共查询到16条相似文献，搜索用时 890 毫秒
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利用液晶相位可变延迟器慢轴折射率随外加电压变化的特性,研制了一台用液晶进行频率调谐的分布反馈(DFB,distributed feedback)外腔半导体激光器。液晶DFB外腔激光器输出激光线宽为475 kHz,液晶电压变化1.6 V(0.5～2.1 V)时,激光频率变化为7 GHz,覆盖了Cs原子D2线的全部饱和吸收谱线。在实现外腔半导体激光器方法中,应用液晶调相较应用压电陶瓷(PZT)改变腔长,其具有调谐电压低,回程误差小,并可以消除机械稳定性差等特点。 相似文献
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《中国科学院上海天文台年刊》2015,(0)
介绍了2014年上海天文台卫星激光测距系统的常规观测、系统升级改造及科研实验情况。在主副镜完成用1064 nm波长镀膜的基础上,突破激光指向监视、发散角调节等关键技术,国内首次完成1064 nm波长激光对卫星的测量;通过引进10 k Hz激光器,以及解决超高重复频率的事件记录、控制采集等关键技术,国际上首次实现10 kHz重复频率激光测距,最远探测距离达40 000 km;使用200 Hz重复频率60 W大功率激光器及低噪高效探测器,基于60厘米望远镜完成最远距离2200 km的激光测距、雷达散射截面(radar cross-section,RCS)最小为0.3 m~2的空间碎片测量,并成功实现1.56米望远镜的空间碎片激光测距。 相似文献
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先来思考一个问题：光总是沿着直线传播的,对吗7……现在,让我们跟随天才的阿尔伯特·爱因斯坦的脚步,来想想这个问题!根据爱因斯坦著名的广义相对论,从遥远的光源发出的光线,会在途经的大质量天体附近“弯折”。对我们生活中常见的那些大小和质量的物体来说,这种效应小得难以想象,但是在宇宙的尺度上,光的这种性质就成为我们研究遥远天体时有用工具。 相似文献
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Balmer发射线是研究星际无碰撞激波物理性质的重要途径之一.星际无碰撞激波的Balmer发射线包括宽线和窄线两个明显的成分.通常认为,这种双线成分是与激波联系在一起的,宽线产生于激波前慢中性粒子与激波后高能质子的电荷交换,反映了激波后粒子的热运动状况,而窄线则产生于激波前慢中性粒子的激发,反映了激波前粒子的热运动状况.但是,近来更细致的观测和理论计算表明,超新星遗迹中Balmer发射线的双线结构很可能还要受到其他因素的影响,并且与激波速度和电子-质子的热平衡有着密切的关系.该文将讨论影响Balmer双线结构的各种因素,并讨论Balmer双线结构在超新星遗迹研究中的一些应用. 相似文献
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The method of stellar radial velocity variations has recently shown its capability by the first discovery of several extra-solar planets. Accuracies achieved today are in the range 3-10 m/s. The AAA (absolute astronomical accelerometer) is an instrument which aims to reach the photon noise limit for the measurement of velocity changes, with systematic errors of about 1 m/s, long term. The principle is to use a servo-controlled CCD spectrograph as a null detector, and to register always the lines of the star on the same CCD pixels. Thus, systematic errors linked to the Earth-induced large variations are cancelled. A tunable Fabry-Perot channelled spectrum is also following the star spectrum, while the FP thickness is measured by heterodyne detection of the beats between a tunable laser diode and a stabilized laser diode. A complete prototype of the instrument is operating with laboratory sources and the first results are presented. It is planned to use this system with a new spectrograph, to be coupled to the 152 cm telescope at Observatoire de Haute Provence. 相似文献
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K.G. Strassmeier I.V. Ilyin M. Woche T. Granzer M. Weber J. Weingrill S.‐M. Bauer E. Popow C. Denker W. Schmidt O. von der Lühe S. Berdyugina M. Collados P. Koubsky T. Hackman M.J. Mantere 《Astronomische Nachrichten》2012,333(9):901-910
We describe the future night‐time spectrograph for the GREGOR solar telescope and present its science core projects. The spectrograph provides a 3‐pixel resolution of up to R = 87 000 in 45 échelle orders covering the wavelength range 390‐900 nm with three grating settings. An iodine cell can be used for high‐precision radial velocity work in the 500‐630 nm range. The operation of the spectrograph and the telescope will be fully automated without the presence of humans during night‐time and will be based on the successful STELLA control system. Future upgrades include a second optical camera for even higher spectral resolution, a Stokes‐V polarimeter and a link to the laser‐frequency comb at the Vacuum Tower Telescope. The night‐time core projects are a study of the angular‐momentum evolution of “The Sun in Time” and a continuation of our long‐term Doppler imaging of active stars (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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《Physics and Chemistry of the Earth, Part C: Solar, Terrestrial & Planetary Science》1999,24(5):439-442
An improved ozone Differential Absorption Lidar (DIAL) system has been designed for tropospheric and lower stratospheric ozone monitoring in Northern Greece. The system is based on a frequency quadrupled pulsed Nd:YAG laser and the Raman shifting technique in D2 and H2 gases. The lidar system emits simultaneously 4 wavelengths (266 mn, 289 nm, 299 nm and 316 nm) at 10 Hz repetition rate using a single low pressure Raman cell. The optical receiving system is based on a 50 cm concave telescope which is directly coupled to a specially conceived grating spectrometer. This lidar system uses analog (12 bits-40 MHz) and photon counting (250 MHz) detection systems, able to measure lidar signals up 16 km height. Ozone vertical profiles are to be measured from 0.8 km up to 15 km height, with a 30–500 m spatial and a 1-minute temporal resolution. In this paper the major technical characteristics of the improved lidar system are presented. The system is foreseen to provide the first daytime/nighttime ozone vertical profiles during early winter 1999. 相似文献
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