用光栅压缩受激布里渊后向散射脉冲

本文报道了使用光栅压缩器对后向受激布里渊散射(SBS)脉冲的时间压缩。实验结果表明后向SBS是以线性扫频为主要成份.获得了脉宽为40ps的1.06μm压缩脉冲,压缩比为20倍.     

光学元件中受激布里渊散射的研究状况及进展

综述了光学元件中受激布里渊散射(SBS)对光学元件的超声波损伤、对激光传输能量的损耗、对光束质量的破坏等问题的研究现状、进展;重点是大口径光学元件中横向受激布里渊散射,并指出其未来的发展前景。     

Interaction between dispersed photochromic compound and polymer matrix

Thin films containing photochromatic spiropyran (SP) was prepared from polymethyl methacrylate (PMMA), polyethyl methacrylate (PEMA), poly(n-butyl methacrylate) (PnBMA), and styrene-butadiene-styrene copolymer (SBS). The thin films were illuminated with the ultraviolet light (365 nm) under various temperatures. The photochromic response was monitored with a multichannel photodetector. The results show that the photocoloring rate of SP was faster in PMMA, while the thermal decoloring rate was faster in SBS. In addition, the decoloring rate was higher in a polymer matrix with lower T_g.     

Compensations of Stimulated Brillouin Scattering Effect with Stimulated Raman Effect in Distributed EDFA

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Improving the aging resistance of styrene-butadiene-styrene tri-block copolymer modified asphalt by addition of antioxidants

The aging properties of base asphalt and styrene-butadiene-styrene tri-block copolymer (SBS) modified asphalts (PMA) are evaluated using Fourier Transform Infrared (FTIR) spectroscopy. An aging cell fitted to the FTIR microscope was used to continually and directly study the oxidation of the PMA. In particular, Attenuated Total Reflectance, ATR, with a zinc selenide prism was used to quantify the changes in the spectra of the PMA before and after thin film oven test (TFOT). The effect of a small amount (1 wt%) of some modifiers, zinc dialkyldithiophosphate (ZDDP), zinc dibutyl dithiocarbamate (ZDBC) or naphthenoid oil, on the chemical and physical properties of the PMA was studied. The modification extent of the modifiers increases in the order: oil, ZDBC, ZDDP. With the aging of the PMA, carbonyl groups formed and the intensity of the absorption peak at 965 cm⁻¹ (the characteristic peak of SBS) decreased. Antioxidants, ZDDP or ZDBC modified PMA are resistant to the formation of carbonyl to some extent, indicating the improvement of aging resistance of the PMA by the addition of the antioxidants. ZDDP and ZDBC as antioxidants can retard the oxidation of the PMA through the inhibition of peroxides and radical scavenging. Furthermore, ZDDP in a liquid state at room temperature acts as plasticiser, giving rise to a good aging resistance of PMA.     

SBS三嵌段共聚物在丁酮溶剂中的降解

论文研究了SBS三嵌段共聚物在选择性溶剂丁酮中的降解。采用超速离心沉降速度法、毛细管粘度法、GPC和IR的研究手段,证实了SBS/丁酮溶液存放时间较长时,溶液中SBS分子发生降解,降解发生在聚丁二烯嵌段的不饱和双键。从而也表明SBS/丁酮溶液中胶束行为的不稳定归国于SBS分子的降解。     

Hydrogenation of polystyrene‐b‐polybutadiene‐b‐polystyrene mediated by group (IV) metal metallocene complexes

Various group (IV) metal complexes, namely bis(cyclopentadienyl) titanium dichloride, bis(pentamethylcyclopentadienyl) titanium dichloride, cyclopentadienyl titanium trichloride, pentamethylcyclopentadienyl titanium trichloride, bis(cyclopentadienyl) zirconium dichloride, and bis(cyclopentadienyl) hafnium dichloride, were used as the catalysts for mediating styrene–butadiene–styrene hydrogenation. The catalytic efficiency of these catalysts was examined. The results show that catalyst activity strongly depends on the chemical structure of the metallocene complex. We also found that trialkylaluminum has a significant influence on the hydrogenation activity and thermal stability of metallocene catalysts. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2141–2149     

市县长距离环网建设的解决方案

结合张家口市县联网的工程实例,从理论分析和工程实践上给出了实现长距离传输的技术难题和整体解决方案,在全国大力推进县级数字电视整体转换的今天,该方案可为各中小有线电视网的建设提供借鉴。     

The damage of the optical components induced by the stimulated Brillouin scattering

A theory of excitation of ultrasonic waves in the stimulated Brillouin scattering (SBS) process is presented in this paper. By using several reasonable approximations, a numerical calculation of the transient longitudinal SBS shows that large amplitude of acoustic waves can be built up by the nanosecond pulse of high-power laser, which may result in the damage of optical glasses. The maximal density change and the maximal acoustic wave intensity in optical glasses of 5\,cm in thickness are calculated by using different parameters of the high-energy laser, such as the intensity, the pulse width, and the wave length. The damage threshold of the optical glasses is about 80 GW/cm^{2} when using a 1064 nm laser. The dynamic mechanism of SBS is the electrostriction effect of the components coupling with the high-power laser.     

Measurement of stimulated Brillouin scattering （SBS） threshold based on waveform variation of SBS optical limiting

This paper proposes a method for measuring the stimulated Brillouin scattering (SBS) threshold based on waveform variation of SBS optical limiting. The output waveforms for different pump power densities are numerically simulated, and validated in the Nd:YAG seed-injected laser system. The results indicate that SBS does not take place in the case of a low pump power density and thus the output power scales up linearly with pump power. Once the pump power density exceeds the SBS threshold, SBS takes place and thereby the energies are transferred from pump to Stokes. As a result, a small shoulder appears in the trailing edge of the output waveform, which provides another method to determine the SBS threshold.