from bend induced reductions in Aeff, consequently leading to increased nonlinearities and offsetting the advantage of the LMA design, with the effect becoming more pronounced as Aeff is increased [5

5. J. M. Fini, “Intuitive modeling of bend distortion in large-mode-area fibers,” Opt. Lett. 32(12), 1632–1634 (2007). [CrossRef] [PubMed]

, 6

6. 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]

].

Recently a new approach to high power fiber lasers was introduced: intentionally operating in a single, large effective area, higher-order mode (HOM) of a specially designed, multi-mode fiber [7

7. 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]

, 8

8. S. Ramachandran, J. M. Fini, M. Mermelstein, J. W. Nicholson, S. Ghalmi, and M. F. Yan, “Ultra-large effective-area, higher-order mode fibers: a new strategy for high-power lasers,” Laser Photonics Rev. 2(6), 429–448 (2008). [CrossRef]

]. Higher-order modes have the advantage that they are less susceptible than the fundamental mode to bend-induced area reduction [9

9. J. M. Fini and S. Ramachandran, “Natural bend-distortion immunity of higher-order-mode large-mode-area fibers,” Opt. Lett. 32(7), 748–750 (2007). [CrossRef] [PubMed]

]. At the same time, compared to the fundamental mode, they are more resistant to nearest-neighbor mode coupling, which scatters the LPM,N mode into the LPM ± 1,N and is typically the dominant form of mode-coupling in multi-mode fibers [10

10. D. Marcuse, Theory of Dielectric Optical Waveguides, 2nd ed. (Academic Press, 1974).

]. The resistance to nearest neighbor coupling occurs because the difference in effective index between the LP0,N and LP1,N modes increases with increasing N.

There have been a number of recent demonstrations of fiber amplifiers and lasers based on higher-order modes [11

11. S. Ramachandran, K. Brar, S. Ghalmi, K. Aiso, M. Yan, D. Trevor, J. Fleming, C. Headley, P. Wisk, G. Fishteyn, E. Monberg, and F. Dimarcello, “High-power amplification in a 2040 µm2 higher order mode,” in Photonics West, Late Breaking Developments—Session 6453–9 (San Jose, 2007).

16

16. J. W. Nicholson, A. M. DeSantolo, S. Ghalmi, J. M. Fini, J. Fleming, E. Monberg, F. DiMarcello, and S. Ramachandran, “Nanosecond Pulse Amplification in a Higher-Order-Mode Erbium-Doped Fiber Amplifier,” in Conference on Lasers and Electro-Optics (CLEO) 2010, paper CPDB5.

]. Amplification in a cladding-pumped, Yb-doped, higher-order mode amplifier has been demonstrated with 200 W output power with a slope efficiency of 57% in the LP0,10 mode with 3300 μm2 Aeff [12

12. C. Headley, J. Phillips, J. Fini, E. Gonzalas, S. Ghalmi, M. Yan, J. Nicholson, P. Wisk, J. Fleming, E. Monberg, F. DiMarcello, R.S. Windeler, M. Fishteyn, K. Brar, S. Ramachandran, and D.J. DiGiovanni, “Amplification of a large-mode area single higher order mode in a fiber amplifier,” in Proceedings of Photonics West 2012 paper 8237–60.

]. A reconverting Yb-doped fiber amplifier with 52% slope efficiency with amplification in the higher-order mode and an output long-period grating to convert the higher-order mode back to the fundamental mode was also reported.

In addition to cladding-pumped Yb-doped HOM amplifiers, core-pumped Er-doped HOM amplifiers have been demonstrated. The HOM-Er amplifier is a core-pumped design, with both single mode pump source and signal propagating in the same higher order mode, allowing for maximum pump-signal overlap and thus short lengths of amplifier fiber. A high power, single mode, Raman fiber laser operating at 1480 nm [17

17. J. W. Nicholson, M. F. Yan, P. Wisk, J. Fleming, F. DiMarcello, E. Monberg, T. Taunay, C. Headley, and D. J. DiGiovanni, “Raman fiber laser with 81 W output power at 1480 nm,” Opt. Lett. 35(18), 3069–3071 (2010). [CrossRef] [PubMed]

, 18

18. V. R. Supradeepa, J. W. Nicholson, C. Headley, Y.-W. Lee, B. Palsdottir, and D. Jakobsen, “Cascaded Raman fiber laser at 1480 nm with output power of 104 W,” in Fiber Lasers IX Technology Systems, and Applications, Proc. of SPIE Vol 8237, paper 8237–48.

