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High-beam-quality 2-kW-class Spectrally Combined Laser Using Narrow-linewidth Ytterbium-doped Polarization-maintaining Fiber Amplifiers

협대역 이터븀 첨가 편광유지 광섬유 증폭기를 이용한 고품질 2 kW급 파장제어 빔 결합 레이저

  • Jeong, Hwanseong (Ground Technology Research Institute, Agency for Defense Development) ;
  • Lee, Kwang Hyun (Ground Technology Research Institute, Agency for Defense Development) ;
  • Lee, Junsu (Ground Technology Research Institute, Agency for Defense Development) ;
  • Kim, Dong-Joon (Ground Technology Research Institute, Agency for Defense Development) ;
  • Lee, Jung Hwan (Ground Technology Research Institute, Agency for Defense Development) ;
  • Jo, Minsik (Ground Technology Research Institute, Agency for Defense Development)
  • 정환성 (국방과학연구소 지상기술연구원) ;
  • 이광현 (국방과학연구소 지상기술연구원) ;
  • 이준수 (국방과학연구소 지상기술연구원) ;
  • 김동준 (국방과학연구소 지상기술연구원) ;
  • 이정환 (국방과학연구소 지상기술연구원) ;
  • 조민식 (국방과학연구소 지상기술연구원)
  • Received : 2020.07.07
  • Accepted : 2020.08.19
  • Published : 2020.10.25

Abstract

In this paper, we have experimentally demonstrated a 2-kW-class spectrally-beam-combined laser with high beam quality, using narrow-linewidth ytterbium-doped polarization-maintaining fiber amplifiers. Five fiber amplifiers with different center wavelengths were implemented for the spectrally-beam-combined laser. The center wavelengths of the five amplifiers were 1062, 1063, 1064, 1065, and 1066 nm, respectively. A phase-modulated laser diode was used as a seed source for each amplifier. The seed sources were modulated by filtered pseudorandom-bit-sequence (PRBS) signals 5 GHz in linewidth. The polarization-maintaining large-mode-area fiber with a core size of 30 ㎛ was used as a delivery fiber to mitigate the stimulated Brillouin scattering (SBS) effect. The laser beams from five amplifiers were spectrally combined by a multilayer dielectric diffraction grating. The maximum output power and beam quality M2 of the combined laser were measured to be 2.3 kW and 1.74, respectively.

본 연구에서는 편광 유지 광섬유 기반의 고출력 이터븀 첨가 광섬유 증폭기를 이용하여 고품질의 2 kW급 출력을 갖는 파장제어 빔 결합 레이저를 구현하였다. 파장제어 빔 결합을 위하여 광섬유 증폭기의 발진 파장은 각각 1062 nm, 1063 nm, 1064 nm, 1065 nm, 1066 nm로서 서로 다른 값을 갖는다. 협대역 광섬유 레이저 증폭 시 발생하는 유도 브릴루앙 산란 비선형 효과를 완화하기 위해 시드 광원은 유사이진난수 신호(pseudo-random bit sequence, PRBS)를 이용하여 위상 변조된 5 GHz의 협대역 선폭을 갖도록 하였으며 전송광섬유는 30 ㎛ 코어 크기를 가지는 대면적 편광 유지 광섬유를 이용하였다. 파장제어 빔 결합으로 얻은 레이저의 최대 출력은 2.3 kW이며 빔 품질(M2)은 1.74이었다.

Keywords

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