한국광학회지 (Korean Journal of Optics and Photonics)

  • 제31권6호
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  • Pages.247-258
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  • 2020
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  • 1225-6285(pISSN)
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  • 2287-321X(eISSN)
한국광학회 (Optical Society of Korea)
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대기외란에 따른 SPGD 기반 결맞음 빔결합 시스템 위상제어 동작성능 분석

Numerical Study of SPGD-based Phase Control of Coherent Beam Combining under Various Turbulent Atmospheric Conditions

  • 김한솔 (서울대학교 전기정보공학부) ;
  • 나정균 (서울대학교 전기정보공학부) ;
  • 정윤찬 (서울대학교 전기정보공학부)
  • Kim, Hansol (Department of Electrical and Computer Engineering, Seoul National University) ;
  • Na, Jeongkyun (Department of Electrical and Computer Engineering, Seoul National University) ;
  • Jeong, Yoonchan (Department of Electrical and Computer Engineering, Seoul National University)
  • 투고 : 2020.11.10
  • 심사 : 2020.11.20
  • 발행 : 2020.12.25
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⟨ 이전 논문 다음 논문 ⟩

초록

본 논문에서는 대기외란에 따른 SPGD 위상제어 알고리즘 기반 결맞음 빔결합 시스템의 위상제어 동작성능을 논의한다. 대기의 외란에 대한 통계적 이론을 바탕으로 전산모사를 통해 대기외란에 의한 레이저빔의 위상 및 파면 왜곡에 대한 분석과 왜곡된 빔을 통해 얻게 되는 7채널 및 19채널 결맞음 빔결합 결과를 도출하고, 이를 통해 대기외란의 정도에 따른 빔결합 시스템의 위상제어 동작성능 및 효율을 수치적으로 비교분석한다. 분석 결과, 7채널 결맞음 빔결합의 경우, 대기외란 파라미터 cn2 값이 10-13 m-2/3 까지 증가한 상황에서도 SPGD 위상제어 알고리즘을 적절히 적용할 경우 90% 이상의 빔결합 효율로 시스템의 위상 잠금이 가능하다는 것을 확인하였다. 19채널 결맞음 빔결합의 경우, 동일한 대기외란 조건에서도 대기의 굴절률 비균질성(refractive index inhomogeneity)의 영향이 더 커서 빔결합 효율이 60% 수준으로 급격하게 감소할 수 있음을 확인하였다. 또한, 대기외란이 있는 상황에서 위상잠금시점까지 요구되는 알고리즘의 반복연산 횟수와 대기현상의 변화간격을 비교분석함으로써, 다채널 결맞음 빔결합 시스템이 ㎲의 간격을 가지는 대기외란 상황에서도 정상동작을 하기 위해서는 SPGD 위상제어 알고리즘의 연산대역폭이 수백 MHz에서 수 GHz까지 확장되어야 한다는 것을 확인하였다. 향후, 대기외란이 SPGD 위상제어 알고리즘 기반 결맞음 빔결합 시스템의 위상제어 동작성능에 미치는 영향을 정량적으로 분석하고 예측하는 데 있어서 본 논문의 결과가 유용하게 활용될 수 있을 것이라 기대된다.

In this paper, based on a stochastic parallel gradient descent (SPGD) algorithm we study phase control of a coherent-beam-combining system under turbulent atmospheric conditions. Based on the statistical theory of atmospheric turbulence, we carry out the analysis of the phase and wavefront distortion of a laser beam propagating through a turbulent atmospheric medium. We also conduct numerical simulations of a coherent-beam-combining system with 7- and 19-channel laser beams distorted by atmospheric turbulence. Through numerical simulations, we characterize the phase-control characteristics and efficiency of the coherent-beam-combining system under various degrees of atmospheric turbulence. It is verified that the SPGD algorithm is capable of realizing 7-channel coherent beam combining with a beam-combining efficiency of more than 90%, even under the turbulent atmospheric conditions up to cn2 of 10-13 m-2/3. In the case of 19-channel coherent beam combining, it is shown that the same turbulent atmospheric conditions result in a drastic reduction of the beam-combining efficiency down to 60%, due to the elevated impact of the corresponding refractive-index inhomogeneity. In addition, by putting together the number of iterations of the SPGD algorithm required for phase locking under atmospheric turbulence and the time intervals of atmospheric phenomena, which typically are of the order of ㎲, it is estimated that hundreds of MHz to a few GHz of computing bandwidth of SPGD-based phase control may be required for a coherent-beam-combining system to confront such turbulent atmospheric conditions. We expect the results of this paper to be useful for quantitatively analyzing and predicting the effects of atmospheric turbulence on the SPGD-based phase-control performance of a coherent-beam-combining system.