] is an effective pump source for core pumping Er-doped fiber amplifiers. Core pumping Er-doped fiber amplifiers helps keep the fiber short (length of few meters) and also allows for large-mode areas, both of which are important for mitigating nonlinearity in high pulse energy systems. Using the core-pumping architecture, CW amplification in an Er-doped HOM fiber in the LP0,10 with an effective area of 2700 μm2 was demonstrated [15

15. J. W. Nicholson, J. M. Fini, A. M. DeSantolo, E. Monberg, F. DiMarcello, J. Fleming, C. Headley, D. J. DiGiovanni, S. Ghalmi, and S. Ramachandran, “A higher-order-mode Erbium-doped-fiber amplifier,” Opt. Express 18(17), 17651–17657 (2010). [CrossRef] [PubMed]

]. Nanosecond pulse amplification in an HOM-Er fiber has also been demonstrated in the LP0,9 mode with an effective area of 2440 μm2 and the nonlinear properties of this amplifier compared to a conventional Er-doped LMA fiber with 800 μm2 Aeff [16

16. J. W. Nicholson, A. M. DeSantolo, S. Ghalmi, J. M. Fini, J. Fleming, E. Monberg, F. DiMarcello, and S. Ramachandran, “Nanosecond Pulse Amplification in a Higher-Order-Mode Erbium-Doped Fiber Amplifier,” in Conference on Lasers and Electro-Optics (CLEO) 2010, paper CPDB5.

]. Both amplifiers were limited by modulation instability. The nonlinearity of the HOM amplifier was found to be significantly lower than a conventional LMA amplifier, decreasing in proportion to the increase in Aeff. Furthermore new wavelengths generated through modulation instability were in the LP0,9 mode as well. A maximum pulse energy of 100 μJ was achieved in these experiments, corresponding to 100 kW peak power in the 1 ns pulse.

In addition to HOM-Er fiber amplifiers, there has been recent interest in other types of Er-doped fiber amplifiers for generating high-energy pulses at 1550 nm. Many high energy pulsed amplifier results in Er-doped fibers often rely on multi-mode operation [19

19. S. Desmoulins and F. Di Teodoro, “High-gain Er-doped fiber amplifier generating eye-safe MW peak-power, mJ-energy pulses,” Opt. Express 16(4), 2431–2437 (2008). [CrossRef] [PubMed]

23

23. V. Khitrov, V. V. Shkunov, D. A. Rockwell, Y. A. Zakharenkov, and F. Strohkendl, “Er-doped high-aspect-ratio core rectangular fiber producing 5 mJ, 13 ns pulses at 1572 nm,” Opt. Lett. 37(19), 3963–3965 (2012). [CrossRef] [PubMed]

].

2. Higher-order-mode, Er-doped, fiber amplifiers

Figure 1
Fig. 1 Index profile of a rare-earth doped, higher-order mode fiber. The LP0,1 mode is guided in the central core whereas the LP0,N higher-order modes reside in the outer core.
shows a schematic of the index profile of a higher-order mode amplifier fiber, illustrating the HOM concept. A center peak in the index of refraction, referred to as the central core, guides the fundamental mode of the fiber, shown in red in Fig. 1. The higher order modes of interest in this work are the symmetric LP0,N modes, where N>1. The higher order mode, shown as a blue line in Fig. 1, resides in the large outer core region. The shaded area is doped with rare-earth ions such as erbium or ytterbium, to provide gain. Interestingly, the LP0,N higher-order modes of an optical fiber are truncated Bessel beams, and an HOM amplifier is an elegant and robust method for naturally generating high-power Bessel beams, which have intriguing properties such as diffraction-free propagation of the center spot and self-healing in the presence of obstructions [24

24. P. Steinvurzel, K. Tantiwanichapan, M. Goto, and S. Ramachandran, “Fiber-based Bessel beams with controllable diffraction-resistant distance,” Opt. Lett. 36(23), 4671–4673 (2011). [CrossRef] [PubMed]

].

A schematic of the Er-doped, HOM fiber amplifier is shown in Fig. 2
Fig. 2 Schematic of the Er-doped higher-order mode fiber amplifier, and associated diagnostics
. A 15xx signal laser and high power 1480 nm Raman pump laser are coupled together using a single-mode fused fiber wavelength division multiplexer (WDM). The output of the WDM is fusion spliced to the HOM fiber, launching both pump and signal into the LP01 mode. An LPG provides high purity (> 99%) coupling to the desired LP0,N higher order mode, where amplification takes place. The output end of the HOM fiber is angle cleaved.

Also shown in Fig. 2 is the typical diagnostic setup used in the amplifier experiments. An uncoated wedge reflected a calibrated portion of the main beam which was measured with power meters, an optical spectrum analyzer, phosphor-coated CCD camera for measuring the beam profile at 1550 nm, digital sampling oscilloscope and photodiode with 30 ps rise time, and an acousto-optic modulator (AOM) for measuring pulse extinction ratio. Long pass and short pass dielectric filters allowed for measuring the relative power in the unabsorbed pump, the signal, and residual Stokes wavelengths from the Raman laser pump [15

15. J. W. Nicholson, J. M. Fini, A. M. DeSantolo, E. Monberg, F. DiMarcello, J. Fleming, C. Headley, D. J. DiGiovanni, S. Ghalmi, and S. Ramachandran, “A higher-order-mode Erbium-doped-fiber amplifier,” Opt. Express 18(17), 17651–17657 (2010). [CrossRef] [PubMed]

, 18

18. V. R. Supradeepa, J. W. Nicholson, C. Headley, Y.-W. Lee, B. Palsdottir, and D. Jakobsen, “Cascaded Raman fiber laser at 1480 nm with output power of 104 W,” in Fiber Lasers IX Technology Systems, and Applications, Proc. of SPIE Vol 8237, paper 8237–48.

