三种橡胶材料的太赫兹光谱研究

本文利用太赫兹时域光谱技术研究了氯丁橡胶、丁腈橡胶和三元乙丙橡胶在0.2～1.8 THz频段的光学性能和光谱特性,得到了三种橡胶的时域谱、折射率谱和吸收谱,进而计算橡胶在0.2～1.8 THz频段的吸收系数和折射率,结果表明可以通过吸收系数与折射率来区分不同种类的橡胶。这种方法为认识橡胶对太赫兹波的响应机制提供了科学依据,有望为橡胶材料鉴别提供一种有效的分析手段。     

太赫兹波段光子晶体温度传感器的研究

使用对太赫兹波段有吸收效应的掺杂硅设计光子晶体结构,使得在光子带隙内的光波被吸收,并加上金属反射镜面将光子晶体的吸收峰和法布里-珀罗(F-P)谐振吸收峰结合,使此结构在0.29～0.31 THz波段达到宽频吸收,并且在0.31～0.34 THz波段通过测量光子晶体的反射率可以计算出对应温度。在使用商业电磁仿真软件CST2014仿真和优化参数后,反射率对应温度变化的变化范围是0.09～0.36,即最大值与最小值有4倍之差,这一特性表明,此结构的反射率变化随温度变化十分明显,是一款十分灵敏的温度传感器。此外,在入射角不大于40°时,结构性能依然良好。     

氧化镁晶体的太赫兹时域光谱测量与分析

氧化镁晶体在太赫兹波段的性质得到了广泛的关注。基于太赫兹时域光谱系统,在0.2～2.6THz对氧化镁晶体的光学特性进行分析。从测得的透过率和相移提取晶体的折射率和吸收谱。通过数据分析处理,实验得到该波段氧化镁晶体的折射率在2.76～2.78之间,且随着太赫兹频率的增加其透过率逐渐减小。进一步分析表明,氧化镁晶体在太赫兹波段无明显反常色散和吸收峰。     

岩石的太赫兹光谱特性研究

本文以太赫兹时域光谱分析技术为手段,研究了侵入岩、喷出岩、沉积岩样品的太赫兹波段光谱特性,在0.3～1.4THz光谱区域间得到了样品的光学参数,并结合偏光显微镜图片分析了样品的吸收系数和折射率值.结果表明,针对样品的结构、成分、类型的不同,透射光谱均出现了不同的吸收和折射特性.通过太赫兹光谱包含的特征信息可以对不同岩石初步进行定性分析,从而为利用太赫兹技术进一步分析岩石的成因、演化特性及其与矿化的关系提供依据和方法.     

太赫兹技术在石油领域的应用进展

石油工业是近代世界工业革命最重要的推动力之一,石油工业对人类文明的发展贡献巨大,因此需要一种快速、可信和简便的无损检测技术来互补于传统的傅里叶变换红外光谱、X射线及近红外光谱技术。太赫兹技术具有高的时间分辨率、相干探测、低能性及相对简单的测试与数据处理方法等优点,在汽油、柴油、润滑油、润滑油基础油、润滑脂、油水混合物、植物油、烃类分子、塑料和有机溶剂中被广泛应用,为石油领域的光谱学研究提供了新的分析手段,显示出了广阔的应用前景。本文从五个方面综述了国内外太赫兹技术在石油领域的应用,主要包含太赫兹技术在油气资源探测与运输、石油炼制、石油精制、石油工业气体以及基础研究的应用现状和发展前景,对太赫兹技术在石油领域的应用进行了展望。     

太赫兹频段硅的光学特性研究

硅是常用的半导体材料,它作为信息时代的基石,一直都在材料领域占有很重要的地位.总结了硅在太赫兹频段的光学特性,得到了一些可靠的光学参数,为进一步研究基于硅衬底的THz光子器件奠定了基础.同时,本文还对硅在THz频段的应用前景进行了展望.     

原油超声处理的太赫兹时域光谱分析

基于太赫兹时域光谱技术研究了经过超声处理的两种原油在0.1～1.4 THz波段的光学性质,得到了样品的吸收谱和折射率谱发现经过不同时间超声作用的原油,其太赫兹光谱曲线变化显著,说明样品的结构组成分子在能级共振位置上,均出现了不同的吸收和折射特性.太赫兹时域光谱可作为波形分析技术为原油超声处理时超声强度、频率、作用时间等参数的选择提供理论依据.     