키워드

참고문헌

  1. Y. Jeong, J. K. Sahu, D. N. Payne, and J. Nilsson, "Ytterbium-doped large-core fiber laser with 1.36 kW continuous-wave output power," Opt. Express 12, 6088-6092 (2004). https://doi.org/10.1364/OPEX.12.006088
  2. D. J. Richardson, J. Nilsson, and W. A. Clarkson, "High power fiber lasers: current status and future perspectives," J. O pt. Soc. Am. B 27, B63-B92 (2010). https://doi.org/10.1364/JOSAB.27.000B63
  3. A. V. Smith and J. J. Smith, "Mode instability in high power fiber amplifiers," Opt. Express 19, 10180-10192 (2011). https://doi.org/10.1364/OE.19.010180
  4. T. Y. Fan, "Laser beam combining for high-power, high-radiance sources," IEEE J. Sel. Top. Quantum Electron. 11, 567-577 (2005). https://doi.org/10.1109/JSTQE.2005.850241
  5. C. Wirth, O. Schmidt, I. Tsybin, T. Schreiber, R. Eberhardt, J. Limpert, A. Tunnermann, K. Ludewigt, M. Gowin, E. T. Have, and M. Jung, "High average power spectral beam combining of four fiber amplifiers to 8.2 kW," Opt. Lett. 36, 3118-3120 (2011). https://doi.org/10.1364/OL.36.003118
  6. S. J. Augst, T. Y. Fan, and A. Sanchez, "Coherent beam combining and phase noise measurements of ytterbium fiber amplifiers," Opt. Lett. 29, 474-476 (2004). https://doi.org/10.1364/OL.29.000474
  7. D. V. Vysotsky and A. P. Napartovich, "Coherent beam combining in optically coupled laser arrays," Quantum Electron. 49, 989 (2019). https://doi.org/10.1070/QEL16978
  8. P. F. Ma, P. Zhou, R. T. Su, Y. X. Ma, and Z. J. Liu, "Coherent polarization beam combining of eight fiber lasers using single-frequency dithering technique," Laser Phys. Lett. 9, 456 (2012). https://doi.org/10.7452/lapl.201210016
  9. Z. M. Huang, C. L. Liu, J. F. Li, and D. Y. Zhang, "A high-speed, high-efficiency phase controller for coherent beam combining based on SPGD algorithm," Quantum Electron. 44, 301 (2014). https://doi.org/10.1070/qe2014v044n04abeh015230
  10. H. K. Ahn, H. Lee, and H. J. Kong, "High power coherent beam combining setup using modified cascaded multi-dithering technique," Curr. Opt. Photon. 2, 431-435 (2018). https://doi.org/10.3807/COPP.2018.2.5.431
  11. G. D. Goodno, S. J. McNaught, J. E. Rothenberg, T. S. McComb, P. A. Thielen, M. G. Wickham, and M. E. Weber, "Active phase and polarization locking of a 1.4 kW fiber amplifier," Opt. Lett. 35, 1542-1544 (2010). https://doi.org/10.1364/OL.35.001542
  12. A. Flores, B. Pulford, C. Robin, C. A. Lu, and T. Shay, "Coherent beam combining of fiber amplifiers via LOCSET (Postprint)," Air Force Research Laboratory, USA, Tech. Rep., AFRL-RD-PS-TP-2015-0007, Jul. (2012).
  13. Z. Huang, X. Tang, D. Zhang, X. Wang, Q. Hu, J. Li, and C. Liu, "Coherent beam combination of ten fiber arrays via stochastic parallel gradient descent algorithm," J. Opt. Technol. 82, 16-20 (2015). https://doi.org/10.1364/JOT.82.000016