]. The main beam transmitted through the glass wedge was measured with a power meter.

3. CW Er-doped HOM amplifier with 3800 μm2 Aeff in the LP0,11 mode

HOM-Er fiber one had an outer core diameter of approximately 118 μm, fiber OD of 243 μm, and erbium absorption of approximately 30 dB/m at 1530 nm.The refractive index for this fiber, as well as the fiber presented in section 4, was similar to that shown in Fig. 1. Broadband LPGs were written that coupled both 1480 nm pump and 1550 nm signal from the fundamental mode to the LP0,11 mode, which had an effective area of approximately 3800 μm2, as calculated from the measured fiber index profile.

The original S2 measurement setup was implemented using a broadband source that was launched into a fiber under test [26

26. 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]

, 27

27. J. W. Nicholson, A. D. Yablon, J. M. Fini, and M. D. Mermelstein, “Measuring the Modal Content of Large-Mode-Area Fibers,” IEEE J. Sel. Top. Quantum Electron. 15(1), 61–70 (2009). [CrossRef]

]. The output beam from the test fiber was imaged onto a single mode fiber which was scanned in position in the near-field image plane and coupled to an optical spectrum analyzer (OSA). An alternative setup for performing S2 imaging uses a tunable laser and CCD camera [21

21. V. N. Philippov, J. K. Sahu, C. A. Codemard, W. A. Clarkson, J.-N. Jang, J. Nilsson, and G. N. Pearson, “All-fiber 1.15-mJ pulsed eye-safe optical source,” Proc. SPIE 5335, 1–7 (2004). [CrossRef]

, 28

28. J. W. Nicholson, L. Meng, J. M. Fini, R. S. Windeler, A. Desantolo, E. Monberg, F. Dimarcello, Y. Dulashko, M. Hassan, and R. Ortiz, “Measuring higher-order modes in a low-loss, hollow-core, photonic-bandgap fiber,” Opt. Express 20(18), 20494–20505 (2012). [CrossRef] [PubMed]

, 29

29. D. M. Nguyen, S. Blin, T. N. Nguyen, S. D. Le, L. Provino, M. Thual, and T. Chartier, “Modal decomposition technique for multimode fibers,” Appl. Opt. 51(4), 450–456 (2012). [CrossRef] [PubMed]

]. By measuring the beam profile as a function of wavelength, the same three dimensional set of data in (x,y,λ) is obtained as with the original S2 setup. A tunable laser with ~100 kHz linewidth and 1 pm wavelength step size was used as the optical source and an InGaAs camera was used to measure the beam profile at 1550 nm. By analyzing the spatial dependence of the optical spectrum in the Fourier domain, the beat notes between modes can be obtained and residual higher-order mode content can be quantified.

For these measurements, the tunable laser was amplified to approximately 50 mW in a single mode amplifier before being launched into a 4.5m long HOM-Er amplifier. The pump power to the HOM-Er amplifier was increased until the 1550 nm output power was approximately 2.5W. The tunable laser was tuned from 1555 nm to 1565 nm in steps of 0.01 nm. At each wavelength the beam profile was measured using the InGaAs camera.

Figure 4
Fig. 4 S2 imaging measurement results from an HOM-Er fiber amplifier. Power in the mode relative to the LP0,11 mode is also shown.
shows the beam profile, mode beats as a function of DGD, and mode images and power relative to the fundamental mode, obtained from the S2 measurement. The beat note as a function of differential group delay is obtained by Fourier transforming the optical spectrum that corresponds to an individual camera pixel. The DGD plot in Fig. 4 is the sum of all the DGD plots from the individual pixels.

4. Er-doped HOM amplifier with 6000 μm2 Aeff in the LP0,14 mode

4.1 CW amplification in the LP0,14 mode

HOM-Er fiber two had an outer core diameter of approximately 148 μm, fiber outer diameter of 256 μm, and erbium absorption of approximately 30 dB/m at 1530 nm. Broadband LPGs were written that coupled both 1480 nm pump and 1550 nm signal from the fundamental mode to the LP0,14 mode, which had an effective area of approximately 6000 μm2, as calculated from the measured fiber index profile.

CW amplification in a 4.5m length of fiber, shown in Fig. 5
Fig. 5 CW performance of an Er-doped HOM amplifier operating in the LP0,14 mode with 6000 μm2 effective area.
, was very similar to the 3800 μm2 fiber. With 1 W of input signal power, the slope efficiency was 66% and the maximum output power at the signal wavelength was 54.5 W. The slightly lower slope efficiency for this amplifier could be attributable to differences such as different cleave quality or different splice loss at the input to the amplifier.

