门控下InGaAs/InP单光子探测器用于符合测量的时域滤波特性研究

基于砷化镓/磷化铟雪崩光电二极管(InGaAs/InP APD)的半导体单光子探测器因工作在通信波段,且具有体积小、成本低、操作方便等优势,在实用化量子通信技术中发挥了重要作用.为尽可能避免暗计数和后脉冲对单光子探测的影响,InGaAs/InP单光子探测器广泛采用门控技术来快速触发和淬灭雪崩效应,有效门宽通常在纳秒量级.本文研究揭示了门控下单光子探测器可测量的最大符合时间宽度受限于门控脉冲的宽度,理论分析与实验结果良好拟合.该研究表明,门控下InGaAs/InP单光子探测器用于双光子符合测量具有显著的时域滤波特性,限制了其在基于双光子时间关联测量的量子信息技术中的应用.     

Composition of structural carbohydrates in biomass: precision of a liquid chromatography method using a neutral detergent extraction and a charged aerosol detector

We adapted and optimized a method to quantify the cellulose, hemicellulose, xylan, arabinan, mannan, galactan contents in lignocellulosic biomass. This method is based on a neutral detergent extraction (NDE) of the interfering biomass components, followed by a sulfuric acid hydrolysis (SAH) of the structural polysaccharides, and a liquid chromatography with charged aerosol detection (LC-CAD) to analyze the released monosaccharides. The first step of this NDE-SAH-LC-CAD method aims at removing all compounds that interfere with the subsequent sulphuric acid hydrolysis or with the subsequent chromatographic quantification of the cellulosic and hemicellulosic monosaccharides. This step includes starch hydrolysis with an analytical thermostable α-amylase followed by an extraction of soluble compounds by a Van Soest neutral detergent solution (NDE). The aim of this paper was to assess the precision of this method when choosing fiber sorghum (Sorghum bicolor (L.) Moench), tall fescue (Festuca arundinacea Schreb.) and fiber hemp (Cannabis sativa L.) as representative lignocellulosic biomass. The cellulose content of fiber sorghum, tall fescue and fiber hemp determined by the NDE-SAH-LC-CAD method were 28.7 ± 1.0, 29.7 ± 1.0 and 43.6 ± 1.2 g/100 g dry matter, respectively, and their hemicellulose content were 18.6 ± 0.5, 16.5 ± 0.5 and 14.5 ± 0.2 g/100 g dry matter, respectively. Cellulose, mannan and galactan contents were higher in fiber hemp (dicotyledon) as compared to tall fescue and fiber sorghum (monocotyledons). The xylan, arabinan and total hemicellulose contents were higher in tall fescue and fiber sorghum as compared to fiber hemp. The precision of the NDE-SAH-LC-CAD method was better for polysaccharide concentration levels above 1 g/100 g dry matter. Galactan analysis offered a lower precision, due to a lower CAD response intensity to galactose as compared to the other monosaccharides. The dispersions of the results (expanded uncertainty) of the NDE-SAH-LC-CAD method were smaller as compared to the Van Soest (VS) method. In addition, the NDE-SAH-LC-CAD method was able to provide additional information on the composition of the hemicellulose (xylan, arabinan, mannan and galactan content) that is not provided by the Van Soest method. The NDE-SAH-LC-CAD method offers also the advantage of a better specificity for hemicellulose and cellulose, as compared to the NREL and Uppsala methods.     

Impacts of oxygen sensitization methods on the deposition and microstructure of ternary lead chalcogenide alloys

Oxygen sensitization and incorporation of ternary lead chalcogenide PbSe_1-xTe_x thin films was investigated with two methods: adding oxygen via PbO to the bulk source alloy and post-deposition oxygen annealing. Characterization of the composition, structure, and morphology of these films confirmed that they follow Vegard's law for lattice parameter, and adding PbO to the source alloy did not impact the lattice parameter. However, adding PbO changed the electrical carrier properties observed in Hall effect measurements without forming any new oxide phase. Conversely, post-deposition annealing increased the lattice parameter due to oxygen incorporation into the lattice via interstitials in samples with appropriate grain boundary orientations. Morphological analysis revealed that PbSe_0.8Te_0.2 films demonstrated (100) texture, while PbSe_0.6Te_0.4 films demonstrated (111) texture with resulting grain boundary orientations more favorable to oxygen diffusion and incorporation. This varying oxygen incorporation from PbO source and oxygen annealing methods reveals trends that can lead to improved photodetector performance.     

