Tradition of geodetic instruments production in the Czech Republic

The article describes the development of geodetic surveying and production of geodetic instruments in what is now Czech Republic. The beginnings of development can be found in the 12th–13th centuries during the colonization of the territory and the consolidation of state administration. Significant development peaks occurred in the 14th century during the reign of the Holy Roman Emperor and King of Bohemia Charles IV and then at the turn of the 16th and 17th centuries during the reign of the Holy Roman Emperor Rudolf II. The new direction is related to the development of industry at the end of the 19th century. At that time, several dozen companies in fine mechanics and optics were operating in Prague. The company J. & J. Frič was a world leader in the use of a glass divided circle in 1864. The production of astronomical and geodetic instruments in Czechoslovakia was successful until the end of the 1960s.

First radiative shock experiments on the SG-II laser

We report on the design and first results from experiments looking at the formation of radiative shocks on the Shenguang-II (SG-II) laser at the Shanghai Institute of Optics and Fine Mechanics in China. Laser-heating of a two-layer CH/CH–Br foil drives a $\sim 40$ km/s shock inside a gas cell filled with argon at an initial pressure of 1 bar. The use of gas-cell targets with large (several millimetres) lateral and axial extent allows the shock to propagate freely without any wall interactions, and permits a large field of view to image single and colliding counter-propagating shocks with time-resolved, point-projection X-ray backlighting ( $\sim 20$ μm source size, 4.3 keV photon energy). Single shocks were imaged up to 100 ns after the onset of the laser drive, allowing to probe the growth of spatial nonuniformities in the shock apex. These results are compared with experiments looking at counter-propagating shocks, showing a symmetric drive that leads to a collision and stagnation from $\sim 40$ ns onward. We present a preliminary comparison with numerical simulations with the radiation hydrodynamics code ARWEN, which provides expected plasma parameters for the design of future experiments in this facility.

Recent Progress in Distributed Fiber Acoustic Sensing with Φ-OTDR

Distributed fiber acoustic sensing (DAS) technology can continuously spatially detect disturbances along the sensing fiber over long distance in real time. It has many unique advantages, including, large coverage, high time-and-space resolution, convenient implementation, strong environment adaptability, etc. Nowadays, DAS becomes a versatile technology in many fields, such as, intrusion detection, railway transportation, seismology, structure health monitoring, etc. In this paper, the sensing principle and some common performance indexes are introduced, and a brief overview of recent DAS researches in Shanghai Institute of Optics and Fine Mechanics (SIOM) is presented. Some representative research advances are explained, including, quantitative demodulation, interference fading suppression, frequency response boost, high spatial resolution, and distributed multi-dimension localization. The engineering applications of DAS, carried out by SIOM and other groups, are summarized and reviewed. Finally, possible future directions are discussed and concluded. It is believed that, DAS has great development potential and application prospect.

THE OVERVIEW OF THE PLANETARY ATMOSPHERIC SPECTRAL TELESCOPE (PAST) IN THE SCIENTIFIC EXPERIMENTAL SYSTEM IN NEAR-SPACE (SENSE)

<p><strong>Abstract.</strong> To investigate mass transport and energy dissipation in space environments for solar system planet, a balloon-borne planetary atmospheric spectral telescope (PAST) is designed with 0.8-m aperture in spectral range from 280&amp;thinsp;nm to 680&amp;thinsp;nm will be floated at 35&amp;ndash;40&amp;thinsp;km altitude to observe and investigate the global space environment of Mercury, Venus, Mars, and Jupiter. The telescope is designed by Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences (CIOMP, CAS), and supported by the Strategic Priority Research Program of Chinese Academy of Sciences, that is the Scientific Experimental system in Near-SpacE (SENSE). The telescope is mainly supported by a Ritchey-Chrétien optical system which can achieve 0.5" angular resolution observation, and the optical system has the function of focusing and stabilizing. The telescope is combined with a two-dimension rotate platform to achieve planetary atmospheric imaging in long exposure time. This paper mainly introduces the PAST scheme briefly.</p>

Research and development of new neodymium laser glasses

This work presents a brief introduction on three kinds of newly developed $\text{Nd}^{3+}$ -doped laser glasses in Shanghai Institute of Optics and Fine Mechanics (SIOM), China. Two $\text{Nd}^{3+}$ -doped phosphate glasses with lower thermal expansion coefficient and thermal shock resistance 4 times higher than that of N31 glass are developed for laser processing. Nd:Silicate and Nd:Aluminate glasses with peak emission wavelength at 1061 and 1065 nm, effective emission bandwidth of 34 and 50 nm, respectively, are developed for Exawatt-class laser system application. Fluorophosphate glasses with low nonlinear refractive index ( $n_{2}=0.6{-}0.86$ ) and long fluorescence lifetime ( $430{-}510~\unicode[STIX]{x03BC}\text{s}$ ) are investigated for the purpose of decreasing B integral in high-power laser system. The properties of all these glasses are presented and compared with those of commercial neodymium laser glasses.