4.2 Nanosecond pulse amplification in the 6000 μm2 HOM fiber

For pulsed amplification experiments, a tunable, pulsed seed source was developed with flexibility in wavelength, pulse repetition frequency, and pulse width (Fig. 6(a)
Fig. 6 (a) Schematic of the pulsed seed source used in the amplifier experiments. (b) Measured pulse extinction ratio at the output of the seed source as a function of pulse repetition frequency.
). A tunable narrow linewidth external cavity laser (few 100 kHz linewidth) was amplified and modulated at 1 MHz repletion frequency with dual electro-optic modulators (EOMs) for high extinction ratio pulse carving. Measurement of the linewidth of the seed source after amplification was limited by the OSA resolution bandwidth of 0.05 nm. For the HOM amplifier experiments, pulses with 1 ns width were used. After modulation the pulses were amplified, filtered to remove ASE and amplified again. An acousto-optic modulator (AOM) was used to select pulses and reduce the repetition frequency. Finally, a large mode area (LMA) Er-doped fiber with 900 μm2 effective area [30

30. J. C. Jasapara, M. J. Andrejco, A. D. Yablon, J. W. Nicholson, C. Headley, and D. DiGiovanni, “Picosecond pulse amplification in a core-pumped large-mode-area erbium fiber,” Opt. Lett. 32(16), 2429–2431 (2007). [CrossRef] [PubMed]

] pumped by a 5W, 1480 nm Raman laser served as a final amplification stage. The output of the LMA amplifier was fusion spliced to SMF with a mode matched splice. At 500 kHz pulse repetition frequency a maximum of 1.2 W average power was available with a peak power of 2.4 kW in 1 ns pulses.

In low duty-cycle pulsed fiber amplifiers, power in between the pulses in the seed laser (due to leakage in the modulators, for example) can be amplified and account for a substantial amount of total output power [31

31. C. Headley, M. D. Mermelstein, K. Brar, M. J. Andrejco, J. W. Nicholson, A. D. Yablon, M. Fisheyn, and D. J. DiGiovanni “Accurate Measurement of Pulse Power in Low Duty Cycle MOPA,” in Conference on Lasers and Electro-Optics (CLEO) 2005 paper CTuC4.

]. For these systems, an AOM can be used to measure the pulse extinction ratio, i.e. the ratio of power in the pulse to the power in between pulses. For the pulsed seed source in Fig. 6(a), a second AOM was used to measure the pulse extinction ratio as a function of repetition frequency. The result of this measurement is plotted in Fig. 6(b). The pulse extinction ratio remained better than 20 dB for pulse repetition frequencies above 10 kHz, but dropped rapidly for lower frequencies.

The seed source was then launched into the HOM amplifier where it was converted to the LP0,14 mode with effective area of 6000 μm2, as shown in Fig. 2. The pulse extinction ratio measurement was repeated for the output of the HOM amplifier as a function of output signal power and repetition frequency. The result of this measurement is shown in Fig. 7
Fig. 7 Pulse extinction ratio measured at the output of the HOM amplifier as a function of pulse repetition frequency and output power at the signal wavelength.
. As the output power was increased, the amount of power in between pulses also increased, with the pulse extinction ratio impairment being more significant for low pulse repetition frequencies. Therefore for a low duty cycle system it is critical to take the pulse extinction ratio into account when calculating pulse energy from the measured average power. All pulse energy and signal power measurements reported for the pulse HOM amplifier in this work were scaled by the measured pulse extinction ratio.

The results of amplification of 1 ns pulses are shown in Fig. 8
Fig. 8 (a) Average signal power as a function of pulse repetition frequency. (b) Energy per pulse as a function of pulse repetition frequency and pump power
. Output signal power versus pump power and pulse repetition frequency is shown in Fig. 8(a). For 500 kHz and 100 kHz pulse trains, the amplifier length was 4.5 m. For the 10 kHz pulse train, the amplifier length was cut to 4 m the limit the nonlinearity as much as possible. For HOM fiber lengths shorter than 4 m, the output power dropped off rapidly. The launch power was primarily limited by nonlinearity in the SMF pigtail between the seed laser (after the LMA pre-amp) and the LPG in the HOM amplifier. For the 100 kHz pulse train the average power of the seed input was approximately 50 mW, and for the 10 kHz pulse train the average power of the seed input was approximately 10 mW. The output pulse energy is shown in Fig. 8(b). Both average power and pulse measurements were calibrated to factor in the measured pulse extinction ratio. A maximum energy of 0.5 mJ per pulse was achieved for 10 kHz pulse repetition frequency, corresponding to 0.5 MW of peak power in the 1 ns pulses.

As the pulse energy was increased the level of nonlinearity also increased. Figure 9(b) shows the optical spectra for 0.2 mJ per pulse and 0.5 mJ per pulse in a 10 kHz pulse train. As the pulse energy was increased further above 0.5 mJ per pulse, the spectrum broadened substantially, leading to continuum generation and visible spectral components in the green.

