Broad and ultra-flattened supercontinuum generation in the visible wavelengths based on the fundamental mode of photonic crystal fibre with central holes

By coupling a train of femtosecond pulses with 100 fs pulse width at a repetition rate of 76 MHz generated by a mode-locked Ti:sapphire laser into the fundamental mode of photonic crystal fibre(PCF) with central holes fabricated through extracting air from the central hole,the broad and ultra-flattened supercontinuum(SC) in the visible wavelengths is generated.When the fundamental mode experiences an anomalous dispersion regime,three phases in the SC generation process are primarily presented.The SC generation(SCG) in the wavelength range from 470 nm to 805 nm does not emerge significant ripples due to a higher pump peak power and the corresponding mode fields at different wavelengths are observed using Bragg gratings.The relative intensity fluctuations of output spectrum in the wavelength ranges of 530 nm to 640 nm and 543 nm to 590 nm are only 0.028 and 0.0071,respectively.     

Frequency measurements of far infrared cw lasing lines in optically pumped CHCl2F

The wavelengths, frequencies, and relative polarizations of 15 FIR cw lasing lines obtained by optically pumping CHCl₂F with a cw CO₂ laser have been measured. The lines are in the wavelength range from 340.3 to 905.4 m and were pumped by P- and R-branch laser lines in the 9 m band of CO₂.Supported in part by a joint grant with the U. S. National Science Foundation grant # INT80-19014 and the Brazilian Consellio Nacional de Pesquisas (CNPq)Contribution of the U. S. Government, not subject to copyright.     

Refractive index and material dispersions of multi-component oxide glasses

Refractive index dispersion curves in the wavelength region of 0.40 to 5.03 μm are presented for multi-component oxide glass systems: borate, silicate, aluminate, germanate, tellurite, antimonate and heavy metal gallate. The material dispersion was determined using the refractive index data. Reflection spectra in the ultraviolet and infrared regions were measured to investigate the effects of electronic transitions and lattice vibrations on the material dispersion. Thallium tellurite, thallium antimonate and lead gallate glasses exhibit zero material dispersion wavelengths (ZMDWs) over 2.4 μm. The factors affecting the ZMDW are discussed.     

Modelling of multi-line Brillouin/erbium fibre lasers

Laser sources with unique properties can be produced using a combination of nonlinear Brillouin gain in single-mode optical fibre (SMOF) and gain in erbium-doped fibre (EDF). Narrow bandwidth nonlinear gain from stimulated Brillouin scattering in SMOF determines the wavelength of operation, and gain in EDF allows efficient operation and large power extraction. Various cascading schemes based on the Brillouin/erbium fibre laser (BEFL) as well as distinctive multi-wavelength versions of the BEFL were proposed, being able to produce 10GHz combs of over 30 lines at 1550 nm. These multi-wavelength sources may be of use in future dense wavelength-division multiplexing systems. We explore fundamental aspects of BEFLs configured to generate multiple wavelengths with particular focus on the effects of the Brillouin and EDF pumps on the number of lines and the relationship between the intensities of the individual lines in the comb.     

高效液相色谱法同时测定无骨海鱼中的维生素A、D和E

采用反相高效液相色谱法,以甲醇(49 1)为流动相,对维生素A、D和E混标进行高速紫外扫描,在Nova Pak C18柱上获得分离良好的三维图谱。据此,选择维生素A、D和E各自最大吸收波长325、265和290nm作为检测波长。实验结果表明:无骨海鱼中维生素A、D和E的质量分数分别为0.80、0.17、4.14mg kg,相对标准偏差为3.7%～5.0%。质量浓度0.10～10mg L范围内,维生素A、D、E均呈现良好的线性关系,检出限为0.05～0.62mg L,回收率在90.0%～110%之间。     

刚竹毒蛾危害下的毛竹叶片光谱特征波长研究

旨在获取刚竹毒蛾危害下的毛竹叶片光谱特征波长,以助于该虫害的有效、准确识别。将于福建省顺昌县实测的105条高光谱数据随机划分为实验组(71条)和验证组(34条)。基于实验组数据,利用单因素方差分析获取健康、轻度危害、中度危害、重度危害等虫害等级间具有极显著差异的波长;结合常用遥感卫星的波段设置对上述波长进行筛选,采用欧式距离、相关系数及光谱角匹配等3种方法判定其虫害判别能力,获取特征波长,并引入验证组样本对其予以验证。结果表明：(1)受害叶片的光谱反射率明显低于健康叶片,虫害等级越高,其反射率越低;(2)受害叶片的光谱特征变化较大,随着虫害等级的上升,其光谱曲线中的“绿峰”及“红谷”趋于消失,“红边”斜率逐渐减小;(3)确定原始光谱703.43~898.56 nm及一阶微分光谱497.68~540.72,554.53~585.25和596.24~618.23 nm为刚竹毒蛾危害下的毛竹叶片光谱特征波长,其对该虫害具有较强的判别能力。该研究从叶片尺度剖析了寄主对刚竹毒蛾的响应机理,是“地-天”耦合的理论基础,可为虫害遥感监测技术体系的建立提供重要依据。     

