Photon Return On-Sky Test of Pulsed Sodium Laser Guide Star with D2b Repumping
Photon Return On-Sky Test of Pulsed Sodium Laser Guide Star with D2b Repumping
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DOI：
10.1086/682672
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发表时间：
2015-08
影响因子：
3.5
通讯作者：
Kai Jin;K. Wei;Lu Feng;Y. Bo;J. Zuo;Min Li;Hanmei Fu;Xiaolin Dai;Q. Bian;Ji Yao;Chang-an Xu;Zhichao Wang;Q. Peng;X. Xue;Xuewu Cheng;C. Rao;Zu-Yan Xu;Yudong Zhang
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文献类型：
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作者：
Kai Jin;K. Wei;Lu Feng;Y. Bo;J. Zuo;Min Li;Hanmei Fu;Xiaolin Dai;Q. Bian;Ji Yao;Chang-an Xu;Zhichao Wang;Q. Peng;X. Xue;Xuewu Cheng;C. Rao;Zu-Yan Xu;Yudong Zhang
钠激光引导星星（LGS）系统已成为现代天文自适应光学系统（AOS）的关键部件之一，特别是对于新一代的超大望远镜，如30米望远镜和欧洲超大望远镜。由于AOS的波前探测性能与LGS的亮度直接相关，因此AOS必须尽可能地提高其光子产生效率。钠D2b谱线再泵浦是一种可以大幅度提高钠连续激光或脉冲激光返回光子数的技术。欧洲南方天文台小组已经对这种技术进行了理论研究，并用20 W连续激光器进行了现场试验。然而，D2b再泵浦的20 W级脉冲激光器的现场测试结果尚未报道。本文将介绍我们最近的现场实验结果，并与20 W准连续脉冲激光器D2b再泵浦的理论比较。对于线偏振光束，当10%的激光功率失谐到D2b线时，光子返回增强达到约40%，这与基于速率方程的Monte Carlo光子返回模拟程序的结果一致。实验和模拟结果都表明，当入射到钠层上的激光强度越大时，D2b再泵浦的效率越高。
Sodium laser guide star (LGS) system has become one of the critical components in modern astronomical adaptive optics system (AOS), especially for the next-generation extremely large telescopes, such as the Thirty Meter Telescope and the European Extremely Large Telescope. Since the wavefront detection performance of AOS is directly related to the brightness of LGS, it is important for AOS to maximize its photon generation efficiency by all means. Sodium D2b line repumping is such a technique that can greatly increase the returned photons for either sodium continuous wave (CW) laser or pulsed laser. This technique has been studied theoretically and field tested with a 20 W CW laser by European Southern Observatory team. However, field test results of a 20 W class pulsed laser with D2b repumping have not been reported yet. In this paper, our latest field test results with theoretical comparison of D2b repumping with a 20 W quasi-continuous wave (QCW) pulsed laser will be presented. With a linearly polarized beam, approximate 40% photon return enhancement was achieved when 10% of laser power was detuned to D2b line, which agreed well with results from a rate equation-based Monte Carlo photon return simulation program. Both experiment and simulation results indicate that with a higher laser intensity projected at the sodium layer, the D2b repumping will be more effective.