Finally, Fig. 10
Fig. 10 Amplified nanosecond pulses from the higher-order mode amplifier. The pulse from the seed laser is compared to output pulses at 0.4 mJ and 0.5 mJ per pulse in a 10 kHz pulse train. Pulses have been offset horizontally for clarity.
compares the amplified pulses at 10 kHz repetition frequency to the seed pulse launched into the HOM fiber. The pulses in Fig. 10 have been offset horizontally for clarity. At 0.4 mJ pulse energy, there was some steepening observed, but otherwise minimal distortion to the pulses. However, above approximately 0.45 mJ noise in the pulse appeared due to the increasing modulation instability.

6. Conclusions

In conclusion, we have demonstrated scaling of the effective area of higher-order mode, erbium doped fiber amplifiers to effective areas as large as 6000 μm2 in the LP0,14 mode. The combination of ultra-large effective areas and core-pumping using a high-power Raman fiber laser is ideal for low-nonlinearity, Er-doped pulse amplifiers in the eye-safe wavelength range of 1550 nm. The residual higher-order mode content was measured using S2 imaging and found to be very low, with most higher order modes being more than 25 dB weaker than the primary mode. Using the HOM amplifier more than 50 W CW power was achieved at 1550 nm. In a 500 kHz pulse train 40 W average power was achieved, and in a 10 kHz pulse train, 0.5 mJ pulse energy with 0.5 MW peak power was obtained directly from the amplifier in a 1 ns pulse. This peak power is, to the best of our knowledge, the highest peak power obtained from a single transverse mode from an Er-doped fiber laser. The single transverse mode together with low residual mode content mean that, although the output beam from an HOM fiber is structured, it also has high spatial coherence and a stable beam profile, allowing the HOM beam to be reshaped to a Gaussian beam using bulk-optic approach [33

33. N. Lindlein, G. Leuchs, and S. Ramachandran, “Achieving Gaussian outputs from large-mode-area higher-order-mode fibers,” Appl. Opt. 46(22), 5147–5157 (2007). [CrossRef] [PubMed]

]. Currently we see no impediment to scaling the HOM amplifier to even larger effective areas.

References and links

1.

J. Limpert, N. Deguil-Robin, I. Manek-Hönninger, F. Salin, F. Röser, A. Liem, T. Schreiber, S. Nolte, H. Zellmer, A. Tünnermann, J. Broeng, A. Petersson, and C. Jakobsen, “High-power rod-type photonic crystal fiber laser,” Opt. Express 13(4), 1055–1058 (2005). [CrossRef] [PubMed]

2.

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]

3.

W. S. Wong, X. Peng, J. M. McLaughlin, and L. Dong, “Breaking the limit of maximum effective area for robust single-mode propagation in optical fibers,” Opt. Lett. 30(21), 2855–2857 (2005). [CrossRef] [PubMed]

4.

Z. Jiang and J. R. Marciante, “Mode-area scaling of helical-core, dual-clad fiber lasers and amplifiers using an improved bend-loss model,” J. Opt. Soc. Am. B 23(10), 2051–2058 (2006). [CrossRef]

5.

J. M. Fini, “Intuitive modeling of bend distortion in large-mode-area fibers,” Opt. Lett. 32(12), 1632–1634 (2007). [CrossRef] [PubMed]

6.

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]

7.

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]

8.

S. Ramachandran, J. M. Fini, M. Mermelstein, J. W. Nicholson, S. Ghalmi, and M. F. Yan, “Ultra-large effective-area, higher-order mode fibers: a new strategy for high-power lasers,” Laser Photonics Rev. 2(6), 429–448 (2008). [CrossRef]

9.

J. M. Fini and S. Ramachandran, “Natural bend-distortion immunity of higher-order-mode large-mode-area fibers,” Opt. Lett. 32(7), 748–750 (2007). [CrossRef] [PubMed]

10.

D. Marcuse, Theory of Dielectric Optical Waveguides, 2nd ed. (Academic Press, 1974).

11.

S. Ramachandran, K. Brar, S. Ghalmi, K. Aiso, M. Yan, D. Trevor, J. Fleming, C. Headley, P. Wisk, G. Fishteyn, E. Monberg, and F. Dimarcello, “High-power amplification in a 2040 µm2 higher order mode,” in Photonics West, Late Breaking Developments—Session 6453–9 (San Jose, 2007).

12.

C. Headley, J. Phillips, J. Fini, E. Gonzalas, S. Ghalmi, M. Yan, J. Nicholson, P. Wisk, J. Fleming, E. Monberg, F. DiMarcello, R.S. Windeler, M. Fishteyn, K. Brar, S. Ramachandran, and D.J. DiGiovanni, “Amplification of a large-mode area single higher order mode in a fiber amplifier,” in Proceedings of Photonics West 2012 paper 8237–60.