原油中硫含量的太赫兹时域光谱检测

原油中硫含量的快速检测对于原油的安全生产、运输、加工和环境保护均具有十分重要的意义.本文运用太赫兹时域光谱技术对不同硫含量的原油进行了实验测量,经过计算得到了样品的吸收谱和折射率谱.通过对这些光谱进行分析,结果表明太赫兹时域光谱不仅能够有效的检测出原油中的硫含量,还能实现对原油中物质的溶解程度进行定性的预测.     

基于太赫兹波谱的液体极性测量

太赫兹波能与极性液体的氢键发生强烈的共振吸收作用,分子极性越大,吸收作用越强。基于此特性,在0.2～1.0 THz波段利用太赫兹时域光谱技术对甲醇、乙醇、正丙醇、正丁醇四种一元醇液体的极性进行检测研究。根据测量得到的四种液体太赫兹波谱数据,得出了液体的极性与其太赫兹波谱的关系式,再利用此关系式求得四种液体的计算值。通过对四种液体极性的标准值和计算值比对,验证了所得液体极性求取公式的有效性。研究结果表明,四种不同液体的时域光谱因分子的极性差异有显著的不同,所用的液体极性测量方法能够对液体的极性进行快速有效的检测与鉴别,可为其他液体极性的检测提供参考。     

太赫兹时域光谱系统光斑大小和位置的测量

本文利用太赫兹时域光谱系统本身的电磁波探测装置具有可测量电磁波的相位、振幅的特点,根据其获得的原始时域光谱信号,设计了一套适用于太赫兹时域光谱系统中太赫兹束光斑大小和位置的测量装置,论述其理论依据.该测量装置不需要辅助电源电路,结构简单、价格低廉、便于携带和制作且测量方法简单实用,为太赫兹时域光谱系统的现场矫正和快速调节提供了一种有效的手段.     

Broadband terahertz spectroscopy of amino acids

Broadband spectra of 20 L-amino acids were obtained at room temperature by terahertz time-domain and infrared spectroscopy. The intensity of terahertz absorption peaks varied with the concentrations of amino acids, and the optimum proportion for each amino acid was obtained. An absorption spectral database of 20 L-amino acids was established from 0 to 6 THz. The associations between terahertz absorption peaks and molecular structures of amino acids were analyzed. The terahertz spectra for L-alanine were compared with the calculated results based on density functional theory using two basis sets that were reliably consistent.     

CO激光在非线性晶体ZnGeP2和GaSe中的混频效应（英文）

为了获得2.15～1 500μm的相干光源,研究了CO激光在高质量非线性晶体ZnGeP2和GaSe中的混频效应。为了提高转换效率,在激光锁模方式下对CO激光器的二次谐波、和频和差频的产生进行了研究。结果显示,利用GaSe晶体和ZnGeP2晶体,调Q多谱线CO激光辐射的谱线内倍频效率分别大于0.3%和1.1%。采用ZnGeP2晶体进行倍频时,可调谐锁膜CO激光器的转换效率为12.5%。模拟结果显示,二次谐波与和频产生的输出光谱相同。相邻谱线下,和频和差频的产生过程中,基波和一次谐波可以分别在4.0～5.0μm和100～≥1 200μm(太赫兹范围)形成振荡。利用锁模CO激光器在ZnGeP2晶体中的混频效应,可以得到2.15～≥1 500μm的相干光源,同时转换效率可达到甚至高于12.5%。     

太赫兹双梳光谱中重复频率差影响的研究

太赫兹双梳光谱技术因其高频率分辨率和高灵敏度等优点,近年来成为一种有力的光谱测量技术。为了提高光谱系统的探测性能,本文分析了双梳光谱技术在时域和频域中的采样原理及方法,基于两台飞秒激光器搭建了一套重复频率可调的太赫兹双梳光谱系统。通过改变一台光频梳的重复频率,系统地研究了不同重复频率差对太赫兹双梳光谱系统性能的影响。结果表明有效范围内的重复频率差越小,探测到光谱质量越高。当重复频率差为10 Hz时,太赫兹双梳光谱系统的探测性能最佳。此研究为太赫兹双梳光谱技术选择最合适的重复频率差提供了方法。     