  14. H. Chang, Q. Chang, J. Xi, T. Hou, R. Su, P. Ma, J. Wu, C. Li, M. Jiang, Y. Ma, and P. Zhou, "First experimental demonstration of coherent beam combining of more than 100 fiber lasers," Photon. Res. (To be published).
  15. L. Daniault, M. Hanna, L. Lombard, Y. Zaouter, E. Mottay, D Goular, P. Bourdon, F. Druon, and P. Georges, "Coherent beam combining of two femtosecond fiber chirped-pulse amplifiers," Opt. Lett. 36, 621-623 (2011). https://doi.org/10.1364/OL.36.000621
  16. M. Muller, C. Aleshire, A. Klenke, E. Haddad, F. Legare, A. Tunnermann, and J. Limpert, "10.4 kW coherently combined ultrafast fiber laser," Opt. Lett. 45, 3083-3086 (2020). https://doi.org/10.1364/OL.392843
  17. I. Fsaifes, L. Daniault, S. Bellanger, M. Veinhard, J. Bourderionnet, C. Larat, E. Lallier, E. Durand, A. Bringnon, and J.-C. Chanteloup, "Coherent beam combining of 61 femtosecond fiber amplifiers," Opt. Express 28, 20152-20161 (2020). https://doi.org/10.1364/OE.394031
  18. T. Weyrauch, M. A. Vorontsov, G. W. Carhart, L. A. Beresnev, A. P. Rostov, E. E. Polnau, and J. J. Liu, "Experimental demonstration of coherent beam combining over a 7 km propagation path," Opt. Lett. 36, 4455-4457 (2011). https://doi.org/10.1364/OL.36.004455
  19. T. Weyrauch, M. Vorontsov, J. Mangano, V. Ovchinnikov, D. Bricker, E. Polnau, and A. Rostov, "Deep turbulence effects mitigation with coherent combining of 21 laser beams over 7 km," Opt. Lett. 41, 840-843 (2016). https://doi.org/10.1364/OL.41.000840
  20. M. A. Vorontsov and V. P. Sivokon, "Stochastic parallel-gradient-descent technique for high-resolution wave-front phase-distortion correction," J. Opt. Soc. Am. A 15, 2745-2758 (1998). https://doi.org/10.1364/JOSAA.15.002745
  21. P. Zhou, Z. Liu, X. Wang, Y. Ma, H. Ma, X. Xu, and S. Guo, "Coherent beam combining of fiber amplifiers using stochastic parallel gradient descent algorithm and its application," IEEE J. Sel. Top. Quantum Electron. 15, 248-256 (2009). https://doi.org/10.1109/JSTQE.2008.2010231
  22. A. Zilberman, E. Golbraikh, and N. S. Kopeika "Propagation of electromagnetic waves in Kolmogorov and non-Kolmogorov atmospheric turbulence: three-layer altitude model," Appl. Opt. 47, 6385-6391 (2008). https://doi.org/10.1364/AO.47.006385
  23. M. Salem, T. Shirai, A. Dogariu, and E. Wolf, "Long-distance propagation of partially coherent beams through atmospheric turbulence," Opt. Commun. 216, 261-265 (2003). https://doi.org/10.1016/S0030-4018(02)02340-4
  24. M. Hulea, X. Tang, Z. Ghassemlooy, and S. Rajbhandari, "A review on effects of the atmospheric turbulence on laser beam propagation - An analytic approach," in Proc. 10th International Symposium on Communication Systems, Networks and Digital Signal Processing - CSNDSP (Prague, Czech Republic, Jul. 2016).