一种基于固定光栅和阵列检测器的新型红外分光测油仪

介绍了一种采用固定光栅、阵列检测器和自动进样等技术的新型红外测油仪。该仪器精密度好,准确度高,分析速度快,减少了操作人员与有毒性的萃取剂直接接触,操作软件功能强大,界面友好。     

Effect of adding Ar gas on the pulse height distribution of BF<Subscript>3</Subscript>-filled neutron detectors

Boron trifluoride (BF₃) proportional counters are used as detectors for thermal neutrons. They are characterized by high neutron sensitivity and good gamma discriminating properties. Most practical BF₃ counters are filled with pure boron trifluoride gas enriched up to 96% ¹⁰B. But BF₃ is not an ideal proportional counter gas. Worsening of plateau characteristics is observed with increasing radius due to impurities in gas. To overcome this problem, counters are filled with BF₃ with an admixture of a more suitable gas such as argon. The dilution of BF₃ with argon causes a decrease in detection efficiency, but the pulse height spectrum shows sharper peaks and more stable plateau characteristics than counters filled with pure BF₃. The present investigations are undertaken to study the pulse height distribution and other important factors in BF₃+Ar filled signal counters for neutron beam applications. Tests are performed with detectors with cylindrical geometry filled with BF₃ gas enriched in ¹⁰B to 90%, and high purity Ar in different proportions. By analysing pulse height spectra, a value of 6.1 ± 0.2 has been obtained for the branching ratio of the ¹⁰B(n,α) reaction.      

非制冷热像仪内部温升对测温精度的影响修正

随着非制冷型热像仪工作时间的增长,其内部器件、机械结构所积累的热量越来越多,其温升所导致的热辐射势必会对热像仪的测温精度产生严重影响。因此,要实现热像仪的准确测温,必须对其内部的各温升影响因素进行相应的修正。本文通过对影响测温精度的镜筒辐射温度、探测器靶面温度以及热像仪工作累积时间三个因素进行评估和建模,并对其相互关系进行评价,根据数据模型对热像仪辐射测温值进行修正。结果表明,在实验室条件下,经过修正,非制冷型红外热像仪测温精度可控制在±1℃以内,其稳定性可控制在±0.5℃以内。修正后的温度结果基本不受内部温升的影响,有效的提高了非制冷测温型热像仪的稳定性、可重复性以及测温精度。     

Parametric oscillatory instability in a Fabry–Perot cavity of the Einstein Telescope with different mirror's materials

We discuss the parametric oscillatory instability in a Fabry–Perot cavity of the Einstein Telescope. Unstable combinations of elastic and optical modes for two possible configurations of gravitational wave third-generation detector are deduced. The results are compared with the results for gravitational wave interferometers LIGO and LIGO Voyager.     

Engineering the optical spring via intra-cavity optical-parametric amplification

The ‘optical spring’ results from dynamical back-action and can be used to improve the sensitivity of cavity-enhanced gravitational-wave detectors. The effect occurs if an oscillation of the cavity length results in an oscillation of the intra-cavity light power having such a phase relation that the light's radiation pressure force amplifies the oscillation of the cavity length. Here, we analyse a Michelson interferometer whose optical-spring cavity includes an additional optical-parametric amplifier with adjustable phase. We find that the phase of the parametric pump field is a versatile parameter for shaping the interferometer's spectral density.     

Stabilized lasers for advanced gravitational wave detectors

Second‐generation interferometric gravitational wave detectors require high‐power lasers with approximately 200 W of output power in a linear polarized, single‐frequency, fundamental‐mode laser beam. Furthermore very high temporal and spatial stability is required. This paper discusses the design of a 200 W pre‐stabilized laser (PSL) system and the underlying concepts. The PSL requirements for advanced gravitational wave detectors as well as for the laser system are described. The laser stabilization scheme proposed for the Advanced LIGO gravitational wave detector and the so‐called diagnostic breadboard will serve as examples to explain the general laser stabilization concepts and the achieved performance and its limitations.     

Semiconductor Terahertz Physics

A rich range of physical phenomena exhibit frequencies in the range of 0.1–10 THz. Within semiconductors, these include phononic, electronic, and mixed modes of oscillations. These fundamental phenomena then serve as the basis for specific devices to produce, manipulate, and detect terahertz radiation.