近红外光谱和特征光谱的山茶油掺假鉴别方法研究

山茶油素有"东方橄榄油"美誉,实现掺假山茶油的鉴别具有重要实用价值,采用近红外光谱技术对掺有葵花油的山茶油进行检测。分别以1%,5%,10%为梯度制备掺假比例不同的山茶油样品,并根据掺假比例将其分为A组(0%~5%)和B组(6%~10%)共11个样品,C组(15%~40%)6个和D组(50%~100%)6个样品。将每个掺假样品充分混匀后再分为9份,依次采集其1 000~2 500nm范围的吸收光谱,共获得207条光谱曲线。每组样品的光谱数据按2∶1随机分为训练集与验证集。经去除首尾噪声后,通过主成分分析法(principal component analysis,PCA)降维,并利用前四个主成分建立了鉴别山茶油不同掺假等级的主成分-支持向量机判别模型,训练集与验证集的总体判别准确率分别达96.38%和94.20%;进一步,通过对前四个主成分的载荷系数的分析,并结合原始光谱,提取建模过程中权重较大的波长并解析其化学含义,最终确定出五个特征波长:1 212,1 705,1 826,1 905及2 148nm,以此波长重新建立近红外特征光谱山茶油掺假等级判别模型,对训练集与验证集的总体判别准确率也达到了94.20%和92.75%。研究结果表明,利用近红外光谱和特征光谱均能够较好实现山茶油掺假等级的鉴别,同时所建立的近红外特征光谱模型也为设计相应的掺假山茶油实用便携式检测仪器提供了理论基础。     

Light flux density threshold at which protein denaturation is induced by synchrotron radiation circular dichroism beamlines

New high‐flux synchrotron radiation circular dichroism (SRCD) beamlines are providing important information for structural biology, but can potentially cause denaturation of the protein samples under investigation. This effect has been studied at the new CD1 dedicated SRCD beamline at ISA in Denmark, where radiation‐induced thermal damage effects were observed, depending not only on the radiation flux but also on the focal spot size of the light. Comparisons with similar studies at other SRCD facilities worldwide has lead to the estimation of a flux density threshold under which SRCD beamlines should be operated when samples are to be exposed to low‐wavelength vacuum ultraviolet radiation for extended periods of time.     

提高特征光谱法在微量气体监测中灵敏度的研究

为了实现对室内微量有毒气体实时监测,提高基于特征光谱检测方法的测量精度,提出了特征波长过滤窗的方法。将高浓度的待测气体作过滤窗,标准空气作参考窗,气室充待测浓度的待测气体,采用组合测量得到的多组光谱进行差分、相关等数据处理求解气室中待测气体的浓度。实验显示,采用WQF-520-FTIR型红外光谱仪得到癸二酸二丙脂红外吸收谱线主要有四条：3 385.26,3 417.64,5 797.11和8 561.65 nm,分别对应的吸光度为1.520 0,1.542 1,2.431 8和1.352 6。对应的可检测的最小含量为50×10-9,而采用特征波长过滤窗的方法波长位置可实现10-4 nm量级的对准,在确定待测气体含量量级的条件下,可检测的最小含量为5×10-9,灵敏度提高约10倍。该方法具有高灵敏度、无中毒、可实时检测等优点。     

光谱仪器信噪比与建模波长数对光谱分析精度的影响

为了研究光谱建模分析中光谱仪器噪声和参与建模的波长数两个因素与定量分析精度之间的关系,针对不同信噪比对模型精度的影响、参与建模的波长数与分析精度的关系、不同信噪比波段中多波长参与建模对分析精度的影响三个方面进行了理想样本建模分析。实验结果表明：光谱测量仪器的噪声水平直接影响建模分析误差,而使用多波长尤其是信噪比较好的波段的光谱参与线性建模,近似满足波长数每增加4倍,分析精度提高2倍的关系,能够在一定程度上弥补信噪比的不足。研究为在光谱分析中充分利用和提高光谱仪器信噪比、合理选择参与建模波长数及波段,从而提高光谱定量分析精度提供了实验基础和理论指导。