13.

S. Suzuki, A. Schülzgen, and N. Peyghambarian, “Single-mode fiber laser based on core-cladding mode conversion,” Opt. Lett. 33(4), 351–353 (2008). [CrossRef] [PubMed]

14.

D. Sáez-Rodriguez, J. L. Cruz, A. Díez, and M. V. Andrés, “Fiber laser with combined feedback of core and cladding modes assisted by an intracavity long-period grating,” Opt. Lett. 36(10), 1839–1841 (2011). [CrossRef] [PubMed]

15.

J. W. Nicholson, J. M. Fini, A. M. DeSantolo, E. Monberg, F. DiMarcello, J. Fleming, C. Headley, D. J. DiGiovanni, S. Ghalmi, and S. Ramachandran, “A higher-order-mode Erbium-doped-fiber amplifier,” Opt. Express 18(17), 17651–17657 (2010). [CrossRef] [PubMed]

16.

J. W. Nicholson, A. M. DeSantolo, S. Ghalmi, J. M. Fini, J. Fleming, E. Monberg, F. DiMarcello, and S. Ramachandran, “Nanosecond Pulse Amplification in a Higher-Order-Mode Erbium-Doped Fiber Amplifier,” in Conference on Lasers and Electro-Optics (CLEO) 2010, paper CPDB5.

17.

J. W. Nicholson, M. F. Yan, P. Wisk, J. Fleming, F. DiMarcello, E. Monberg, T. Taunay, C. Headley, and D. J. DiGiovanni, “Raman fiber laser with 81 W output power at 1480 nm,” Opt. Lett. 35(18), 3069–3071 (2010). [CrossRef] [PubMed]

18.

V. R. Supradeepa, J. W. Nicholson, C. Headley, Y.-W. Lee, B. Palsdottir, and D. Jakobsen, “Cascaded Raman fiber laser at 1480 nm with output power of 104 W,” in Fiber Lasers IX Technology Systems, and Applications, Proc. of SPIE Vol 8237, paper 8237–48.

19.

S. Desmoulins and F. Di Teodoro, “High-gain Er-doped fiber amplifier generating eye-safe MW peak-power, mJ-energy pulses,” Opt. Express 16(4), 2431–2437 (2008). [CrossRef] [PubMed]

20.

E. Lallier and D. Papillon-Ruggeri, “High energy pulsed eye-safe fiber amplifier,” in CLEO/Europe and EQEC 2011 Conference Digest, OSA Technical Digest (CD) (Optical Society of America, 2011), paper CJ1_5.

21.

V. N. Philippov, J. K. Sahu, C. A. Codemard, W. A. Clarkson, J.-N. Jang, J. Nilsson, and G. N. Pearson, “All-fiber 1.15-mJ pulsed eye-safe optical source,” Proc. SPIE 5335, 1–7 (2004). [CrossRef]

22.

E.-L. Lim, S. U. Alam, and D. J. Richardson, “High-energy, in-band pumped erbium doped fiber amplifiers,” Opt. Express 20(17), 18803–18818 (2012). [CrossRef] [PubMed]

23.

V. Khitrov, V. V. Shkunov, D. A. Rockwell, Y. A. Zakharenkov, and F. Strohkendl, “Er-doped high-aspect-ratio core rectangular fiber producing 5 mJ, 13 ns pulses at 1572 nm,” Opt. Lett. 37(19), 3963–3965 (2012). [CrossRef] [PubMed]

24.

P. Steinvurzel, K. Tantiwanichapan, M. Goto, and S. Ramachandran, “Fiber-based Bessel beams with controllable diffraction-resistant distance,” Opt. Lett. 36(23), 4671–4673 (2011). [CrossRef] [PubMed]

25.

S. Ramachandran, “Dispersion-tailored few-mode fibers: a versatile platform for in-fiber photonic devices,” J. Lightwave Technol. 23(11), 3426–3443 (2005). [CrossRef]

26.

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]

27.

J. W. Nicholson, A. D. Yablon, J. M. Fini, and M. D. Mermelstein, “Measuring the Modal Content of Large-Mode-Area Fibers,” IEEE J. Sel. Top. Quantum Electron. 15(1), 61–70 (2009). [CrossRef]

28.

J. W. Nicholson, L. Meng, J. M. Fini, R. S. Windeler, A. Desantolo, E. Monberg, F. Dimarcello, Y. Dulashko, M. Hassan, and R. Ortiz, “Measuring higher-order modes in a low-loss, hollow-core, photonic-bandgap fiber,” Opt. Express 20(18), 20494–20505 (2012). [CrossRef] [PubMed]

29.

D. M. Nguyen, S. Blin, T. N. Nguyen, S. D. Le, L. Provino, M. Thual, and T. Chartier, “Modal decomposition technique for multimode fibers,” Appl. Opt. 51(4), 450–456 (2012). [CrossRef] [PubMed]

30.

