激光钠导引星技术研究进展

望远镜是人类探索宇宙奥秘最重要的科学工具之一。大型地基光学望远镜对天观测时,大气扰动使星光波前畸变导致其实际分辨率大幅下降,是长期困扰高精度天文观测的重大科技问题。因此世界各大望远镜均在竞相发展自适应光学技术,以校正大气造成的波前畸变,使望远镜达到近衍射极限分辨率,这标志着地基光学望远镜正在进入自适应光学望远镜时代。激光钠导引星是用激光激发海拨约90 km电离层中的钠原子产生的人造亮星,作为自适应光学校正的信标源,是自适应光学望远镜的核心技术之一。文中介绍了激光钠导引星技术的原理、方法与国内外发展状况,尤其是该实验室采用的固体激光和频技术,实现了钠D2线光谱匹配和钠层激发匹配的微秒脉冲钠导引星激光,并在国内外大望远镜上使用获得成功。

Progress on sodium laser guide star

Astronomical telescope is always one of the vital tools that help human kind to unveil hidden natural laws in the universe. However, spatial resolution of the large ground-based telescope was severely limited because the turbulence of atmosphere degenerates the perfect wavefront from stars into an aberrated one, which was the key science and technology difficult problem to achieve high resolution astronomical observation. So adaptive optics(AO) was being pursuit by many teams internationally to correct the wavefront aberration and make large ground-based telescope resolving power to near diffraction limitation. It indicates that the ground-based optical telescope was currently turning into the AO telescope age. Sodium laser guide star(LGS) generated by laser exciting sodium atoms in the mesospheric layer at an altitude of about 90 km, as a beacon of AO correction, was the cutting-edge technology for the AO telescope. The theory, methods and development status of the sodium LGS were described in this paper. Especially in our lab, micro-second sodium LGS laser system suitable for efficient excitation of the sodium layer was developed with spectral format matched to the mesospheric D2 line. The sodium LGS laser system was successful to apply in some domestic and overseas large telescopes.