Near-field Raman imaging of morphological and chemical defects in organic crystals with subdiffraction resolution

In this study we report on the application of an aperture near‐field optical microscope for Raman imaging of organic materials. Spectral analysis and detailed Raman imaging are performed with integration times of 100 ms per point, without the aid of field enhancement effects. The studied samples consist of two high Raman‐efficiency molecular samples: a 7,7′,8,8′‐tetracyanoquinodimethane crystal showing surface defects and a 7,7′,8,8′‐tetracyanoquinodimethane thin film characterized by the presence of submicrometre‐sized organometallic copper–salt complexes. In the first case, the effect of the surface deformation was studied, whereas in the second sample we were able to chemically image the formation of salt complexes. Subdiffraction resolution was achieved in both studies.     

Fabrication of a novel micron scale Y-structure-based chiral metamaterial: Simulation and experimental analysis of its chiral and negative index properties in the terahertz and microwave regimes

In this report, we describe the fabrication of a chiral metamaterial based on a periodic array of Y-shaped Al structures on a dielectric Mylar substrate. The unit cell dimensions of the Y-structure are approximately 100 microm on a side with 8 microm linewidths. The fabricated Y-structure elements are characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Quantitative elemental analyses were carried out on both the Y-structure, comprised of Al and its oxide, as well as adjacent regions of the underlying mylar substrate using the energy dispersive X-ray spectroscopy (EDS) capability of the SEM. Finite-Difference Time-Domain (FDTD) calculations of the negative index of refraction for a 3D wedge of multiple layers of the 2D metamaterials showed that these metamaterials possess double negative (-mu,-epsilon) electromagnetic bulk properties at THz frequencies. The same negative index of refraction was determined for a wedge comprised of appropriately scaled larger Y-structures simulated in the microwave region. This double negative property was confirmed experimentally by microwave measurements on a 3D wedge comprised of stacked and registered Y-structure sheets.     

Electron energy-loss spectroscopy (EELS) of iodine in thyroxine: parameters of radiation-induced loss of iodine

The loss of iodine during irradiation with electrons was measured in order to determine whether it can be detected by electron spectroscopic imaging (ESI). Since iodine can be bound to organic molecules, it could be a candidate for tracer studies by ESI in biomedical research. A solution of thyroxine spread over a carbon film was used as a test specimen. Thyroxine contains four iodine atoms covalently bound to aromatic rings. For ESI, higher doses have to be used than in conventional electron microscopy. The iodine content was therefore measured after irradiation with doses of up to 3 × 10⁷ el nm^?2. The measurements were carried out for different specimen thicknesses, temperatures and dose rates, and it was found that iodine can be detected with ESI if moderate dose rates are used at a temperature of ?160 °C.     

Topography of YBa2Cu3O7-δ single crystals,spectroscopy of thin films and sintered YBa2Cu3O7-δ: theory and STM observations

We report topographic scanning tunnelling microscopy measurements on the (001) and (100) surfaces of YBa₂Cu₃O_7-δ single crystals, together with a theoretical basis by which the surface structures can be understood. We show that it is possible to obtain reproducible topographic data on a clean (001) and (100) surface in air. The results show various structures at scales from 0·1 to 100 nm. Among the observed features on the (001) surface were growth steps which had heights that were multiples of the lattice constant in the [001] direction. This indicates that the bulk crystal structure extends to the surface, and that the surface is relatively stable, even in humid air. We also found small (013) facets on the (001) surface, in accordance with theoretical pradictions. Occasionally, we found evidence for a one-dimensional corrugation on the surface. This is possibly a direct consequence of the orthorhombic distortion in the a-b plane with ordered oxygen vacancies, which gives rise to chain-like Cu-O structures along the b-axis. In addition, we measured the energy gap of sintered pellets and thin films of this superconductor, using a low-temperature STM. We discuss some effects which may influence the measurements and present criteria to check for these effects. We found an energy gap of δ=14±2 eV, in good agreement with the BCS pradiction 2δ/kT_c=3·5. This is not contradicted by the results we obtained by far infrared spectroscopy and Andreev reflection measurements.