J. C. Jasapara, M. J. Andrejco, A. D. Yablon, J. W. Nicholson, C. Headley, and D. DiGiovanni, “Picosecond pulse amplification in a core-pumped large-mode-area erbium fiber,” Opt. Lett. 32(16), 2429–2431 (2007). [CrossRef] [PubMed]

31.

C. Headley, M. D. Mermelstein, K. Brar, M. J. Andrejco, J. W. Nicholson, A. D. Yablon, M. Fisheyn, and D. J. DiGiovanni “Accurate Measurement of Pulse Power in Low Duty Cycle MOPA,” in Conference on Lasers and Electro-Optics (CLEO) 2005 paper CTuC4.

32.

P. Wysocki, T. Wood, A. Grant, D. Holcomb, K. Chang, M. Santo, L. Braun, and G. Johnson, “High Reliability 49 dB Gain, 13 W PM Fiber Amplifier at 1550 nm with 30 dB PER and Record Efficiency,” in Optical Fiber Communication Conference and Exposition and The National Fiber Optic Engineers Conference, Technical Digest (CD) (Optical Society of America, 2006), paper PDP17.

33.

N. Lindlein, G. Leuchs, and S. Ramachandran, “Achieving Gaussian outputs from large-mode-area higher-order-mode fibers,” Appl. Opt. 46(22), 5147–5157 (2007). [CrossRef] [PubMed]

OCIS Codes
(060.2280) Fiber optics and optical communications : Fiber design and fabrication
(060.2320) Fiber optics and optical communications : Fiber optics amplifiers and oscillators

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: August 30, 2012
Revised Manuscript: October 5, 2012
Manuscript Accepted: October 9, 2012
Published: October 12, 2012

Citation
J. W. Nicholson, J. M. Fini, A. M. DeSantolo, X. Liu, K. Feder, P. S. Westbrook, V. R. Supradeepa, E. Monberg, F. DiMarcello, R. Ortiz, C. Headley, and D. J. DiGiovanni, "Scaling the effective area of higher-order-mode erbium-doped fiber amplifiers," Opt. Express 20, 24575-24584 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-22-24575


