Abstract

Pseudo random phase modulation signals have been shown to provide considerable stimulated Brillouin scattering (SBS) suppression in narrow linewidth Yb-doped all-fiber amplifiers. In terms of coherent beam combining, however, pseudo random signals display a linear drop in visibility; leading to pronounced drops in combining efficiencies for small path length deviations. To that end, we report a novel filtered pseudo random modulation approach for enhanced combining efficiency and coherence length performance. Here a low pass radio frequency (RF) filter is used to mitigate the PRBS high frequency components, thereby suppressing the sidelobes in the optical spectrum. This leads to an approximate Gaussian visibility function and improved coherence lengths of up to 27% in a kW class fiber amplifier (954 W). In addition, the spectral sidelobe suppression leads to concurrent SBS threshold enhancement due to a reduction in the spectral overlap between the Rayleigh reflected light and the Stokes shifted light. This reduction in the SBS seeding phenomena leads to ~10% SBS threshold improvements in a kW class fiber amplifier. Theoretical and experimental data is presented to substantiate the improved coherence length and SBS suppression. More importantly, the simultaneous nonlinear SBS suppression and coherence length benefits of the filtered PRBS approach can have a significant impact for high power, narrow linewidth, all-fiber amplifiers.

© 2017 Optical Society of America

Full Article  |  PDF Article
OSA Recommended Articles
Pseudo-random binary sequence phase modulation for narrow linewidth, kilowatt, monolithic fiber amplifiers

Angel Flores, Craig Robin, Ann Lanari, and Iyad Dajani
Opt. Express 22(15) 17735-17744 (2014)

Comparison of phase modulation schemes for coherently combined fiber amplifiers

Brian Anderson, Angel Flores, Roger Holten, and Iyad Dajani
Opt. Express 23(21) 27046-27060 (2015)

Suppression of stimulated Brillouin scattering in high power fibers using nonlinear phase demodulation

Gregory D. Goodno and Joshua E. Rothenberg
Opt. Express 27(9) 13129-13141 (2019)

References

  • View by:
  • |
  • |
  • |

  1. L. Zhang, J. Hu, J. Wang, and Y. Feng, “Stimulated-Brillouin-scattering-suppressed high-power single-frequency polarization-maintaining Raman fiber amplifier with longitudinally varied strain for laser guide star,” Opt. Lett. 37(22), 4796–4798 (2012).
    [Crossref] [PubMed]
  2. C. Zeringue, C. Vergien, and I. Dajani, “Pump-limited, 203 W, single-frequency monolithic fiber amplifier based on laser gain competition,” Opt. Lett. 36(5), 618–620 (2011).
    [Crossref] [PubMed]
  3. N. A. Naderi, A. Flores, B. M. Anderson, and I. Dajani, “Beam combinable, kilowatt, all-fiber amplifier based on phase-modulated laser gain competition,” Opt. Lett. 41(17), 3964–3967 (2016).
    [Crossref] [PubMed]
  4. A. Flores, C. Robin, A. Lanari, and I. Dajani, “Pseudo-random binary sequence phase modulation for narrow linewidth, kilowatt, monolithic fiber amplifiers,” Opt. Express 22(15), 17735–17744 (2014).
    [Crossref] [PubMed]
  5. N. A. Naderi, I. Dajani, and A. Flores, “High-efficiency, kilowatt 1034 nm all-fiber amplifier operating at 11 pm linewidth,” Opt. Lett. 41(5), 1018–1021 (2016).
    [Crossref] [PubMed]
  6. C. Zeringue, I. Dajani, S. Naderi, G. T. Moore, and C. Robin, “A theoretical study of transient stimulated Brillouin scattering in optical fibers seeded with phase-modulated light,” Opt. Express 20(19), 21196–21213 (2012).
    [Crossref] [PubMed]
  7. B. Anderson, A. Flores, R. Holten, and I. Dajani, “Comparison of phase modulation schemes for coherently combined fiber amplifiers,” Opt. Express 23(21), 27046–27060 (2015).
    [Crossref] [PubMed]
  8. T. M. Shay, V. Benham, J. T. Baker, B. Ward, A. D. Sanchez, M. A. Culpepper, D. Pilkington, J. Spring, D. J. Nelson, and C. A. Lu, “First experimental demonstration of self-synchronous phase locking of an optical array,” Opt. Express 14(25), 12015–12021 (2006).
    [Crossref] [PubMed]
  9. G. D. Goodno, C. C. Shih, and J. E. Rothenberg, “Perturbative analysis of coherent combining efficiency with mismatched lasers,” Opt. Express 18(24), 25403–25414 (2010).
    [Crossref] [PubMed]
  10. Nufern Product Brief. NukW: Kilowatt laser amplifier platform.

2016 (2)

2015 (1)

2014 (1)

2012 (2)

2011 (1)

2010 (1)

2006 (1)

Anderson, B.

Anderson, B. M.

Baker, J. T.

Benham, V.

Culpepper, M. A.

Dajani, I.

Feng, Y.

Flores, A.

