钠信标自适应光学系统波前探测问题研究

发布时间：2018-01-06 02:10

本文关键词：钠信标自适应光学系统波前探测问题研究　出处：《中国科学院光电技术研究所》2017年博士论文　论文类型：学位论文

【摘要】：自适应光学系统已经成为大口径地基望远镜的基本组成部分之一,而人造钠信标的使用可以极大地提高天文自适应光学系统的天空覆盖率。但利用钠信标进行波前探测时会存在光斑亮度低、光斑拉长以及波前探测的非等晕性等问题。本论文根据中国科学院光电技术研究所在丽江1.8米望远镜上的钠信标自适应光学系统,针对系统中波前探测部分在实验过程中遇到的主要问题:钠信标光斑亮度较低和钠信标波前探测的非等晕误差,完成了如下主要研究工作。首先建立钠信标激光器激发大气中钠原子的理论模型,针对丽江1.8米望远镜上中国科学院光电技术研究所钠信标自适应光学系统所用的中国科学院理化技术研究所20 W级百微秒脉冲激光器,完成了该激光器对钠原子激发效率(耦合效率)的数值仿真,并重点分析了激光的偏振状态、弛豫震荡、光谱分布以及D2a+D2b双峰泵浦对耦合效率的影响。数值仿真结果表明,对于给定类型的激光器,存在一个最优的功率密度,当激光处在此功率密度下与钠原子的耦合效率最高。同时,通过数值仿真得到的结果也给未来该激光器的升级提供了更好的建议。然后,基于丽江1.8米望远镜平台,搭建了一套完整的钠信标测光系统,并提出了对于钠信标回光亮度实验测量的理论和方法。在此平台上,完成了对钠信标光斑形态和回光亮度的优化,并对钠信标的回光亮度和激光器的耦合效率进行了实验测量。并且,搭建了钠信标激光器D2a+D2b双峰泵浦实验平台,实验验证了双峰泵浦对钠信标回光亮度提升的有效性。最后,针对钠信标波前探测带来的非等晕误差,通过设定大气湍流相位屏及光波前传播方程,数值仿真了在利用钠信标进行波前探测时所带来的非等晕误差,并分别分析了其中高度非等晕误差和角度非等晕误差的大小。并根据该仿真方法的思路,设计了一套钠信标非等晕波前探测误差的实验测量系统。本文数值仿真并实验测量了钠信标的回光亮度和钠信标激光器与钠原子间的耦合效率,完成了对钠信标光斑形态和回光亮度的优化。同时,数值仿真了钠信标自适应光学系统中非等晕误差的影响,并设计了非等晕误差的实验测量系统。文中所做工作为国内钠信标自适应光学系统的首次闭环奠定了基础,同时为后期钠信标自适应光学系统波前探测器的设计也提供了参考依据。
[Abstract]:Adaptive optics system has become one of the basic components of large aperture ground-based telescope. The use of artificial sodium beacons can greatly improve the sky coverage of astronomical adaptive optical systems, but the spot brightness will be low when using sodium beacons to detect wavefront. Based on the sodium beacons adaptive optical system of the Institute of Optoelectronic Technology of the Chinese Academy of Sciences in Lijiang 1.8m telescope. In view of the main problems encountered in the experiment of the wavefront detection part of the system: the low luminance of the sodium beacon and the non-equal-halo error of the detection of the wavefront of the sodium beacon. The main work is as follows. Firstly, the theoretical model of sodium atom excited by sodium beacons laser is established. Aimed at the sodium beacons adaptive optical system of the Institute of Optoelectronic Technology of the Chinese Academy of Sciences on the 1.8m telescope in Lijiang, the 20W nanosecond pulse laser was used by the Institute of Physicochemical Technology of the Chinese Academy of Sciences. The numerical simulation of the excitation efficiency (coupling efficiency) of the laser to sodium atom is completed, and the polarization state and relaxation oscillation of the laser are analyzed. The spectral distribution and the effect of D2a D2b double peak pumping on the coupling efficiency. The numerical simulation results show that there is an optimal power density for a given type of laser. The coupling efficiency between the laser and the sodium atom is the highest at this power density. At the same time, the numerical simulation results also provide better suggestions for the future upgrade of the laser. Based on the 1.8m telescope platform of Lijiang, a complete light measuring system of sodium beacon is built, and the theory and method of experimental measurement of the brightness of sodium beacon are put forward. The optimization of the spot shape and the light return brightness of the sodium beacon has been completed, and the coupling efficiency of the sodium beacon and the coupling efficiency of the laser have been measured experimentally. A double-peak pump experimental platform of sodium beacons laser D2a D2b is built, which verifies the effectiveness of bimodal pumping on the enhancement of the brightness of sodium beacons. Finally, the non-equal-halo error caused by the detection of sodium beacons wavefront is studied. By setting the phase screen of atmospheric turbulence and the propagation equation of light wavefront, the non-equal-halo error caused by using sodium beacons to detect wavefront is numerically simulated. The magnitude of the height non-isobaric error and the angular non-isobaric error are analyzed respectively. A set of experimental measurement system for the detection error of nonisohalo wavefront in sodium beacons is designed. In this paper, the backlight brightness of sodium beacons and the coupling efficiency between sodium beacons laser and sodium atoms are numerically simulated and experimentally measured. At the same time, the influence of non-isobaric error in the adaptive optical system of sodium beacons is numerically simulated. The experimental measurement system of non-isobaric error is designed. The work in this paper lays a foundation for the first closed loop of the domestic sodium beacon adaptive optical system. It also provides a reference for the design of the wavefront detector of the late sodium beacon adaptive optical system.
【学位授予单位】：中国科学院光电技术研究所
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TH751;TN248

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