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References

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  6. 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]
  7. 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]
  8. S. Ramachandran, J. M. Fini, M. Mermelstein, J. W. Nicholson, S. Ghalmi, and M. F. Yan, “Ultra-large effective-area, higher-order mode fibers: a new strategy for high-power lasers,” Laser Photonics Rev.2(6), 429–448 (2008). [CrossRef]
  9. J. M. Fini and S. Ramachandran, “Natural bend-distortion immunity of higher-order-mode large-mode-area fibers,” Opt. Lett.32(7), 748–750 (2007). [CrossRef] [PubMed]
  10. D. Marcuse, Theory of Dielectric Optical Waveguides, 2nd ed. (Academic Press, 1974).
  11. S. Ramachandran, K. Brar, S. Ghalmi, K. Aiso, M. Yan, D. Trevor, J. Fleming, C. Headley, P. Wisk, G. Fishteyn, E. Monberg, and F. Dimarcello, “High-power amplification in a 2040 µm2 higher order mode,” in Photonics West, Late Breaking Developments—Session 6453–9 (San Jose, 2007).
  12. C. Headley, J. Phillips, J. Fini, E. Gonzalas, S. Ghalmi, M. Yan, J. Nicholson, P. Wisk, J. Fleming, E. Monberg, F. DiMarcello, R.S. Windeler, M. Fishteyn, K. Brar, S. Ramachandran, and D.J. DiGiovanni, “Amplification of a large-mode area single higher order mode in a fiber amplifier,” in Proceedings of Photonics West 2012 paper 8237–60.
  13. S. Suzuki, A. Schülzgen, and N. Peyghambarian, “Single-mode fiber laser based on core-cladding mode conversion,” Opt. Lett.33(4), 351–353 (2008). [CrossRef] [PubMed]
  14. D. Sáez-Rodriguez, J. L. Cruz, A. Díez, and M. V. Andrés, “Fiber laser with combined feedback of core and cladding modes assisted by an intracavity long-period grating,” Opt. Lett.36(10), 1839–1841 (2011). [CrossRef] [PubMed]
  15. J. W. Nicholson, J. M. Fini, A. M. DeSantolo, E. Monberg, F. DiMarcello, J. Fleming, C. Headley, D. J. DiGiovanni, S. Ghalmi, and S. Ramachandran, “A higher-order-mode Erbium-doped-fiber amplifier,” Opt. Express18(17), 17651–17657 (2010). [CrossRef] [PubMed]
  16. J. W. Nicholson, A. M. DeSantolo, S. Ghalmi, J. M. Fini, J. Fleming, E. Monberg, F. DiMarcello, and S. Ramachandran, “Nanosecond Pulse Amplification in a Higher-Order-Mode Erbium-Doped Fiber Amplifier,” in Conference on Lasers and Electro-Optics (CLEO) 2010, paper CPDB5.
  17. J. W. Nicholson, M. F. Yan, P. Wisk, J. Fleming, F. DiMarcello, E. Monberg, T. Taunay, C. Headley, and D. J. DiGiovanni, “Raman fiber laser with 81 W output power at 1480 nm,” Opt. Lett.35(18), 3069–3071 (2010). [CrossRef] [PubMed]
  18. V. R. Supradeepa, J. W. Nicholson, C. Headley, Y.-W. Lee, B. Palsdottir, and D. Jakobsen, “Cascaded Raman fiber laser at 1480 nm with output power of 104 W,” in Fiber Lasers IX Technology Systems, and Applications, Proc. of SPIE Vol 8237, paper 8237–48.
  19. S. Desmoulins and F. Di Teodoro, “High-gain Er-doped fiber amplifier generating eye-safe MW peak-power, mJ-energy pulses,” Opt. Express16(4), 2431–2437 (2008). [CrossRef] [PubMed]
  20. E. Lallier and D. Papillon-Ruggeri, “High energy pulsed eye-safe fiber amplifier,” in CLEO/Europe and EQEC 2011 Conference Digest, OSA Technical Digest (CD) (Optical Society of America, 2011), paper CJ1_5.
  21. V. N. Philippov, J. K. Sahu, C. A. Codemard, W. A. Clarkson, J.-N. Jang, J. Nilsson, and G. N. Pearson, “All-fiber 1.15-mJ pulsed eye-safe optical source,” Proc. SPIE5335, 1–7 (2004). [CrossRef]
  22. E.-L. Lim, S. U. Alam, and D. J. Richardson, “High-energy, in-band pumped erbium doped fiber amplifiers,” Opt. Express20(17), 18803–18818 (2012). [CrossRef] [PubMed]
  23. V. Khitrov, V. V. Shkunov, D. A. Rockwell, Y. A. Zakharenkov, and F. Strohkendl, “Er-doped high-aspect-ratio core rectangular fiber producing 5 mJ, 13 ns pulses at 1572 nm,” Opt. Lett.37(19), 3963–3965 (2012). [CrossRef] [PubMed]
  24. P. Steinvurzel, K. Tantiwanichapan, M. Goto, and S. Ramachandran, “Fiber-based Bessel beams with controllable diffraction-resistant distance,” Opt. Lett.36(23), 4671–4673 (2011). [CrossRef] [PubMed]
  25. S. Ramachandran, “Dispersion-tailored few-mode fibers: a versatile platform for in-fiber photonic devices,” J. Lightwave Technol.23(11), 3426–3443 (2005). [CrossRef]
  26. 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. Express16(10), 7233–7243 (2008). [CrossRef] [PubMed]
  27. J. W. Nicholson, A. D. Yablon, J. M. Fini, and M. D. Mermelstein, “Measuring the Modal Content of Large-Mode-Area Fibers,” IEEE J. Sel. Top. Quantum Electron.15(1), 61–70 (2009). [CrossRef]
  28. J. W. Nicholson, L. Meng, J. M. Fini, R. S. Windeler, A. Desantolo, E. Monberg, F. Dimarcello, Y. Dulashko, M. Hassan, and R. Ortiz, “Measuring higher-order modes in a low-loss, hollow-core, photonic-bandgap fiber,” Opt. Express20(18), 20494–20505 (2012). [CrossRef] [PubMed]
  29. D. M. Nguyen, S. Blin, T. N. Nguyen, S. D. Le, L. Provino, M. Thual, and T. Chartier, “Modal decomposition technique for multimode fibers,” Appl. Opt.51(4), 450–456 (2012). [CrossRef] [PubMed]
  30. J. C. Jasapara, M. J. Andrejco, A. D. Yablon, J. W. Nicholson, C. Headley, and D. DiGiovanni, “Picosecond pulse amplification in a core-pumped large-mode-area erbium fiber,” Opt. Lett.32(16), 2429–2431 (2007). [CrossRef] [PubMed]
  31. C. Headley, M. D. Mermelstein, K. Brar, M. J. Andrejco, J. W. Nicholson, A. D. Yablon, M. Fisheyn, and D. J. DiGiovanni “Accurate Measurement of Pulse Power in Low Duty Cycle MOPA,” in Conference on Lasers and Electro-Optics (CLEO) 2005 paper CTuC4.
  32. P. Wysocki, T. Wood, A. Grant, D. Holcomb, K. Chang, M. Santo, L. Braun, and G. Johnson, “High Reliability 49 dB Gain, 13 W PM Fiber Amplifier at 1550 nm with 30 dB PER and Record Efficiency,” in Optical Fiber Communication Conference and Exposition and The National Fiber Optic Engineers Conference, Technical Digest (CD) (Optical Society of America, 2006), paper PDP17.
  33. N. Lindlein, G. Leuchs, and S. Ramachandran, “Achieving Gaussian outputs from large-mode-area higher-order-mode fibers,” Appl. Opt.46(22), 5147–5157 (2007). [CrossRef] [PubMed]

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