Goodno, G. D.

Holten, R.

Hu, J.

Lanari, A.

Lu, C. A.

Moore, G. T.

Naderi, N. A.

Naderi, S.

Nelson, D. J.

Pilkington, D.

Robin, C.

Rothenberg, J. E.

Sanchez, A. D.

Shay, T. M.

Shih, C. C.

Spring, J.

Vergien, C.

Wang, J.

Ward, B.

Zeringue, C.

Zhang, L.

Opt. Express (5)

Opt. Lett. (4)

Other (1)

Nufern Product Brief. NukW: Kilowatt laser amplifier platform.

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 Experimental diagram for measuring the visibility of the phase modulated amplifier. The 1064 nm seed is linewidth broadened using a phase modulator before being split into two paths using a 3dB coupler. One portion of the beam is amplified to high power and an AR coated wedge is used to sample the beam. The other portion of the beam is RF tagged using a phase modulator controlled by LOCSET and path length matched to the high power beam. The two beams are interfered, and the bright and dark fringes are measured using a slow photodiode.
Fig. 2
Fig. 2 Heterodyne measurement of the optical spectrum for a variety of phase modulations schemes: 1) 2.88 GHz 29-1 PRBS with no RF filter, 2) PRBS with 3.08 GHz filter, 3) PRBS with a 1.3 GHz filter, 4) A WNS with 3.06 GHz FWHM.
Fig. 3
Fig. 3 Measurements of the visibility comparing the unfiltered PRBS (blue), to the filtered PRBS (green, red) and the reference WNS (black).
Fig. 4
Fig. 4 SBS threshold measured for the 2.88 GHz PRBS (blue) and compared to the filtered PRBS (green, red) and WNS (black). Filtering the PRBS increases the SBS threshold due to the suppressed sidelobes.
Fig. 5
Fig. 5 Theoretical modeling of the SBS enhancement factor without seeding. (a) No RF filter is used showing the expected dependence on PRBS modulation frequency. (b) A 5th order Butterworth filter is used to filter the PRBS reducing the SBS enhancement factor for low PRBS patterns.
Fig. 6
Fig. 6 Theoretical modeling of the SBS enhancement factor with seeding. (a) No RF filter is used, the SBS threshold is reduced due to spectral overlap. Fluctuations seen are due to the change in the overlaps of the Stokes and reflected spectrums. (b) An RF filter is used with the PRBS modulation, increasing the SBS enhancement factor to levels approaching the enhancement factor without seeding.
Fig. 7
Fig. 7 Heterodyne setup for measuring the spectrum of the Stokes signal.
Fig. 8
Fig. 8 (a) Heterodyne measurement of the backwards reflected signal with the unfiltered PRBS. (Red) PRBS frequency has been tuned to 7.506 GHz to maximize the spectral overlap between the Stokes and Rayleigh signal. (Black) PRBS frequency has been tuned to 7.480 to minimized the spectral overlap. (b) Backwards reflectivity vs. output power.
Fig. 9
Fig. 9 (a) Heterodyne measurement of the backwards reflected signal with the filtered PRBS. (Red) The PRBS has been tuned to maximize the seeding effect. (Black) The PRBS has been tuned to minimize the seeding effect. Note that the amplitude of the Rayleigh signal has been reduced by more than 10dB. (b) Backwards reflectivity vs. output power.

Tables (3)

Tables Icon

Table 1 Summary of 2.88 GHz PRBS measurements.

Tables Icon

Table 2 Summary of 5 GHz PRBS measurements.

Tables Icon

Table 3 Summary of 7.5 GHz PRBS measurements.

Equations (11)

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

E ˜ = A LF (z,t) e i( k L z ω L t) + A LB (z,t) e i( k S z ω S t) e i Ω B (zn/c+t) + A S (z,t) e i( k S z ω S t) +c.c.
2 E ˜ n 2 c 2 2 E ˜ t 2 = 1 ε 0 c 2 2 P ˜ t 2
P ˜ = ε 0 γ e ρ ˜ E ˜
c n A LF z + A LF t = ω γ e 2 n 2 ρ 0 ρ( A S + A LB e i Ω B (zn/c+t) )
c n A LB z + A LB t = ω γ e 2 n 2 ρ 0 ρ * A LF e i Ω B (zn/c+t)
c n A S z + A S t = ω γ e 2 n 2 ρ 0 ρ * A LF
2 ρ ˜ t 2 Γ B q 2 2 ρ ˜ t ν S 2 2 ρ ˜ = 1 2 ε 0 γ e 2 E ˜ 2 + f ˜
2 ρ t 2 +( Γ B 2i Ω B ) ρ t i Ω B Γ B ρ = ε 0 γ e q 2 A LF ( A S * + A LB * e i Ω B (zn/c+t) )2i Ω B f
A LB (z=L,t)= R A LF (z=L,t)
| V( τ ) |=| + PSD( ω ) e iωτ dω |= I max I min I max + I min
PSD( ν )= | + A LF (z=0,t) e iωt dt | 2

Metrics